And now for something completely different...
I've installed six panels into a new church near here. The panels are 1,000mm x 400mm. The membrane is 5mm EPS skinned with maple veneer, edged with weather tape in a white-washed pine frame. There are 4 x 25FHE drivers per panel. The back has a honeycomb holes laser-cut into it, lined internally with underfelt.
Front
Back.
This is where you play 'Spot the Loudspeakers'
This place seats about 800 people, and it has NO SOFT SURFACES... The roof/ceiling is easily 15m high. RTA60 is more than 5 seconds!!
When standing even in the middle rows, it's extremely difficult to hear what somebody is saying (unamplified, no microphone) at the front due to the massive reverb. The panels did make a small difference to those in the first 10 rows or so, obviously more panels need to go up at the back.
I have advised them to get carpets, or tapestries, curtains or seat cushions etc, but they are completely against such ideas. Surprisingly, they're not so averse to installing acoustic absorption panels. We'll wait to see at the opening service if 500 or so human bodies make sufficient difference to the reverb to make the speakers intelligible.
I'm holding my breath.
I've installed six panels into a new church near here. The panels are 1,000mm x 400mm. The membrane is 5mm EPS skinned with maple veneer, edged with weather tape in a white-washed pine frame. There are 4 x 25FHE drivers per panel. The back has a honeycomb holes laser-cut into it, lined internally with underfelt.
Front
Back.
This is where you play 'Spot the Loudspeakers'
This place seats about 800 people, and it has NO SOFT SURFACES... The roof/ceiling is easily 15m high. RTA60 is more than 5 seconds!!
When standing even in the middle rows, it's extremely difficult to hear what somebody is saying (unamplified, no microphone) at the front due to the massive reverb. The panels did make a small difference to those in the first 10 rows or so, obviously more panels need to go up at the back.
I have advised them to get carpets, or tapestries, curtains or seat cushions etc, but they are completely against such ideas. Surprisingly, they're not so averse to installing acoustic absorption panels. We'll wait to see at the opening service if 500 or so human bodies make sufficient difference to the reverb to make the speakers intelligible.
I'm holding my breath.
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Very nice work Andre, congratulations 👍
Questions:
1/Did you test a panel before installation?? If so what are your comments?
2/ is the veneer on both faces?
3/ how much gap is there between the panel and the underfelt?
Eucy
Questions:
1/Did you test a panel before installation?? If so what are your comments?
2/ is the veneer on both faces?
3/ how much gap is there between the panel and the underfelt?
Eucy
Andre,
That is so awesome. They look great! Would love to hear more details about your construction if you are willing to share.
Eric
That is so awesome. They look great! Would love to hear more details about your construction if you are willing to share.
Eric
My experience, is that it really helps when you actually show a couple of things first and maybe even take some with you and show customers and clients.
These days there are very modern materials that will completely camouflage. Like you literally can't see it.
Fact is that most people find it hard to picture how it will look.
In this case things could even easily be themed, a nice classic picture wall or so is also possible.
Another take is to go into active reverb cancelling, but that's quite the rabid hole to go down to.
It's also not perfect.
Thanks Eucy,
1/ I had less than three weeks from order to installation, to import materials, get the woodwork done, and build the panels. Unfortunately, I didn't even have a spare hour or so to do any response testing except to see if they would go loud enough.
2/ Yes, veneer on both faces otherwise 2nd harmonic distortion would go through the roof, and the panels would bend in or out depending on humidity levels.
3/ The gap is about 10mm. The panels are not mounted flush against the walls, and the back panel is perforated and damped to allow some of the sound through, and not to kill it completely. So the resultant directivity is more cardioid than omni.
Thanks Eric
After I built the membranes (EPS/veneer) I put 12mm x 8mm weather foam all around the edges of the panels. It is then clamped onto the front frame by an internal back frame.
So the total edge thickness is 5mm for the panel, plus 2 x 8mm for the foam, = 21mm. There's an internal frame between the back and front frame allowing a 16mm gap, so the foam gets squashed firmly to hold the panel in place.
