Auralex SubDude vs. Spike feet

The following quoted claims are taken straight from the websites of manufacturers of these devices.

The Isolation Claim: ‘Its purpose is to prevent sound from transmitting through your subwoofer to surrounding surfaces. Subwoofers create big vibrations (low frequencies) that you can feel in the floor and in objects placed nearby. When the source of the vibrations is coupled directly to the floor it causes these objects to vibrate or resonate…’

The Truth: The source of these vibrations is the movement of the driver cone creating pressure waves in the room. The claim would only be true if you coupled the driver cone to the floor. If the cabinet panels vibrate enough to cause the floor to vibrate the speaker is defective.

The Decoupling Claim: ‘Isolators for your speakers…will decouple your speakers from the surface they rest upon, resulting in a more pure, accurate tone. Low frequencies will be projected and will no longer lack the definition you desire. Mid and high frequencies will be crisp and intelligible. Rattles and resonances will be a thing of the past.’

The Spike Claim: ‘By rigidly coupling a loudspeaker enclosure to a floor by means of a spiking system, it is possible to dramatically improve clarity, stereo imaging and bass response. This is very apparent with subwoofer systems.’

The Quandary: These sources claim the same benefits from coupling and from decoupling. Who’s telling the truth?

The Truth: Both are lying. Isolation and coupling makes no difference. To test this I measured the response of my THT and my David with the test mic in the room, in the next room, and in the room below, with the cabinet sitting on the carpeted floor, on four inches of high density acoustic foam, on rubber feet and on spikes. I’d post the measured results for each set of comparisons, but there would be no point. In each case the measured responses of the four options were identical.
Note that this was on a carpeted floor. There may be some slight benefits to isolation devices or rubber feet on a bare floor, or on a bare shelf or stand. But you never want a bare floor, it’s an acoustical nightmare. If you only have area rugs in your listening room stick a piece of felt carpet padding, a carpet scrap or rubber feet under your speaker. If you're using bookshelves on a bare shelf or stand small rubber feet or felt pads are all you need to prevent spurious vibrations.

The Endorser Claim: ‘I tried them and they work, I know what I’m hearing!’

The Truth: The first thing you learn in an acoustical engineering course is that you don’t know what you’re hearing. If you did you’d be able to listen to a speaker, take pencil and graph paper in hand, and draw a frequency response chart, THD chart and waterfall plot, all with 1/24 octave resolution and 1/10dB accuracy. Our ears just aren’t that good, not by a very wide margin. But our imagination works very well, and that clouds our audio judgment, leading to placebo effect. In short, if you think something will make a difference in the sound, it will.


One item that's always missing from both manufacturers and owners claims are measured results, before and after. We often say 'If you don't have a picture it didn't happen'. In this case that picture is measured in-room response. When virtually anyone who's really serious about their sound has REW or the like that's not a lot to ask for.

For an in depth examination of why we really don’t know what we’re hearing check out this video:
http://www.youtube.com/watch?v=BYTlN6wjcvQ

I'll field this one...

Depends upon what your definition of "performance" is I suppose. I have a Gramma, and it definitely quieted down things that were rattling in my room (like the blinds). The Auralex stuff is pricey for what you get, but it made a difference for me.

That pretty much covers it. Speakers are the most critical, as they're mechanical devices, and the last link in the chain. No matter how good the source it won't sound good through a bad speaker. Electronics reach the point of diminished returns very early on; you'd be surprised to find out how many $2k AVRs use the same internals as $500 AVRs. Wire is wire.

Stuff vibrates because your sub is sending out ten to fifty foot long wavelengths that will cause large surfaces, such as floors, walls, ceilings, doors and tables, to vibrate. Smaller objects on or hanging from those surfaces will also vibrate. Putting the sub on a platform does not stop the transmission of those long wavelengths, so it won't stop the vibrations they cause.

The Gramma definitely cut down on the sympathetic vibrations I was getting, so it's proven quite beneficial for me. Does the bass sound "cleaner" because of it? Empirically yes, but that's a bit more difficult to quantify. Since virtually all the objects in my room are no longer vibrating it can't help but make the overall sound quality -- or at least the viewing experience -- that much better.

I've noticed zero benefit from my great gramma.

I put 1" thick foam/felt under the feet of my outlaw plus - not for sound improvement, but because my floor is not perfectly flat and I needed some compliance so the sub would not vibrate on the floor. I think subs and other speakers should only have three feet.

Funny how here most consider them snake oil. but if you go to bluray.com there is pages of people that have built them and swear they made there $100 subs sound like a million bucks. Im with Bill I will save my money. like he said my room doesnt rattle hardly at all but when i go upstairs to the room above I swear on some movies the floor jumps about an inch. No pad is going to stop that.

I am still learning, but that seems to make sense though.

I do not want to put words in Bill's mouth, but if I understood his posts correctly, he was saying that a nice and well-constructed sub should not be producing those vibrations in the first place - if it is, then there may be some sort of fault with it.

If you have a $100 sub, the likelihood that it may be poorly constructed is higher, and if so, isolating the sub with a subdude (or whatever) might really have a positive effect. However, this is essentially a way to remedy a symptom rather than absolve the actual problem (but maybe that is all you want to do).

If the hype was true that couldn't happen unless the sub was bolted to the ceiling.
Those who make isolation devices are no different than the cable crooks or any of a hundred other outfits who are interested in one thing and one thing only: Your money. You have it, they want it. And like all snake oil merchants the less you understand about how audio actually works, the better a mark you are. Caveat Emptor.