Earl, I would like to know more about the spray foam you referred to because the ones I know don't stay flexible and I guess it's important to not hinder the wall from resonating in any possible way.
Best, Markus
Best, Markus
Earl, thanks for clarifying. I take your point about it not being necessarily bad. At first I thought they said it would be better for you to just put the 2nd layer of drywall with CLD, than to add rc1 and 2 layers of drywall in CLD. I am trying to find what they measured in the lower ranges on this, but thats not as easy to compare because they are mixing scales on their charts.
I guess I would like to better understand what the significance of the sound isolation is? These tests are measuring sound transmission. So if the sound level is quieter on the other side of the wall, after changing the composition of the wall, did the change occur because the wall absorbed it, or reflected it? I would think that adding a damping layer would mean that it absorbs it rather than reflect it, but I guess my error is that this can't be assumed, correct? -Maybe there is another possibility other than absorption or reflection, that I am missing?
As for sealant, well, green glue has a solution for this too...
http://www.greengluecompany.com/silenseal.php
Not sure how it compares in cost to great stuff...
(- I must sound like a rep or something, but I assure you I am not!)
-Tony
I guess I would like to better understand what the significance of the sound isolation is? These tests are measuring sound transmission. So if the sound level is quieter on the other side of the wall, after changing the composition of the wall, did the change occur because the wall absorbed it, or reflected it? I would think that adding a damping layer would mean that it absorbs it rather than reflect it, but I guess my error is that this can't be assumed, correct? -Maybe there is another possibility other than absorption or reflection, that I am missing?
As for sealant, well, green glue has a solution for this too...
http://www.greengluecompany.com/silenseal.php
Not sure how it compares in cost to great stuff...
(- I must sound like a rep or something, but I assure you I am not!)
-Tony
Dr. Earl, just what is the "2-part soft polyurethane" that you sometimes refer to? I don't know what to look for in a store or catalog.
I'd be interested in results for DBA variants that use more typical placement along the floor near the walls, but still attempt to use active cancellation, to see if it's worth doing over the recipes in Todd's pre SFM papers.john k... said:
While I'm at it, I'd really like to thank EG, TW and JK for their participation. Your sometimes disagreement is the most interesting content in this forum, IMHO.
Just to clear something up with which Earl will disagree, dipoles will produce sound below the room fundamental. What they won't do is exhibit the 12dB rising response that a occurs in a perfectly sealed room. In other words, unlike a monopole, they don't care if the room leaks. Below the fundamental the dipole behaves as if it is in free space, except for what influence the fundamental may have at lower frequency due to the finite bandwidth of the resonance. If you doubt it, build one and measure it.
Member
Joined 2003
John,
Is Bohdan planning to include this feature in SoundEasy V16? (I vote yes 😎 )
Thanks,
Paul
john k... said:
That was actually my thought in another thread, where I considered to use multiple 15" AE IB15 in monster dipole, and now they have made a 15" OB15, with better sensitivity
Maybe one should consider some pushpull ripoles 😎
john k... said:
Ants produce sound - its the levels that we are talking about. An unequalized dipole will drop at -12 dB/ oct below the lowest resonance - i.e. its free field response. Sooner or later this is going to be what I would call "no sound".
A monopole will not do this and can benefit from whatever gain is to be had from the Helmholtz resonance - the dipole cannot.
markus76 said:
Great stuff stays pretty flexible. It can get brittle if its in sunlight, but hidden it never really hardens.
TRADERXFAN said:
Tony
Your not missing a thing, you've got it exactly right. You don't know if the sound that is NOT transmitted is reflected or absorbed, thats why I made such a big deal out of the difference between transmission and absorption. The data being shown says nothing about absorption at all. It would be nice to assume that its all absorbed, but you can't do that. In fact with the "mass law" that they expound the sound will be mostly reflected not absorbed. The movable CLD is pretty certain to be mostly absorption (especially at LFs). You have to read these sites very carefully. When they know what they are talking about they can word things is tricky ways. Then there are those that don't know what they are talking about and they just lie.