The order for the church system was placed by the owner of the restaurant where I perform using my twinwall polycarb PA panels. He, the owner, happened to be one of the project managers for the church build, and he knew the sound and the capabilites of the system pretty well.
I did offer to do FoamX panels with designs printed on the front, but they wanted it as unobtrusive and natural as possible. Hence maple veneer.
I do have other enquiries lined up for which I will do silk-screened designs on the front, and others for family photos laser printed on the front.
I can use a variety of materials for membrane construction, so I can do any bespoke designs depending on the application.
Further,
When the venue had a few hundred people in it the reverb problem was significantly reduced, as expected.
Volume levels were very acceptable without the panels drawing attention to themselves (as in 'THIS is where the sound is coming from!') As far as the audience is concerned there's no PA, and the guys on stage simply appear to project their voices very very well.
But the thing about DML panels is that when you wind them up, they do not gradually increase in distortion like a cone speaker does. There's just no warning before the drivers hit their excursion limits, and then they rattle. So I'll have to go and set compressors and limiters properly some time this week.
When the venue had a few hundred people in it the reverb problem was significantly reduced, as expected.
Volume levels were very acceptable without the panels drawing attention to themselves (as in 'THIS is where the sound is coming from!') As far as the audience is concerned there's no PA, and the guys on stage simply appear to project their voices very very well.
But the thing about DML panels is that when you wind them up, they do not gradually increase in distortion like a cone speaker does. There's just no warning before the drivers hit their excursion limits, and then they rattle. So I'll have to go and set compressors and limiters properly some time this week.
More detail:
The red bit is the outside frame.
Here's the whole thing without the DML membrane which fits into the slot between the front and back frames.
Marketing...
There's still a helluva lot of tweaking to be done. I think the honeycomb perforations on the back are too large and allow too much sound through. And I think I prolly need thicker damping cloth over those perforations. TBC.
For PA use and professional installations, I want to damp the rear signal a bit more. But for home/hifi installations, I might want to allow more of the rear signal through for a better open-baffle sound.
2 way DML panels using 2 panels with one exciter on each panel with a 1st order high pass cap and a low pass inductor.
When it comes to vocal intelligibility DML's rule you can hear the coherency and clarity in his voice, not to mention that everything else sounds phenomenal ....thats if you BUILD it right though.😉
Ice Ice baby too cold to cold. Word to ya mutha. 😀
When it comes to vocal intelligibility DML's rule you can hear the coherency and clarity in his voice, not to mention that everything else sounds phenomenal ....thats if you BUILD it right though.😉
Ice Ice baby too cold to cold. Word to ya mutha. 😀
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AF...I'd very, very much like to compliment you on your build quality etc but.....I can't see it 😵💫...'bout time you dived in and lifted the veil (carpet in your case).
And in my time on this forum, even though a number of different designs have been posted with considerable detail, I've yet to see or hear of anyone actually copying a design, so you can rest easy
Come on AF.... DO IT! 👍
Eucy
Unless it can increase sound quality I dont concentrate on aesthetics. My main goal is sound quality everything else is secondary.
Well done AF 👍 AND they're sitting ON THE CARPET!!
Almost there... Now for the panels etc
👌
Eucy
Almost there... Now for the panels etc
👌
Eucy
Completely agreed.
I battle to see what the problem is with somebody "copying " somebody else's "design."
Anybody is free to copy and improve on anything that I post, for example. That would be an enormous compliment to me.
There are not so many different ways of building panels and then mounting them somehow. Chances are that anybody building panels will invariably use the same techniques as somebody else at some stage. But if there is really some apparently secret way of doing it then it should be patented!
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👆Is the very point of posting on any DIY forum. To help others to achieve great results and learn from those who are more experienced. I don’t see the point of posting here if you don’t want people to learn from you.
I have been reading through a lot of scholarly articles on material design for acoustic properties.
