Pure Electrostatics?

[griffin]

Hello!

I'm looking for a pair of desktop speakers that are purely electrostatic in nature. I'd like to avoid any magnetic-voice-coil cone based subwoofers in these speakers.

I understand that electrostatics will not be able to faithfully reproduce lower frequencies without this extra speaker. I'd be interested in seeing a plot of the frequency response of an electrostatic speaker without this extra cone speaker.

I'm planning on using these speakers to deliver stimuli in an environment that is sensitive to extra electro-magnetic noise, specifically -- an EEG recording room. I have a theory that our current cone based speaker system is causing magnetic interference with our recordings, resulting in narrow-band artifacts that interfere with our analyses. I'd like to test this theory out.

Does Martin Logan (or any other electrostatic speaker manufacturer) make these, or will I just have to purchase a pair and clip the wires headed to the subwoofer output?

Thanks for the help!

-Griff

 

[Hocky]

I don't think anything like this exists. Electrostatic speakers need to be a bit bigger than a desktop size speaker to work correctly. It is probably worth noting that a magnetic field exists with electrostats, too.

 

[beek]

stax

Stax made a small tabletop full range stat. A bitch to drive & prob. very difficult to find these days
http://www.google.com/imgres?imgurl=http://www.estatsolution.com/img/scan0001.jpg&imgrefurl=http://www.estatsolution.com/index.php?bod%3D7&h=185&w=185&sz=51&tbnid=F4qhclJQvsRbbM:&tbnh=102&tbnw=102&zoom=1&usg=__I_r5WlpauxbI997l-cF0AsLf3t4=&docid=XfwRd-6gM7uQkM&hl=en&sa=X&ei=X9AKUZmDB6uI0QGFhIHQCg&ved=0CE8Q9QEwBQ&dur=126

 

[Nielsen]

Magnepan had, or have, dont know, small speakers intended for such a setup. Would recommend you go for a headphone setup, Stax Signature II system or something like that, you will never find speakers that sound that good, no matter the price. If your theory about magnetic interference hold water the worlds studios are in trouble.

 

[sleepysurf]

... I'm planning on using these speakers to deliver stimuli in an environment that is sensitive to extra electro-magnetic noise, specifically -- an EEG recording room. I have a theory that our current cone based speaker system is causing magnetic interference with our recordings, resulting in narrow-band artifacts that interfere with our analyses. I'd like to test this theory out...

Are you intentionally playing background music while testing patients? Wouldn't that stimulus alone potentially impact the recording? As for your current cone drivers causing interference, couldn't you just temporarily remove them from the room (or simply disconnect them), and see what difference that makes?

 

[griffin]

Hey guys,

Thanks for the replies.

Sounds like this is going to be difficult to find. Probably not worth the effort. I should probably just go with an old gramophone and press my stimulus sets to vinyl.

We aren't playing music to the patients -- we're simply delivering auditory stimuli for experimental reasons. For example, we have the computer say a word that they're supposed to repeat. The timing is absolutely critical, so its better if a computer is in control.

We're recording from implanted epilepsy patients who have a portion of their skull temporarily removed, and massive head-dressings to keep the craniotomy from getting infected. This head-dressing tends to cover ears and make it impossible to use headphones. The further we can keep the noise source from the recording devices, the better.

Finally, the E/M noise from the speaker is absolutely crucial. This doesn't particularly matter for studio setups because the recording devices aren't as sensitive. With our sensitive microelectrode grids, we can see a massive response by simply walking into the room, or waving our hands around the patient.

Large loudspeaker systems are difficult to wheel into the patient's room, and the room is typically very small to begin with.

If desktop electrostats aren't available, we'll just have to re-think how we deliver auditory stimuli in the first place. It isn't the end of the world, but I was just curious if anything existed. I figured you guys would know best.

-Griff

 

[projectormovielover]

I second the desktop maggies http://www.innerfidelity.com/content/mini-maggie-system-honey-i-shrunk-speakers

 

[sleepysurf]

Have you queried EEG or Neuroscience discussion forums/mailing lists? Certainly others performing such delicate EEG studies (for research or peri-implant care) face the same issues.

Another thought is to temporarily incorporate a (sterilized, if need be) cheap disposable stethoscope (with the chest-piece removed) into the head-dressing, and connect it to "piped in" sound from an adjacent room location. Perhaps something like these bulk versions... http://www.amazon.com/Disposable-St...80985&sr=8-3&keywords=disposable+stethoscopes

 

[griffin]

Have you queried EEG or Neuroscience discussion forums/mailing lists? Certainly others performing such delicate EEG studies (for research or peri-implant care) face the same issues.

Another thought is to temporarily incorporate a (sterilized, if need be) cheap disposable stethoscope (with the chest-piece removed) into the head-dressing, and connect it to "piped in" sound from an adjacent room location.

We're actually one of the first labs to incorporate these new implanted microelectrodes, and we're seeing artifacts we've never seen before. I can only imagine other labs are too. The only thing to do at the moment is to change the experimental design so that we can throw out the data around the stimulus presentation.

