Some more studies on this: http://www.tonestack.net/articles/speaker-building/cabinet-sound-insulation-measurement.html
But the thing is, what many here try to say, is that the way the cabinet is constructed is way more important than the material used. Some make speakers out of metal, that rings like hell. Even some top measuring speakers like from Genelec and Neumann are made like that. Others use plastic, that is not stiff nor dense. But if you implement the material on the right way, you can remove that ringing or vibrating. So it does not matter that much.
But the thing is, what many here try to say, is that the way the cabinet is constructed is way more important than the material used. Some make speakers out of metal, that rings like hell. Even some top measuring speakers like from Genelec and Neumann are made like that. Others use plastic, that is not stiff nor dense. But if you implement the material on the right way, you can remove that ringing or vibrating. So it does not matter that much.
Abraham Cohen wrote that back in the day. Pre-1974 is when I bought it, not sure when it was published.
Just picked up new tweets to go with my 15's, so will be doing further examination on fiberglass built structures. Looking to minimize weight, but keep it strong enough for use as well as panel resonances above where the woof can excite it.
Actually, the panels don't have to be stiffened above the range of the bass driver, just high enough so that sound that is not absorbed by the filler material will not excite the panels. If the stuffing absorbs 700 hz up for example, no need to stiffen beyond 1Khz..
Boden.. any reasonable discussion has to have a bit more than just measurements. Discussion of the technicals is always needed to fill in the gaps left when presenting just data. I find in my work, people tend to get lost in the data, not really understanding the results.
John
Hello John, as much as I agree with your "reasonable discussion statement" I was under the impression the OP wanted no religion or opinions, but a thread with a bit more flesh on the bones. In my book that means back up of conclusive statements (material X is far superior over Y, coz my wife clearly heard it..) by at least some measurements or literature refs, and that is precisely how this thread started. To be clear: that does not mean there should be no general technical discussion.
BTW : there is a somewhat parallel thread by Augerpro: https://www.diyaudio.com/community/...of-loudspeaker-questions.391771/#post-7161771
BTW : there is a somewhat parallel thread by Augerpro: https://www.diyaudio.com/community/...of-loudspeaker-questions.391771/#post-7161771
yep I use real marble on 1990 when I own a small speakers firm, we use nero marquinia ,salome' ,carrara,granito too with cnc work
Last edited by a moderator:
Some posts have been moved here from this thread - https://www.diyaudio.com/community/...frpc30-8-8-fullrange-cheap-monster-ii.385062/Hello,
have you read this:
https://www.somasonus.net/box-construction-methods
The comparison it's not easy but it's an interesting work.
Regards
Guglielmo
have you read this:
https://www.somasonus.net/box-construction-methods
The comparison it's not easy but it's an interesting work.
Regards
Guglielmo
Alas, the axis numbers are kinda too small.
But from what I can figure out, the felt has effects out in the 2 to 5K range. I would rather go with a thinner wall with bracing and line the inside with 1 inch rockwool for absorption of stuff way up there in frequency.
John
Sorry if I ask, have you seen how measurements affect a box? Thinking about whether to use the Golden Ratio calculator. You spread out resonances, I understand. Will the material for the box be less affected then?
Just the various types of metal boxes I designed for all manner of electrical power & motor controls systems from lunch pail size to 'erector set' multi-door cabs up to 120" x 84" x 36" being UL/CSA tested for seismic, shipboard, tornado, hurricane, etc., apps, but the only wood products were the pallets, various containers they were transported in/on with no consideration of the golden, room ratios we should be using since it's all about shipment 'packaging', making light as practical, fitting an existing location's dims, etc.; learned plenty WRT bracing, component locations on a panel though.
That said, 'somebody' did post some results from building a sealed box with a driver internally attached to one of the wall to excite it, but it was ages ago and no longer remember his name/moniker. 🙁
Anyway, until it becomes a high enough aspect ratio for eigenmodes to develop in the speaker's pass-band it's presumed to have a ~uniform particle density, so in this case the golden ratio, the ancient Greek's? 1:1.4:2, etc., are more about aesthetics with no audible impact on material types, just box shape, i.e. differing BSC, etc..
