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Northstar engine series
Development and features
The Northstar's design was initiated as a response to the advanced dual overhead cam V8 engines introduced by European and Japanese competitors of Cadillac in the late 1980s. At that time, Cadillac was using the aluminum HT Overhead Valve (OHV) V8 which had been pushed hastily into production after the failure of the V8-6-4 of 1981.
Cadillac was developing new models like the Allant and updated Eldorado and Seville STS which they hoped would compete against the best from BMW, Mercedes-Benz, Lexus, and Infiniti. They developed a laundry list of items that must be included in these new models, including sophisticated steering, braking, and suspension technologies, which became known as the Northstar System. One key element was a high-tech V8 engine with all of the features and performance of the competitors' offerings.
The "Northstar" V8, as it was then known, was an evolution of the Lotus-designed Chevrolet LT5 all-aluminum DOHC 32-valve V8 used in the Corvette ZR-1. Archrival Ford Motor Company was developing a similar engine at that time as well, and Ford's Modular engine would precede the Northstar into production with its introduction on the 1991 Lincoln Town Car. Both continue in production at 4.6 L of displacement.
Capable of producing 300 hp (224 kW) out of its 4565 cc displacement, the Northstar featured a cast aluminum 90 V8 block with 102 mm (4 in) bore spacing split into unitary upper and lower halves. The lower crankcase assembly supported the crankshaft without conventional main bearing caps. An oil manifold plate with an integrated silicon gasket forms the oil gallery under this. A typical oil change used 7.58 quarts of oil.
Cast-iron cylinder liners were specified and the forged aluminum pistons included valve clearance. Northstar is an interference engine, with bronze pin bushings and free-floating piston pins used.
Cast aluminum cylinder heads were used featuring 4 valves per cylinder. The heads used dual overhead cams which are driven through the "maintenance-free" cam-drive chain case. The cams act directly on hydraulic lifters on the ends of the valves and are fed with a lubrication passage drilled through the cylinder head lengthwise. The intake valves are inclined at 25, while the exhaust valves are canted to 7 with center-mounted platinum-tipped spark plugs. The cam covers are magnesium for light weight.
Eight thermoplastic tubes were used in the induction system, leading to sequential fuel injection. The engine used a distributorless ignition system with a waste spark setup. The PCM controls spark and fuel injection timing as well as the shift points for the new 4T80-E transmission.
One notable feature, advertised at the time, was the "limp home" fail-safe mode which allowed the engine to continue running for a limited time without any coolant. Supplying fuel to only one cylinder bank in turn, the engine would "air cool" the inactive bank. This technique, combined with its all-aluminum construction and large oil capacity, allows the engine to maintain safe temperatures, allowing a Northstar-equipped car to be driven with no coolant for about 100 mi (161 km) without damage.
Another unusual feature of some Northstar-equipped cars is a liquid-cooled alternator used on Cadillac's Seville, DeVille, and Eldorado. The liquid-cooling helped prolong the life of the alternator in these electronic-laden models, though GM reverted to a traditional air-cooled setup for 2001 to eliminate potential leak points and extraneous tubing.
All engines of this family share the same Northstar bellhousing pattern.
Later developments included direct coil-on-plug ignition, and variable valve timing, which can vary intake by up to 40 and the exhaust by up to 50. VVT was devised for the longitudinal LH2 version, and has not, to date, been used on the transverse front wheel drive engines due to packaging considerations.
Northstar series
The engine was introduced in mid-1992 in the 1993 Cadillac Allant and continues to be used in most Cadillac models. The original Northstar Allant also introduced the Northstar System which included traction control, adaptive suspension, and antilock brakes. Early Northstar required premium grade gasoline to run safely.
The Northstar was sold exclusively by Cadillac for over a decade before being introduced in the 2004 Pontiac Bonneville and 2006 Buick Lucerne. However, the 4.0L L47 V8 variant was used in the Oldsmobile Aurora and the 3.5L LX5 V6 in the Oldsmobile Intrigue. The engine received a forged steel crankshaft in October 2003. Cadillac had planned to introduce a V12 Northstar this decade, likely for use in the Escalade, but economics and new CAFE standards have killed this idea.
Most Northstar engines produce 275 hp (205 kW) to 315 hp (235 kW). The engines were revised for 2000 with coil-on-plug ignition and roller follower valvegear for improved fuel economy and reduced emissions. Though power output did not change, this update eliminated the need for premium fuel.
All but the supercharged Northstar displace 4.6 L (279 cu in) with a 93 mm (3.7 in) bore and 84 mm (3.3 in) stroke. For better head gasket sealing between cylinders, the supercharged version is de-bored to 91 mm (3.6 in) for a total displacement of 4.4 L (266 cu in) . The block is said[who?] to be capable of expansion up to 5.4 L, though no such engine has been produced.
The Northstar was on the Ward's 10 Best Engines list for 1995, 1996, and 1997.
The Northstar System was Cadillac's trademarked name for a package of automobile performance features. Introduced in mid 1992 on the 1993 Cadillac Allant and later on that year's Seville and Eldorado, the Northstar name continues in use to this day.
The Northstar System included the following components:
L37 high-output 300 hp (224 kW) and 295 ftlbf (400 Nm)
LD8 high-torque 275 hp (205 kW) and 300 ftlbf (407 Nm)
GM 4T80-E 4-speed automatic transmission
Road Sensing Suspension
RSS was available in both standard and CV-RSS (continuously-variable) systems. It monitored damping rates of the shock absorbers every 15 milliseconds, selecting between two settings.
4-wheel disc brakes with Bosch antilock brakes
Magnasteer speed-variable power steering
Magnasteer combines conventional hydraulic power steering and magnetized "doughnuts" mounted around the output shaft, which stiffen the steering as vehicle speed increases.
The latest versions of the Northstar engine include the 4.6L 320 hp (239 kW) and 315 lbft (427 Nm) LH2 which began in 2004, and supercharged 4.4L 469 hp (350 kW) LC3 created for the STS-V which are detailed below.
General Motors employed a continuously variable system for the Cadillac Northstar System, VVT (Variable Valve Timing). The Northstar VVT provides a continuously variable system throughout the RPM range, increasing fuel economy. GM engines use the double overhead cam, varying both intake and exhaust for better performance.
L37
The L37 (VIN "9") was the original Northstar. It is tuned for responsiveness and power, while the later LD8 is designed for more sedate use. The L37 code has been used on all high-output transverse Northstars, even as the exact engine specifications evolved. Its displacement is 4600cc flat the compression ratio for the L37 is 10:1, shared with the LD8.
