FDP Home Page / FDP Forum / FAQ's

The FDP is made possible by the following companies and individual members like you.
Please use the links below to show them we value their sponsorship.

Jensen Loudspeakers

WD Music

Antique Electronics Supply

Sweetwater

Amplified Parts

Yellowjackets Tube Converters

MOD KITS DIY

Apex Tube Matching

Advertise here

Guitar Center

Musician's Friend


* God bless America and our men and women in uniform *

* Illegitimi non carborundum! *

If you benefit and learn from the FDP and enjoy our site, please help support us and become a Contributing Member or make a Donation today! The FDP counts on YOU to help keep the site going with an annual contribution. It's quick and easy with PayPal. Please do it TODAY!

Chris Greene, Host & Founder

LOST YOUR PASSWORD?

......................................................................

   
FDP Jam
Calendar
Find musicians
in your area!
  Search the Forums  

FDP Forum / Amp Mods, Repairs, and Projects / Speakers...distributed mode speakers, that is

Next 20 Messages  
Peegoo
Contributing Member
**********
**********
********

Get ready for the

Buena Buena
Apr 1st, 2018 11:09 PM   Edit   Profile  

Leftee suggested I start a thread on this since I mentioned it in another thread.

AvE did a vid on DMLs (distributed mode loudspeakers) last week and that got me looking through my box of speaker parts, since I've been fiddling with this technology off and on for a few years. I found some acoustic exciters (they were really cheap when I got 'em...about $5 apiece), and I did some calculations and stuck them to some Borden foamboard.

The foamboard is 5mm thick, hard closed-cell foam with kraft paper bonded to both sides. It's the stuff you find in an arts/crafts supply store to use as backing for posters or when making thick matte mounts for framed photos.

I made each panel 20" x 30" and rounded the corners a bit.

Smaller panels (e.g., 12" x 14", etc.) require a subwoofer in addition to the DMLs because small panels can't reproduce lows very well. Since I used four exciters per panel, no need for a subwoofer. I get plenty of low end, and the overall sound is very balanced.

These are really cheap to build. You can use almost any surface or panel material as the resonator for the exciters. Ideally, the panel is lightweight, non-compressible, somewhat flexible, and with good damping characteristics. Corrugated cardboard sheet is a favorite in the DML community because it's readily available and meets all the above criteria. And it sounds fantastic. It's just not very good looking or durable (absorbs moisture, etc.). I've tried it with a thin fabric glued to the face, and that does dress it up.

Where you mount the exciter(s) on the panel is critical to help prevent standing waves, which can create resonant peaks and result in less than optimal sound.

Done correctly, these speakers create the illusion that the sound is coming from everywhere in the room, not from two speakers. It's a strange (in a good way) and different sort of listening experience.

Many acoustic instrument musicians claim that acoustic music sounds better from a DML than a conventional speaker.

I agree, and I believe it is because the DML creates sound just like an acoustic guitar or violin makes sound: by vibrating a panel that acts as a resonator--not a cone that squirts out sound in a manner similar to a flashlight projecting photons.

I also think DMLs are improperly named. They should be distributed *node* loudspeakers because harmonic nodes and anti-nodes of multiple frequencies become spread out around the panel at the same time, and they're always in motion. This is not how a traditional speaker cone responds and is why DMLs sound so articulate.

A panel couples with the surrounding air better than a cone, and it's relatively non-directional. There are no "beaming" issues that create loss of highs when your ears are off axis to a speaker cone.

I'm going to make a speaker system for a guitar amp and see how that works.

I'm also thinking of finding some old acoustic guitars and turning them into "bookshelf" speakers. I may use a single guitar and run both stereo channels from it because DMLs maintain stereo separation on a single panel.

If you've heard of the Tonewood amp (I have one...these came out a few years ago), it's the same technology, but with effects added to the circuit.

It's also the same technology as the Sustainiac. This was a transducer that attached to an electric guitar's headstock; it fed back signal into the guitar by vibrating the neck and creating infinite sustain. Sustainiac came out in the 1980s. Dunno if they're still available.

This is really fun and inexpensive stuff to play with. If you're interested in this, Parts Express is the best place to get audio exciters. The Dayton brand is good stuff, and they make a bunch of different models. Get the ones you need based on your wattage and impedance requirements. They're cheap!

There's a ton of good info on the Web about this. Here's a pretty good white paper on the topic:

Click on "PUI Audio Exciters" in the hyperlink list for the PDF.

(This message was last edited by Peegoo at 01:31 AM, Apr 2nd, 2018)

twangdoodles

michigan usa

Apr 2nd, 2018 04:01 AM   Edit   Profile  

Interesting, this is the first I've heard of this.

