Lunch with Paul: Servo woofers
Subscribe to Ask Paul Ask a QuestionWhen PS Audio began their long-awaited loudspeaker project it was with Arnie Nudell and servo woofers. After an audio shootout PS has abandoned servo woofers in favor of Chris Brunhaver's design. Find out why.
Hi Paul,
I asked this question earlier but got no satisfying answer:
If the components of a high-quality woofer are built in with laser precision as Chris told , then I wonder why spiders are still used for centering, although it must be clear that they themselves produce tones that do not coincide with the input?
Sorry for the delayed response.
Woofers require a 2 -point suspension system (surround and spider) to prevent/minimize canting/rocking of the voice coil and former and keep things centered in the magnetic gap.
Some companies use a second rubber or plastic suspension instead of a cloth spider but this is a bit of a rarity.
Babb/DC Gold speakers used a teflon friction suspension and no spider, but issues with noise and stiction have made that kind of a curiosity.
Keeping the gap as tight as possible (without contacting the pole / top plate) and filling that volume with the winding of the coil is key to a number of aspects of the driver: lowering modulation distortion, minimizing the amount of magnet weight required, high system efficiency etc.
The laser alignment in klippel QC is really just to ensure that all of the components are assembled correctly and that you are operating in the lower distortion point of the motor/coil, and suspension ranges and that those are aligned with each other.
hmmmm, rerun season?
Don’t think so. This is the first it’s run I know of.
Dear Paul,
You have a nice garden, nice terraces, and probably a nice house, why not have those “lunches with Paul” there instead of that horrible cafeteria?
And why not with a fine glass of wine ?
From Pierre in Bordeaux, France
Worst example yet of how to record an interview…ambient noise galore…
Agreed. Couldn’t have picked a place much worse. Also there’s that annoying green masked guy in the lower left. I suggest interviewing on the same topic again in a better environment.
The irony of this being from a recording / audio company is hard to ignore;-)
When I worked at Professional Audio Systems in Harbor City CA in 89 their signature tech was time offset tech among with electronically manipulating speaker parameters VIA feedback circuits. I always thought that doing this was making the drivers do things un-naturally which to me made for a very unnatural un-dynamic sound. They made great drivers. They made speakers for many other companies. I know. I was the guy that pulled the parts including all the different dust caps. I’m not sure if this is what is meant by servo woofers.
I have a Velodyne 18″ servo Mosfet AB sub. Sounds great. Has none of the problems Chris described.
Chris, that was a very definitive and enlightening talk. I get it! I have been a long time advocate for accelerometer bass feedback systems. I have designed these systems for Infinity Systems , Genesis Technologies and Genesis Advanced Technologies. I genuinely regret that I never was able to master the art of a limiter system that did not have bad audible artifacts. I thought that Velodyne seemed to have solved that in a reasonable way.
I now hope that I can find a way to experience the sound of your new woofer designs. Ah, dumb question: I presume in the electronics for your bass systems that you apply some bass boost equalization and possibly phase equalization to make the result come out flat?