What is the ideal directivity pattern for stereo speakers? - Page 190 - diyAudio
 What is the ideal directivity pattern for stereo speakers?
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 Multi-Way Conventional loudspeakers with crossovers

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diyAudio Member

Join Date: Dec 2004
Location: Novi, Michigan
Quote:
 Originally Posted by speaker dave Finally. The answer we've all been waiting for. We can all go home.
You beat me to it. I read that comment and thought the same thing.

diyAudio Member

Join Date: May 2003
Location: Suomi
Quote:
 Originally Posted by KSTR Exactly. I've extensively played with static 2-->3 rematrixing, simplest form is : C=L+R, L'=L-0.5R, R'=R-0.5L, and +45, 0, 45 deg angles, known as Trinaural. ... - Klaus

Klaus !

Are you sure about the equation ? For C I think C = 0.5L + 0.5R ?

- Elias
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Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets

 8th November 2011, 01:00 PM #1893 diyAudio Member     Join Date: Jul 2007 Location: Central Berlin, Germany ^^ Elias, you're right, thanks for correcting that. The more generic equation, as given by Michael Miles from MilesTech and coined "Optimum Linear Matrix", is : L' = L - kR R' = R - kL C = (1-k)(L+R) With k = 0.5 it's "Trinaual - Klaus
just another
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Join Date: Aug 2003
Location: Sydney
Blog Entries: 22
I made myself a new speaker testing stand today with swivel at the top to allow me to easily do off axis measurements. I've attached the results of 0 through 90 degrees off axis for my MTM, same ones that were used for the pink noise tests above, just to give some context I guess

First pic is all the measurements in 15 deg increments through 90 degrees. Note that there were a bunch of plants that the speaker would have been pointing directly at between 30 and about 75 deg, whether or not these affected the measurements I can't say because I was too lazy to move them

I did fairly low spl level measurements as it was after 9:00pm

the second pic is the holm measurements for zero 15 and 30 showing the impulse response as well.

Tony.
Attached Images
 horizontal_polar.png (45.1 KB, 171 views) new_crossover_1.27M_with_15_and_30_off_axis.png (73.6 KB, 170 views)
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 9th November 2011, 12:27 PM #1895 diyAudio Member     Join Date: Oct 2004 Location: The Netherlands It look like the distance between speaker and mic is a bit larger at larger angles. Did you turn the speaker around it's baffle centre-axis, or at some axis more to the rear of the speaker? __________________ Dutch & Dutch
 9th November 2011, 01:36 PM #1896 diyAudio Member     Join Date: Oct 2004 Location: The Netherlands Damn, more than one typo in a two-sentence post. Too bad I can't fix it anymore. __________________ Dutch & Dutch
 9th November 2011, 03:24 PM #1897 diyAudio Member     Join Date: Apr 2005 Location: KyOhWVa tristate RD75 dipoles Here's my 6' dipoles at 0, 15,30,45, & 60 (green,red,purple,blue,brown) offset in ARTA for ease of reading. I'll have to set up to do the in/out of phase measurements smoothed 1/24 octave back in 2008 And here's an on-axis attempt to maximally flat (which sounded way too brite, btw, hence the subsequent designed-in tilt) All measurements taken @ ~ 15 feet from speaker @ 3' height John L. __________________ "I've forgotten more than I care to remember" The Last Conspirators Last edited by auplater; 9th November 2011 at 03:29 PM.
just another
diyAudio Moderator

Join Date: Aug 2003
Location: Sydney
Blog Entries: 22
Quote:
 Originally Posted by keyser It look like the distance between speaker and mic is a bit larger at larger angles. Did you turn the speaker around it's baffle centre-axis, or at some axis more to the rear of the speaker?
Yes the pivot point is not quite on the front baffle axis, it is about 1" behind it, which does introduce a little error. I could move the speaker back a little further but then I start to get diffraction effetcs off the platform.

edit: I guess you picked that up from the impulse response? I time zero locked it so that time of flight was absolute between the measurements

Tony.
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planet10 needs your help: Let's help Ruth and Dave

Last edited by wintermute; 9th November 2011 at 08:10 PM. Reason: add impulse response comment.

 9th November 2011, 11:42 PM #1899 diyAudio Member     Join Date: Dec 2004 Location: Novi, Michigan 1" of offset is not going to make any difference. I often have 3" or so and I don't see any effects from this. I also worried about diffraction from the platform, but I haven't found that to be much of a problem either. __________________ Earl Geddes Gedlee Website Read about the highly acclaimed Geddes loudspeakers
 10th November 2011, 01:58 PM #1900 diyAudio Moderator     Join Date: Oct 2004 Location: SW Florida Blog Entries: 4 See Tony's pivoting measurement stand here: A Low Cost Speaker Testing Stand

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