Speedskater said:
You cant buy that stuff "at a store". Its sold only by the chemical company which is Anderson Development Company in Adrian, MI. Its the best CLD material that I have seen, but its messing and expensive and you have to buy it in large quantities. Otherwise use Liquid Nails.
gedlee said:
This was somewhat unavoidable: Can you show – in an objectve way – what effect this design has on the low frequency sound field and how it performs against other approaches?
Best, Markus
Multiple speaker projects in the same room has been on my wish list for quite some time. Hope the wish comes true.john k... said:
Speedskater said:
gedlee said:
Or ... you could take a look at Green Glue and Quiet Glue as constrained layer damping is their primary function. I'm not entirely sure if the price/performance of these products is worth it though.
http://www.greengluecompany.com/
http://www.quietsolution.com/html/quietglue.html
gedlee said:
It's no problem to design a dipole that has significant output below the lowest mode in a room so what you say makes no sense. Besides that a dipole falls at 18db/oct below Fs, not 12dB/oct.
Better do it right and end up with "later" then! 🙂
A closed box woofer will also end up at "no sound" if you look far enough and mic's don't pick up DC. It's about bandwith and all type of systems can give you what you need (cost and size is another discussion).
A helmholtz resonator will ultimately fall at 24dB/oct and will end up producing "no sound" as well with basically the same acoustic shortcut as the dipole.
/Peter
Paul W said:
I expect he will. I don't think he would have gone to the effort of making the code mods if he didn't think it would be a valuable update to the FEM. I first asked for this a few years ago so I could look at cardioids in SE, but he didn't follow through at that time. The DBA must have done caught his attention though. 🙂
gedlee said:
What are your thoughts about this stuff?
http://www.acoustica.com.au/quietwave.html
Cheers,
Alex
markus76 said:
The effect of LF absorption on the sound field is in my books. How one approach differs from another objectively in terms of absorption, I have no data, and know of none. Its very difficult to get LF absorption data.
Earl, you are full of contradictions.
You said,
Note, this says nothing about equalization. It says, not a monopole? NO SOUND BELOW THE 1st MODE. That's pretty clear.
To which I replied
which is an accurate statement to which you replied;
First of all, you have gone from NO SOUND to "...it's free space response". That is exactly what I said. But still, it's free space response is -6dB/per octave not -12. Just to be perfectly clear I'm referring to a dipole composed of souces that are theoretically flat to DC.
Second, it should not be necessary to discuss whether the dipole is eq'ed or not. It's not relevant. The relevant thing is NO SOUND or FREE FIELD SOUND below the fundamental, if it's not a monopole.
Well here is the measurement:
Red is a B3, 27 Hz target. Green is the theoretical free field response of one of my H-frame woofers obtained by
DP = MP - (MP x exp( x Td))
where Td is the front to back delay of the H frame.
Blue is the in room response at 2.5M. It matched the free field response below the obvious fundamental of at 25 Hz.
The point is just as I said, the dipole doesn't care if the room leaks or not. Below the fundamental the room has no effect on a dipole's response. Isn't that what we are discussing, the effect of the room on the response? If you want to contend that a dipole is inefficient because of the required EQ to compensate for the -6dB/octave roll off then fine, I couldn't agree more.
The point is simple what is the roll of the room, not what does the source do. Oh, and by the way, a cardioid benefits from room pressurization too, not just monopoles.
Sorry if sound irritated but I guess those ants are crawling up my butt.
You said,
Note, this says nothing about equalization. It says, not a monopole? NO SOUND BELOW THE 1st MODE. That's pretty clear.
To which I replied
which is an accurate statement to which you replied;
First of all, you have gone from NO SOUND to "...it's free space response". That is exactly what I said. But still, it's free space response is -6dB/per octave not -12. Just to be perfectly clear I'm referring to a dipole composed of souces that are theoretically flat to DC.
Second, it should not be necessary to discuss whether the dipole is eq'ed or not. It's not relevant. The relevant thing is NO SOUND or FREE FIELD SOUND below the fundamental, if it's not a monopole.
