I'm starting my research on building a center channel. It seems like the most popular designs are MTM (2/2.5way) or WMTW (3-way) type of designs. I also read a lot that MTMs have pretty crummy off-axis behavior. It seems like people are refering to nodes and lulls created by the 2 element "line array" of the Ms for this conclusion. But if the CC is horizontal, wouldn't it mean that you are always listening on-axis? My listening angle would be something like +/- 30deg.
thx.
--
Danny
thx.
--
Danny
At c/o a vertical 2-way MTM can be treated as a 3 element line array.
Horizontal dispersion is not a problem, but vertically due to the
3 elements dispersion has more nulls than a MT 2-way.
(Typically 4 versus 2, and the angle of the 1st null is smaller)
When turned on its side, so the vertical dispersion becomes
the horizontal dispersion basically the extra nulls are not
a good idea in terms of horizontal seating position coverage.
For a horizontal box :
--T--
WMW
Is the way to do it, have vertical MT array with woofers either side.
sreten.
Horizontal dispersion is not a problem, but vertically due to the
3 elements dispersion has more nulls than a MT 2-way.
(Typically 4 versus 2, and the angle of the 1st null is smaller)
When turned on its side, so the vertical dispersion becomes
the horizontal dispersion basically the extra nulls are not
a good idea in terms of horizontal seating position coverage.
For a horizontal box :
--T--
WMW
Is the way to do it, have vertical MT array with woofers either side.
sreten.
Ok, I just missed something. I've also been reading up on line arrays and I thought the papers indicated increased sensitivity on-axis with line arrays while the lulls started appearing off-axis. The sound field becomes more like a cylinder so any point vertically on-axis should be the same as any ohter point. Is this wrong? That's the way it's indicated in the vpr excel program.
Timn8ter said:It's interesting how much it cleans up when you add a 4th source at nearly the same point as the center source. This seems to simulate what would happen if you add a mid-ranger under/over the tweeter. This app is way
Not really, adding a dominant source which is what you are
doing effectively will prevent the deep nulls of equal sources.
I can't see your second point, c/o frequencies are quite different.
The point of the
--T--
WMW
arrangement is that at M/W c/o wavelength is far greater
than spacing, and at M/T c/o you have a vertical array.
sreten.sreten said:
The point of the
--T--
WMW
arrangement is that at M/W c/o wavelength is far greater
than spacing, and at M/T c/o you have a vertical array.
But from what you've said, horizontal or vertical arrays should suffer from the same interferance pattern regardless of orientation.
So... let me see if I can explain my confusion better so I can get fixed in the head..
If you were to have an array like so:
S
S
S
...
S
Then (supposedly, according to the write papers on line arrays) if you listen on-axis.. so that basically means the speakers are pointed at your head (toed in a bit), you get increased sensitivity but if you are listen slightly off to the left or right (say 30-deg), off axis, then you'll start to move into a lull, at freq >= ctc spacing, which is caused by interference patterns of the point sources. However, it doesn't matter what height you're listening at as long as it's comparable to the array, so not extremely above or below it.
By this logic, if you place it on it's side:
SSS...S
I would reason that those lulls get generated close to the floor or towards the ceiling.
But... It was stated that a horizontal array will cause interference patterns if you were to move left or right of the array (apparently while still maintaining your head at the same level as the speaker) and this was shown in the applet. So I stand to reason that if you took this horizontal array and turned it vertical, then you should have the same interference lulls if you were listening anywhere other than at the center height of the array.
So, there is a contradiction that I am not following I guess.
Sorry if I'm missing something completely obvious.
If you were to have an array like so:
S
S
S
...
S
Then (supposedly, according to the write papers on line arrays) if you listen on-axis.. so that basically means the speakers are pointed at your head (toed in a bit), you get increased sensitivity but if you are listen slightly off to the left or right (say 30-deg), off axis, then you'll start to move into a lull, at freq >= ctc spacing, which is caused by interference patterns of the point sources. However, it doesn't matter what height you're listening at as long as it's comparable to the array, so not extremely above or below it.
By this logic, if you place it on it's side:
SSS...S
I would reason that those lulls get generated close to the floor or towards the ceiling.
But... It was stated that a horizontal array will cause interference patterns if you were to move left or right of the array (apparently while still maintaining your head at the same level as the speaker) and this was shown in the applet. So I stand to reason that if you took this horizontal array and turned it vertical, then you should have the same interference lulls if you were listening anywhere other than at the center height of the array.
So, there is a contradiction that I am not following I guess.
Sorry if I'm missing something completely obvious.
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