There’s a lot of good research into how to reduce or remove resonance or natural frequencies in the mechanical fields, due to its need in the fields of building design, bridge design, and large machine design where natural frequencies can cause the whole to shake apart.
And there’s good research in the material, vehicle, and building design fields for novel approaches to sound insulation.
There are two key sets of issues faced when designing a DML.
Low frequency modes cause modal shapes in the panel which are alternating between efficient then inefficient. This happens up to about 1000hz but varies between materials and board sizes.
High frequency modes are either affected by natural resonances in the material, or coincidence resonance where different frequencies amplify or attenuate each other because of having mode overlaps.
For low frequencies I was for ways to mitigate the inefficient modes.
And for high frequencies i was looking for ways to reduce the modal overlap caused by edge reflection.
Damping the edge by suspending the panel with rubber introduces a smoothing of the SPL frequency graph. However for the high frequencies it adds a attenuation slope.
In a paper I linked to in a previous post, when looking for ways to reduce low frequency resonances in a material a side affect of the study showed that the higher frequencies were amplified and the number of modal overlaps were reduced.
The addition of perforation to a board introduces smoothing to the SPL frequency graph too but it attenuates low frequencies and amplifies the high frequencies by doing a frequency shift on the modal resonances.
Resonance frequencies are affected in the majority by weight and stiffness of the panel so the perforations are changing these factors, while also diffusing the sound waves which reduces the modal overlap.
So this is why I started testing perforated panels and highly dampened panels.
My current best speaker is two panels side by side, one with a single 1mm carbon fiber 30x30cm glued to a 2mm neoprene sheet which handles 70-1500hz, and a basswood 3mm aramid honeycomb basswood sandwich with free edges and a planar spring which has a ring of 5mm holes drilled around the edge of the foot of the exciter, positioned at the recommended 2/3rds position.
The average of these two panels is producing a spl response that follows the harmon curve all the way to 18khz.
I’m currently just refining this build to figure out a good way to frame it up.
If someone has the time and budget and a calibrated mic.
Throw an exciter on one of these and see what it’s spl graph is like.
It’s already a wood composite panel, has a hole pattern, and is designed for wall mounting already.
It could be the new pink XPS speaker.
https://www.homedepot.com/p/OUTDECO...-Decor-and-Privacy-Panel-USADLT2-BL/315586089
Or if you’re in Germany one of these would work awesome.
https://www.richter-akustik-design.de/de/acoustic-lightboard.html
Throw an exciter on one of these and see what it’s spl graph is like.
It’s already a wood composite panel, has a hole pattern, and is designed for wall mounting already.
It could be the new pink XPS speaker.
https://www.homedepot.com/p/OUTDECO...-Decor-and-Privacy-Panel-USADLT2-BL/315586089
Or if you’re in Germany one of these would work awesome.
https://www.richter-akustik-design.de/de/acoustic-lightboard.html
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Hello Jamie
Do you have source for that? sorry if already posted... I ask because at the same time, I have read the post from Eric in a sub-thread showing the good result of Poron as suspension material. The panel is damped but no slope. Have a look Effect of Boundary Conditions on the Ringing of DML Speaker Panels #178
Christian
Thats the problem, you dont see it. 🙄 Like I said many times before just because I wont post my own personal design it doesnt mean I dont help others as I have helped many people on this forum as well as other forums on DML. I give out a lot of advice and try to steer people in the right direction, its not my problem if you choose to ignore/not believe my advice.
Its ironic that anything I say people like to challenge me and argue that my theories are all wrong as if they are the experts, yet ask to see my design? hmmmm I wonder why? It must be the "CARPET". 🤣 🤣 🤣
The reason why most people are skeptical to copy a design is because they have never heard it yet. Only those that have actually heard it and liked it will copy a design as that is where the pudding or carpet is at🤣🤣🤣
AF... Unless you're selling these designs, is there any harm in having people copy them?... After all, "Imitation is the sincerest form of flattery"... I've tried my darnedest to get someone to try the alu dome and failed miserably, so I am definitely lacking in flattery.
Eucy
Eucy