Isolation platform for subwoofer? - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 32 Old 06-22-08, 12:39 AM
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Steve
 
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Re: Isolation platform for subwoofer?

deadhead,
Glad it worked out for you. What kind of floor do you have?

-Steve
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post #22 of 32 Old 06-22-08, 03:26 PM
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Re: Isolation platform for subwoofer?

Padding and carpet over plywood. Crawlspace underneath. The helicopter crashing into the office building scene in The Matrix is much more about the movie and much less about the room now.

deadhead
post #23 of 32 Old 07-12-08, 04:38 PM
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Re: Isolation platform for subwoofer?

Just a quick comment...

There seems to be a bit of confusion as to the nature of the coupling between the sub and the floor, with some mention of the wavelengths of the sound being a factor...

Not really. Yes, there may be acoustic coupling due to the stimulus of the floor by the sub, but that will be via air transmission of the sound, and a stand will do little if anything to mitigate this.

This is a simple (in words anyway!) issue of mechanical coupling. And in this sense, you want Lossy materials acting as an intermediary material layer between the sub and the floor.

This is not actually too hard to achieve, and there should be little need to pay for an exotic commercial product.

The principle material that comes to mind is Sorbothane. While not inexpensive, allot of it is not required.

Simply placing a sheet of the material between 2 rigid surfaces and allowing the top rigid surface to float - maintained by the weight of the sub, will work great.

There are other ways to achieve this, but the concept is the same - only the compliance of the intermediate lossy material will vary.

{And as far as acoustical coupling, short of major structural modifications to the floor, you will not have a significant effect on this coupling vector.}
 
post #24 of 32 Old 07-13-08, 03:53 PM
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Mike Bentz
 
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Re: Isolation platform for subwoofer?

Why would you want to decouple the sub from the floor? Or basically, what "distortion" (unwanted sound) are you trying to get rid of?

Just to throw something out there...if you perfectly decoupled the sub from the floor, then you would be relying solely on the mass of the cabinet to fight against the momentum of the diaphragm. Even with the sub on the floor, the cabinet vibrates from this momentum - so any decoupling is just going to make that cabinet vibration worse.

It would seem to me that in order to maximize the coupling of the driver to the air, that one would want the cabinet to be as motionless as possible, which would require a critically damped mechanical system. I guess I just don't see how decoupling the sub from the floor increases the damping.

This brings me back to my original question...what are you trying to get rid of? And then why not find a way to measure what you're trying to get rid of and then engineer a proper solution?

Also, why is mechanical coupling to the floor a bad thing? The floor has a huge surface area, which will require very little movement to create audible sounds. If you coupled the sub to the floor in such a way as to maintain a flat mechanical response, then you're only going to lower the distortion of the entire system. Since most mechanical systems are high Q, then why not tune it such that you use the floor to extend the low frequency extension of your system?

I suppose some of what I'm suggesting is a bit academic and idealistic, but some of the best sounding systems I've heard were certainly not in the demo rooms of vendors trying to sell their fancy solve everything isolation pads. Beyond the basics of keeping the sub from walking all over the room, there are far more important areas to sink your money into.

-Mike Bentz
~It's all about compromise~


"It's territorial with the soundboard. So you're mixing and some dude comes by spewing opinions and trying to turn knobs. It's akin to going up to an artist and painting over his unfinished masterpiece. You just want to shove your paint brush up his nose and throw the soundboard out the window!"
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post #25 of 32 Old 07-13-08, 06:11 PM
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Re: Isolation platform for subwoofer?

How does placing the sub on something that is a transference of more energy equal less vibration? The more it travels, the more there is the possiblity of distortion?
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post #26 of 32 Old 07-13-08, 06:56 PM
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Re: Isolation platform for subwoofer?

All I can say is I have a nasty room. The floor seems loose and rattles, and I have gross room modes at 40Hz and 80Hz with a suckout at around 60Hz. The Gramma makes the sub sound better--no, it makes movies sound better. I don't know why and I don't really care. All I know is instead of hearing the room rattle, I hear the movie. To me, it was worth every penny, but YMMV.

deadhead
post #27 of 32 Old 07-13-08, 08:03 PM
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Re: Isolation platform for subwoofer?

That is what they are intended for to reduce structural vibration. They in no way claim to improve sound. They do claim that the sound will not have any variation. In this I would assume that to "tighten bass and low-end clarity" in the example of a subdude pitch that it might translate to as less problems.. The opposite of good bass being muddy bass and poor low-end clarity which then in most likelyhood would be the room, where most bass is predominantly a controlling factor.