That said, 'somebody' did post some results from building a sealed box with a driver internally attached to one of the wall to excite it, but it was ages ago and no longer remember his name/moniker. 🙁
Anyway, until it becomes a high enough aspect ratio for eigenmodes to develop in the speaker's pass-band it's presumed to have a ~uniform particle density, so in this case the golden ratio, the ancient Greek's? 1:1.4:2, etc., are more about aesthetics with no audible impact on material types, just box shape, i.e. differing BSC, etc..
I have good results in constructing a wooden box with thin walls like 10mm or 12mm. And putting through the loudspeaker hole on every side concrete inside the box. Doing this wall after wall always giving it at least 24 hours of hardening time. In the end the ends of the concrete meet and make a box in the box. I use for that ready made concrete for floors - just add water and use it. The wooden box needs to be air and water tight so no water/concrete leaks out.
For the front where the speaker hole or reflex opening is I use silicone inside the box and put it 1cm in height a line of it at the edge of the loudspeaker cutout. So the concrete I put there does not leak out.
The acoustic is far beyond anything made with wood alone in my ears. I do not have measurements of this of any kind.
For the front where the speaker hole or reflex opening is I use silicone inside the box and put it 1cm in height a line of it at the edge of the loudspeaker cutout. So the concrete I put there does not leak out.
The acoustic is far beyond anything made with wood alone in my ears. I do not have measurements of this of any kind.
I did some material research and measurements for a customer and can't publish everything here. But the main things are no secrets.
*) Stay STIFF for low frequencies. You need to push the material resonances to high frequencies, out of the range of a sub woofer. No big areas, interrupt with braces. Best bracing from one side to the other.
*) Get DAMPENED for mid frequencies. Sandwich materials can get pretty good but are a pain to build.
If you want to get deeper into this read about coincidence frequency and Berger's mass law.
Very good without to much thinking - just use 40mm thick wood.
Standard thickness wood always has it's weak point in the 1-2k area.
A 6mm Aluminium plate ... follows theory nearly perfect and shows the validity of my measurements.
*) Stay STIFF for low frequencies. You need to push the material resonances to high frequencies, out of the range of a sub woofer. No big areas, interrupt with braces. Best bracing from one side to the other.
*) Get DAMPENED for mid frequencies. Sandwich materials can get pretty good but are a pain to build.
If you want to get deeper into this read about coincidence frequency and Berger's mass law.
Very good without to much thinking - just use 40mm thick wood.
Standard thickness wood always has it's weak point in the 1-2k area.
A 6mm Aluminium plate ... follows theory nearly perfect and shows the validity of my measurements.
not too serious but more info is nice ,good reference .....
- Beranek, Leo, Acoustics,
- Briggs, Gilbert, Loudspeakers, the how and why of good reproduction, Wharfedale Ltd.
- Briggs, Gilbert, The [loudspeaker] Cabinet Handbook,
- Colloms, Martin, High Performance Loudspeakers,
- Driscoll, Roger, Practical HiFi Sound
- Wheeler, Mark, Navigating Speaker design Part 1: Defining the Problem, Speaker Builder 6/99
- Wheeler, Mark, Navigating Speaker design Part 3: Listening to walls, Speaker Builder 8/99
https://www.tnt-audio.com/clinica/cabinet_walls_e.html
There are objective measurements possible with the hand and by the ear.
Vibrating surfaces can be detected by putting your hand on them. After modifying one speaker (with bracing for example) you can compare with the untweaked loudspeaker.
By putting your ear on the surface or using a stethoscope you can detect the amount of sound still getting through the material (=called coincidence effect). Here, too, you can compare tweaked with untweaked speaker.
However quantifying the difference is subjective but the absolute change can be objectively stated.
This is a comment to the thread title "only measurements please"
Vibrating surfaces can be detected by putting your hand on them. After modifying one speaker (with bracing for example) you can compare with the untweaked loudspeaker.
By putting your ear on the surface or using a stethoscope you can detect the amount of sound still getting through the material (=called coincidence effect). Here, too, you can compare tweaked with untweaked speaker.
However quantifying the difference is subjective but the absolute change can be objectively stated.
This is a comment to the thread title "only measurements please"
even better is a mechanics stethoscope. One can quickly figure out where there is any box ringing.
Some of the software tools that use the accelerometer in your phone might allow some quantitative analysis.
dave
Just to add... Bracing an existing speaker may produce what seems like a disappointing result, because it upsets the balance you previously achieved and can uncover other distortions. It's worth pointing out that this doesn't mean it's not the way forward, but you may have to then begin looking at other things.