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.


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Showing 4 responses by bcgator

@nonoise 
Thanks for the input, I think I was surprised given that the speakers don't have big cabinets - they're really just slightly oversized monitors - and they're out into the room away from the walls, and toed-in so that even the rear firing driver on one points off into a wide-open space.   They're not getting much help from nearby walls, or at least I didn't think they were but maybe that's not the case.

@georgelofi 
I don't have suspended floors, and the speakers are on slabs, not spiked.  But that's moot - I don't feel I have a solidity problem, or a positioning/toe-in problem.  I don't have muddy bass, I just have more than I expected given the size of the speaker, hence the question.
davehrab, thanks for that excellent post.  This is where I get confused...I don't have a technical background so I while I enjoy music and audio equipment I don't understand the technicals as well as most of you do.  Nonoise's post made sense to me, that the speaker by itself isn't producing the low-frequencies, it's doing so in combination with the room and the walls.  What you seem to be saying is that the room and walls aren't creating the low frequency, they're simply responding to what the speaker is outputting and if the frequency of the speaker's output matches the wall's resonant frequency I get the LFE that I hear and feel.  Am I following you correctly?  
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.   The purpose of my question wasn't to complain about the low-frequency effects, or figure out how to remove them.  The purpose of my question was to understand how I was getting such great bass response from relatively small speakers (albeit sealed cabinets, and bipolar), in a room that I wouldn't consider small or closed-in, and with the speakers out in free space away from the walls.  I've had larger speakers in that same space, with bass response not close to this.  As I mentioned, BMC doesn't publish frequency response for these, and I figured from the size that if they got down to the 40hz level I'd be happy with them.  But it seems they're going lower.  I just didn't understand if it was the speakers themselves, or as Nonoise mentioned I was just getting lucky with the way this particular speaker was interacting with this particular room.  
So far I've been lucky with placement...I've had fun playing with the bipolar configuration of the speakers and trying zero toe-in, extreme toe-in, even toeing them outward and pointing the rear-firing drivers upwards towards each other which creates an amazing wall-of-sound effect.   But this hasn't changed or hurt the bass response...no matter where they're pointing, I get nice tight bass that seems to dip lower than I expected given the size of them.  Thanks to everyone for the input.