The original L37 was specified at 290 hp (216 kW), but 1993 production examples were rated at 295 hp (220 kW). The engine topped out at 300 hp (224 kW) from 1996 through 2004 on the STS, DTS and ETC models, making these some of the most powerful domestic front wheel drive cars ever built, the most powerful title still belonging to the 1970 Cadillac Eldorado 500 cu in (8.2 L) with 400 hp (298 kW) (although the latter's rating is in the older SAE gross horsepower system, figured without accessories or muffler, where the current engine outputs are as-installed, net ratings). For 2005 the high output Northstar became Northstar NHP, and was downrated to 290 horsepower (220 kW) under the new SAE certified horsepower rating system. In 2006, the updated DTS "Performance Package" model got a slight bump to 292 hp (218 kW). Vehicles using the L37 include:
Year
Model
Power
Torque
1993
Cadillac Allant
295 hp (220 kW) @ 5600 rpm
290 lbft (393 Nm) @ 4400 rpm
1993-1994
Cadillac Eldorado ETC
295 hp (220 kW) @ 5600 rpm
290 lbft (393 Nm) @ 4400 rpm
19952002
Cadillac Eldorado ETC
300 hp (224 kW) @ 6000 rpm
295 lbft (400 Nm) @ 4400 rpm
1993
Cadillac Seville STS
295 hp (220 kW) @ 5600 rpm
290 lbft (393 Nm) @ 4400 rpm
19942004
Cadillac Seville STS
300 hp (224 kW) @ 6000 rpm
295 lbft (400 Nm) @ 4400 rpm
19962004
Cadillac DeVille Concours/DTS
300 hp (224 kW) @ 6000 rpm
295 lbft (400 Nm) @ 4400 rpm
2005
Cadillac DeVille DTS
290 hp (216 kW) @ 5600 rpm
285 lbft (386 Nm) @ 4400 rpm
2006resent
Cadillac DTS Performance
292 hp (218 kW) @ 6300 rpm
288 lbft (390 Nm) @ 4500 rpm
2008-present
Buick Lucerne Super
292 hp (218 kW) @ 6300 rpm
288 lbft (390 Nm) @ 4500 rpm
LD8
The LD8 (VIN "Y") is a transverse V8 for front-wheel drive cars. Introduced in 1994, it is designed to provide more torque than the high-revving L37. The LD8 code has been used on all torque-tuned transverse Northstars, even as the exact engine specifications evolved. Compression ratio is 10:1.
The 1998 revision is quieter than previous Northstar engines, due to hydraulic engine mounts, and performs better due to a tuned intake system.
Most LD8 Northstars are rated at 275 hp (205 kW) and 300 lbft (407 Nm).
Year
Model
Power
Torque
1994
Cadillac Eldorado
270 hp (201 kW)
300 lbft (407 Nm)
19952001
Cadillac Eldorado
275 hp (205 kW) @ 5750 rpm
300 lbft (407 Nm)
2002
Cadillac Eldorado
275 hp (205 kW) @ 5600 rpm
300 lbft (407 Nm) @ 4000 rpm
1994
Cadillac Seville SLS
270 hp (201 kW)
300 lbft (407 Nm)
19952001
Cadillac Seville SLS
275 hp (205 kW)
300 lbft (407 Nm)
20022004
Cadillac Seville SLS
275 hp (205 kW)
300 lbft (407 Nm)
1994
Cadillac DeVille Concours
270 hp (201 kW)
300 lbft (407 Nm)
1995
Cadillac DeVille Concours
275 hp (205 kW) @ 5750 rpm
300 lbft (407 Nm)
19962001
Cadillac DeVille
275 hp (205 kW) @ 5750 rpm
300 lbft (407 Nm) @ 4000 rpm
20022005
Cadillac DeVille
275 hp (205 kW) @ 5600 rpm
300 lbft (407 Nm) @ 4000 rpm
2006resent
Cadillac DTS
275 hp (205 kW) @ 6000 rpm
295 lbft (400 Nm) @ 4400 rpm
20042005
Pontiac Bonneville GXP
275 hp (205 kW) @ 5600 rpm
300 lbft (407 Nm) @ 4000 rpm
20062007
Buick Lucerne CXS
275 hp (205 kW) @ 6000 rpm
295 lbft (400 Nm) @ 4400 rpm
LH2
The Northstar was designed originally for transverse front-wheel drive applications. It was modified substantially in 2004 for longitudinal rear- and all-wheel drive use in the SRX and XLR, as well as receiving continuously variable valve timing on both intake and exhaust sides. The RWD (LH2) Northstar produces 320 hp (239 kW) and 315 lbft (427 Nm). An increased compression ratio of 10.5:1 enables most of the increase in power from the L37 and LD8 Northstars.
Year
Model
Power
Torque
20042009
Cadillac SRX
320 hp (239 kW) @ 6400 rpm
315 lbft (427 Nm) @ 4400 rpm
20042009
Cadillac XLR
320 hp (239 kW) @ 6400 rpm
310 lbft (420 Nm) @ 4400 rpm
2004resent
Cadillac STS
320 hp (239 kW) @ 6400 rpm
315 lbft (427 Nm) @ 4400 rpm
Supercharged LC3
A 4.4 L (266 cu in) supercharged Northstar is used in the 2006 Cadillac STS-V and Cadillac XLR-V. The bore was reduced for increased strength and improved head gasket sealing. Variable valve timing is used on both the intake and exhaust sides. The STS-V engine produces 469 hp (350 kW) at 6400 rpm and 439 lbft (595 Nm) at 3900 rpm with 9:1 compression and the XLR-V engine produces 443 hp (330 kW) at 6400 rpm and 414 lbft (561 Nm) at 3900 rpm.
Year
Model
Power
Torque
20062009
Cadillac STS-V
469 hp (350 kW) @ 6400 rpm
439 lbft (595 Nm) @ 3900 rpm
20062009
Cadillac XLR-V
443 hp (330 kW) @ 6400 rpm
414 lbft (561 Nm) @ 3900 rpm
L47
A L47 inside an Aurora's engine bay
The L47 Aurora engine was a special V8 designed for the Oldsmobile Aurora, based on the Northstar engine. It is a DOHC 3,995 cc (3.995 L; 243.8 cu in) V8 which produced 250 horsepower (186 kW) and 260 ftlb (353 Nm) of torque. The bore is 87 mm (3.4 in) and the stroke is 84 mm (3.3 in). The L47 has a 10.3:1 compression ratio and uses premium fuel.
An early version or prototype of this engine was used in the 2nd generation Oldsmobile Aerotech.
Although most of the Northstar's features, including the coolant loss system, remained intact, the decreased bore increased weight unacceptably. To reduce it, Oldsmobile used a one-piece glass-filled thermoplastic intake manifold and simplified AC Rochester sequential fuel injection. A new die-cast structural aluminum oil pan incorporated baffling to reduce oil starvation in hard driving. A starter interlock prevents the starter from engaging if the quiet L47 is already running.
A highly modified 650 hp (485 kW) version of this engine was used by General Motors racing division initially for Indy Racing League competition starting in 1995, then was later used in the Cadillac Northstar LMP program in 2000. Both engines retained the 4.0 L capacity, but the Northstar LMP version was twin-turbocharged.
The Aurora was also used in the Shelby Series 1 car.
The Aurora engine was introduced in 1994 for the 1995 model year, and General Motors has not used this engine since the demise of the marque in 2004.
Year
Model
Power
Torque
19952003
Oldsmobile Aurora
250 hp (186 kW) @ 5600 rpm
260 lbft (353 Nm) @ 4400 rpm
LX5 (Shortstar)
A "Shortstar" LX5 inside an Intrigue's engine bay
The LX5 V6 is a DOHC engine from Oldsmobile, introduced in 1999 with the Oldsmobile Intrigue. It was produced by the Premium engine group at GM and was thus called the Premium V6, or PV6, while it was being developed. It is based on the L47 Aurora V8, which is itself based on the Northstar engine, so engineers called it the Short North, though Oldsmobile fans have taken to calling it the Shortstar.