Subdudes prevent sound rattling my ceiling which although since may not completed, does not mean that it is ignored. I also notice that sound felt which is not intended for a high impact is less agressive, more tame.

I would say the OP has made a correct choice and by no means is making things more worse off. It isn't magic.

Last edited by thewire; 07-13-08 at 08:24 PM. Reason: spelling
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post #28 of 32 Old 07-14-08, 01:04 AM
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Re: Isolation platform for subwoofer?

The Doc makes a very valid point!

I am a bit amused by seemingly simultaneous rush to buy the many available 'decoupling' speaker mounts while others rush to buy the ever popular tip toes without a thorough examination of what is actually the problem.

More often then not, we erroneously begin with a solution and then go looking for a problem to solve.

Why would one want to acoustically or mechanically isolate a component? One item come to mind. That being a turntable. But there are not too many turntables being employed in home theaters nowadays...while they are still around in the audio listening world. But my focus would be on isolating the turntable, NOT the speaker.

If the priority was the attempt to isolate a listening space in order to minimize the transmission of sound through a surface into an adjoining space, I could imagine the potential to attempt to isolate a mechanically coupled source...

If we are worried about items in the room 'rattling, the effort would be better spent isolating them, as their mass will likely be small and they will be the victim of some mechanical coupling, but also significant acoustical coupling. And one would be better off utilizing such methods as earthquake anchors for items such as pictures and nik naks..

But again, we need to identify the actual problem to be solved...and additionally we need to determine if this is this a real problem, or merely an imagined one. After all, an optimal answer is predicated upon the formulation of a concise and accurate question.

The mention of room modes will not be be resolved by decoupling of a subwoofer.

And as Doc has mentioned, decoupling the sub will NOT make the sound of the sub more defined.

We could likewise take the opposite approach and examine the notion that rigidly coupling a speaker to the floor will significantly 'tighten ' the response (such as is so often claimed by those selling such devices as 'tip toes') - especially as most are using passive crossovers and the various acoustic centers of the drivers within the speaker - let alone the various drivers amongst the various speakers - are not aligned in time!

Thus, in this case, we are faced with the dilemma where upon we ignore the gross misalignment of the various source signals in the time domain and instead maintain that the minute oscillation of the cabinet measurable in fractions of an inch (and of which the damped system will move out of sync with the cone motion!!!) and the resultant group delay errors are more critical than mis-aligned delays measurable in ms or much greater - equivalent to the offset of acoustic origins ranging from several inches to many feet! Hence, what we have is the preoccupation with fractions of an inches while we blithely ignore feet! Hmmm. A clear case of being penny wise and dollar foolish!

Yet how many systems employ passive crossovers which lack the ability to adjust and align the acoustic centers of the various drivers, let alone the ability to accurately align the various separate real and virtual sources such as the speaker and the sub and the associated reflections?

So while a minimum phase alignment is important, such a 'posterior backward' focus of obsessing over minute group delay issues while ignoring issues that constitute orders of magnitude larger signal alignment errors utterly misses the point! Or to put this in a none acoustical POV ...This is like worrying if we have the correct change to pay for a purchase while we lack a thousand dollars from meeting the sales price!

So...to return to the original problem...Perhaps we need to better frame the problem. What is the actual problem, and what are we trying to solve! Simply selecting one variable out of context simply because we can, or because one might have seen a purported solution marketed somewhere is not the optimal approach to addressing issues.

(And in a sardonic effort to contribute to another ever popular cause all sorts of problems (misunderstandings), this topic reminds me of the perennial issues surrounding the seeming endless debates over 'magic' interconnects!..a deceptively simple subject that has assumed an air of mystical significance for many who live in the realm of marketing literature. :raped:)

Last edited by mas; 07-14-08 at 02:21 AM.
post #29 of 32 Old 07-14-08, 09:46 AM
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Re: Isolation platform for subwoofer?

Quote:
deadhead wrote: View Post
All I can say is I have a nasty room. The floor seems loose and rattles, and I have gross room modes at 40Hz and 80Hz with a suckout at around 60Hz. The Gramma makes the sub sound better--no, it makes movies sound better. I don't know why and I don't really care. All I know is instead of hearing the room rattle, I hear the movie. To me, it was worth every penny, but YMMV.

deadhead
So is the real problem the coupling of the sub, or the integrity of the floor?

From an overly simplistic viewpoint, you've increased sub distortions to decrease floor distortions, which in the end has had a positive result. But would it not yield an even better result to decrease sub distortions AND address the floor distortion directly (ie, fix the floor)?

