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Old 5th November 2011, 05:12 PM   #1891
gedlee is offline gedlee  United States
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Quote:
Originally Posted by speaker dave View Post
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.
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Old 5th November 2011, 05:59 PM   #1892
Elias is offline Elias  Finland
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Quote:
Originally Posted by KSTR View Post
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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Old 8th November 2011, 01:00 PM   #1893
KSTR is offline KSTR  Germany
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^^
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
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Old 9th November 2011, 11:13 AM   #1894
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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
File Type: png horizontal_polar.png (45.1 KB, 160 views)
File Type: png new_crossover_1.27M_with_15_and_30_off_axis.png (73.6 KB, 159 views)
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Old 9th November 2011, 12:27 PM   #1895
keyser is online now keyser  Netherlands
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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?
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Old 9th November 2011, 01:36 PM   #1896
keyser is online now keyser  Netherlands
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Damn, more than one typo in a two-sentence post. Too bad I can't fix it anymore.
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Old 9th November 2011, 03:24 PM   #1897
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Default 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

Click the image to open in full size.

And here's an on-axis attempt to maximally flat (which sounded way too brite, btw, hence the subsequent designed-in tilt) Click the image to open in full size.

All measurements taken @ ~ 15 feet from speaker @ 3' height

John L.
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Last edited by auplater; 9th November 2011 at 03:29 PM.
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Old 9th November 2011, 08:07 PM   #1898
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Quote:
Originally Posted by keyser View Post
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

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Last edited by wintermute; 9th November 2011 at 08:10 PM. Reason: add impulse response comment.
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Old 9th November 2011, 11:42 PM   #1899
gedlee is offline gedlee  United States
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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.
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Old 10th November 2011, 01:58 PM   #1900
Pano is offline Pano  United States
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See Tony's pivoting measurement stand here:
A Low Cost Speaker Testing Stand
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