It is not a simple cut-down V8. Although it has a 90 vee-angle like the Northstar and Aurora, the engine block was engineered from scratch, so bore centers are different. It has chain-driven dual overhead cams and 4 valves per cylinder, but is an even-firing design with a split-pin crankshaft similar to the modern GM 3800 engines. The LX5 displaced 3,473 cc (3.473 L; 211.9 cu in) and produced 215 hp (160 kW) @ 5,600 rpm and 230 ftlb (312 Nm) @ 4,400 rpm. Bore is 89.5 mm (3.52 in) and stroke is 92 mm (3.6 in). Compression ratio is 9.3:1.
The cost of building this engine was high, and it was not used in many vehicles. It was said at the time that a family of premium V6s would follow, with displacements ranging from 3.3 L to 3.7 L, but only the LX5 was ever produced.
The LX5 was entirely different from any other V6 in the GM inventory - the only other DOHC V6 engines offered by GM were the Chevrolet Twin Dual Cam produced from 1991-1997 and the Cadillac/Holden HFV6 available from 2004 to the present day. These three designs are completely unrelated and oddly enough leave two gaps in 1998 and 2003 where no DOHC V6 was available from GM. This contrasts starkly with competitors practices of evolving engineering over multiple, continuously improving designs.
As with the Aurora V8, production stopped with the demise of Oldsmobile.
Year
Model
Power
Torque
19992002
Oldsmobile Intrigue
215 hp (160 kW) @ 5600 rpm
230 lbft (312 Nm) @ 4400 rpm
20012002
Oldsmobile Aurora
215 hp (160 kW) @ 5600 rpm
230 lbft (312 Nm) @ 4400 rpm
The 3.5L LX5 was on the Ward's 10 Best Engines list for 1999 and 2000.
See also
GM 60-degree DOHC V6 engine
GM High Feature engine
Cadillac V8 engine
GM Ultra Engine
List of GM engines
Notes
^ http://74.125.47.132/search?q=cache:6nj6yREp_4wJ:www.ehow.com/facts_5467367_northstar-engine-information.html+LT5+northstar&cd=10&hl=en&ct=clnk&gl=us
^ Weitzman, Larry (2001).The Aurora by Oldsmobile (2001), Better in every respect. Autochannel. Retrieved on June 28, 2009.
References
Frank Markus. "1993 Technical Highlights". Car and Driver (October 1992): 5960.
"Technical Highlights". Car and Driver (October 1993): 115.
Joel D. Pietrangelo. "Northstar is heart of Allante re-do for '93 - V-8 engine, General Motors' Cadillac Motor Car Div.'s new model roadster". Ward's Auto World (February 1992).
External links
Northstar engine - official website
Technical article from AutoSpeed
Ward's article
GM Premium V Performance Discussion Forums
Categories: Cadillac engines | GM engines | Automotive technology tradenamesHidden categories: All articles with specifically-marked weasel-worded phrases | Articles with specifically-marked weasel-worded phrases from September 2008
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Echo sounding
Technique
Scheme of echo sounding in the ocean
Distance is measured by multiplying half the time from the signal's outgoing pulse to its return by the speed of sound in the water, which is approximately 1.5 kilometres per second. Echo sounding is effectively a special purpose application of sonar used to locate the bottom.
Common use
As well as an aid to navigation (most larger vessels will have at least a simple depth sounder), echo sounding is commonly used for fishing. Variations in elevation often represent places where fish congregate. Schools of fish will also register. Most charted ocean depths use an average or standard sound speed. Where greater accuracy is required average and even seasonal standards may be applied to ocean regions. For high accuracy depths, usually restricted to special purpose or scientific surveys, a sensor may be lowered to observe the factors (temperature, pressure and salinity) used to calculate sound speed and thus determine the actual sound speed in the local water column.
Special applications
In areas where detailed bathymetry is required, an Autonomous Underwater Vehicle (AUV) can be deployed to make a high resolution map. These maps are made using a multibeam echosounder (MBES) that measures the time it takes for a pulse of sound emitted from the AUV to travel to the ocean floor and back. The MBES transmitting and listening devices are known as transducers. A good MBES will have around one hundred transducers, the output from which can be combined in such a way as to enhance the sound transmitted towards or arriving from a particular direction. This technique is known as beam forming. The travel time and direction of the sound return can be converted to a depth relative to the AUV. The vertical position of the AUV in the ocean is determined using a pressure gauge. The accuracy of this process is in the order of centimeters.
See also
Acoustical oceanography
AUV
Fisheries Acoustics
Fishfinder
Hydroacoustics
Sonar
Sounding line
Soundings
Underwater acoustics
v d e
Hydroacoustics
Sonar
Acoustic Doppler Current Profiler Baffles (submarine) Bistatic sonar Echo sounding GLORIA sidescan sonar Scientific Echosounder Side-scan sonar Sonar 2087 Sonar beamforming Sonobuoy Surveillance Towed Array Sensor System Synthetic aperture sonar Towed array sonar Upward looking sonar
Ocean acoustics
Ocean acoustic tomography Sofar bomb SOFAR channel Underwater acoustics
Acoustic ecology
Acoustic tags Animal echolocation Beached whale Bioacoustics Biophony Fishfinder Fisheries acoustics Marine mammals and sonar Noise map Soundscape Whale song
v d e
Physical oceanography
Landforms
Abyssal fan Abyssal plain Atoll Bathymetric chart Cold seep Continental shelf Continental margin Contourite Hydrography Guyot Oceanic basin Oceanic plateau Oceanic trench Passive margin Seabed Seamount Submarine canyon Coastal geography More...
Plate tectonics
Black smokers Convergent boundary Divergent boundary Fracture zone Hydrothermal vents Marine geology Mid-ocean ridge Mohorovii discontinuity Morleyineatthews hypothesis Oceanic crust Outer trench swell Ridge-push Seafloor spreading Slab window Subduction Transform fault Volcanic arc More...
Circulation
Baroclinity Boundary current Coriolis effect Downwelling Eddy Ekman layer Ekman spiral Ekman transport El Nio-Southern Oscillation Geostrophic current Gulf Stream Halothermal circulation Humboldt Current Hydrothermal circulation Global circulation model Langmuir circulation Longshore drift Loop Current Maelstrom Ocean current Ocean dynamics Oceanic gyre Thermohaline circulation Shutdown of thermohaline circulation Subsurface currents Sverdrup balance Whirlpool Upwelling GLODAP MOM WOCE More...
Waves
Airy wave theory Ballantine Scale Boussinesq approximation Breaking wave Clapotis Cnoidal wave Cross sea Dispersion Infragravity waves Edge wave Equatorial waves Fetch Freak wave Gravity wave Internal gravity waves Internal wave Kelvin wave Luke's variational principle Mild-slope equation Rogue wave Rossby wave Rossby-gravity waves Sea state Seiche Significant wave height Sneaker wave Soliton Stokes drift Surf wave Swells Tsunami Undertow Ursell number Wave base Wave height Wave power Wave shoaling Wave radar Wave turbulence Waves and shallow water Shallow water equations Wind wave Wind wave model More...
Tides
Amphidromic point Earth tide Head of tide Internal tide Lunitidal interval Perigean spring tide Rip current Rule of twelfths Slack water Spring/neap tide Tidal bore Tidal force Tidal power Tidal race Tidal range Tidal resonance Tide Tide gauge Tideline More...
