In article , "Serge Auckland" wrote:

"Don Pearce" wrote in message
...
On Fri, 6 Feb 2009 09:30:41 -0800 (PST),
wrote:

On Feb 6, 9:36 am, "Serge Auckland"
wrote:
"David Looser" wrote in message

...

"Karl Uppiano" wrote in message
...

Fortunately, long wavelengths and large excursions are mostly in the
low
frequencies, which tend to have minimal out of phase characteristics
(which is why subwoofers are practical).

More to the point as far as subwoofers are concerned, the ability of
human
hearing to determine the direction of a sound source becomes less
effective as the wavelength lengthen, becoming pretty well
non-existent at
frequencies of 50Hz and below. So not only does it not matter if these
frequencies are presented in mono, but it doesn't matter much where
the
subwoofer is in relation to the subs either.

David.

That has not been my experience. I ended up with two subs, each sitting
alongside each main, as I couldn't get on with one only. If the sub was
centred between the two loudspeakers, that wasn't too bad, as at least
the
extreme bass was mono, but when the sub was to one side, it was most
peculiar.

That's primarily because most subwoofers aren't: they tend to have
substantial output at higher frequencies anyway. The very low
frequency material could well be in mono, but stuff an octave or
two higher could have substantial difference information, and
that can easily find its way through many subwoofers.

That was indeed my own experience until I built my own subwoofer. It
turns over at about 50Hz, and is impossible to localize in the room by
sound.

d
--
Pearce Consulting
http://www.pearce.uk.com

My subs (Meridian D1500) are designed to work with the D5000 mains, and have
a 2nd order Butterworth response at 36 Hz. And yet, having one to the side,
it's very obvious where the bass is coming from.

I built a single sub for my son some years ago, and it had to integrate with
a pair of small Missions, which meant a rollover around 70Hz, 2nd order.
That was very noticeable, and disturbing when not between the main
'speakers. Either my room acoustics are peculiar, or I'm particularly
sensitive to bass positioning. Perhaps to make up for my complete
insensitivity to cables, CD players, amplifiers, spikes, cable lifters etc
etc.

I suspect some crossovers having cutoff at some point, but may not
be true at the second and third harmonic, depending how good
the design is. Easy on active crossovers but requiring Zoebles otherwise.
I can sometimes hear spyder noise and of course wind noise.
In general I would prefer using a bandpass box, but you still have to
watch wind noise.

greg