The stethoscope is actually a pretty darn good idea. I'll look into that.

As for the mini maggies, those look to be about what I was originally looking for. Unfortunately their price tag is going to require something more than a hunch. I'm going to look into our noise sources a bit more heavily, perhaps do some tests without any speakers, or with analog instruments (guitar, violin, etc) and figure out the common element before purchasing.

-Griff

 

[Bernard]

Have you tried a comparison between headphones and a cone speaker, using a normal (non-patient) subject, just to check out your theory, granted you would not be able to use headphones on the patient?

 

[griffin]

Have you tried a comparison between headphones and a cone speaker, using a normal (non-patient) subject, just to check out your theory, granted you would not be able to use headphones on the patient?

Intending to do so. Only problem is that the electrode cannot be implanted with a healthy. Another possible explanation is due to mechanical vibration from external sources of sound or volume conduction from vocal chord vibration. That wouldn't show up in our healthy test.

I'm planning to get one of our microelectrode sets and run it right next to our current speakers, then at a distance, finally, delivering the stimulus using some analog means to see where the artifact drops out.

 

[Tosh]

It is probably worth noting that a magnetic field exists with electrostats, too.

I've never heard that said before. Can you expand on this? (not speaking of the audio step-up transformer?)

 

[Tosh]

Griffin, you may be able to ask DIYers at DIYAudio.com (in the 'exotics' section!) if they are interested in lending you a smaller ESL system? Or find a local ML dealer or owner who would be willing to lend you one with its woofer removed.

 

[|Tch0rT|]

I've never heard that said before. Can you expand on this? (not speaking of the audio step-up transformer?)

Since ESL panels lack a magnet they don't have a natural magnetic field like conventional cone speakers but once the panel is powered it will create an electromagnetic field. From WHO:

Whenever electricity flows, both electric and magnetic fields exist close to the lines that carry electricity

 

[Hocky]

As for the mini maggies, those look to be about what I was originally looking for. Unfortunately their price tag is going to require something more than a hunch. I'm going to look into our noise sources a bit more heavily, perhaps do some tests without any speakers, or with analog instruments (guitar, violin, etc) and figure out the common element before purchasing.

-Griff

mini magnepans are not going to help, they're driven by powerful magnets just like cone drivers are.

Why not try removing the speakers from the room entirely by putting them into the next room? You could easily cut a hole in a ceiling tile, run ducting from that ceiling to the speakers, and let the speakers play into the ducting. That should be audible in the room, cost virtually nothing, and 100% eliminate the EM energy.

 

[griffin]

Since ESL panels lack a magnet they don't have a natural magnetic field like conventional cone speakers but once the panel is powered it will create an electromagnetic field. From WHO:

Point is, the interference is significantly reduced. The movement of the charge involved is pretty negligible, and the magnetic field produced from this is significantly less disruptive than a typical cone speaker. The magnetic field fluctuations produced by that voice coil are non trivial!

 

[griffin]

mini magnepans are not going to help, they're driven by powerful magnets just like cone drivers are.

Why not try removing the speakers from the room entirely by putting them into the next room? You could easily cut a hole in a ceiling tile, run ducting from that ceiling to the speakers, and let the speakers play into the ducting. That should be audible in the room, cost virtually nothing, and 100% eliminate the EM energy.

When I was reading about them, the only magnets I was able to find were those around the ribbon tweeters. It isn't really the permanent magnets that I care about, its the fluctuation in magnetic fields from the voice coil. These wouldn't do that.

As for cutting holes in the room; our room is a faraday cage. Cutting holes in it would defeat the purpose. As does sticking all sorts of medical instrumentation inside of it... bleh. I'm going to do some tests in one of the empty rooms next week and figure out if any of this is really necessary.

 

[Hocky]

When I was reading about them, the only magnets I was able to find were those around the ribbon tweeters. It isn't really the permanent magnets that I care about, its the fluctuation in magnetic fields from the voice coil. These wouldn't do that.

I am not sure that the maggies would be any different. They work the exact same way as a cone driver does, but they're laid out differently. Obviously, I've never tried testing the EM energy around a ribbon or tradition driver, but I can't imagine that they're too much different. If anything, I would think that the chance for creating a large magnetic field would be greater with a planar driver just because the surface area that is being driven by EM forces is so much larger.

 

[MiTT]

Another option might be to search out an older pair of ML Scripts and just disconnect the dynamic woofer. Frequency response would certainly suffer, but the result would be an "all electrostatic" source They've been discontinued for several years, and they aren't exactly "desk sized" at about 43" tall, but it's an idea.

 

[projectormovielover]

Here is the Filo desktop mini electrostats that will be retailing for $300 with no woofer and they can even run off a battery. They were at the CES show this year so browse that tofindout more as this article is around 6 month old but here is a link

http://news.cnet.com/8301-17938_105-57448447-1/meet-in2uits-stylish-portable-electrostatic-speakers/