Well here is the measurement:
Red is a B3, 27 Hz target. Green is the theoretical free field response of one of my H-frame woofers obtained by
DP = MP - (MP x exp( x Td))
where Td is the front to back delay of the H frame.
Blue is the in room response at 2.5M. It matched the free field response below the obvious fundamental of at 25 Hz.
An externally hosted image should be here but it was not working when we last tested it.
The point is just as I said, the dipole doesn't care if the room leaks or not. Below the fundamental the room has no effect on a dipole's response. Isn't that what we are discussing, the effect of the room on the response? If you want to contend that a dipole is inefficient because of the required EQ to compensate for the -6dB/octave roll off then fine, I couldn't agree more.
The point is simple what is the roll of the room, not what does the source do. Oh, and by the way, a cardioid benefits from room pressurization too, not just monopoles.
Sorry if sound irritated but I guess those ants are crawling up my butt.
John
I don't disagree with what you are saying, but its just as irritating when someone nit-picks your comments to death. This is a casual forum not a refereered publication and I don't take extremes to make sure that every word and phase cannot be misconstrued, as you tend to do. You seem to assume that I don't know what I am talking about and take every comment to its most illogical extreme.
I think that it would have been obvious that I was talking about an un-eq'd dipole since EQing is something that you have to add to a dipole discussion not something that can be assumed as you did. The EQ is NOT part of the dipole. And "no sound" was taken far too litterally and I think that everyone knew that. To me once the response is down by 12 dB at LFs it is not sufficient to be "audible" and hence results in "no sound" - and I'm sure you'll pick that statement apart about what you "can hear" or not - but remember that the ears sensitivity is dropping like a stone at these LFs too and to be SOUND, in this context, it has to BE HEARD. The point about the ant was simply that sure there is Sound Pressure for a dipole all the way down to .0001 Hz., but just because there is sound pressure does not mean that there is "audible sound". So maybe I should have said "no audible sound", but I would have thought that the "audible" part was the obvious intent of the statement.
Whether the dipole drops at -6 dB, -12 dB or -18 dB as someone else stated (whom I noticed you didn't correct) is not the point and I didn't check this as fact. But - 6 dB does not seem correct since a ported enclosure drops at -24 dB, and 12 of that is due to the dipole aspects below tuning. But again, the slope is not the point, nor is "free field" the point. The point is that a monopole CAN excite a sealed room at DC and a dipole cannot. One source has to go to zero and the other doesn't. What a cardiod does is also not the point.
I don't disagree with what you are saying, but its just as irritating when someone nit-picks your comments to death. This is a casual forum not a refereered publication and I don't take extremes to make sure that every word and phase cannot be misconstrued, as you tend to do. You seem to assume that I don't know what I am talking about and take every comment to its most illogical extreme.
I think that it would have been obvious that I was talking about an un-eq'd dipole since EQing is something that you have to add to a dipole discussion not something that can be assumed as you did. The EQ is NOT part of the dipole. And "no sound" was taken far too litterally and I think that everyone knew that. To me once the response is down by 12 dB at LFs it is not sufficient to be "audible" and hence results in "no sound" - and I'm sure you'll pick that statement apart about what you "can hear" or not - but remember that the ears sensitivity is dropping like a stone at these LFs too and to be SOUND, in this context, it has to BE HEARD. The point about the ant was simply that sure there is Sound Pressure for a dipole all the way down to .0001 Hz., but just because there is sound pressure does not mean that there is "audible sound". So maybe I should have said "no audible sound", but I would have thought that the "audible" part was the obvious intent of the statement.
Whether the dipole drops at -6 dB, -12 dB or -18 dB as someone else stated (whom I noticed you didn't correct) is not the point and I didn't check this as fact. But - 6 dB does not seem correct since a ported enclosure drops at -24 dB, and 12 of that is due to the dipole aspects below tuning. But again, the slope is not the point, nor is "free field" the point. The point is that a monopole CAN excite a sealed room at DC and a dipole cannot. One source has to go to zero and the other doesn't. What a cardiod does is also not the point.