A quick look-around led to a comment that some report a loss of the stereo effect with these type speakers; have you noticed such a thing?

Leftee
Contributing Member
**********
**********
*

VA

I say stuff
Apr 2nd, 2018 05:21 AM   Edit   Profile  

Thanks! This is really groovy stuff. I’ll give this a whack some day.

I’m curious to hear how your guitar speaker version turns out.

Leftee
Contributing Member
**********
**********
*

VA

I say stuff
Apr 2nd, 2018 05:38 AM   Edit   Profile  

I also found this article.

External link

Peegoo
Contributing Member
**********
**********
********

Get ready for the

Buena Buena
Apr 2nd, 2018 10:06 AM   Edit   Profile  

Twangdoodles, I've read the same thing, and I think it gets reported because stereo recording very often artificially increases audio separation.

I think we've become programmed to expect music to sound like that because that's how we've always listened to it. It's the same effect a person would experience if they had listened to recorded music for years only through headphones, and then switched to speakers. They're going to notice quite a difference.

I've always thought the absolute best way to record something for the most realistic playback experience would be to have a stereo microphone in a model of a human head, with ears, etc., and then listen to the playback through headphones.

That would create a more realistic audio image than a stereo pair of mics in a room, because our brains can detect the fraction-of-a-microsecond difference between the arrival of the same sound at each ear. That is how the brain identifies and places sound sources in the 3D space around us.

The truly fascinating thing about human hearing is even though we have right and left sound detectors (ears), the brain goes way beyond simple left and right audio discrimination. It *automatically* includes the presence or lack of reflective surfaces in the 3D space around us, and can very accurately place high, low, and moving sound sources. Even sound sources behind us. It accurately estimates the distance from a sound source. All this--strictly via time differentials.

It's like a microphone system that not only detects sound, but recalibrates itself thousands of times per second to compensate for varying listening environments. This compensation doesn't occur only when you move from one place to another. It happens when you move your head even a teensy bit. It is mind blowing to me.

I'm not an audiophile sorta dude, but I've read that a stereo pair of conventional speakers requires at least six feet of distance between them to optimize the stereo effect.

With DMLs, you still get stereo separation, but distance between the units is not as critical as with conventional speakers. These certainly work differently.

Check this out.

Prepare for a nerdgasm.

(This message was last edited by Peegoo at 12:38 PM, Apr 2nd, 2018)

Hammond101
Contributing Member
**********
**

So. Cal. USA

Apr 2nd, 2018 12:09 PM   Edit   Profile  

Is this what Magneplanar did? I think they used ribbon tweeters and this tech for mids/lows?

It looks like the driver is stuck to the panel with a 3M double sided tape?

Very cool stuff.

I've always enjoyed speakers with large baffle board area. My Boston Acoustics A200 for example. Perhaps this is why.

Peegoo
Contributing Member
**********
**********
********

Get ready for the

Buena Buena
Apr 2nd, 2018 01:04 PM   Edit   Profile  

No, Maggies uses large, thin foil coils on a Mylar panel that react to long strip magnets.

DML is a bit different in that it permits nodes and anti-nodes to migrate on the panel because a large proportion of the panel is not directly driven by the transducer. At least that's how I understand this stuff.

Hammond101
Contributing Member
**********
**

So. Cal. USA

Apr 2nd, 2018 01:10 PM   Edit   Profile  

If I had no projects I'd build a pair or 5 or 7. Very neat stuff.

My mind is going to 5 and 7 channel surround systems.

Peegoo
Contributing Member
**********
**********
********

Get ready for the

Buena Buena
Apr 2nd, 2018 02:30 PM   Edit   Profile  

These are ideal for satellite surrounds, combined with a sub.

One thing I've discovered is the panels sound better with the transducers on the front (listening side) of the panel. The twinkly highs are much better when radiating from the same surface the transducer is attached to.

Logic says there should be no remarkable sound difference between the front and back on a relatively hard panel. But there sure is a difference.

Hammond101
Contributing Member
**********
**

So. Cal. USA

Apr 2nd, 2018 03:27 PM   Edit   Profile  

I think this may be from the nature of the medium used as the baffle if that is the correct term. I would think a foam sandwich would exhibit some difference front to back. I would think the distance from a reflective surface may enter big as well. Maybe a double smooth side Masonite material would work.

I have surrounds that sit on stands at the rear of my viewing/listening room. This type of panel speaker could easily be mounted to the vaulted ceiling above and sound great. It would be the narrow end of the vault so sound would be reflected into the room. Proximity to the wall might help low end response if these respond anything like a regular cone driver. The system has a sub, a big Klipsch sub!

