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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 25th April 2016, 07:36 AM   #1001
skyunlimited is offline skyunlimited  Germany
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It is easy to limit the Numbers of Filters to 17, so that they will fit to a single Bank(Screenshot) and I never found Notch Filters in automated Corrections.
Usually I do not get more then 5 -6 Filters..

REW Filters Sets are more a "Suggestion" to me and in most of the Times not final, but they are a very good start and make Work faster....

Regards
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Last edited by skyunlimited; 25th April 2016 at 07:58 AM.
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Old 25th April 2016, 06:52 PM   #1002
pos is offline pos  Europe
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Originally Posted by Zero D View Post
You do NOT need to install a Full Java package There are versions of REW which come with it's own Very light install of Java Index of /installers
I did not know about these "offline" versions, thank you!
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2019-01-16: rePhase 1.4.3
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Old 25th April 2016, 06:54 PM   #1003
pos is offline pos  Europe
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Quote:
Originally Posted by skyunlimited View Post
It is easy to limit the Numbers of Filters to 17, so that they will fit to a single Bank(Screenshot) and I never found Notch Filters in automated Corrections.
Usually I do not get more then 5 -6 Filters..

REW Filters Sets are more a "Suggestion" to me and in most of the Times not final, but they are a very good start and make Work faster....

Regards
I will start implementing an import functionality for the next release.
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2019-01-16: rePhase 1.4.3
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Old 25th April 2016, 08:46 PM   #1004
skyunlimited is offline skyunlimited  Germany
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Wow this are great news. Thanks a lot!
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Old 26th April 2016, 05:19 PM   #1005
Osse is offline Osse  Sweden
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Hi guys, total newb on this interesting concept here, I have mainly one question to this:

I'm into club-sound systems and currently run a 3-way system, I've been reading up a bit on miniDSP site and forum and it seem that the best way to get a Phase-linear three way system with the rePhase is to use for example a DCX-2496 with IIR filters, and use the filter linearization in the rePhase plugin to linearize the total stereo signal with a openDRC box before the DCX-2496, using a measurement microphone in front of the sound system?

What made me a bit confused is the title of this thread, "fir filtering tool" which made me think I could implement a three way FIR filter with balanced outputs to be able to ditch the IIR processor totally, but the multi-channel openDRC boxes seem to only supply unbalanced connectors. (It seem that Pos also adressed this "problem" in a post about "blurring the original purpose of the software" on the miniDSP forum) which I guess is what I experienced

So is this for example the correct signal chain to use it?: mixer - openDRC - dcx2496 - amp - speaker - measurement mic

And then manually correct the phase in the program with the filter linearization tool?

Another question: would this method yield equal or similar results as implementing FIR filters to begin with? With for example the Lake LM26.

Thank you for everything you provide to the DIY community!

Last edited by Osse; 26th April 2016 at 05:34 PM.
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Old 26th April 2016, 06:06 PM   #1006
pos is offline pos  Europe
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Hello Osse

rephase will let you generate FIR that can correct an existing crossover, or implement the crossover. As you mentioned if you want hardware solutions there is not currently that much of a choice on the market.
openDRC-D8 and 2x4HD are good solutions if the number of taps they offer is enough for your needs and you can accommodate unbalanced outputs.
Another solution is to use several openDRC (either DA or DI with a DAC, which is the solution I use in my system) and split the input signal between them.
Najda in another good integrated solution, but with unbalanced outputs again.
Other FIR devices will probably come to market in the near future, like for example Tranquility Bass's solution, which looks pretty impressive.

There are other FIR units, especially on the pro market, like the EV DX46, some Xilica units, BSS and Crown units, and Dolby Lake as you mention. The problem with these units is that FIR capabilities are limited to textbook crossovers (brickwall shaped by windowing, or linear phase LR types), you cannot import externally generated FIR (in a documented format at least, or maybe I missed something).
Textbook linear phase filters are of no use in a real world situation (unless you resort to sharp brickwall filters, which bring their own problems) because you have to take into account the existing rolloff (and assiociated phase shift) of your drivers. This *can* be done using IIR, but once again these units do not offer the right tools for that (linkwitz transform/asymetric shelving) and there is only so much you can do with PEQ alone.
The Ev DX46 is particularly frustrating in this regard, as it is a fixed point unit and the IIR section takes place *before* the FIR one, making it impossible to use large positive EQs without clipping the whole thing...
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Last edited by pos; 26th April 2016 at 06:11 PM.
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Old 26th April 2016, 06:23 PM   #1007
Osse is offline Osse  Sweden
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Thanks for your response Pos.

What is intriguing to me about the openDRC concept is the ready-to-use box and balanced connectors(the DI,AN,DA ones) and not only a PCB-board like with for example the Tranquility bass solution.

