I'd urge a bit of caution putting an exciter on a glass or glass tube. The wrong frequency or resonance might produce glass shrapnel.
That said I've got a little exciter on my workbench just begging to try this on something and a long holiday weekend in the US to do it!
A couple of years back on this thread I've shared the DMLs in the first of the attached images.
My wife has urged me to consolidate this setup (dedicated to music) with my more modest home theater setup in another part of our loft currently served by the more recent described set of DMLs (see photo to the left).
My audio interests have spread from our living room, den, and my workshop (repurposed when our daughter went off to university ;-)
Perhaps I've reached just a bit too far.
Moving the large DML's introduces a challenge.
To use these large aluminum DMLs in the home theater setting, I will need to mount them very close to the back wall - perhaps just a couple of inches away from it.
Does this seem feasible?
Do I need to consider either absorbing or defusing the back wave.
Should I place some sound absorbing material directly behind (but not touching) the DML panels?
If yes, what would make sense to use? Acoustic ceiling tile? Acoustic (grey) foam (see attached image)? Fiberglass mat?
Strategies appreciated.
(I've got a long weekend to play).
My wife has urged me to consolidate this setup (dedicated to music) with my more modest home theater setup in another part of our loft currently served by the more recent described set of DMLs (see photo to the left).
My audio interests have spread from our living room, den, and my workshop (repurposed when our daughter went off to university ;-)
Perhaps I've reached just a bit too far.
Moving the large DML's introduces a challenge.
To use these large aluminum DMLs in the home theater setting, I will need to mount them very close to the back wall - perhaps just a couple of inches away from it.
Does this seem feasible?
Do I need to consider either absorbing or defusing the back wave.
Should I place some sound absorbing material directly behind (but not touching) the DML panels?
If yes, what would make sense to use? Acoustic ceiling tile? Acoustic (grey) foam (see attached image)? Fiberglass mat?
Strategies appreciated.
(I've got a long weekend to play).
Attachments
I never came across anything like these sub woofers used with Quads.
I'll search around for something.
I found a discussion about them at My Open Baffle Speaker Journey. From my posting on that site under (AlphaSquared":
Note: I later learned one has to wire the woofers out of phase. They sounded even better. My wife still doesn't care for them much ;-(Inspired by this thread, I dug up a pair of OB-A15SEN (NEO) 15" open baffle optimized drivers produced for PureAudioProject by Eminence I had languishing in a closet.
I found a pair of steel coffee table legs on Amazon for around US$37 that seemed just the right size for a project.
I screwed the legs onto a wooden base, used some home made aluminum offsets (3" long) to bolt drivers together.
I hung the paired drivers using a pair of 30" heavy rubber EPDM tarp bungee straps, which I secured to the frame with heavy zip ties (it just seemed easy).
You can just make it out in the right most image behind the plants flanked by my DMLs.
While a concession to my architect wife, the plants may actually serve to defuse the DMLs a bit (OK wishful thinking on my part?).
A miniDSP SHD processes the digital audio signal:
I drive each woofer separately, with a 75 W per channel Audiophonics (Hypex module) stereo amp.
- L & R to the respective DMLs and
- L+ R to each of the bass drivers
I currently:
Suggestions/guidance welcome.
- drive the woofers in phase, but may play with it and
- crossover the woofers at 100 Hz.
Another Audiophonics amp (same model) drives the DMLs.
Note: I made the DMLs from salvaged aluminum honeycomb core skinned with aluminum panels that an Italian kitchen store across the street from me planned to sling in a dumpster. I drive them with one Dayton Audio Thruster exciter each.
I haven't measured the woofers yet (just finished them yesterday).
I'll report back when I do.
Subjectively, they pair very well with the DMLs.
I've tried a variety of other low frequency solutions including conventional boxes , H-baffles, and loading a slot (like Nelson Pass's idea), nothing else has sounded as effortless.
They seem to extend the character of the DMLs into the lower frequencies.
One of these doesn't necessarily rattle everything off the walls, but I don't feel like I miss anything in say the first movement of Mahler's 2nd Symphony, anything orchestral by Charles Ives, or even the dynamics of Japanese drumming.
With the Bob Dylan | Johnny Cash duet of Girl from the North Country (which sounds fantastic on the DMLs by themselves) I feel another octave (maybe more) of depth in Cash's voice. So much fun!
Just getting started with these, lots of tuning possible.
I also have another pair of the a pair of OB-A15SEN (NEO) 15" in the closet
Thoughts/suggestions/comments much appreciated.
Attachments
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Sorry for the confusion.
By "back wall" I meant the wall behind these panels which I intend to try as the main left and right speakers.
Anything placed over the exciter voice coil/spider plate would amplify sound, that is anything with a thin edge, thinner the edge the sound is better. A part of the edge or the whole edge (as in a tube) can be placed over the voice coil/spider plate. It could be a tube (enclosed circle) or just a thin edge of a sheet.
A cone over the voice coil is a flared tube, angle larger than 90 degrees. In a flat panel the angle is pushed to 180 degrees. Thinner edge of a flat panel gives crispy clear sound than the larger surface. Most probably, the panel doesn't have to be a rectangle. Maybe it could be half a circle, or half an ellipse or any other shape (This company had tried this in 2009). Sony, anyway, is selling tube (candlelight) Bluetooth speakers to the general public. But, I think Ammos had the better idea.
A cone over the voice coil is a flared tube, angle larger than 90 degrees. In a flat panel the angle is pushed to 180 degrees. Thinner edge of a flat panel gives crispy clear sound than the larger surface. Most probably, the panel doesn't have to be a rectangle. Maybe it could be half a circle, or half an ellipse or any other shape (This company had tried this in 2009). Sony, anyway, is selling tube (candlelight) Bluetooth speakers to the general public. But, I think Ammos had the better idea.
