# Speaker cabinet size and bass question



## sharkane (Oct 4, 2007)

In building my HT I want to put two floor to ceiling columns either side of the screen both to house the speakers and the audio equipment. The speakers I am currently using are B&W with two 8 in. woofers and a tweeter in a roughly one foot square by 3 feet high enclosure.

What I was wondering was if I made these columns into huge speaker enclosures say 2 feet square by 6 feet high would I get an increase in bass or would the sound just muddy up.

I'd love to upgrade to better speakers, but just blew the budget on projector and PS3.

Kane


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## Anthony (Oct 5, 2006)

Chances are, the crossover in those B&W's was chosen to compensate for that exact baffle placed roughly a certain distance from the back wall. By enclosing it in a pillar, you'll be doing two things: adding resonance chambers and widening the baffle, which will affect the response.

Now you could damp the resonance chambers in the column and possibly rework the baffle compensation circuit in the crossovers, but that's probably more trouble than it's worth.

B&W put a lot of R&D into those speakers, just enjoy em already


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## ISLAND1000 (May 2, 2007)

It'd screw things up and I'm not saying you'd couldn't find a way to do it right but it wouldn't be cheap.


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## Joe L. (Jan 23, 2007)

The amount of "bass" at a given frequency is dependent on the enclosure internal volume and tuning (if it is a ported enclosure)

With everything else equal, your proposed column enclosures would be eight times the internal volume. 

The actual SPL (sound-*pressure*-level) able to be produced will depend largely on the amount of air your woofers can displace. In other words, they need to pressurize the air in the room each time their cone moves in and out.

If the original manufacturer did their job right, they designed the woofer, box, and amplifier to allow the driver to reach its excursion max without going over the max (bottoming out, or reaching the physical limits of the spider and/or the surround.)

If the driver is already reaching its excursion max, it is already displacing as much air as it can, and therefore pressurizing the room as much as it can... 

All that means it is probably getting as loud as it can within the physical design of the drivers. (To get louder/lower bass you need to displace more air with bigger and/or higher excursion drivers)

Putting your current woofers in a larger box will not make them louder, but instead more efficient. (they need to pressurize the air in the enclosure when the cone moves inward and it will be easier with the larger volume of air behind them than with the original boxes, since it has to pressurize the greater volume less, for the same movement of the driver cone)

The other effects that were mentioned by others will also occur... the crossover, if well designed, will have baffle-step-compensation built in. Changing the front baffle width to make it wider will make it sound very different in the midrange. Putting the entire speaker closer to the wall will also affect the balance. (you would need less baffle step compensation (or none) designed into the crossover)

So... If you tried as you described, built new enclosures and kept the audio volume low, the relative SPL of the bass will be louder than the midrange and treble... and not matched at all in their efficiency. If you increase power, the woofers will reach their excursion max before the tweeter is anywhere near as loud as in the old enclosure. Unfortunately, the woofers would not be able to get much louder, if at all, than they are in the current enclosures. (they can only displace so much air) If you try to get the midrange/treble to the same level as the old enclosures, the woofers are likely to bottom out.

Joe L.


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