Understanding low-frequency reproduction....room or speaker


Hi all, I have a question about low-frequencies and whether my speakers are doing it or its my room.  Allow me to explain...

I own BMC PureVOX speakers, and in our living room space approximately 16x17 with open hallways and a half-wall (not a fully closed square area) if I play the opening track of the "Titanic" soundtrack the low-frequency effects will shake my wife's trinkets off the wall if I'm not careful with the volume.   This is with the speakers out into the room, about 8 feet apart, not close to side walls and at least 2+ feet from the wall behind them.

Just for info, the PureVOX is a bipolar speaker, aluminum cabinet, sealed enclosure, with (2) 6.9" kevlar drivers in addition to the AMT tweeters.  BMC does not provide frequency specs, I assume this is because measuring frequency response is less relevant with bipolar designs.

We recently went to hear the new B&W 802D3, just out of curiosity, and when listening to that same track the 802D3 barely produced any of that low-frequency effect.   This surprised me, because just in terms of size (and price) the 802D3 is in a different league - it's much larger than the PureVOX.

In trying to understand, I pulled up one of those websites where you can listen to low-frequency tones to test audio system boundaries, and on the PureVOX the test tone becomes audible in between 20hz and 30hz.   

So my question is...does this mean the PureVOX actually goes that low, OR is this all just a function of my living room size and configuration, which also explains why my speaker did something the much-larger 802D3 couldn't do?   In my smaller office, I know my Wilson Benesch Arcs sound fuller when they're closer to the wall, so I at least superficially understand wall proximity and room reinforcement and want to understand if that's also what's happening with the PureVOX.


128x128bcgator

Showing 3 responses by georgehifi

maplegrovemusic

How does one isolate the speakers from a "suspended" floor ? Thought that’s what the spikes are for .


Many get this confused, spikes couple the speaker or stand to the floor, this is fine for cement slab floors, and the best. 

But with any suspended floor the speaker or stand should be de-coupled from it to get the best bass response, as the manufacturer would have voiced it. As they would have been crazy to voice it spiked into a suspended floor acting as a sound board to any bass notes from the speaker.

To de-couple from a suspended floor you need to use an isolating puck or device like a sorbothane filled disc. Like these which you can still use your spikes with 

"Cone/Spike Decoupling Glider"  that are half way down the page.

http://herbiesaudiolab.net/spkrfeet.htm

Or you can substitute your spikes for these "Threaded Stud Glider " a bit further down the page. 


Cheers George

bcgator 

davehrab, I want to clarify something - and I think George had the same idea - the bass response I’m getting, and the resonance, is absolutely not a problem.  It’s not something I’m trying to cure, or eliminate.  

 I think you probably lucked out with a room standing wave problem that just happens to be just below the natural roll off of that 6.9" bass driver, giving you another octave lower perceived bass. Shh it’s free don’t tell anyone, and whatever you do don't move the speakers or you may loose it.


Cheers George 

First of all you need to look at the way speakers need to be supported correctly on the floor or if they are on stands.

Never spike a speaker (floor stander)or (stand mount) into a suspended floor, as you only make that floor a sound board for the low frequencies, and that will muddy up or ruin your bass. The speaker need to isolated from a suspended floor.

The only times a speaker (floor stander or stand mount) should be spiked into the floor, is if that floor is a cement slab, and not be able to act like a sound board. Start with this first, then positioning.


Cheers George