Interesting article on constrained layer damping by "Art" Ludwig - he is a retired rocket scientist, PHd, and music lover: http://www.silcom.com/~aludwig/Loudspeaker_construction.html#Panel_vibration_damping
ps Thanks Art - if you should happen to stop by 😀
BTW - he has some very good stuff on his web site! 😉
ps Thanks Art - if you should happen to stop by 😀
BTW - he has some very good stuff on his web site! 😉
Although I haven't tried it myself yet, Green Glue is supposed to be the king of DIY constrained layer damping.
http://www.greengluecompany.com/soundproofingDampingOptions.php
I spent some time reading about it over the past year or so, though not as much lately. I don't recall seeing anything with similar or superior results (with supporting evidence). Quite a bit of good reading off their site alone.
http://www.greengluecompany.com/soundproofingDampingOptions.php
I spent some time reading about it over the past year or so, though not as much lately. I don't recall seeing anything with similar or superior results (with supporting evidence). Quite a bit of good reading off their site alone.
Hmm, this stuff is pretty impressive too: http://www.soundproofing.org/infopages/flooring.htm?gclid=CITp6IrygJACFVB1OAodbly3ug
Mass Loaded Vinyl is compared here:
http://www.greengluecompany.com/greenGlue-vs-MLV.php
Most of the old-style sound proofing / control materials are compared with lab results. It should be no surprise that (on their site) they always come out on top. Unlike other materials and products though, they actually have test results to back it up.
As far as sand goes, it does add mass, but after it has settled it really does not serve any other purpose. It could be used if you need removable mass, but that's the only way I can see it being of benefit.
i.e. you build a light weight enclosure to save shipping costs and have the end user add the mass by filling it with sand.
http://www.greengluecompany.com/greenGlue-vs-MLV.php
Most of the old-style sound proofing / control materials are compared with lab results. It should be no surprise that (on their site) they always come out on top. Unlike other materials and products though, they actually have test results to back it up.
As far as sand goes, it does add mass, but after it has settled it really does not serve any other purpose. It could be used if you need removable mass, but that's the only way I can see it being of benefit.
i.e. you build a light weight enclosure to save shipping costs and have the end user add the mass by filling it with sand.
Interesting! I've been in a MLV damped room and it was like a tomb, so regardless of how good Green Glue is, I'd be inclined to use whichever is the cheapest/easiest to use.
GM
GM
There's a lot of discusion about baffle construction on the Hawthorne Audio web site. The hardcore fanatics seem to prefer a magnet mount type of construction with the speaker physically isolated from the baffle. The next best option may be two layers of baltic birch ply with some type of contrained layer in between and the speaker mounted to the back piece of ply. Green glue is frequently used as the constrained layer and Hawthorne sells it by the tube. If a one piece baffle is used, baltic birch is probably best.
That's not an definitive "what's best" list, just my conclusion from reading many posts.
I used two layer of baltic birch with Green glue for my build of the MJK design). The Green glue is very easy to apply. You can screw the two layers of ply together with the glue sandwiched in between. I did this only for the woofer area. I couldn't see that it would make much difference on the Fostex driver. I didn't try it any other way so I cannot say that it is better than a single layer. Since the good baltic birch comes in 5 x 5 sheets (don't use the HD stuff), I had plenty of excess to use for two layers.
I'm now trying to balance a coin on edge but it's hard. 🙂
That's not an definitive "what's best" list, just my conclusion from reading many posts.
I used two layer of baltic birch with Green glue for my build of the MJK design). The Green glue is very easy to apply. You can screw the two layers of ply together with the glue sandwiched in between. I did this only for the woofer area. I couldn't see that it would make much difference on the Fostex driver. I didn't try it any other way so I cannot say that it is better than a single layer. Since the good baltic birch comes in 5 x 5 sheets (don't use the HD stuff), I had plenty of excess to use for two layers.
I'm now trying to balance a coin on edge but it's hard. 🙂
I use to use quarters, but they're too rounded over now, though I did manage to get a new one balanced for a recent demo, but normally use a nickel now.
Monacor fr in open baffle?
What about using monacor SP165 x , or SP130 x "all purpose" FR in OB with Alpha15? SPL =93(92) dB/w/m ,Qts=1,48 (1,47) , and Fs=120 (145) Hz. High Fs makes them more mid-high then fr I guess, but if they go reasonably flat to 200 - 300 Hz in OB (high Qts) Ouch , I do. Power handling is just 10W . Does it mean this drivers must be protected of bass signal by crossover? I wanted crossoverless main driver. There is SP 200MX : SPL=94dB,Fs=78Hz, Qts =0,91. Vas=25l. And finally , if a FR is 8Ohm driver, would 4Ohm Alpha15 give a boost to bass region?Thanks
What about using monacor SP165 x , or SP130 x "all purpose" FR in OB with Alpha15? SPL =93(92) dB/w/m ,Qts=1,48 (1,47) , and Fs=120 (145) Hz. High Fs makes them more mid-high then fr I guess, but if they go reasonably flat to 200 - 300 Hz in OB (high Qts) Ouch , I do. Power handling is just 10W . Does it mean this drivers must be protected of bass signal by crossover? I wanted crossoverless main driver. There is SP 200MX : SPL=94dB,Fs=78Hz, Qts =0,91. Vas=25l. And finally , if a FR is 8Ohm driver, would 4Ohm Alpha15 give a boost to bass region?Thanks
Re: Monacor fr in open baffle?
scorpion has used the SP-130x in his "Volks-OB":
http://www.diyaudio.com/forums/showthread.php?postid=1342553#post1342553
http://www.audiocircle.com/circles/index.php?topic=46951.0
SB.
nesha said:
scorpion has used the SP-130x in his "Volks-OB":
http://www.diyaudio.com/forums/showthread.php?postid=1342553#post1342553
http://www.audiocircle.com/circles/index.php?topic=46951.0
SB.
