Measured monopole and dipole room responses
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 12th October 2012, 01:48 PM #341 markus76   Banned   Join Date: May 2008 Location: Switzerland Amen.
Omholt
diyAudio Member

Join Date: Jun 2009
Quote:
 Originally Posted by gedlee The difference between a monopole and a dipole (at modal frequencies) can be stated quite simply: A dipole excites the modes velocity while the monopole excites the modes pressure.
What do you mean? Given sound velocity is fixed.

 12th October 2012, 03:26 PM #343 markus76   Banned   Join Date: May 2008 Location: Switzerland Monopoles are pressure sources and dipoles are velocity sources.
 12th October 2012, 03:32 PM #344 Rudolf   diyAudio Member     Join Date: Mar 2003 Location: Germany A monopole placed in a room corner excites all room modes maximally - thereby delivering maximal energy into the room. A dipole placed in the same room corner excites all modes minimally – delivering minimal energy into the room. A monopole placed in the middle of the room excites the first degree room modes (half wavelength between walls) minimally. A dipole in the same position excites them maximally – except the modes perpendicular to the dipole axis. Rotation of a monopole in the room doesn't change anything. Rotation of a dipole in the room can excite or attenuate a room mode relative to room modes perpendicular to it. This should explain why measurements of a dipole and a monopole at the same position in the room can't decide on the best aptitude for either M or D for the room. Even if one can find different optimal placements for M and D in the same room, they need not be the best placements in another room of different size and proportions. Rudolf __________________ www.dipolplus.de
gedlee
diyAudio Member

Join Date: Dec 2004
Location: Novi, Michigan
Quote:
 Originally Posted by Omholt What do you mean? Given sound velocity is fixed.
"Velocity" here refers to the "particle velocity" or the velocity of motion of the particles in space. This velocity can be any value from zero and up. The velocity of sound is the speed at which the pressure disturbance moves and is not the same as the velocity at which the particles in space oscilate.

This is exactly like voltage and current in a circuit. The pressure is like voltage and the current is like the particle velocity. We know that the electrons in a wire don't move back and forth very fast, in fact the actual motion about the mean is actually pretty slow, but the electric field that drives the electrons moves at near the speed of light.

And thanks John - sensibility is finally creaping into this discussion. But it's all "theoretical" and has no relavence to "beliefs" based on "what I hear".
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Last edited by gedlee; 12th October 2012 at 04:15 PM.

Elias
diyAudio Member

Join Date: May 2003
Location: Suomi
Quote:
 Originally Posted by john k... The only thing that can be said categorically about dipoles comparedf to other sources is that they can not pressurize a room, and this is what I think drives listeners to prefer a dipole woofer.
What is the connection of the pressurisation ability and the modulation reproduction ability ?
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Rudolf
diyAudio Member

Join Date: Mar 2003
Location: Germany
Quote:
 Originally Posted by Elias What is the connection of the pressurisation ability and the modulation reproduction ability ?
Sorry to say that, but the connection is:
We are still lacking a controlled, fair and equal comparison, that shows categorically a better modulation reproduction ability of the dipole. Either by theory or by measurement.

Rudolf
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 12th October 2012, 06:21 PM #348 badman   diyAudio Member     Join Date: Sep 2003 Location: Sunny Tustin, SoCal Perhaps part of the advantage of dipole subs is in the directional nature above the passband, effectively creating a steeper filter on the power response than the filter on the axial? Just a brief thought. __________________ "The dawn of Bose created the "Man Cave" and reduced testoterone levels worldwide by 18.5 per cent" Peteleoni
_Wim_
diyAudio Member

Join Date: Nov 2001
Location: Belgium
Quote:
 Originally Posted by gedlee When I do EQ for my clients I often find that turning on one of the subs actually reduces the mean sound level in the room. Thus, this sub is working as a sink at that frequency, i.e. an active absorber. In this example then it would be very possible that a multi sub implimentation was reducing the modal decay.
How do you setup this EQ. Do you start with one sub and EQ all major peaks (leaving the dips alone), then add a second sub and again EQ the peaks, add a third sub...

Or do you use something proprietary?

 12th October 2012, 07:15 PM #350 Wavebourn   Designer & Technologist diyAudio Member     Join Date: Sep 2006 Location: Pleasant Hill, CA Is it enough to measure PH difference between apple and orange juices to tell why they taste differently? __________________ The Devil is not so terrible as his math model is!

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