Motor-based planar speakers-can it be done?

Spasticteapot · 3rd June 2006, 05:05 AM

I've been looking through speakers, and it appears that some rather decent speakers (which more-or-less fit the definition of "planars") use a combination of a standard electromagnetic motor and another non-electrically active material to actually make the sound. Examples include the Soundpads and "Personal Planars".

Soundpads:
http://www.thinkgeek.com/electronics/audio/6bd8/

Odd wire-magnet-and-diaphragm design I don't quite understand:
My DIY planar speaker!

"Personal Planars"
http://www.decware.com/panels.htm

I personally like the idea of using a standard electromagnet assembly to drive a flat panel; that way, one can use a standard amplifier without transformers or high voltage, while keeping a large degree of the excellent sound associated with planars.

Also, I was thinking about using a method of driving these speakers used in "featherweight" R/C airplanes: Rotational actuators.

You can see one here:
http://www.ekmpowershop2.com/ekmps/s...T&productid=77

By placing a magnet in the center of a coil, you can make it spin in alternating directions by putting A/C current through the coil. Once the vibrations are produced, you then just apply 'em to the speaker membrane. However, due to inertia, I doubt these would work well at high frequencies.

Alternately, one could put a coil on the membrane and have it around a centrally placed magnet, somewhat like conventional speakers.

Finally, one could also try a piston-style design, with a small magnet with a coil on each side, running push-pull. You then thread a pushrod out to the membrane; using a high-strength magnet, you'd likely get decent efficiency, too.

So, any tips for doing this?
Or am I out of my gourd?

dshortt9 · 3rd June 2006, 06:00 AM

It must be something in the Bratwurst.

dshortt9 · 3rd June 2006, 06:12 AM

Seriously:

http://www.magnepan.com/maggie_tech.php

thadman · 4th June 2006, 01:00 AM

by using a voicecoil you raise the moving mass of the driver greatly, which defeats the main purpose of the planar/ribbon design (excellent transient response).

theAnonymous1 · 4th June 2006, 01:30 AM

I have no personal experience with much of what you posted other than the "soundpads", and I don't recommend them for anything other than pure novelty.

"Distributed Mode Loudspeaker" is the technical term for them, developed by a company called NXT. Its takes a lot of research, development, and access to the right materials to even come close to making a "DML" worthy of listening to. Even "DML" products made by big companies fall extremely short of anything close to HiFi.

I have spent many hours and quite a few dollars messing with this technology, and I don't consider any of it well spent.

el`Ol · 4th June 2006, 03:37 PM

Maybe you don`t know these:
http://www.sibatech.co.jp/FAL/FAL%20index.htm

Spasticteapot · 4th June 2006, 04:38 PM

I guess you've got a point.

One idea (shown in the second link) is to put an extrelely long, thin coil of ordinary copper magnet wire along the length of a mylar ribbon. Although not as thin or as light as a real ribbon driver, you would'nt need transformers to drive it, and it could be made relatively cheaply if a source for neodiyum magnets could be found. Efficiency likely would'nt be too bad, either.

EDIT:
Now with picture! Can you tell I made it in MS-paint?

el`Ol · 5th June 2006, 08:37 PM

Search for neodymium at Ebay yields 632 hits.

Ron E · 6th June 2006, 10:22 PM

Museatex did the voice coil on planar diaphragm thing many years ago.
I know they cost a lot for what they were and they never went over well. Supposedly they sounded good when dialed in, but I don't believe what I don't hear. 90%+ of high end audio is just a con game.

Manger is essentially what you describe, but with damping elements and variable stiffness. I haven't seen a DIY Manger, why not try your own?

Spasticteapot · 6th June 2006, 11:06 PM

Hmm...interesting.

I was wondering about the viability of speakers using a standard coil mounted in the center of a taut-streched piece of plastic. (This would be a lot like an electrostatic speaker.) Using a magnet on each side of the coil, you could drive it in both directions equally. As an added bonus, the field remains somewhat linear througout; as the coil moves farther from one, it moves closer to the other.

Also, could someone explain how the "personal planars" speakers work? I can't figure it out.

I wish I was'nt going on a !#$!$!@#$ vacation in three days.