Sea level
Current sea level rise Future sea level Sea-level curve DART GLOSS NOOS OSTM WGS
Acoustics
Ocean acoustic tomography Sofar bomb SOFAR channel Underwater acoustics Hydroacoustics
Other
Alvin Argo Benthic lander Deep ocean water Deep sea Littoral zone Marginal sea Mooring Ocean energy Ocean observations Ocean reanalysis Ocean surface topography Ocean thermal energy conversion Oceanic zone Pelagic zone Sea surface microlayer Sea surface temperature Seawater Science On a Sphere Thermocline Underwater glider Water column World Ocean Atlas NODC More...
Categories: Surveying | Oceanographic instrumentationHidden categories: Articles lacking sources from December 2009 | All articles lacking sources
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Electrostatic loudspeaker
Design and functionality
The speakers use a thin flat diaphragm usually consisting of a plastic sheet impregnated with a conductive material such as graphite sandwiched between two electrically conductive grids, with a small air gap between the diaphragm and grids. For low distortion operation, the diaphragm must operate with a constant charge on its surface, rather than with a constant voltage. This is accomplished by either or both of two techniques: the diaphragm's conductive coating is chosen and applied in a manner to give it a very high surface resistivity, and/or a large value resistor is placed in series between the EHT (Extra High Tension or Voltage) power supply and the diaphragm (resistor not shown in the diagram here).
The diaphragm is usually made from a polyester film (thickness 220 m) with exceptional mechanical properties, such as PET film. By means of the conductive coating and an external high voltage supply the diaphragm is held at a DC potential of several kilovolts with respect to the grids. The grids are driven by the audio signal; front and rear grid are driven in antiphase. As a result a uniform electrostatic field proportional to the audio signal is produced between both grids. This causes a force to be exerted on the charged diaphragm, and its resulting movement drives the air on either side of it.
In virtually all electrostatic loudspeakers the diaphragm is driven by two grids, one on either side, because the force exerted on the diaphragm by a single grid will be unacceptably non-linear, thus causing harmonic distortion. Using grids on both sides cancels out voltage dependent part of non-linearity but leaves charge (attractive force) dependent part. The result is near complete absence of harmonic distortion. In one recent design, the diaphragm is driven with the audio signal, with the static charge located on the grids (Final Sound).
The grids must be able to generate as uniform an electric field as possible, while still allowing for sound to pass through, and should be perfectly flat. Suitable grid constructions are therefore perforated metal sheets, a frame with tensioned wire, wire rods, etc.
To generate a sufficient field strength, the audio signal on the grids must be of high voltage. The electrostatic construction is in effect a capacitor, and current is only needed to charge the capacitance created by the diaphragm and the stator plates. This type of speaker is therefore a high-impedance device. In contrast, a modern electrodynamic cone loudspeaker is a low impedance device, with higher current requirements. As a result, impedance matching is necessary in order to use a normal amplifier. Most often a transformer is used to this end. Construction of this transformer is critical as it must provide a constant (often high) transformation ratio over the entire audible frequency range and so avoid distortion. The transformer is almost always specific to a particular electrostatic speaker. To date, Acoustat built the only "transformer-less" electrostatic loudspeaker. In this design, the audio signal is applied directly to the stators from a built-in high-voltage valve amplifier, without use of a step-up transformer.
Advantages
Advantages of electrostatic loudspeakers include the extremely light weight of the diaphragm, and exemplary frequency response (both in amplitude and phase) because the principle of generating force and pressure is not as prone to resonances as in the operating principle of the more common electrodynamic driver. Musical transparency can be better than in electrodynamic speakers because the radiating surface has much less mass than most other drivers and is therefore far less capable of storing energy to be released later. For example, typical dynamic speaker drivers can have moving masses of tens or hundreds of grams whereas an electrostatic membrane only weighs a few milligrams, several times less than the very lightest of electrodynamic tweeters. The concomitant air load, often insignificant in dynamic speakers, is usually tens of grams because of the large coupling surface, this contributing to damping of resonance buildup by the air itself to a significant, though not complete, degree. Electrostatics can also easily be executed as full-range designs, lacking the usual crossover filters and enclosures that could color or distort the sound.
Since most electrostatic speakers are tall and thin designs without an enclosure, they act as a vertical dipole line source. This makes for rather different acoustic behavior in rooms compared to conventional electrodynamic loudspeakers. Generally speaking, a large-panel dipole radiator is more demanding of a proper physical placement within a room when compared to a conventional box speaker, but, once there, it is less likely to excite bad-sounding room resonances, and its direct-to-reflected sound ratio is higher by some 45 decibels. This in turn leads to more accurate stereo reproduction of recordings that contain proper stereo information and venue ambience. Planar (flat) drivers tend to be very directional giving them good imaging qualities, on the condition that they have been carefully placed relative to the listener and the sound-reflecting surfaces in the room. Curved panels have been built, making the placement requirements a bit less stringent, but sacrificing imaging precision somewhat.
Disadvantages
Disadvantages include a lack of bass response (due to phase cancellation from a lack of enclosure, and the difficult physical challenge of reproducing low frequencies with a vibrating taut film with little excursion amplitude), and sensitivity to ambient humidity levels. While bass is lacking quantitatively, it can be of better quality ('tighter' and without 'booming') than that of electrodynamic (cone) systems. Phase cancellation can be somewhat compensated for by electronic equalization (a so-called shelving circuit that boosts the region inside the audio band where the generated sound pressure drops because of phase cancellation). Nevertheless maximum bass levels cannot be augmented because they are ultimately limited by the membrane's maximum permissible excursion before it comes too close to the high-voltage stators, which may produce electrical arcing and burn holes through it. Recent, technically more advanced solutions for lack of bass include the use of large, curved panels (Sound Lab, MartinLogan CLS), electrostatic subwoofer panels (Audiostatic) and long-throw electrostatic element allowing large diaphragm excursions (Audiostatic). Another trick often practised is to step up the bass (2080 Hz) with a higher transformation ratio than the mid and treble.
This relative lack of loud bass is often remedied with a hybrid design using a dynamic loudspeaker, e.g. a subwoofer, to handle lower frequencies with the electrostatic diaphragm handling middle and high frequencies. Many feel that the best low frequency unit for hybrids are transmission line woofers or horns, since they possess roughly the same qualities (at least in the bass) as electrostatic speakers, i.e. good transient response, little box coloration, and (ideally) flat frequency response. However, there is often a problem with integrating such a woofer with the electrostatics. This is because most electrostatics are line sources, the sound pressure level of which decreases by 3 dB for each doubling of distance. A cone speaker's sound pressure level, on the other hand, decreases by 6 dB for each doubling of distance because it behaves as a point source. This can be overcome by the theoretically more elegant solution of using conventional cone woofer(s) in an open baffle, or a push-pull arrangement, which produces a bipolar radiation pattern similar to that of the electrostatic membrane. This is still subject to phase cancellation, but cone woofers can be driven to far higher levels due to their longer excursion, thus making equalization to a flat response easier.
The directionality of electrostatics can also be a disadvantage in that it means the 'sweet spot' where proper stereo imaging can be heard is relatively small, limiting the number of people who can fully enjoy the advantages of the speakers simultaneously.
Because of their tendency to attract dust, insects, conductive particles and moisture, electrostatic speaker diaphragms will gradually deteriorate and need periodic replacement. They also need protection measures to physically isolate their high voltage parts from accidental contact with humans and pets. Cost-effective repair and restoration service is available for virtually every current and discontinued electrostatic loudspeaker model.
