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Old 6th October 2012, 09:53 AM   #201
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Originally Posted by 6.283 View Post
Every dipole speaker can do this where

a. The sub is "separated" from the rest
b. the sub goes up to your desired F.

To get to the Schröder F (or a little beyond) with reasonable output you might require already 2 drivers per side.
Yes but my point was that it's not done. Being able to adjust mode coupling is one of the biggest advantages of a dipole but it's not utilized. Recognize any of these dipoles?

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Old 6th October 2012, 10:11 AM   #202
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Originally Posted by markus76 View Post
Again, the topic was LF. One can make the dipole null "point" in different directions by rotation. This shouldn't change the direct sound significantly but it will alter the way the dipole couples to modes.
Markus,
I have done that with my earlier dipole speakers. Significant altering of modes will only start if you rotate the dipole at least ~45° against the mode axis. You don't want to switch off single modes, but probably want to attenuate one mode and raise another mode at the same time. Inevitably that led me to a 45° toe-in of the LF dipoles - every time. And it did change the direct sound significantly!
At 45° an ideal dipole should be 3 dB attenuated compared to 0°. If you keep the mid/high part of the dipole at 0°, you have a matching problem. JohnK discussed that at Power matching
Again the easiest way to solve it is to rotate the mid/high part of the dipole too - which has some advantages in itself. In the end I never had a convincing reason to rotate the dipole LF part independently from the upper part.

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Old 6th October 2012, 10:19 AM   #203
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Significant altering of modes will only start if you rotate the dipole at least ~45° against the mode axis.
45° is a lot, probably already too much. Did you try different source locations and rooms?
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Old 6th October 2012, 10:23 AM   #204
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I have four separate dipole woofers, where two are located at the sides and almost 90 degrees rotated. This concept works very very well indeed. The resulting response is smooth and free from dips and bumps from room modes.
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Old 6th October 2012, 10:31 AM   #205
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Stig, if I remember correctly, the woofers are located pretty close to the listening position?
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Old 6th October 2012, 10:36 AM   #206
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Well.. sort of. They are placed close to the front and side walls actually.
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Old 6th October 2012, 10:45 AM   #207
Rudolf is offline Rudolf  Germany
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Originally Posted by markus76 View Post
45° is a lot, probably already too much. Did you try different source locations and rooms?
Mainly one room, but dipoles located at the long wall and the short wall. Measured results were different of course, but the conclusion the same for both installments. You find measurements and a discussion (in German) of the short wall version at Dipole und Kontrolle der Raummoden, Lautsprecher - HIFI-FORUM
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Old 6th October 2012, 10:51 AM   #208
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Well.. sort of. They are placed close to the front and side walls actually.
Found the floor plan. Looks like you're listening with an opening angle >60°?
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Old 6th October 2012, 10:52 AM   #209
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Since there is discussion about position I thought I would post this quote from one of my web pages:

Dipole:

Consequences of source position (independent of orientation):

There will be no contribution to the in room SPL from an axial mode aligned with the dipole axis when dipole is centered at a pressure anti-node (velocity node) for that mode.

Additional consequences due to directionality (orientation):

There will be no SPL contribution from any mode in the direction orthogonal to the dipole axis.


Monopole:

Consequences of source position:

There will be no SPL contribution from a mode when placed at a position where that mode has a pressure node.

Additional consequences due to directionality:

Being omni directional, a monopole has no consequences arising from directivity.

Cardioid:

Consequences of source position:

In general a cardioid is not limited by position alone with regards to modal contributions to the SPL.

Additional consequences due to directionality:

There will be no SPL contribution from a mode when placed at a position where that mode has a pressure node if it is also oriented such that the mode is orthogonal to the axis of the cardioid.


These are under idealized conditions but give a sense of why different woofer formats behave so differently. Also, recognize that it is a two way street. A woofer may excite a mode very strongly but it will have no effect at the listening position is the listener is sitting at a pressure node for that mode.

Also, regarding separating the main speakers and woofers, that was one of the features of the Mini:

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Old 6th October 2012, 10:54 AM   #210
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Originally Posted by markus76 View Post
Found the floor plan. Looks like you're listening with an opening angle >60°?
It has been changed somewhat since then. The listening angle for the main dipoles is close to 90 degrees, and the side woofer towers are at almost 90 degrees angle from the listening pos. The woofers are closer to the walls as well.
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