[medium jim]

I'm a believer in them.  Even-though my B&W subs do not appear to have any Cabinet Resonances by touch, we know they do and benefited from having a Auralex Bass Isolation Platform under each of them.  For me the bass got sweeter, faster, easier to integrate and more importantly less distortion and more clarity.

Please share your experiences and DIY plans. 

Question, is there any box Sub that is completely free of standing resonances?  I don't think so, what about you?

Here's a link to a review of the Auralex SubDudes....

http://hometheaterreview.com/auralex-acoustics-subdude-hd-subwoofer-isolation-platform-reviewed/

Thanks,

Jim

[Rclark]

I felt the sub bottom as you asked and there is no vibration, it is totally inert enclosure based on the design of parallel sealed drivers.

The Seaton Submersive is a large room, high power version of this concept. Never see them on platforms either.

[kevin360]

Hey Jim,

I'm a believer too. All it took was placing an ASC SubTrap beneath each sub to convince me. It made a significant improvement.

[medium jim]

I felt the sub bottom as you asked and there is no vibration, it is totally inert enclosure based on the design of parallel sealed drivers.

The Seaton Submersive is a large room, high power version of this concept. Never see them on platforms either.

I really don't think you fully understand, there are more issues with subsonic bass than being able to feel vibrations on your subwoofer cabinet.  For instance, you have floor vibrations that transfer to your subs, ergo the principle of room decoupling.  It is more about that than the vibrations from the subwoofer.

Even as such, it would a rare subwoofer that didn't have some standing waves. The benefits of Iso platforms are immediate.

Jim

[Danny Richie]

I just read through some of the rest of your thread here and really scratching my head. I am not sure where some of these notions come from, but let me see if I can clear some of them up.

First of all, putting a woofer on each of two opposing sides of a box does NOT cancel out vibrations of the cabinet. It cancels out the force effect that tries to move or push the sub in the opposite direction of each movement of the woofer. The moving mass is counteracted, but the pressure put on the rest of the four walls of the cabinet are exactly the same as that of a single woofer. The walls of the cabinet have positive and negative pressures jerking them around. So cabinet wall flexing or resonating and any coloration from that will still remain.

Secondly, unless your subs lightly constructed and are on an elevated wooden stage then your are not going to have to worry to much about isolating them from the floor or using some rubber pad under them.

The idea is not to isolate the sub from the floor or de-couple it from the floor. The floor is not the problem. The problem is that the movement of a heavy mass wants to rock the sub in an opposite direction of the motion. This is especially bad if a box sub sets flat on a carpeted floor.

Platforms do not have any effect on cabinet resonances. They also do not separate or isolate the cabinets from room interactions. There is no "de-coupling" them from the room. The room pressures, resonances, and vibrations are huge sources of coloration, but they have no effect on the sub, its output, or its performance. The sub effects the room. The room does not effect the sub.

What you want is the opposite. You want to couple the sub solidly to the floor so that no matter how much force placed on it, it doesn't move.

A heavy bass or stand does just that. It helps to couple the sub to the floor so that it doesn't move. Ideally you want to run huge lag bolts right through your concrete floor and bolt your sub down to it. But that isn't practical.

The number one source or coloration (especially in cheap subs) is cabinet wall vibration. A solid box that is well braced goes a long way. Floor spikes really help too.


Most of what I was referring to in this post was stated in another thread in this circle before the thread was split. 

[JLM]

Jim,

Please define what you mean by "standing waves."

I agree that isolation from a typical wooden framed floor would be beneficial as that type of floor represents a huge diaphragm, but not if supported by a (relatively massive) concrete slab.  In that case the sub would be less coupled to anything that would help secure it and could be expected to actually reduce self vibration.

[medium jim]

Jim,

Please define what you mean by "standing waves."

I agree that isolation from a typical wooden framed floor would be beneficial as that type of floor represents a huge diaphram, but not if supported by a (relatively massive) concrete slab.  In that case the sub would be less coupled to anything that would help secure it and could be expected to actually reduce self vibration.

http://forum.blu-ray.com/showthread.php?t=48286


Thanks,
Jim

[gooberdude]

I used a pair of auralex subdudes under subs for a few years while in a condo in Chicago that had concrete floors.  It was only to keep noise from entering my neighbors unit below me though. 

The sound quality was much better with the subs spiked to the floor, but then the sound of my neighbor knocking on my door sorta ruined it all.   

[Danny Richie]

I checked them out: http://www.americanmusical.com/Item--i-AUR-GRAMMA-LIST

Read the info on them there and about the application that they are designed for. Your typical sub used in live performances have to be light weight and moved before and after each gig. They resonant a LOT. And they will literally buzz across the floor. These pads put a damping layer between them and the floor to keep the floor from becoming a large resonating diaphragm.

