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TOPIC: 2x4HD ask some questions

2x4HD ask some questions 3 years 10 months ago #27818

  • denver8me4dinner
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Strictly in regards to the 2x4HD with rephase,
Weather running a single or multiples for 4way or more .

Obviously pairing a tweeter and a subwoofer together if using another one for midrange and midbass for making the most of taps across units.

Now , what about how to tune and make a good filter with rephase and the 2x4HD.

The limited number of taps ( 2048 % 2 (x2) ><)
So, we've learned linearized filters are more coefficient efficient. So what is the best method using the IIR controls in conjunction with the FIR bank? :oops:

We can try all kinds of windowing and centering in rephase and change our filters to what works best with our drivers, what about using PEQ to ajust acoustical slopes to match the electrical slope using a rta for better phase alignment with the FIR filter. Do we do the PEQ before or after the FIR filter is live? :sick: Does it make any difference in FR or alignment to have the FIR filter active when using PEQ to cut sideband interference? ;)

Not enough taps to import or even bother importing a measurement into rephase it seems because I can't make a crossover and do any phase Eq to fine tune and have enough taps so the PEQ method seems the only way. Or Am I missing something? I guess someone could simply use a post measurement to validate your Eq skills :P that measurement doesn't have to go into rephase - does it? Or can we be confident that a linearized crossover that has a acoustical responce that matches be correct.







Next :

When stretching taps to max with limited options. When making filters, do they have to look good all the way down the graph? :blink:
If I make a filter and -60db down there's ripples in the FR at the heel of the filter and phase goes crazy up/down way past crossover. Does that matter? Is that still a usable filter if after convolution The projected filter and actual filter are very different past the filter but look good in the passband.? If so how much ripple is acceptable?
:silly:




Those are the questions that float around my head. A Consolidated responce would be fantastic

:)

Andrew




Thanks in advance :)
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2x4HD ask some questions 3 years 10 months ago #27836

  • pos
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Hello Andrew

Regarding mixed IIR/FIR use, what you can do is import your measurement(s) and build the correction in rephase, and then transfert EQ and filter points one by one into the biquad section of the 2x4HD until the remaining correction can fit the target number of taps.

Of course you would have to use filter and EQ types that correspond to the one found in the 2x4HD, eq proportional Q EQs.
Regarding linear-phase filters, you can decompose them into a minimum-phase filter, and the coresponding filter linearization, and only transfer the minimum-phase filter while keeping the linearization part inside the FIR.

Of course the lower the fc and higher the Q/slope, the more benefit you will get transferring it to the biquad section in term of taps efficiency.


Regarding stop band ripples, if you use minimum-phase filter (biquads) and use the FIR section to linearize their phase only you should not have any of these ripple issues.
if you do the actual filter inside the FIR, you might at some point have to make a decision between a result that follows the target slope better, or a low "ripple floor", by using different windowing algorithm.
Albrecht windows are the perfect candidate for this kind of thing: if for example you set a brickwall filter and then go through all these Albrecht variants you will see their effect on both the "ripple floor" and the slope.
https//wavetracing.com | rephase.org
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2x4HD ask some questions 3 years 10 months ago #27838

  • denver8me4dinner
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Didn't realize I could do it that way. Thank you!
That had me really messed up not being able to work lol the correction from one platform

I have to start completely over again but am very anxious to get started.

:-)
Andrew
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