Amateur-built speakers
Electrostatic speakers enjoy some popularity among do-it-yourself (DIY) loudspeaker builders. They are one of the few types of speakers in which the transducers themselves can be built from scratch by an amateur. Basic hardware for complete ESL DIY projects is available all over the web. Such supplies include resistors and capacitors for RC-circuit frequency equalization, if necessary; step-up transformers; perforated metal sheets or grids and insulating plastics for the stators; polymer film and conductive paint (e.g. a liquid graphite suspension) for the membrane; simple tensioning equipment for proper membrane tuning; and a frame, usually of wood, to hold everything together. A widely-read resource by ESL enthusiasts is The Electrostatic Loudspeaker Design Cookbook (ISBN 978-1-882580-00-2) by notable ESL specialist Roger Sanders.
Commercial speakers
Arthur Janszen was granted U.S. Patent 2,631,196 in 1953 for the first practical electrostatic loudspeaker. The developers of the Tri-Ergon sound-on-film sound film system had developed a primitive design of electrostatic loudspeaker as early as 1919.
Among the first full-range electrostatics, and also among the most respected, was the Quad Electrostatic Loudspeaker (Quad ESL, later ESL-57) from Quad Electroacoustics, of Huntingdon, England. These were shaped somewhat like a home radiator curved slightly on the vertical axis. They were widely admired for their clarity and precision, but can be difficult to run while achiving low frequency bass output. The Quad ESLs were designed by Peter Walker, founder of the company, and David Williamson. The first in the series was the ESL-57, based on U.S. Patent 1,983,377 developed by Edward W. Kellogg for General Electric in 1934. It was introduced in 1955, put into commercial production in 1957, and discontinued only in 1985. In 1981, Quad introduced the ESL-63 as a successor to the ESL-57. It attempted to address both the deficiency in bass reproduction of the ESL-57 and its extreme directionality at high frequencies. The latter goal is achieved by splitting the stators into eight concentric rings, each fed with a slight time delay compared to the ring immediately inwards, thereby attempting to simulate a point source. The ESL-63 remained in production until 1999. In 1999 Quad introduced the ESL-988 and the ESL-989, both currently in production. Two new models, the smaller 2805 and the larger 2905, have been introduced as of late 2005, which return to the slightly back-tilted stance of the original designs, albeit user-adjustable. Largely retaining the larger bass panels of the 98x models and concentric ring design of the ESL-63, the 2x05's feature heavier and far more rigid construction, and several electronic and transducer refinements.
Innersound, Martin-Logan,Metrum Acoustics, and Sanders Sound Systems, build hybrid designs with conventional subwoofers.
Final Sound builds stand-alone electrostatic panels with freestanding bass-modules as an option. Final Sound also has two separate patents for producing electrostatic panels. They use an inverted audio drive to the panels, compared to conventional electrostatic speakers. The standard drive method is to apply the high voltage bias to a high resistance coating on the inner diaphragm and apply the audio signal from a center tapped audio transformer to the low resistance outer stators. In the Final Sound design, the stators are high resistance and a complementary, meaning a plus and minus high voltage bias supply is connected to opposite stators. The diaphragm is then driven by the audio transformer. According to their white paper only half the required turns ratio is needed for the same output. This lowers the cost and size of the transformer and makes it an easier load to drive with an amplifier.
Audiostatic,, Sound Lab exclusively build full-range electrostatic panels. The only active electrostatic loudspeaker currently in production is the Audiostatic DCA-5.
Among electrostatic full-range speakers which are no longer made are the KLH 9, one of the earliest US full-range designs, although the bass dropped of rapidly below 70 Hz . There were several Acoustat models manufactured, and the Infinity Servo-Statik and its successors which used a dynamic subwoofer at low frequencies.
Another full-range speaker that is out of production was the Canadian manufactured Dayton Wright XG-8 and the XG-10 from 1968 to the 1990s. They were distinctly different in design, by enclosing the panels in an airtight bin, containing sulphur hexaflouride, a gas used in high voltage arc suppression devices. This gas, even with a 50% dilution has a breakdown voltage compared to air of about 2.5 times. This allowed a much higher than usual polarization voltage of up to 16 kV, more than twice as high as any other electrostat. The advantages were higher sensitivity approaching that of conventional speakers and not requiring the insulation of the stators. The higher bias was not used to just increase the efficiency, but mainly to produce high output by increasing the gap between stator and driven diaphragm to almost 0.2 in. This coupled with an enormous step-up transformer allowed the audio voltages to also reach 16 kV for higher output levels than any other design then and now. With an amplifier of 500 W rms per channel, sound pressure levels equal to conventional speaker could be produced. The bass response down to 40 Hz was achieved by several things. First the cell diaphragm coating had a resistance exceeding 1000 M per square, requiring charge times of several days, but this increased the charge migration time to a few seconds, reducing the low frequency distortion. A large core transformer that did not saturate at 600 W at 20 Hz. Taking advantage of the advantage of the SF6 gas to provide heavier than air loading to the electrostatic cells to drive the front and rear external diaphragms being 1.6 times larger than the cells. In addition the propagation of sound is 2.3 times slower in the gas, giving the effect of a much longer acoustic path and so lowering the cancellation frequency of the speaker caused by the out of phase rear wave. In addition, the transformer primary inductance was resonated with a capacitor to produce a low Q circuit at about 45 Hz to lift the response. The earlier models (XG8) had 8 cells per speaker and the later models has 10 cells. The cells were not full range due to their width causing too much beaming at high frequencies and the attenuation of the front diaphragm. The high frequency driver was a Motorola piezoelectric tweeter crossing over at about 7 kHz which was then replaced with a Panasonic leaf tweeter in the later generation models, crossed over at 6 kHz. The piezoelectric tweeter was mounted inside the bin as it performed actually better with the gas than in air, but the leaf tweeter was mounted on the outside of the exterior diaphragm. Dayton Wright ,
Other manufacturers currently producing electrostatic loudspeakers include Immersion from Australia; and Solosound in The Netherlands, King's Audio, and Panphonics from Finland
Specialized electrostatic high frequency drivers (i.e., tweeters) are still in common use by many manufacturers,
References
^ The theory of electrostatic forces in a thin electret (MEMS) speaker Eino Jakku, Taisto Tinttunen and Terho Kutilainen, proceedings IMAPS Nordic 2008 Helsingr - September 1416
^ Fritz, Jeff; Mickelson, Marc (May 2004), "Innersound Factory Tour", SoundStage! (Schneider Publishing), http://www.soundstagelive.com/factorytours/innersound/, retrieved 2009-05-16
^ http://history.sandiego.edu/GEN/recording/loudspeaker.html
^ http://innersound.net/
^ http://www.metrum-acoustics.nl/
^ Sanders Sound Systems Products
^ http://www.finalsound.com/
^ http://www.finalsound.nl/downloads/whitepaper2007.pdf/
^ http://http://www.acoustat.co.uk/loud-speakers-about-acoustat.html/
^ http://www.soundlab-speakers.com/
^ http://www.stereophile.com/floorloudspeakers/666klh/
^ http://http://www.acoustat.co.uk/loud-speakers-about-acoustat.html
^ http://www.dayton-wright.com/
^ http://www.iti-plc.com/
^ http://www.solostatic.com/
^ http://www.kingsaudio.com.hk/
^ http://www.panphonics.com/
External links
The Audio Circuit - An almost complete list of manufacturers of electrostatic loudspeakers including DIY speakers, materials and parts, and 'how do they work' sections.