3rd June 2006, 05:05 AM	#1
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	Motor-based planar speakers-can it be done? I've been looking through speakers, and it appears that some rather decent speakers (which more-or-less fit the definition of "planars") use a combination of a standard electromagnetic motor and another non-electrically active material to actually make the sound. Examples include the Soundpads and "Personal Planars". Soundpads: http://www.thinkgeek.com/electronics/audio/6bd8/ Odd wire-magnet-and-diaphragm design I don't quite understand: My DIY planar speaker! "Personal Planars" http://www.decware.com/panels.htm I personally like the idea of using a standard electromagnet assembly to drive a flat panel; that way, one can use a standard amplifier without transformers or high voltage, while keeping a large degree of the excellent sound associated with planars. Also, I was thinking about using a method of driving these speakers used in "featherweight" R/C airplanes: Rotational actuators. You can see one here: http://www.ekmpowershop2.com/ekmps/s...T&productid=77 By placing a magnet in the center of a coil, you can make it spin in alternating directions by putting A/C current through the coil. Once the vibrations are produced, you then just apply 'em to the speaker membrane. However, due to inertia, I doubt these would work well at high frequencies. Alternately, one could put a coil on the membrane and have it around a centrally placed magnet, somewhat like conventional speakers. Finally, one could also try a piston-style design, with a small magnet with a coil on each side, running push-pull. You then thread a pushrod out to the membrane; using a high-strength magnet, you'd likely get decent efficiency, too. So, any tips for doing this? Or am I out of my gourd?

6th June 2006, 10:22 PM	#9
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	Museatex did the voice coil on planar diaphragm thing many years ago. I know they cost a lot for what they were and they never went over well. Supposedly they sounded good when dialed in, but I don't believe what I don't hear. 90%+ of high end audio is just a con game. Manger is essentially what you describe, but with damping elements and variable stiffness. I haven't seen a DIY Manger, why not try your own? __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

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3rd June 2006, 06:00 AM	#2
dshortt9 diyAudio Member Join Date: Apr 2001 Location: Milwaukee, Wisconsin	It must be something in the Bratwurst.

3rd June 2006, 06:12 AM	#3
dshortt9 diyAudio Member Join Date: Apr 2001 Location: Milwaukee, Wisconsin	Seriously: http://www.magnepan.com/maggie_tech.php

4th June 2006, 01:00 AM	#4
thadman diyAudio Member Join Date: Dec 2005 Location: west lafayette	by using a voicecoil you raise the moving mass of the driver greatly, which defeats the main purpose of the planar/ribbon design (excellent transient response).

4th June 2006, 01:30 AM	#5
theAnonymous1 diyAudio Member Join Date: Feb 2004 Location: Anonymityville	I have no personal experience with much of what you posted other than the "soundpads", and I don't recommend them for anything other than pure novelty. "Distributed Mode Loudspeaker" is the technical term for them, developed by a company called NXT. Its takes a lot of research, development, and access to the right materials to even come close to making a "DML" worthy of listening to. Even "DML" products made by big companies fall extremely short of anything close to HiFi. I have spent many hours and quite a few dollars messing with this technology, and I don't consider any of it well spent.

4th June 2006, 03:37 PM	#6
el`Ol diyAudio Member Join Date: May 2005 Location: Bavarian Forest	Maybe you don`t know these: http://www.sibatech.co.jp/FAL/FAL%20index.htm

5th June 2006, 08:37 PM	#8
el`Ol diyAudio Member Join Date: May 2005 Location: Bavarian Forest	Search for neodymium at Ebay yields 632 hits.

6th June 2006, 11:06 PM	#10
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	Hmm...interesting. I was wondering about the viability of speakers using a standard coil mounted in the center of a taut-streched piece of plastic. (This would be a lot like an electrostatic speaker.) Using a magnet on each side of the coil, you could drive it in both directions equally. As an added bonus, the field remains somewhat linear througout; as the coil moves farther from one, it moves closer to the other. Also, could someone explain how the "personal planars" speakers work? I can't figure it out. I wish I was'nt going on a !#$!$!@#$ vacation in three days.

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