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Multi-Way Conventional loudspeakers with crossovers

rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool
rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool
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Old 7th September 2016, 10:03 PM   #1171
jtalden is offline jtalden  United States
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Quote:
Originally Posted by SwissBear View Post
Hi jtalden, thanks for answering. I was wondering how you were generating your sweep signal with a 96kHz sampling rate and recording it. And also, how you were doing your measures ? Are you using REW and playing the sweep at the same time ?
In the current REW version the 'signal generator / measurement sweep' feature provides a 'save-to-file' option. Just enter the desired parameters, make a sweep to apply the settings, and then select the button to save it.

REW also has an 'acoustic timing' feature. Just start the measurement in REW, it will pause waiting for the timing sound. Play the measurement sweep file you created file and REW will start the measurement after the timing tone is played. [REW will also play a the sweep, but if it is not connected or muted there is no interference with the played sweep. These features are very handy.

Quote:
Also, you are mentioning some rooms problems btwn 200 and 600 Hz. Can I ask what they are ? I just finished installing an acoustic stretched ceiling which considerably reduced reverberation in this range.
This is not the place to discuss this, but the short version is; I will not move the speakers and after lots of experiments have not been able to identify/understand the cause of the problems.
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Old 8th September 2016, 06:52 AM   #1172
pda0 is offline pda0
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Hi jtalden, thanks for the input.
I have already been using the signal generator and the "save-to-file" option, but I do not think that it enables the creation of a sweep at 96KHz. I believe you can get it at 48KHz and 44.1KHz depending on the setting inside REW parameters, but I haven't been able to get more than that. It enables the selection of 16, 24 or 32bits however.

Then, measuring with REW with the acoustic timing feature works very fine, although my experience with it has provided incorrect results on the impulse response. I assume it is due to some latency in the whole recording system but I have not really digged into it to figure out what was the problem. In practice, the very beginning of the impulse is missing which screws the STEP and phase as well. However the magnitude is correct.
I am using a USB microphone (UMIK-1) which may be the source of the problem as well.

This being said, I can't see how you can record at 96KHz even by using a 96KHz sweep signal since REW seems to be limited to 48KHz. But I may have missed something in the settings...
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Old 8th September 2016, 07:52 AM   #1173
jtalden is offline jtalden  United States
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I think there is a limit to 48k when using the Java drivers. I use the 2i2 ASIO driver on my PC. ASIO4ALL is a generic ASIO option for PC users. 96k works well using those drivers. I am not sure about the Mac options.
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Old 8th September 2016, 09:47 AM   #1174
pda0 is offline pda0
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You are right, I am using the java drivers. I will try with ASIO drivers on a PC.
Thanks.
Philippe.
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Old 8th September 2016, 12:28 PM   #1175
1201 is offline 1201  United States
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Hi guys, ive been using rephase (love it ) for my active speakers and want to know if im doing it right.

i havent been interested in correcting the phase out of the speaker yet, so ive really only used rephase to generate the crossover and correct the magnitude response. do you guys hear a sonic improvement by linearizing the phase coming out of the tweeter?

so here is what i do.

1. i generate a 48 dboct lr low pass and high pass and save to two files. that creates generic linear phase crossovers for my woofer and tweeter.

2. i measure with rew and create the eqs.

3. i come back into rephase. start with a flat line, and make the corrections.

4. once the eq is applied, i add a low pass 48db oct filter and save to a file for my woofer
5. remove the low pass, then add a high pass 48db oct filter and save to a file for my tweeter.

then i measure again in REW and everything looks good from a magnitude perspective. is this the Zen way?
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Old 19th September 2016, 07:36 AM   #1176
jmbee is offline jmbee  France
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Hello Pos,

I noticed strange results in rePhase when simulating a général 2nd order low (or high pass) minimum phase filter, defined with (F, Q ) when using low values for Q :
Screen for the low pass, phi at Fc is no longer constent at -90° if Q < 0,5 ?????

cdt


rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool
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Old 19th September 2016, 08:55 AM   #1177
pos is offline pos  Europe
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Hello Jmbee,

Indeed something weird is happening there!
Thank you for the bug report
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Old 23rd September 2016, 05:17 PM   #1178
jmbee is offline jmbee  France
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Hello Pos,

Please also if you may have a look at:
Filter Linearization - Subsonic - butt18dB/oct -
witch compensates 360° instead of 270° imho
(unless i missed something in the way to use this fonction ? )

cdt

Last edited by jmbee; 23rd September 2016 at 05:24 PM.
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Old 23rd September 2016, 07:47 PM   #1179
pos is offline pos  Europe
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That one is not a bug, but an actual (undocumented) feature

Beside the Butt 12dB/oct one, all subsonic filter linearization functions are approximations made to use less taps in this taps-hungry LF range, while still being accurate where it matters. They are not supposed to be used for other purpose than subsonic filter linearization.

Here are some illustrations with an actual Butterworth minimum-phase filter at 20Hz and the associated subsonic linearization function.

Subsonic butt 12dB/oct corresponds to an actual But 12dB/oct, no surprise there:
rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool-subsonic12-png


Subsonic Butt 24dB/oct and 48dB/oct correspond to a Butt that smoothly transition to a LR below fs:
rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool-subsonic24-png
rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool-subsonic48-png


Subsonic Butt 18dB/oct is the trickiest one, as you noted. A "real" butt 18dB/oct linearization would require a phase shift that does not reach a 180° multiple towards DC (270°), and that kind of target would require a huge amount of taps to approach. So it is considered as a LR 24dB/oct with a fs set to fs/sqrt(2) :
rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool-subsonic18-png
Attached Images
File Type: png subsonic12.png (5.7 KB, 226 views)
File Type: png subsonic24.png (6.0 KB, 217 views)
File Type: png subsonic48.png (6.1 KB, 216 views)
File Type: png subsonic18.png (6.1 KB, 214 views)
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Last edited by pos; 23rd September 2016 at 07:53 PM.
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Old 24th September 2016, 02:15 AM   #1180
pos is offline pos  Europe
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please read fc instead of fs in the above post...
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