Categories: Electrostatics | LoudspeakersHidden categories: Articles needing additional references from May 2009 | All articles needing additional references
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Maple syrup
History
Native Americans
Pre-contact native peoples, living in the northeastern part of North America, were the first people known to have produced maple syrup and maple sugar. According to their oral traditions, as well as archaeological evidence, maple tree sap was being processed for its sugar content long before Europeans arrived in the region.
The Algonquins recognized the sap as a source of energy and nutrition. At the beginning of the spring thaw, they used stone tools to make V-shaped incisions in the trees, then inserted reeds or concave pieces of bark to run the sap into buckets, which were often made from birch bark. The maple sap, already rich in sugar content and yet not sweet-tasting, was concentrated either by dropping hot cooking stones into the buckets, or by leaving them exposed to the cold temperatures overnight, and disposing of the layer of ice which formed on top.
First Nations and Native Americans also used earthenware cooking pots to boil the maple sap. They heated it over simple fires protected only by a roof of tree branches.
Colonial to modern times
A 19th-century illustration, "Sugar-Making Among the Indians in the North" (note the use of metal containers, introduced as a result of European contact)
In the early stages of European colonization, in north-eastern North America, native peoples showed the arriving colonists how to tap (into) the trunks of certain types of maple tree during the end-of-winter/early-spring thaw, harvest the sap, and boil it to evaporate some of the water, concentrating the sugar content within the remaining liquid, and altering its taste somewhat, by heat-caramelizing some of the sugars. This activity quickly became an integral part of colonial life. Well before the beginning of the 1700s, European settlers and fur traders, as well as Native Americans, were intensively involved in the industry. During the 17th and 18th centuries, processed maple sap was a major source of concentrated sugar, in both liquid and crystallized-solid form. The Europeans revised the processing methods somewhat, with their access to more advanced technologies; particularly in metallurgy, toolmaking, and the use of domesticated animals. Typically, maple sugaring parties began to operate at the start of the spring thaw in regions of woodland known to contain sufficiently large numbers of maples, concentrated within a reasonable range of transportation to justify the effort. They first bored holes in the trunks of the maples, usually more than one hole per large tree, inserted home-made (usually carved wooden) spouts into the holes, and then hung a wooden bucket from the protruding end of each spout to collect the sap. The buckets were commonly made by cutting bucket-sized cylindrical segments from an appropriately large tree-trunk and then hollowing out each segment's core from one end of the cylinder, creating a seamless watertight container. Sap slowly filled the buckets, drop by drop. Periodically, members of the sugaring party returned to retrieve the sap that had accumulated. It was then either transferred to larger holding vessels ( barrels, large pots, or hollowed-out wooden logs) often mounted on sledges or wagons pulled by draft animals or it was carried in buckets, or similarly convenient containers. The sap-collection buckets were returned to the spouts mounted on the trees, and the process was repeated for as long as the flow of sap remained "sweet". The specific weather conditions of the late-winter/early-spring "thaw" period were, and still are, critical in determining the length of the "sugaring" season. As the weather continues to warm, a maple tree's normal early spring biological process eventually alters the taste of the sap, making it unpalatable. Depending on conditions, a sugaring party could spend several days to several weeks engaged in these activities. The boiling process was time consuming. The harvested sap was transported back to the party's base camp, where it was then poured into large, (almost always) metal vessels and boiled to achieve the desired consistency. The sap was usually processed at a central collection point, either over a fire built out in the open, or inside a shelter built for that purpose. To protect themselves from the weather conditions of the very early spring, sugaring parties built a small camp. Often, whole families moved into the woods together to collect and boil the sap producing both maple syrup and maple sugar.
By the 1850s, the "sugar shack" or "sugarhouse" (the outdoor shack or building used to boil down the sap) arrived as we know it today. The settlers had refined the methods for collecting the sap. The sap was transported using large barrels pulled by horses or oxen and brought to the sugar shack for processing. At this time, maple sugar was the only sugar available as other types of sugar were hard to find and expensive and was called "country sugar". Production methods have been streamlined since colonial days, yet remain basically the same. Sap must first be collected and boiled down carefully to obtain pure syrup without chemical agents or preservatives.
Early maple syrup was made by boiling approximately forty gallons (160 l) of sap over an open fire until one gallon (4 l) of syrup was obtained.
This process underwent little change over the first two hundred years of recorded maple syrup making. Around the time of the American Civil War, syrup makers started using a large flat sheet metal pan as it was more efficient for boiling than a heavy rounded iron kettle which let much of the heated air slide past.
Virtually all syrup makers in the past were self-sufficient dairy farmers who made both syrup and sugar for their own use and for extra income. The process continued to evolve as a result of the innovations developed in their work. In 1864, a Canadian borrowed some design ideas from sorghum evaporators and put a series of baffles in the flat pans to channel the boiling sap. In 1872 a Vermonter developed an evaporator with two pans and a metal arch or firebox which greatly decreased boiling time. Seventeen years later, in 1889, another Canadian bent the tin that formed the bottom of a pan into a series of flues which increased the heated surface area of the pan and again decreased boiling time.
The technology remained the same until the 1960s, when it was no longer a self sufficient enterprise with large families as farm hands. Because syrup making was so labor intensive, farmers could no longer afford to hire the large crews it took to gather all the buckets and haul the sap to the evaporator house. During the energy crunch of the 1970s, syrup makers responded with another surge of technological breakthroughs. Tubing systems, which had been experimented with since the early part of the century were perfected and the sap came directly from the tree to the evaporator house. Vacuum pumps were added to the tubing systems. Pre-heaters were developed to recycle heat lost in the steam. Reverse-osmosis machines were developed to take a portion of water out of the sap before it was boiled. Several producers even obtained surplus desalinization machines from the U.S. Navy and used them to take a portion of water out of the sap prior to boiling.
The technological developments continue. Improvements in tubing, new filtering techniques, "supercharged" preheaters, and better storage containers have been developed. Research continues on pest control and improved woodlot management. In 2009, the University of Vermont unveiled a new type of tap which prevents backflow of sap into the tree, reducing bacterial contamination and preventing the tree from attempting to heal the bore hole.
Production
Maple syrup production is centered in northeastern North America, and is commonly associated with Quebec in Canada; however, given the correct weather conditions, it can be made wherever maple trees grow. Usually, the maple species used are the sugar maple (Acer saccharum) and the black maple (Acer nigrum), because of a high sugar content in the sap of roughly two percent. A maple syrup production farm is called a "sugar bush" or "the sugarwoods". Sap is often boiled in a "sugar house" (also known as a "sugar shack" or cabane sucre), a building which is louvered at the top to vent the steam from the boiling sap.
Canada makes more than 80 percent of the world's maple syrup, producing about 26.5 million litres in 2005. The vast majority of this comes from Quebec: the province is by far the world's largest producer, with about 75 percent of the world production (24.66 million litres in 2005). Production in Quebec is controlled through a supply-management system, with producers receiving quota allotments from the Fdration des producteurs acricoles du Qubec. The province also maintains it own "strategic reserves" of maple syrup, which reached its highest point in 2004, when it totalled 60 million pounds, or 17.03 million litres.
The provinces of Ontario, Nova Scotia, New Brunswick, Prince Edward Island, and British Columbia produce smaller amounts. The province of Manitoba produces maple syrup using the sap of the Manitoba maple tree (Acer negundo, also known as the "box-elder"). Manitoba maple syrup has a slightly different flavor than sugar-maple syrup; because it contains less sugar and the sap flows more slowly, the Manitoba maple tree's yield is usually less than half that of a similar-sized maple tree.