[medium jim]

I checked them out: http://www.americanmusical.com/Item--i-AUR-GRAMMA-LIST

Read the info on them there and about the application that they are designed for. Your typical sub used in live performances have to be light weight and moved before and after each gig. They resonant a LOT. And they will literally buzz across the floor. These pads put a damping layer between them and the floor to keep the floor from becoming a large resonating diaphragm.

Didn't know 300lbs was light....that's what their rated to handle.   I use them and the improvement was day and night....


I suppose a lot depends on how your floors are constructed....

Jim

[Danny Richie]

Didn't know 300lbs was light....that's what their rated to handle.   I use them and the improvement was day and night....


I suppose a lot depends on how your floors are constructed....

Jim

They will make a very notable improvement in many cases. In most cases involving home audio and especially well made subs, it could actually soften the sound and reduce output. Yes, it depends on your floors and the sub.

[JLM]

Jim,

Standing waves as shown are wave lengths in a room which happen to match the room dimensions (at various multiples) that could produce +/- 20 dB swings in frequency response (errors).  Below the Schroeder or "transition" frequency of a given room (typically 120 - 250 Hz), sound is dominating by standing waves (like waves going back and forth in a bathtub).  An isolation base can do nothing for standing waves, only a 2nd out of phase bass generator located at the opposite end of the room can (like this rather innovative one):

http://www.spatialcomputer.com/page9/page10/page10.html

The alternative is to use 3 or 4 subs strategical placed around the room.

[medium jim]

Danny:

I don't know if it softened them, maybe a less spl's. Without sounding too cliche, it sharpened them and they were able to go deeper cleanly.

It is good that this isn't a fanboy thing and there are opposing viewpoints.  It would have been more concise if I noted the flooring makes a difference as well on the onset. I have crappy floors, wood with Berber carpet.

Jim

[medium jim]

Jim,

Standing waves as shown are wave lengths in a room which happen to match the room dimensions (at various multiples) that could +/- 20 dB frequency response errors.  Below the Schroeder or "transition" frequency of a given room (typically 120 - 250 Hz), sound is dominating by standing waves (like waves going back and forth in a bathtub).  An isolation base can do nothing for standing waves, only a 2nd out of phase bass generator located at the opposite end of the room can (like this rather innovative one):

http://www.spatialcomputer.com/page9/page10/page10.html

The alternative is to use 3 or 4 subs strategical placed around the room.

I agree, I used the wrong term...won't be the first time hopefully the last!

Thanks,
Jim

[Danny Richie]

Yeah there really is no standing waves inside a sub cabinet. The wavelengths that it is producing are far to long to propagate even once inside the box.

There is a huge pressure wave though. It not only effects the walls of the box but it also jerks around on the cone with only the woofers suspension to try to control it.

Here is some good info on it here: http://www.rythmikaudio.com/re-radiation.html

[Rclark]

Ok, either way the Epic subs are really well built because they are super inert to where there is simply zero vibration from the cabinet. I'll post an impressions thread in a couple days. Very impressive sub, especially for the money.

[Danny Richie]

Danny:

I don't know if it softened them, maybe a less spl's. Without sounding too cliche, it sharpened them and they were able to go deeper cleanly.

It is good that this isn't a fanboy thing and there are opposing viewpoints.  It would have been more concise if I noted the flooring makes a difference as well on the onset. I have crappy floors, wood with Berber carpet.

Jim

Yeah, if you have a elevated wood floor that is allowing the movement of the sub to cause it to become a giant diaphragm of some kind then the thick rubber mate may well indeed help it out.

[Danny Richie]

Ok, either way the Epic subs are really well built because they are super inert to where there is simply zero vibration from the cabinet. I'll post an impressions thread in a couple days. Very impressive sub, especially for the money.

I have heard that they are well built and pretty solid. That is the name of the game for subs. Looks like they may be a really good value too. I'd like to check one out.

[kevin360]

Ok, either way the Epic subs are really well built because they are super inert to where there is simply zero vibration from the cabinet. I'll post an impressions thread in a couple days. Very impressive sub, especially for the money.

Speaking for the ASC SubTraps, the point isn't to squelch cabinet resonances, and the isolation isn't just about the physical interaction with the floor. The greatest benefit is the control of vertical room modes. It acoustically decouples the sub from the room in the vertical dimension. Likewise, the ASC TubeTraps help control horizontal modes.

I have as much invested in traps to control the bass as I have in the subs which produce it, but the room dominates when it comes to bass - control is mandatory for the best results.

[Danny Richie]

Moving the subs around in the room does change its effect on the room. This includes height. Placement is a big deal. Using absorbers to trap and break up standing waves is also a big deal.

I have built huge tube traps. I have gone all open baffle on subs, I have used the swarm method of multiple subs, etc. All have their advantages.

But you will not really decouple the sub from the room unless you take it out of the room. The sub is producing the energy that is loading the room. You can't separate them from the equation.