-Mike Bentz
~It's all about compromise~


"It's territorial with the soundboard. So you're mixing and some dude comes by spewing opinions and trying to turn knobs. It's akin to going up to an artist and painting over his unfinished masterpiece. You just want to shove your paint brush up his nose and throw the soundboard out the window!"
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post #30 of 32 Old 07-14-08, 02:23 PM
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Re: Isolation platform for subwoofer?

Quote:
mas wrote: View Post
The Doc makes a very valid point!

I am a bit amused by seemingly simultaneous rush to buy the many available 'decoupling' speaker mounts while others rush to buy the ever popular tip toes without a thorough examination of what is actually the problem.

More often then not, we erroneously begin with a solution and then go looking for a problem to solve.

Why would one want to acoustically or mechanically isolate a component? One item come to mind. That being a turntable. But there are not too many turntables being employed in home theaters nowadays...while they are still around in the audio listening world. But my focus would be on isolating the turntable, NOT the speaker.

If the priority was the attempt to isolate a listening space in order to minimize the transmission of sound through a surface into an adjoining space, I could imagine the potential to attempt to isolate a mechanically coupled source...

If we are worried about items in the room 'rattling, the effort would be better spent isolating them, as their mass will likely be small and they will be the victim of some mechanical coupling, but also significant acoustical coupling. And one would be better off utilizing such methods as earthquake anchors for items such as pictures and nik naks..

But again, we need to identify the actual problem to be solved...and additionally we need to determine if this is this a real problem, or merely an imagined one. After all, an optimal answer is predicated upon the formulation of a concise and accurate question.

The mention of room modes will not be be resolved by decoupling of a subwoofer.

And as Doc has mentioned, decoupling the sub will NOT make the sound of the sub more defined.

We could likewise take the opposite approach and examine the notion that rigidly coupling a speaker to the floor will significantly 'tighten ' the response (such as is so often claimed by those selling such devices as 'tip toes') - especially as most are using passive crossovers and the various acoustic centers of the drivers within the speaker - let alone the various drivers amongst the various speakers - are not aligned in time!

Thus, in this case, we are faced with the dilemma where upon we ignore the gross misalignment of the various source signals in the time domain and instead maintain that the minute oscillation of the cabinet measurable in fractions of an inch (and of which the damped system will move out of sync with the cone motion!!!) and the resultant group delay errors are more critical than mis-aligned delays measurable in ms or much greater - equivalent to the offset of acoustic origins ranging from several inches to many feet! Hence, what we have is the preoccupation with fractions of an inches while we blithely ignore feet! Hmmm. A clear case of being penny wise and dollar foolish!

Yet how many systems employ passive crossovers which lack the ability to adjust and align the acoustic centers of the various drivers, let alone the ability to accurately align the various separate real and virtual sources such as the speaker and the sub and the associated reflections?

So while a minimum phase alignment is important, such a 'posterior backward' focus of obsessing over minute group delay issues while ignoring issues that constitute orders of magnitude larger signal alignment errors utterly misses the point! Or to put this in a none acoustical POV ...This is like worrying if we have the correct change to pay for a purchase while we lack a thousand dollars from meeting the sales price!

So...to return to the original problem...Perhaps we need to better frame the problem. What is the actual problem, and what are we trying to solve! Simply selecting one variable out of context simply because we can, or because one might have seen a purported solution marketed somewhere is not the optimal approach to addressing issues.

(And in a sardonic effort to contribute to another ever popular cause all sorts of problems (misunderstandings), this topic reminds me of the perennial issues surrounding the seeming endless debates over 'magic' interconnects!..a deceptively simple subject that has assumed an air of mystical significance for many who live in the realm of marketing literature. :raped:)
So you are recommending that I:

1: Remove my subwoofers from subdudes
2: Place sticky foam feet the size of quarters on the subwoofer
3: Place the subwoofer on the concrete floor, or plywood (insualtion filled) riser.
4: Permanantly seal my PVC ceiling to reinforce it from vibration (as instructions note) prior to wiring my equipment to their home.

Result -

1: I will have less support for my subwoofer
2: I will have wires running across my floor

Lets say the OP takes your advise and does his floor over

Result -

1: Subwoofer will have unknown improvement. We don't know what the cabinet is
2: Maybe he needs to hire a builder, get permits, all to fix something that is already fixed. Not going to be high WAF if that is of importance. I'm sure the OP is intellegent enough to know that securing something that will rattle will stop it from rattling. Hopefully he is not treating room modes.
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