Vermont is the biggest U.S. producer, with 920 thousand US gallons (3,500,000 l) in 2009, followed by Maine with 395 thousand US gallons (1,500,000 l) and New York with 362 thousand US gallons (1,370,000 l). Wisconsin, Ohio, New Hampshire, Michigan, Pennsylvania, Massachusetts, and Connecticut all produced marketable quantities of maple syrup of less than 120 thousand US gallons (450,000 l) each in 2009.
Traditional tap
Two taps in a maple tree, using plastic tubing for sap collection.
A small scale evaporation pan used in Ohio.
A sugar house where sap is boiled down to maple syrup.
Traditionally, maple syrup was harvested by tapping a maple tree through the bark and into the wood, then letting the sap run into a bucket, which required daily collecting; less labour-intensive methods such as the use of continuous plastic pipelines have since superseded this, in all but cottage-scale production.
Production is concentrated in February, March, and April, depending on local weather conditions. Freezing nights and warm days are needed to induce sap flows. The change in temperature from above to below freezing causes water uptake from the soil, and temperatures above freezing cause a stem pressure to develop, which, along with gravity, causes sap to flow out of tapholes or other wounds in the stem or branches. To collect the sap, holes are bored into the maple trees and tubes (taps, spouts, spiles) are inserted. Sap flows through the spouts into buckets or into plastic tubing. Modern use of plastic tubing with a partial vacuum has enabled increased production. A hole must be drilled in a new location each year, as the old hole will produce sap for only one season due to the natural healing process of the tree, called walling-off. Maple sap is collected from the buckets and taken to the sugar house; if plastic tubing and pipelines are used, then the pipelines are arranged so that the sap will flow by gravity into the sugar house, or if that is not possible, into holding tanks from which the sap is pumped or transported by tanker truck to the sugar house.
It takes approximately 40 litres (10 gal) of sap to be boiled down to 1 litre (1 quart) of syrup. A mature sugar maple produces about 40 litres of sap during the 4- to 6-week sugaring season. Trees are not tapped until they have a diameter of 25 cm (10 in) at chest-height and the tree is at least 40 years old. If the tree is more than 45 centimetres (18 in) it can be tapped twice on opposite sides. It is recommended that the drilled tap hole have a width of 8 mm ( in) and a depth of 25 to 40 mm (1.0 to 1.6 in). During cooking, the sap is fed automatically by pipe from a storage tank to a long and narrow ridged pan called the evaporator. The evaporator is usually divided into two sections, the front pan and the back pan. As the sap boils, the water evaporates; it becomes denser and sweeter. As the density of the sap increases, it works its way from the rear of the back evaporator pan to the front evaporator pan. The syrup is boiled until it reaches the correct density of maple syrup, 1333 kg/m3.[citation needed] The proper density of at least 66% sugar is reached when the boiling sap reached a temperature of 219 F (104 C). The density is tested with a hydrometer. If the density is too low the syrup will not be sweet enough and the syrup will spoil. If the density is too high the syrup will crystallize in bottles. When the syrup has reached the proper density, it is drawn off, filtered and bottled while hot.
Starting in the 1970s, some maple syrup producers started using reverse osmosis to remove water from sap before being further boiled down to syrup. The use of reverse osmosis allows approximately 75 to 80% of the water to be removed from the sap prior to boiling, reducing energy consumption and exposure of the syrup to high temperatures. Microbial contamination and degradation of the membranes has to be monitored.
Maple syrup is sometimes boiled down further to make maple sugar, a hard candy usually sold in pressed blocks, and maple taffy. Intermediate levels of boiling can also be used to create various intermediate products, including maple cream (less hard and granular than maple sugar) and maple butter (creamy, with a consistency slightly less thick than peanut butter). During the production season in New England, a traditional delicacy known as "sugar-on-snow" is often prepared by drizzling superheated maple syrup over snow or shaved ice, resulting in a chewy taffy-like confection.
Starting in the mid 80's, northern communities in the province of Quebec began to open the "Cabane Sucre" or Sugar Shacks to the public. These sugar shacks were generally located on large maple farms and often were built solely for tourist purposes. These sugar shacks serve maple syrup direct to the public and also are often restaurants serving maple syrup inspired meals and treats.
Grades
Canadian, U.S., and Vermont grading
U.S. Syrup grades. Left to right: Vermont Fancy, Grade A Medium Amber, Grade A Dark Amber, Grade B
In Canada, there are three grades containing several color classes, ranging from Canada #1, including Extra Light (sometimes known as AA), Light (A), and Medium (B); through #2, Amber (C); and finally #3 Dark (D). A typical year's yield will include about 2530% of each of the #1 colors, 10% Amber, and 2% Dark. Number 2 grade syrups are aimed at baking and flavouring but are also popular on pancakes and waffles. In addition, Canada #2 Amber may be labeled Ontario Amber for farm sales in that province only. Number 3 grade syrup is heavy, and restricted for use in commercial flavourings.[citation needed]
The United States uses somewhat different grading standards. Maple syrup is divided into two major grades: Grade A and Grade B. Grade A is further broken down into three subgrades: Light Amber (sometimes known as Fancy), Medium Amber, and Dark Amber. Grade B is darker than Grade A Dark Amber. The Vermont Agency of Agriculture Food and Markets uses a similar grading system of color and taste. The grade Vermont Fancy is similar in color and taste to U.S Grade A Light (Fancy). The Vermont grading system differs from the U.S. system in maintaining a slightly higher standard of product density. Vermont maple is boiled just a bit longer for a slightly thicker, denser product. The ratio of the volume of sap to the yielded volume of finished syrup is higher in the Vermont system. Maple syrup is sold by liquid volume, not weight. The Vermont graded product has one-half percent more solid material and less water in its composition. A non-table grade of syrup called commercial, or Grade C, is also produced. This is very dark, with a very strong flavor. Commercial maple syrup is generally used as a flavoring agent in other products.
The grades roughly correspond to various times within the season when syrups are produced. Canada #1 Extra Light and U.S. Grade A Light Amber are early-season grades, while Canada #2 and #3 and U.S. Grade B are late-season grades. Typically #1 Extra Light and Grade A (especially Grade A Light Amber) has a milder, more delicate flavor than #3 or Grade B, which is very dark with a robust flavor. The dark grades of syrup are primarily used for cooking and baking.
Off-flavours
Sometimes off-flavours are found in maple syrup. While this is more common toward the end of the season in the production of commercial grade product, it may also be present early in the season during the production of Canada #1 grade or U.S. Grade A Light. Identification of off-flavour in table grades is cause for ceasing production and either dumping the product or reclassifying the product as commercial grade if the off-flavour is slight. Off-flavours are described as: metabolism, derived from metabolic changes in the tree as spring arrives and having either a woody, popcorn, or sometimes peanut butter-like flavour; buddy, referring to the swelling of the new buds and its impact on the flavour and having a bitter chocolate or burnt flavour; and ferment, an off-taste caused by fermentation and having a honey or fruity flavour, often accompanied by surface foam. Additionally, if trees are stressed or fighting off disease or insects (e.g. gypsy moths), they will produce a folic-like acid causing a bad taste. After an ice storm, trees may also produce the same acid.
