I had been conditioned to the idea of coupling speakers (and subwoofers) to the listening room floor via spikes and the like.

Along comes Elemental Designs - their Blog discusses "...subwoofer isolation pads. The main purpose of the isolation pad is to decouple the sub from the floor to reduce loss energy spent traveling through the floor and to give the sub just a little more height..."

The height thing doesn't really concern me.

But that whole concept of directing all the energy into the room gave me pause. It made me consider the notion of suspending speakers/subs from cables rather than setting them on something. Not that I would DO this, it just seemed like the ultimate expression of isolating the speaker from the floor.

Do you think there could be a perceptible difference based on the degree of mechanical coupling between a speaker system and the listening room?

I'm not sure I'm following the physics. Doesn't an isolation pad absorb energy, thus subtracting it from the system, and wouldn't that also be energy loss?

Tom, that's the second comment by ED that's been brought up recently(the other related to Audyssey)and neither seem to make any sense. As Alan has pointed out, neither spikes nor pads make any difference in the sound; they simply hold the speaker more firmly in place. As far as an "isolation" pad goes, whether enclosure vibrations are partially absorbed in the pad rather than the floor appears to be a meaningless distinction.

If you look at the isolation platform that ED is offering, it bears a striking resemblance to the "Gramma" and/or "Great Gramma" that Auralex Acoustics has offered for years primarily for guitar and bass players to decouple their large amplifier speaker cabinets from the floor. Last year I bought two "Grammas", one for a front-firing Paradigm sub and a second for a down-firing Outlaw which I felt in this case would be more appropriate giving the sound a smoother surface for the woofer to distribute the bass rather than a rug. It cuts down on the vibration to the floor but |I guess that raises the question as well should the floor be an integral part of the sound coming from that speaker? One thing I did notice was that whether or not the sub was on the isolation platform, it didn't seem to affect the distribution of bass within the room.

Bottom line, did they make a difference? Really hard to say since whatever subtle differences there might be, as in much of audio, it could be something that grows on you over time that really wouldn't be noticed until you removed it. I have yet to do that.

You don't want your bass player's cabinet playing the drums, right?

Hi Casey01 and all,

Interesting discussion, but the applications are rather different. For performers in a band on a stage, you certainly do not want the mechanical vibrations in the floor from bass cabinets to travel to floor-stand supported microphones used for other instruments or vocals.

In a domestic hi-fi playback, the situation is quite different. There is a persuasive argument that floor-borne deep bass vibration is part of the experience, if you are trying to replicate live concerts. The vibration of a church pew and floor in a pipe-organ recital is certainly part of "hearing" ultra-deep pedal notes, and you can certainly sense some of the vibration of concert-hall orchestral bass drum reverberating through halls in good concert halls or small clubs for jazz.

Some of the worst concert hall acoustics of halls built in the 1960s and '70s partly resulted from concrete floors that didn't conduct any sense of mechanical feedback of orchestral power. Those halls are often acoustically refurbished by putting in wooden floors over the concrete, so audience members will get some sensory mechancial feedback.

Regards,
Alan

I thought you were supposed to buy the isolation pads to remove bass vibrations from the floor and then buy the buttkicker to put them in the couch.

Thank you all very much for your thoughtful and always-amusing replies.

I was only considering the impact of the floor vibrations on the listener, not on other instruments or equipment, so that angle was a revelation to me.

I appreciate you confirming my suspicion that isolating the speakers from the floor might actually be counterproductive to what we're trying to accomplish.

This topic certainly did reinforce for me (again) the notion of how important the room is to sound reproduction, though. It seems that we have to consider not only the shape, size, materials and proportion of the room, but also the elasticity of the floor. Too many variables!

I'm beginning to appreciate living in a concrete bunker. Its all one variable and there is nothing you can do about it: so simple.

I take you are a bi-product of the cold war era Fred?

Hi Tom,

If we put all of this in context, the actual floor-borne mechanical vibration from a sub or speaker is a relatively small component of the total output from a powerful subwoofer and/or full-range loudspeaker. It's the acoustically generated energy in the bass combined with the room's standing waves that set all kind of things in a room resonating, including the sheetrock, studs and wooden floor, often to an annoying degree at high volume levels (especially for easily annoyed neighbors in nearby apartments or condos).

Of course, as pmbuko notes, isolation pads would absorb mechanical energy but do nothing for the bulk of acoustical energy a subwoofer or speaker generates.

Regards,
Alan

Hanging speakers from cables could be a bad idea. If the speaker hits just the right notes then it would excite the tensioned cable supporting it and cause it to vibrate.

Back in the 70's, I met a guy named Tom.. He was in a band and played guitar. The story goes, he went on to "higher" education studied music theory using keyboards mostly... thought he understood it all got bored and became an airline pilot.

The interesting part and I have seen this happen... he could find the harmonics of a structure (the house we were partying in) and if he wanted to shake the sucker to the ground... it was amazing! He would just play around till everything was shaking. If I recall correctly, he had a sun amp. would turn it towards the wall and just go at it.

or it was the acid and a good story!

The reason my front stage is insulated (some use sand) is to reduce the bass from the sub traveling to the user through the floor.