Hello Aagas
I entered in the DML world by a reading of this thread. Your large DML are in the short list of the clean realizations!
I opened the back wall reflection in previous post but I can't say it leads to conclusions...
I made tests with a canvas parallel to a back wall at different distance
Clearly, reflections will occur. My canvas was about 40cmx30cm, the consequences were visible on a FR at 75cm.
My first intention with DML was to have them on the wall. This is not a good option
Your panels are large, will the consequence be the same... Something to test.
A patent (I could find it later) proposed to put the DML in a closed box with a low depth. The idea is to smooth the FR with the effect of a close wall. They show the consequences on the FR. The work around was EQ.
Do you have a possibility of an angle (panel not parallel to the wall)?
For now I have only 2 examples in my notes of absorber (refer to the history file) : Burnt post #993, Jaxboy post post #4133 with magic sponge (melamine). I had a short test with that but I understood that in fact the main problem I had were from the panel it self!
All of that to say : as DML are strange things, absorption is frequency dependent (low efficient at low freq), start by testing and understand what is the change?
Christian
Regarding the DML sound production, why not try placing the exciter in the middle (on front or back) of a cheap Ikea Oftast plate to check which side gives the better sound? It is made out of tempered opal glass.
Christian.
The Ammos only uses front firing radiation.
The rear is blocked be a thicker sheet of glass.
I could imagine my rigidly mounted ply panels screwed rigidly to a wall with some sort of damping in-between the panel and wall.
You would obviously loose the rear radiation but you might use a port in the side or instead of 3x2 inch wood, you could use a heavy sound absorbing foam ?
If the panel was rigidly mounted to a frame on a stud wall , the wall would become part of the speaker?
So there are a few options to think about?
Steve
The Ammos only uses front firing radiation.
The rear is blocked be a thicker sheet of glass.
I could imagine my rigidly mounted ply panels screwed rigidly to a wall with some sort of damping in-between the panel and wall.
You would obviously loose the rear radiation but you might use a port in the side or instead of 3x2 inch wood, you could use a heavy sound absorbing foam ?
If the panel was rigidly mounted to a frame on a stud wall , the wall would become part of the speaker?
So there are a few options to think about?
Steve
Chdsl.
It has been a long time since I tried class dmls.
But I remember the sound as being quite hard and bright.
Maybe they reduce this a little by having the exciter inside the base to help block some of these sounds?
I'm still wondering if they use a solenoid type exciter?
Clear plastic panels usually come with a plastic film coating, I wonder if leaving this on would help damp this harshness a little , also?
One of the glassonic speakers weighs 250lb !
Steve.
It has been a long time since I tried class dmls.
But I remember the sound as being quite hard and bright.
Maybe they reduce this a little by having the exciter inside the base to help block some of these sounds?
I'm still wondering if they use a solenoid type exciter?
Clear plastic panels usually come with a plastic film coating, I wonder if leaving this on would help damp this harshness a little , also?
One of the glassonic speakers weighs 250lb !
Steve.
Thank you Steve.
Hmm...Why this solution for the Ammos?
The energy from the rear is the same than the front (of course!). Blocking it or absorbing it might be probably even more difficult as for cone and cabinet speaker. The energy not absorbed will bounce to the front with the risk to go through the membrane? Even more critical with light membrane?
My thinking about that leads me to solution to have a long absorbing path on the rear. I even found ideas of a 3D diffuser. Only thinking... trying to understand and improve the design of a DML with an open back is by itself a good challenge.
Christian
From James Dyson website.
Maybe the Ammos people made their own actuators. It is all about a voice coil, tiny or not. They had lot of technical help from Dyson Awards. Anyway, whether Ammos would get crowdfunding or venture capital is to be seen in the future. But, in the meantime, we might be able to do some work around that idea.
and,
and,
The Bluetooth connectivity, haptic touch is not of the main interest, but the vertical glass panel vibration speaker and the subwoofer enclosure are of real interest. The speaker is quite nice to look at, and high WAF.
Interesting what might be those tiny actuators. Could they be in-ear headphone speakers? So, I took out few in-ear headphones I have and tried them on the EPS sheet and on glass edge. That didn't work. Neither the earmuff nor the plastic acoustic chamber passed the vibrations to the sheet. If I had pushed some stick through the hole onto the voice coil cover, the vibrations would've come through, but I didn't want to damage the expensive earphones. Interestingly, I found out that without the silicone earmuffs, the sound didn't get crisp and amplified. I didn't know anything about the insides of in-ear earphones before.
Maybe the Ammos people made their own actuators. It is all about a voice coil, tiny or not. They had lot of technical help from Dyson Awards. Anyway, whether Ammos would get crowdfunding or venture capital is to be seen in the future. But, in the meantime, we might be able to do some work around that idea.
Here's a detailed wall installation guide of Amina Sound speakers in the drywall. On the 9th page, you'd see the back of the DML system.
Counter intuitive work in progress...
Turned my large aluminum honeycomb core DMLs sideways and leaned them against the wall behind the TV.
It just shouldn't sound good, but gees, it does.
No tweaking or equalization yet.
I have it set up with an Apple TV by HDMI to LG TV optical to minDSP SHD out to a pair of NCore stereo amps driving both DMLs and the woofers.
I plan to raise the panels so they center (vertically) on the TV.
More to come.
Turned my large aluminum honeycomb core DMLs sideways and leaned them against the wall behind the TV.
It just shouldn't sound good, but gees, it does.
No tweaking or equalization yet.
I have it set up with an Apple TV by HDMI to LG TV optical to minDSP SHD out to a pair of NCore stereo amps driving both DMLs and the woofers.
I plan to raise the panels so they center (vertically) on the TV.
More to come.
