Magnepan 3.7

"That's interesting and a bit surprising! I think everyone was expecting the 3.7's to use foil in the woofer."

Yes it is, I thought they would be a full foil/"ribbon" design. I would still like to see an official overview. Magnepan's comments don't really talk about the bass at all just the mid and tweeter.

Hello Magfan,

Maggie is not using a foil backing on their tweeters,they are using corrugation to move/control the resonant freq. Some do it this way, others use damping. IMO corrugation works on the tweeters ( which maggie do ) but have found that damping the foil is much better sonically than corrugation. They use mylar with foil elsewhere and describe the 20.1 as,

"3-Way / Ribbon Tweeter - Planar-Magnetic"

Mylar is necessary if you are running foil traces. On ribbons with more than 1 foil trace, you have to use some kind of backing , mylar is used when this is necessary, if running a straight foil then no mylar backing is necessary unless for sonics.

Extra foil traces are necessary to make the impedance more realistic to the amplfier ( 3 or 4 ohm vs .25ohm) Maggie apparently is running there ribbon direct
(.25ohm) and is then compensating in the xover, 99% of ribbon speakers are built with multiple foil traces and mylar.

IMO direct ( no foil traces) is the best way, a direct ribbon ( my choice also) is the correct approach unfortunately it does not lend itself readily to most amplifiers and efficiency is lost in the xover.

3.6 description:

Description: Three-way, floorstanding, planar dipole loudspeaker. Drive-units: 500-in2 planar-magnetic bass driver, 199-in2 planar-magnetic midrange driver, 0.16" by 55" ribbon tweeter. Crossover frequencies: 200Hz and 1.7kHz. Frequency response: 34Hz-40kHz, ±3dB. Impedance: 4 ohms nominal, constant, resistive (4.7 ohms bass, 4.2 ohms midrange/tweeter, 3.3 ohms tweeter only). Sensitivity: 86dB/2.83V/m. Recommended power: 75-250W.

Making only the tweeter a true ribbon ....

If they were to use a straight foil for the woofer, a transformer would be necessary due to the impedance.

Yankee Ribbon used a push pull ribbon for there speakers all other magnostats that i'm aware of use planer bass units
( maggies , apogee's , et al). The Yankee approach is better as the planers tend to be one legged and do not have a linear field.

regards,

Josh358, Yankee ribbon has a true "ribbon woofer" ....

James,

Yeah, I'm leery too of initial reports since in the case of the 1.7 there was a fair amount of misinformation at first.

BTW, I see from the Planar Asylum that the first review is in:

http://www.computeraudiophile.com/content/CES-Day-Two-Notes