As always thanks for sharing Martin. I am using your paper as a guideline in a project I've started a few months ago. I'm sure abusing your good work by applying your theory in obscure ways especially since I don't really know what I'm doing 🙂
I'm trying to build something similar to the R909 and hopefully with some critique and assistance would be able to get to something listenable. I'm willing to experiment (model, build and measure) based on any input received.
I'm posting my findings in this forum.
http://www.diyaudio.com/forums/showthread.php?postid=1394848#post1394848:) 🙂
I'm trying to build something similar to the R909 and hopefully with some critique and assistance would be able to get to something listenable. I'm willing to experiment (model, build and measure) based on any input received.
I'm posting my findings in this forum.
http://www.diyaudio.com/forums/showthread.php?postid=1394848#post1394848:) 🙂
has any one tried these: http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-817
I had some luck with the 3" in ob.
I had some luck with the 3" in ob.
Art Ludwig's article is interesting and comes to much the same conclusion as Dudley Harwood in the 1970s BBC research which led to the LS3/5A and related designs. He used bitumen felt pads for constrained layer damping, testing how many were required and the effects on different thickness wood. This last test revealed that 18mm vs 9mm ply was no better at limiting vibration but required twice as much damping.
After a brief period in the late 70s, the techniques he described are no longer common commercially, going out of fashion around the time MDF came in, possibly for cost reasons. Also I seem to recall that a number of manufacturers ignored his finding on thin vs thick wall enclosures, using 18mm walls and slapping on inadequate damping. Harbeth continue to use the damped, thin-wall technique and have refined it further.
It may not apply to OB design but the paper is interesting reading and is available as a PDF download.
Although off-topic, I'd be interested in GM's and MJK's thoughts on this construction technique for MLTLs, as well as OB.
After a brief period in the late 70s, the techniques he described are no longer common commercially, going out of fashion around the time MDF came in, possibly for cost reasons. Also I seem to recall that a number of manufacturers ignored his finding on thin vs thick wall enclosures, using 18mm walls and slapping on inadequate damping. Harbeth continue to use the damped, thin-wall technique and have refined it further.
It may not apply to OB design but the paper is interesting reading and is available as a PDF download.
Although off-topic, I'd be interested in GM's and MJK's thoughts on this construction technique for MLTLs, as well as OB.
And here's the half completed pair.
Note the important point that they are in my workshop / diningroom, rather than my summerhouse / workshop where such projects are usually completed!
Quote from distaff: "Aren't they nice?" "And don't they sound nice?"
Incidentally, this more or less confirms my initial impression that they are a little bright, she being a little deaf... LOL....
The imaging is excellent, hanging between and behind the loudspeakers, which disappear (acoustically!). I really like the way open baffles drive the room and these are my 3rd pair and by some margin the smallest! The bass in particular has lots of air and tonal detail. I was listening to something on R3 this morning and was struck by how nice they really were in this respect.
I'm going to put a pad in for the 108ez and tone down the top a bit, but, on the whole, quite pleased.
Thanks (again!) Martin....
Note the important point that they are in my workshop / diningroom, rather than my summerhouse / workshop where such projects are usually completed!
Quote from distaff: "Aren't they nice?" "And don't they sound nice?"
Incidentally, this more or less confirms my initial impression that they are a little bright, she being a little deaf... LOL....
The imaging is excellent, hanging between and behind the loudspeakers, which disappear (acoustically!). I really like the way open baffles drive the room and these are my 3rd pair and by some margin the smallest! The bass in particular has lots of air and tonal detail. I was listening to something on R3 this morning and was struck by how nice they really were in this respect.
I'm going to put a pad in for the 108ez and tone down the top a bit, but, on the whole, quite pleased.
Thanks (again!) Martin....
Attachments
MartinQ said:
Actually, sand is very well damped indeed. I remember a table of material parameters in the AIP handbook, with characteristic Q values of different solids under some test condition. They ranged from some metals with values well over 1000, to 10-30 for elastomers to 0.7 for sand. The difficulty with sand is getting effective coupling of the panels into the lossy material, exactly because it has no cohesion.
Additional information: When driven a little harder, the image collapses, the sound becomes confused.
At the listening levels used early morning I was delighted that i could detect no vibration on the speaker. At the later levels, there was significant vibration on the baffle.
If the flapping baffle is responsible for this degradation, I have two solutions:
(1) Mass load the driver and isolate from the baffle
(2) Improve the characteristics of the baffle.
Any suggestions?
If it isn't the baffle vibration, what else might it be?
Mark
At the listening levels used early morning I was delighted that i could detect no vibration on the speaker. At the later levels, there was significant vibration on the baffle.
If the flapping baffle is responsible for this degradation, I have two solutions:
(1) Mass load the driver and isolate from the baffle
(2) Improve the characteristics of the baffle.
Any suggestions?
If it isn't the baffle vibration, what else might it be?
Mark
marec said:
another possible explanation is FE108EZ, cannot handle higher power, distortion creeping in.
Ah, you mistake me!
I would imagine that the 108 was nowhere near it's limits. This is a small room and I don't listen loud....
I did wonder whether a cheap inductor might be saturating, but I even doubt that.
I could stick an ac voltmeter across the loudspeaker if this might help. Personally I wouldn't know what was ok!!
Mark
I would imagine that the 108 was nowhere near it's limits. This is a small room and I don't listen loud....
I did wonder whether a cheap inductor might be saturating, but I even doubt that.
I could stick an ac voltmeter across the loudspeaker if this might help. Personally I wouldn't know what was ok!!
Mark
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