Bass directionality etc.

[Kongen]

Hello, i'm wondering when directionality, phase problems and perhaps other issues arise in a subwoofer - my reason far asking is that i'm considering building a three-way speaker - the mid will start rolling off around 250 hz and was wondering if i could build it as a small sattelite with mid and tweeter, and move the bass into the corner of my room in its own enclosure. To make things clear - i would build two small sattelites and two subs which would probably be placed near the wall behind the sattelites. Probably in a corner or rather close to one.

I'm in doubt when it comes to phase issues - how do these affect the overall sound ? Do they exist at all at frequencies this low ? am i wrong in assuming that the phase issues stop existing at some point - when the wavelength become long enough ? when is this and is this very dependent on the room in which the speakers play.

Directionality is an issue - but again directionality stops being an issue when frequencies get low enough - but how low ? we are still talking stereo-subs so does this make a difference ?

are there any other issues to be aware of ?

thank you...

[badman]

Compare the wavelengths of the frequencies you're concerned with (approx XO frequency +/- 1 octave) and the space you're considering between drivers.

Short answer- for 250Hz XO, keep the sub fairly close to the satellite.

[sreten]

Hi,

250 Hz = 1.3m wavelength - not long enough.

/sreten.

[zigzagflux]

Originally posted by badman
Short answer- for 250Hz XO, keep the sub fairly close to the satellite.

I'll second that, based on listening tests. I currently use a set of MTM speakers with stereo 10" woofers in separate boxes. My crossover point is a full octave lower, 126Hz 6 dB on the satellites, and 85Hz 12dB for the woofers.

Satellites are mounted on top of the woofer boxes, with some isolation pads. Height was perfect to bring the tweeters up to ear level.

The higher I went up in frequency on the woofers, the more separation I could hear (a bad thing). At present, it is very difficult to tell I have woofers; it sounds like the bass is coming from the satellites (a good thing, IMO).

As I increased the crossover freq. on both of them with the DCX2496, I could hear more and more that the bass was coming from the floor, not the satellites. Imaging got messed up. My conclusion is that 250 Hz is quite directional. Hearing a bass guitar note coming from two locations just isn't natural.

Oh yeah, I've also tried placing the woofers further back, further apart, etc. While I DO get an increase in bass and greater efficiency, I do NOT get an improved blend between them and the satellites. I guess it's a matter of opinion (as is much in audio).

Good luck. Never hurts to try.