Re: Bass speaker/cabinet question

Mike Rieves <mriev@xxxxxxxxxxx> wrote:
"Brian Running" <brunning@xxxxxxx> wrote in message
news:b8Aml.185$cW.46@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Mike Rieves wrote:

The reason for having the drivers set up like a standard 4X10
setup is that they couple at low frequencies to act llike a single
piston the size of all four speakers, so you gain some efficiency
on the bottom end.

No, because you get the coupling effect no matter how you arrange the
drivers, as long as they're within close proximity to one another.

No, Brian, the farther the speakers are apart, the less they couple,
and the bottom and top speakers are far enough apart to lose
considerable coupling. Four speakers arranged in a 2x2 square
arrangment couple best, enough for a measurable and audible
difference. Try it if you don't believe it.

>The advantage of aligning them vertically is that you get narrower
dispersion in the vertical axis, which is desirable in most places we
play, because our audiences are usually in a horizontal plane in
front of us.

I don't disagree with this, you're right, and if the 2x2 square
arrangement is too bass heavy, a vertical array may sound
considerably better.

A square 4x10 will have equal dispersion in the vertical and
horizontal axes.

Yes, and if the 2x2 square cab is on the floor, it will mean even
more boost in the low bass.

The taller the cabinet, the lower the frequencies at which the
dispersion control works. A vertical 4x10 would control dispersion
down to about 280 Hz, so it would be effective in the range of bass
guitar harmonics that create "punch."

A vertical 4X10 will also have somewhat ragged response due to the
top and bottom drivers being so far apart. The radiation pattern from
the top and bottom drivers will cause some phase cancellation at
frequencies where they are a quarter wavelength apart, around 160 Hz
and multiples of that. Don't get me wrong, lots of folks like the
sound of vertical arrays, and they have all the advantages you've
mentioned, but at low frequencies the vertical array will not be as
efficient as will a 2x2 square array. In short, the 2x2 square array
array will act as a single speaker the diameter of the width of the
array at low frequencies, the 4x1 vertical array will not. I'm not
arguing that the 2x2 array will sound better, it very well may
not, but it will have higher efficiency at low frequencies.

There isn't any phase cancellation on-axis (i.e., if you're standing in
a direction that's perpendicular to the face of the cabinet).

If you're off-axis, the frequencies at which phase cancellation is most
prominent depend on how far off-axis you are. It depends on whether the
path lengths from the various speakers to where you're standing differ
by half odd integer multiples of the sound wavelength. It's destructive
interference.

Given that people are usually on a dance floor in front of an amp, it's
unlikely that phase cancellation from a vertical cabinet ever becomes an
issue in practice (unless you like to listen from the balcony).

In this context, I fail to see the validity of the statement "the
farther the speakers are apart, the less they couple, and the bottom and
top speakers are far enough apart to lose considerable coupling." If
you're standing away at a distance that's many times the speaker
separation and your ears are basically in the same vertical plane as the
cabinet, you hear all the speakers in phase with one another, period.


.

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