rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool - Page 51 - diyAudio
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Multi-Way Conventional loudspeakers with crossovers

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Old 29th September 2013, 09:39 AM   #501
cristig is offline cristig  Romania
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Hi pos,

I have done the measurements and I can confirm everything you said: I was able to correct for the open baffle loss with the paragraphic phase and gain EQs and also if I set the frequencies for filter linearization based on actual measurements and not on the design frequencies the result is very good. Thank you!

In fact rePhase is so easy to use and I made a complete crossover using only convolutions designed with it. Also I could correct for the baffle loss with a linear 1st order filter. Excellent software! Well done!

Based on this experience I have an idea that you may find useful: if you are doing an iterative optimization, maybe you can make possible to determine the minimum number of taps needed for a level of precision. Now I did this by hand, but I think you can ask for the desired level of precision and make iterations to try to lower the number of taps.

It may be also helpful to set the length of the impulse in time units instead of samples, in order to be independent of the sample rate. If you want the same precision at 96Khz as at 48Hz you need to double the number of taps, but in fact the impulse is the same length in the time domain.

Christian
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Old 29th September 2013, 08:24 PM   #502
pos is offline pos  Europe
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Hi Christian,

Glad you were able to do what you were looking for!
What convolution engine are you using?

Thanks for your suggestions about the impulse length. I will see how I can integrate something like this in a next release
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Old 30th September 2013, 06:33 AM   #503
cristig is offline cristig  Romania
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I am using jRiver's internal convolution, with a configuration file for 2 inputs to 8 outputs (4-way) and 4 wav files generated with rePhase.
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Old 4th October 2013, 04:05 AM   #504
Pano is offline Pano  United States
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I'm listening now to a 2-way system using convolation of rephase impulse files as crossover, phase and EQ. Sounds surprisingly clean and clear. What seems to benefit most are recordings in large spaces, like opera. It does seem to pull farther left and right, tho, dimensioning the center phantom image as compared to a passive crossover.

Each driver (and box) was corrected for phase and EQ, then a linear 4th order Linkwitz-Riley filter applied. I suppose a crossover without the linear phase should be built and compared to this one. Can I really hear the phase differences? I think so.
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Old 4th October 2013, 11:50 AM   #505
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Pano,

Would you post a wave file of impulse responses of system for raw tweeter, raw woofer, and for corrected woofer, corrected tweeter? Are tweeter and woofer measurements made with microphone at single location?

How big are the boxes? What is driver compliment, spacing and crossover point?

Have you explored this set up with steep crossover using FIR filter?

Generating standard Linkwitz-Riley filters for convolution is easy to do.

I also find recordings in large spaces benefiting greatly from correction. My thoughts are that many of these recordings use microphone arrays that capture hall sound with stereo cues.
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Old 4th October 2013, 01:06 PM   #506
Pano is offline Pano  United States
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High B.W. Sure, I think I can post the impulse files. Will have to record the "after" file, don't have it yet. Beware, they won't be pretty.

The boxes are fairly large, 40"H x 30"W x 24" deep. Horn is the Altec 1005, drivers are 416A woofer and 288 driver. I usually run with a tweeter above 6.5K, but wanted to try a simple 2-way. Crossover is circa 700Hz, 4th order, Linkwitz-Riley. Yes, mic was in 1 position 5' from the speaker face, vertically in between the woofer and horn (the listening axis).

I did try some some steep filters a few years back and did not like them. The drivers I use seem to work better with some blend area, maybe a matter of harmonics. But I could try again, for sure.
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Old 4th October 2013, 06:37 PM   #507
ra7 is offline ra7  United States
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Another question for Pano: how are you splitting the signal after the crossover. I'm guessing the processing is happening in your computer or an outboard processor/gadget. What is the signal chain?
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Old 4th October 2013, 08:08 PM   #508
Pano is offline Pano  United States
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Good Question. At the moment I'm using my M-Audio Fast Track Pro as the output, it has 4 channels out. The player is JRiver. I just tell JRiver that I want 4 output channels and the convolver script text file does the routing, crossovers and such. I currently have a file for HP and a file for LP, each 24 bit mono wav. JRiver hits the 4 channels with Left Low, Right Low, Left High, Right High, then it's straight out of the Fast Track to the amps. So JRiver is doing the splitting into 4 channels, I tell the convolver which impulse to use and where to route it. Simple, but took some time to figure out.

JRiver also has crossovers built in, they work. No idea of the phase.
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Old 4th October 2013, 08:26 PM   #509
ra7 is offline ra7  United States
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Thanks! That's all I needed to know and more

This is not so easy to do for those of us chained to our turntables. The signal must be digitized before it can be acted upon. From the MiniDSP stable, it looks like OpenDRC could be used:
The rePhase FIR tool | MiniDSP

But it seems like 2 of them will be needed for a two-way. Any other suggestions for a simpler chain (with the option of digitizing the source)?

Btw, I had almost convinced myself that I can hear the correction applied to a BR box phase response. But then I realized I was listening without enabling the correction. Since then, I've been a little skeptical about hearing changes in phase. I can be convinced though

Pano, on a side note, with my new speakers (A7 + SEOS-24), the sound from some of the records is next to untouchable. Even the transformer-modded CS4398 DAC struggles to be as artifact-free as the SL-1200+DL103+Pearl II combo.

Last edited by ra7; 4th October 2013 at 08:31 PM.
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Old 5th October 2013, 03:19 PM   #510
Pano is offline Pano  United States
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Cool! Glad the speakers are work well for you.
Yes, there is something to be said for the all analog signal chain. CD can sound very, very good certainly, but there is a joy in the good playback of an LP. As you say, artifact free.

It's a struggle I have, too. How to integrate the turntable into the signal chain. I can run it in via an ADC, but kinda hate to. All this rephasing and active crossover work is fun, but it certainly leads to complex systems.
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