mark58 wrote:

I don't find the Bass Boomy at the levels I listen but I do know that there is vibration coming through the floor...I can sometimes feel it in my feet..

Mark58 wrote:

DBC,  I've got another question for you.  When I move the HR-1s back into the Cave in June, do you think the Sub Dudes will have a similar effect as with the Omegas?  The HR-1s have a Plinth on the bottom with a fixed gap through which the Bass passes, so it really doesn't fire directly into the floor as the Omegas do. By the way,  I'm having a Ball!  Mark.

From above link:

Awesome! I am SO pleased that you found the SubDude to make a worthwhile improvement. I try not to use hyperbole when recommending that people decouple their subwoofer and speakers, but I do make very strong statements because it typically takes that level of persuasion in order to get people to try it!

So it comes as a great relief when other people discover that decoupling really does improve the sound both inside and outside of your theater! Results do vary, but I have yet to come across anyone who found zero improvement with a decoupling device in place.

One thing that can make the SubDude/GRAMMA's improvement less noticeable is if the subwoofer or speaker was already sitting on top of a very thick carpet pad and carpet. Essentially, a thick carpet pad will already act as a decoupling device. However, most subwoofers and speakers have "feet" or some sort - either "spikes" or just small, rubber feet that stick out from the bottom. These "feet" will typically sink deep into any carpet and will often sink deep enough to still couple the subwoofer or speakers to the floor. So even with carpet, the SubDude/GRAMMA can often still deliver a noticeable improvement.

Ara mentioned that the bass in his theater actually sounded louder with the SubDude in place and surmised that perhaps the reason was because more bass was entering the room due to no longer entering the floor. This isn't actually the case. What is actually happening is that - without the SubDude in place - the room itself is shaking in sympathy with the subwoofer. In essence, the walls, floor and ceiling all end up acting as huge speaker surfaces. They shake along with the shaking of the subwoofer and, as a result, produce sound waves of their own. These sound waves (which are a clear form of distortion) interact with the soundwaves coming from the subwoofer - in exactly the same way that reflected soundwaves interact with the direct soundwaves. In other words, the shaking of the walls/ceiling/floor creates destructive and constructive interference when the soundwaves created by the shaking walls/ceiling/floor interact with the direct soundwaves from the subwoofer AND the reflected soundwaves.

The bottom line is that decoupling greatly reduces one major source of distortion and one major source of additional soundwaves within the room. With fewer instances of either destructive or constructive interference, the result is a somewhat flatter frequency response within the room. To be clear, both the direct soundwaves and the reflected soundwaves still exist, so decoupling is NO panacea for frequency response! But you DO eliminate the soundwaves that were the result of shaking walls/ceiling/floor, so that has an audible effect!

Some people experience LESS bass volume when they add the SubDude. That would be because the shaking walls/ceiling/floor happened to be creating constructive interference at that person's particular seating location. In Ara's case, it is very likely that the shaking walls/ceiling/floor happened to be creating destructive interference at his seating location, so that is why the bass seemed to get louder with the SubDude in place!

Regardless of whether the shaking walls/ceiling/floor happen to create either constructive or destructive interference at your particular seat though, you can expect to hear "tighter" bass with a decoupling device in place. And that is because, regardless of your room acoustics or seating location, reducing additional distortion soundwaves will always result in fewer instances of either constructive or destructive interference. As I said earlier, that means some measure of improvement in the frequency response and you are also removing a major source of distortion, which is always a good thing

Archie wrote:

I have my HR1s on isolation platforms that I designed and built and I agree with most everything being said here.  What I am wondering is why manufactures of speakers are constantly marketing their speakers to mount on spikes given that spikes are a way of coupling to the floor?  Are they trying to artificially enhance the bass "sound" even at the expense of boom?

I also think that one can't predict how any given speaker will perform in any given room due to the complexity of the structural interplay between the sound and the building structure.  Sometimes the structure will damp out the bass waves and other times it might enhance the bass waves.  Consequently it will never be one size fits all.  Each of us has to decide what sounds best for our rooms with any given speaker.

Archie wrote:

I think it was Will who has the HR1s on a brick floor and spikes or soft feet.  His floor, brick on sand or concrete is probably pretty "dead" unlike my framed floor with 3/4 inch plywood over-layed with 3/4 inch wood planking that acts like a piano soundboard!

Quote from above link:

First, re: concrete - having a decoupling device in place absolutely makes a difference when you have a concrete floor! Many people are under the misconception that concrete is inert. Concrete is FAR from inert. Concrete moves and shakes. Typically, a concrete floor or walls will have more mass than typical wood-frame construction. So it takes more energy to get more mass to move. But when that greater mass DOES move, it actually transmits sound energy more effectively because it is a denser material. Ever seen that famous film of the concrete bridge rolling like a wave when a strong wind got it moving at its resonant frequency? Concrete is anything but solid and inert!

Fellow audio enthusiast with carpet over concrete 02/16/15:

I dug out my isolation platforms ...and to be honest, I have mixed feelings. With the MBM on the floor, I can easily forgo having a sub. Not so on the platform. While the platforms certainly clean up the bass, SPL levels seem to have been reduced by about 6 db, perhaps even more. I've tried to compensate by turning up the volume on the MBM from 11 o clock to 12:30. Also the bass doesn't seem as extended / deep as it does when resting on the carpet.

Fellow audio enthusiast with carpet over concrete 02/28/15:

DBC, I haven't had as much time as I'd like to listen. Having said that, I have continued to readjust the levels and now I find the bass to be quite satisfying. Is it better than before... I cannot say for sure at this point. My gut feeling is yes, it is cleaner - but all I know for sure is at the time I made the switch, the difference was anything but subtle. I wait another month or so and then place the MBM back on the floor. I should be able to reach a conclusion by then.