Cal-Woody

USA/California

Why do I keep fixing things that work?
Apr 2nd, 2018 05:58 PM   Edit   Profile  

One thing I find interesting is that high frequencies travel faster and take less volume and the low/mid frequencies travel slower, so it sounds like you are creating an acoustic environment/cabinet extension for the mid/low frequencies to reflect from the wall/ceiling, but do the high frequencies get blaring before the other sounds catch up or does the coupling of the surfaces create a better spacial effect for the other frequencies, thus making for a better surround sound?
Does it feel more like a theater sound system?
This is truly some dark magic that you're dabbling with! Lol

Leftee
Contributing Member
**********
**********
*

VA

I say stuff
Apr 2nd, 2018 07:06 PM   Edit   Profile  

I once made a pair of telephones with some string and two tin cans. This is way more groovy.

Peegoo
Contributing Member
**********
**********
********

Get ready for the

Buena Buena
Apr 2nd, 2018 07:29 PM   Edit   Profile  

The distance from a wall does matter because the center of the reflected frequencies will be a wavelength 2x the distance of the panel from the wall. You'll get partial phase cancellation at that frequency.

But it's really not that noticeable, and if it's an issue, it helps to apply some sound absorptive material to the wall surface.

I've got some little 10" x 12" foam trays that I'll make small DMLs with and see if they are adaptable as a guitar speaker.

The very cool thing about these is their efficiency: they are pretty loud, even when running low power to them.

Order up some audio exciters and play around with 'em. They is cheep! Rest one on your desktop and it turns the desk into a speaker. Attach one to a textbook and it turns it into a speaker. It's weird.

This is the same technology the medical community uses to help people with impaired hearing due to faulty ear drums. A small transducer is placed against the bones of the skull and the person hears better.

I may try mounting one on my

foil helmet.

stratcowboy
Contributing Member
**********
**

USA/Taos, NM

Apr 7th, 2018 01:38 PM   Edit   Profile  

The kitty looks very impressed.

Peegoo
Contributing Member
**********
**********
********

Get ready for the

Buena Buena
Apr 7th, 2018 09:25 PM   Edit   Profile  

My next experiment with these is foam picnic plates.

You can buy a hundred for a nickel.

A nickel, I tellya!

Peegoo
Contributing Member
**********
**********
********

Get ready for the

Buena Buena
Apr 10th, 2018 10:59 PM   Edit   Profile  

I got sidetracked and tried these exciters on a bunch of flat flexible surfaces...one of which was an empty steel gallon can that once held mineral spirits.

I've made a few "oil can" guitars and ukuleles, so why not turn one into an amp or a speaker cab? The lid on top could be the volume control. These are a cinch to cut and drill because they're super-thin steel.

Because the diaphragm is metal, the thing makes an electric guitar sound like a resonator guitar when played from a clean amp. Playing with a slide and a little overdrive sounds downright wicked.

I'm working up a prototype to see if this is something that will be useful.

Might even make sense to install a small battery-powered amp into an oil can guitar and amplify the thing through the steel body.

This is getting more fun.

(This message was last edited by Peegoo at 01:17 AM, Apr 11th, 2018)

Leftee
Contributing Member
**********
**********
*

VA

Apr 11th, 2018 04:54 AM   Edit   Profile  

(-:

Peegoo
Contributing Member
**********
**********
**********
*

Get ready for the

Buena Buena
Apr 15th, 2018 09:56 PM   Edit   Profile  

I stuck an exciter to a thick paper plate and it sounds pretty amazing. I'm going to make a speaker cab from foamboard and mount the plate on the front.

It will be the lightest 1x12 guitar cabinet ever!

Leftee
Contributing Member
**********
**********
********

VA

Apr 16th, 2018 07:03 AM   Edit   Profile  

A true geezer cab!

willie
Contributing Member
********

Too Near Atlanta GA

Amp Tech Emeritus
Apr 16th, 2018 08:20 AM   Edit   Profile  

Interesting stuff....this old dog learning new tricks, thanks for the edification. :)

w

Next 20 Messages  

FDP Forum / Amp Mods, Repairs, and Projects / Speakers...distributed mode speakers, that is




Reply to this Topic
Display my email address             Lost your password?
Your Message:
Link Address (URL):
Link Title:




Moderators: Chris Greene  Iron Man  reverendrob  

FDP, LLC Privacy Policy: Your real name, username, and email
are held in confidence and not disclosed to any third parties, sold, or
used for anything other than FDP Forum registration unless you specifically authorize disclosure.

Furtkamp.com 
Internet Application Development

Copyright © 1999-2018 Fender Discussion Page, LLC   All Rights Reserved