Use in food and cultural significance
Maple syrup
Nutritional value per 100 g (3.5 oz)
Energy
1,093 kJ (261 kcal)
Carbohydrates
67.09 g
Sugars
59.53 g
Dietary fiber
0 g
Fat
0.20 g
Protein
0 g
Thiamine (Vit. B1)
0.006 mg (0%)
Riboflavin (Vit. B2)
0.01 mg (1%)
Niacin (Vit. B3)
0.03 mg (0%)
Pantothenic acid (B5)
0.036 mg (1%)
Vitamin B6
0.002 mg (0%)
Folate (Vit. B9)
0 g (0%)
Vitamin C
0 mg (0%)
Calcium
67 mg (7%)
Iron
1.20 mg (10%)
Magnesium
14 mg (4%)
Phosphorus
2 mg (0%)
Potassium
204 mg (4%)
Zinc
4.16 mg (42%)
Percentages are relative to US recommendations for adults.
Source: USDA Nutrient database
Maple syrup and its artificial imitations are the preferred toppings for pancakes, waffles, and French toast in North America. Maple syrup can also be used for a variety of uses, including: biscuits, chicken, fresh donuts, fried dough, fritters, ice cream, hot cereal, and fresh fruit (especially grapefruit). It is also used as sweetener for applesauce, baked beans, candied sweet potatoes, winter squash, cakes, pies, breads, fudge and other candy, milkshakes, tea, coffee, and hot toddies.
Maple syrup and maple sugar were used during the American Civil War and by abolitionists in the years prior to the war because most cane sugar and molasses was produced by Southern slaves. During food rationing in World War II, people in the northeastern United States were encouraged to stretch their sugar rations by sweetening foods with maple syrup and maple sugar, and recipe books were printed to help housewives employ this alternate source.
In Quebec, New Brunswick, eastern Ontario, and New England, the process has become part of the culture. One tradition is going to sugar houses (cabanes sucre) in early spring for meals served with maple syrup. A typical offering is pancakes, baked beans and sausages, usually followed by a sugar on snow ("tire sur la neige" in Quebec), or sometimes by maple taffee in English Canada. Sugar on snow is thickened hot syrup poured onto fresh snow, and then eaten off sticks as it quickly cools. This thick maple syrup-based candy is occasionally served with yeast-risen doughnuts, sour dill pickles, and/or coffee.
Owing to the sugar maple tree's predominance in southeastern Canada (where Europeans settled in what was to become Canada), its leaf has come to symbolize the country, and is depicted on its flag. Several U.S. states, including New York and Vermont, have the sugar maple as their state tree. A scene of sap collection is depicted on the Vermont state quarter as well as the tins of the Vermont Maple Sugar Makers' Association, a non-governmental agricultural organization that works to protect the integrity and purity of Vermont maple products, and to promote its historic significance to the culture of Vermont.
Imitation maple syrup
In the United States, "Maple syrup" must be made entirely from maple sap (small amounts of substances such as salt may be added). "Maple-flavored" syrups contain maple, but also other (cheaper) ingredients. "Pancake syrup", "waffle syrup", "table syrup", and similarly-named syrups are imitations, which are less expensive than real maple syrup. In these syrups, the primary ingredient is most often high fructose corn syrup flavored with sotolon, having no genuine maple content. They are usually thickened far beyond the viscosity of real maple syrup. U.S. labeling laws prohibit these products from having "maple" in their names.
The fenugreek seed, a spice, can be prepared to have a maple syrup-like flavor, and is used to make a very strong commercial flavoring that is similar to maple syrup, but much less expensive; Mapleine is an example of this.[citation needed] Smells from a Frutarom fenugreek processing factory produced a maple syrup-like odor that occasionally covered New York City starting in 2005, being identified in 2009 as coming from a Hudson County Frutarom factory.
Qubcois sometimes refer to imitation maple syrup as sirop de poteau ("pole syrup"), a joke referring to the syrup as having been made by tapping telephone poles.
In 1905, Crescent Foods Inc. created the imitation maple flavoring called Mapleine. Bought out by McCormick spices, it still distributes "Crescent Mapleine" from limited production runs.
In Australia and South Africa, imitation maple syrup is sold as "Maple flavoured syrup".[citation needed]
Identification of maple trees
Maple trees most commonly tapped for sap collection are Sugar Maple, Black Maple, Red Maple, and Silver Maple. These maple trees are common in Eastern Canada and the Northeast United States. The Sugar Maple and Black Maple provide the highest sugar content, and therefore are ideal for a better maple syrup yield and shorter boiling times. Quicker boiling often makes for a higher grade syrup. The bark on the Sugar Maple is dark gray to brown and has developed vertical grooves and ridges, often broken up by plates of bark. The leaf is rounded at the base, extending to generally 5 lobes without fine teeth (compared to Red and Silver Maples). The color is bright green, with a paler green underside. Sugar Maple fruit has seeds joined in a straight line, while the wings are separated by approximately 60 degrees. Each winged seed is about 1 inch (25 mm) long and matures in the fall.
See also
Food portal
Agave nectar
Birch syrup
Hickory syrup
Palm syrup
Plant sap
Rubber tapping
Sweet sorghum
Syrup
Yacon syrup
References
^ http://www.canadianmaplesyrup.com/maplehistory.html
^ http://www.boston.com/news/local/vermont/articles/2009/08/17/new_maple_tap_developers_foresee_a_sweet_season/
^ http://www.nass.usda.gov/nh/mapleconf2005.pdf
^ Johnston, David (2009-03-01). "Producers fear consumers will sour on maple syrup". Montreal Gazette (Canwest). http://www.montrealgazette.com/Producers+fear+consumers+will+sour+maple+syrup/1334062/story.html. Retrieved 2009-03-01.
^
^
^ Ontario Maple Syrup Producers Association
^ E.g., 21 CFR 168.140 (USA).
^ E.g., 21 CFR 168.180 (USA).
^ 21 CFR 168.140(a), 168.180(c).
^ MacInnis, Craig (July 6, 2008). "Not just for breakfast anymore". The Ottawa Citizen. http://www.canada.com/ottawacitizen/news/life/story.html?id=600c9b51-d198-4796-acfe-464b8cdb8fe3.
^ HistoryLink Essay: Crescent Manufacturing Company
^ Identification of Maple Trees
External links
Wikimedia Commons has media related to: Maple syrup
Wikibooks Cookbook has a recipe/module on
Maple syrup
The Canadian Encyclopedia: Maple Sugar Industry
Statistics by State (U.S. Department of Agriculture, June 2005).
Taste and nutrition:
Nutritional Information
Maple Sugar Sweetness Scale
Production:
"North American Maple Syrup Producers Manual" (1st edition), edited by Melvin R. Koelling and Randall B. Heiligmann, Ohio State University Extension (Bulletin 856), 1996. (archived at Internet Archive#Wayback Machine) "The Bible" of maple syrup production.
"Maple Syrup Quality Control Manual" by Kathryn Hopkins, University of Maine Cooperative Extension (Bulletin 7038)
Categories: Breakfast foods | Canadian cuisine | Food made from maple | New England cuisine | Quebec cuisine | Vermont cuisine | Syrup | Aboriginal cuisine in CanadaHidden categories: Articles needing additional references from January 2008 | All articles needing additional references | All articles with unsourced statements | Articles with unsourced statements from December 2008 | Articles with unsourced statements from June 2009 | Articles with unsourced statements from August 2009
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