It doesn't matter to me if i generate FIR filters or compensate IIR filters with a FIR phase compensation tool as long as it gets the job done and is cheaper than the LM26(the openDRC boxes are very humbly priced).

I've only played around with IIR filters in my LMS and can get my system to sound really good with it, but I'm curious what a FIR linear phase and EQ would bring to the table as icing on the cake.
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Old 26th April 2016, 06:38 PM   #1008
pos is offline pos  Europe
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Even for minimum-phase corrections (such as EQs), and if you have enough taps at hand to do the job, FIR has a theoretical advantage over IIR: quantization noise can rise quickly with IIR, due to the recursive nature of its biquad implementation, whereas FIR convolution implementations (especially direct temporal domain one, like in the openDRC and most other hardware units) are much more simple and will not accumulate errors.

And then of course you have the linear-phase thing
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Old 26th April 2016, 07:17 PM   #1009
mark100 is offline mark100  United States
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Quote:
Originally Posted by Osse View Post
Hi guys, total newb on this interesting concept here, I have mainly one question to this:

I'm into club-sound systems and currently run a 3-way system, I've been reading up a bit on miniDSP site and forum and it seem that the best way to get a Phase-linear three way system with the rePhase is to use for example a DCX-2496 with IIR filters, and use the filter linearization in the rePhase plugin to linearize the total stereo signal with a openDRC box before the DCX-2496, using a measurement microphone in front of the sound system?

What made me a bit confused is the title of this thread, "fir filtering tool" which made me think I could implement a three way FIR filter with balanced outputs to be able to ditch the IIR processor totally, but the multi-channel openDRC boxes seem to only supply unbalanced connectors. (It seem that Pos also adressed this "problem" in a post about "blurring the original purpose of the software" on the miniDSP forum) which I guess is what I experienced

So is this for example the correct signal chain to use it?: mixer - openDRC - dcx2496 - amp - speaker - measurement mic

And then manually correct the phase in the program with the filter linearization tool?

Another question: would this method yield equal or similar results as implementing FIR filters to begin with? With for example the Lake LM26.

Thank you for everything you provide to the DIY community!
Hi Osse, near total noob here too, other than I've been playing with rePhase and some mini-dsp units for a month or two..
I'm trying to do the same thing you are with some 4-way PA gear (3-way main and sub).

I'll post comments with the hope they will be supported or corrected as need be... IOW, don't bank on anything I say, haha

As you allude, it seems there are two main paths to phase flattening.
One is too use our IIR equip as usual, and insert miniDSP / rephase (may i term this 'MDR' ?) into the chain as a global phase correction.
The second is to use MDR as the complete crossover solution on its own, and perform driver by driver phase flattening.

From what I understand, either will work nearly identical for a single point in space.
But, using MDR as a complete driver by driver solution, is superior for multiple points in space.

Reason...well, when thinking about on and off axis response like we have to with club/live sound gear...
We know that we have ultimately to measure off axis response at different x-over frequencies and typologies within the possible range of crossover freqs, to find optimal off axis response. On axis is relatively easy.
If we use MDR as a global correction, trying different x-over freqs and typologies without rerunning an entire new global response for each attempt is invalid, because we flattened phase based on the combined response of drivers at a previously given freq and topology..
If we use MDR driver by driver, we have a lot of room to move x-over freq and topology around as we search for optimal, because we should have good summation.....because each driver is flat with the range we deem possible...

I'm going through the MDR driver by driver route right now.
I hear you regarding the lack of balanced outs on the minDSP units.
Second bummer, even one of the OpenDRC which does have a pair of balanced outs, isn't capable of pro voltage.
I'm solving this temporarily, by running the miniDSP outs into an x-32 rack on the way to the amps. I hate to tie up the rack for this duty, but right now the combo of MDR and the rack seem to be a poor man's LM26 (that's a hell of alot more powerful/capable than a LM26 haha)
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Old 26th April 2016, 08:37 PM   #1010
pos is offline pos  Europe
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Originally Posted by mark100 View Post
From what I understand, either will work nearly identical for a single point in space.
But, using MDR as a complete driver by driver solution, is superior for multiple points in space.
If your original IIR crossovers are complementary (eg acoustical symmetrical LR) then linearizing the phase will bring the exact same result as if you did build the crossover using acoustical LR slopes with linear phase, on and off axis.

The advantage of going "full-blown" FIR is that you can choose different complementary acoustical filter slopes than the one you could achieve with IIR (overlapping, very steep, asymmetrical, H-K, etc.). It will also be much easier to design, as you noted: phase tracking becomes a lot easier when the only thing you have to shoot for is a flat phase trace, and you also don't have to worry anymore about the effect of one crossover point phase shift on the others.

... and IMHO when applied with a direct convolution FIR is conceptually (and effectively) so much cleaner than a recursive IIR implementation
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Last edited by pos; 26th April 2016 at 08:43 PM.
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