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?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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.
Rudolf
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
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:
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:
An externally hosted image should be here but it was not working when we last tested it.
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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Thanks Rudolf. Did you also test monopoles? That room looks really ugly (acoustically). Looks like John's right and the solution is not in the source type.
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I think the rotation is not the biggest advantage but the biggest advantage is the cleaner impulse response dipole produces in a small room within the first 100-200 ms.
For the input of this:
An externally hosted image should be here but it was not working when we last tested it.
Dipole response:
An externally hosted image should be here but it was not working when we last tested it.
Monopole response:
An externally hosted image should be here but it was not working when we last tested it.
Source type is the biggest effecting factor, but you must use the relevant metrics to realise this.
Since, if you take old fashioned long time window FFT the difference between monopole and dipole gets smaller. In that case they are very different but it's getting harder to decide which one is better.
No. Haven't had a monopole woofer for years. But since you have both types at hand now, we finally can rely on your test skills
In fact it is ugly looking - but not acoustically
With better positioning of speakers and listener in the room (a la john k...) the response is a lot better now.Right and wrong imho. Of course you can make a dipole out of two monopoles with inverse phase anytime. In that regard source type doesn't matter. But ...
there have been quite some people asking me for my opinion/advice WRT a dipol bass solution in their room. If they were already pleased with their monopole solution and just wanted to satisfy their curiosity about dipoles, final reactions where mostly like this: "Now I see, what this fuss is all about, but I don't really see enough reason to change what I already have."
But there was another group of people who had moved their monopole (sub)woofers or speakers to every possible position in the room and never found a satisfying sound. Without any exception those people were incredibly happy about the change, which the dipole made for them. Sometimes the solution is in the source - at least practically.
Rudolf
In my case I do not feel that I have a need but haven't looked into this further.
I once had a standalone 12" H-Frame that I had been pushing throughout the room and turned it as well to check how the sound changes but I did not do measurements. Anyway, the sound did diminish noticeably at the listening position when toed in too much.
That sounds like a nice offer !
Then you can add one to the list. That was true in my old flat.
No. Haven't had a monopole woofer for years. But since you have both types at hand now, we finally can rely on your test skills
How convenient, isn't it
Slight delay though, my carpenter is on vacation.In fact it is ugly looking - but not acoustically
Right and wrong imho. Of course you can make a dipole out of two monopoles with inverse phase anytime. In that regard source type doesn't matter. But ...
there have been quite some people asking me for my opinion/advice WRT a dipol bass solution in their room. If they were already pleased with their monopole solution and just wanted to satisfy their curiosity about dipoles, final reactions where mostly like this: "Now I see, what this fuss is all about, but I don't really see enough reason to change what I already have."
But there was another group of people who had moved their monopole (sub)woofers or speakers to every possible position in the room and never found a satisfying sound. Without any exception those people were incredibly happy about the change, which the dipole made for them. Sometimes the solution is in the source - at least practically.
Rudolf
Maybe they did something wrong
Double Bass Array (DBA) - The modern bass concept!What I'm after is beyond monopole/dipole but about low modal ringing and smooth frequency response.
In those cases the dipole solved the problem with the least added amount of material and man hour. Effectively the better engineering solutionMaybe they did something wrong
Yeah, finally another breakthrough brought to us from the Swiss
But honestly, every fresh look at the problem is laudable.
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