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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 10th September 2019, 08:00 PM   #2771
pos is online now pos  Europe
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Quote:
Originally Posted by Oabeieo View Post
Try using rectangular window with exact centering.
That sounds the best for me.
"exact centering" should only be used when you really want the exact delay you specified, for some reason.
"closest perfect impulse" is the recommended setting in any other scenario, and will result in a delay that matches the specified on +/- half a sample (which you can check in the status report below the generate button)
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Old 10th September 2019, 09:57 PM   #2772
mark100 is offline mark100  United States
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Quote:
Originally Posted by pos View Post
The minimum-phase filter "compensate" mode is a good way to obtain this, as noted by BYRTT above.
With care and a proper distance and gating you can often obtain stop-band measurement that are good and usable down to the measurement noise floor.
Thank you Pos, I have had good success with "compensate" for that purpose.
But I have to admit, I still feel my use of it is too much trial and error, without a well understood sequence.

Is there a process you would recommend?
Maybe using a mid-bass driver with both low freq and high freq roll-off, as an example....

Or if easier, pls critique/guide the way I've been trying to use compensate...?
Typically, I'll start with LPF compensation with a BW, with the frequency set where rolloff looks to occur. Been using BW because it has both odd and even order.
I'll play with that and 'time offset' until mag and phase start to look reasonable.
Then I go to the lower end with a compensate BW HPF ....same process.
And just keep trial and error going until between both compensate filters and time offset.

I'm thinking there has to be a better, more structured way
Or at the very least, am i starting from the correct end..(HF)?

Oh, and I don't understand what you meant with "proper distance and gating"
Sorry, and thx again !
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Old 10th September 2019, 10:51 PM   #2773
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Your process sounds good: this is an iterative process and you often have to combine several low order compensate filters with different corner frequencies.
It can be quite fast if you can rely on good measurements, and if your drivers are reasonably well behaved.

Quote:
Originally Posted by mark100 View Post
Oh, and I don't understand what you meant with "proper distance and gating"
Mic distance and measurement windowing/gating.

In the case of a band-pass, you might need two different measurements to address the high-pass (close range, long window) and the low-pass (further away, shorter window).

The high-pass is of course the most difficult one to address.
You want to get a clean stop-band, so you need sufficient resolution and low enough reflections. With HOLM, manually playing with the gating cursor should let you assert the best possible stop-band. I bet the same is possible with REW.

Additionally, you also want to get the lowest possible noise floor to be able to dig deep into the stop-band (ie further from fc), so you need to adjust levels accordingly to optimize the dynamic range (low hissing from drivers, high signal level, adjusted mic gain, ...)

You also need to carefully note the frequency at which the measurement stops being meaningful (either the slope getting too soft because of the windowing, or the noise floor starting to creep up) and avoid trying to correct past that mark, letting it derivative from flat.
Of course you absolutely don't want to flatten a compensated noise floor

Hope that makes sense
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Old 10th September 2019, 11:34 PM   #2774
mark100 is offline mark100  United States
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Quote:
Originally Posted by pos View Post
Your process sounds good: this is an iterative process and you often have to combine several low order compensate filters with different corner frequencies.
It can be quite fast if you can rely on good measurements, and if your drivers are reasonably well behaved.

Mic distance and measurement windowing/gating.

In the case of a band-pass, you might need two different measurements to address the high-pass (close range, long window) and the low-pass (further away, shorter window).

The high-pass is of course the most difficult one to address.
You want to get a clean stop-band, so you need sufficient resolution and low enough reflections. With HOLM, manually playing with the gating cursor should let you assert the best possible stop-band. I bet the same is possible with REW.

Additionally, you also want to get the lowest possible noise floor to be able to dig deep into the stop-band (ie further from fc), so you need to adjust levels accordingly to optimize the dynamic range (low hissing from drivers, high signal level, adjusted mic gain, ...)

You also need to carefully note the frequency at which the measurement stops being meaningful (either the slope getting too soft because of the windowing, or the noise floor starting to creep up) and avoid trying to correct past that mark, letting it derivative from flat.
Of course you absolutely don't want to flatten a compensated noise floor

Hope that makes sense
That all made great sense, big thanks !
Glad to hear I wasn't totally goofing up with compensate.

I work very hard to get as reflection free measurements as possible, but still as you say, the low freq is the tough nut ....even with best-efforts reflection-free testing ..

And I realize garbage measurements in, equals garbage tuning out.

I had not considered multiple low order compensate filters with different frequencies,... till now

SmaartLive, my go-to measurement software, is a very robust measurement platform. It accurately defines the time/phase info needed for measurement imports into rePhase that need the least phase adjustment.
I really think its multi-time-windowing FFT algorithms work better than gating for lower frequency measurement,...... it also gates for measurement comparisons.



Hey, rePhase ROCKS !
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Old 11th September 2019, 04:30 PM   #2775
mark100 is offline mark100  United States
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Hey Pos, your comment to use multiple low order compensations lit my mellon last night.
I finally get not to try to find 'one compensate fits all' for roll-off.

It's like you have designed/implemented whole new class(es) of IIR shelving filters.... built off xover typologies.

Very clever !!!
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Old 11th September 2019, 07:24 PM   #2776
Oabeieo is offline Oabeieo  United States
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The one oactave overlapping 48db filter is by far my favorite and go to filter for horns to midbass . The SQ and ease of tuning is amazing. It works excellent!


And so far so good on the bass driver with 15.5ms . Still sounds great haven’t got sick of it at all. They compensate worked excellent, told me exactly what the box was doing along with the filter added.

Such a excellent software



So I’ve made some filters that have some bumpy side lobes .
They seem to sound good. When is side lobing considered too much in the lower stop band ?

If I have clean attenuation to -50db would that be okay? Or do I really want it to look clean all the way to the noise floor?
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Old 11th September 2019, 07:52 PM   #2777
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Quote:
Originally Posted by mark100 View Post
I really think its multi-time-windowing FFT algorithms work better than gating for lower frequency measurement,...... it also gates for measurement comparisons
frequency-dependent gating certainly is a good way of squeezing more information out of a single measurement, but it often cannot beat several measurements specifically tailored to a given frequency range.
For example you can analyse the lower frequency range of a driver with maximum resolution using a close range measurement, pushing reflections further away, but you will need more distance to get an accurate view of the higher frequency range, depending on the driver diameter.
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Old 11th September 2019, 07:59 PM   #2778
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Quote:
Originally Posted by Oabeieo View Post
So Iíve made some filters that have some bumpy side lobes .
They seem to sound good. When is side lobing considered too much in the lower stop band ?

If I have clean attenuation to -50db would that be okay? Or do I really want it to look clean all the way to the noise floor?
That is probably due to the rectangular windowing you are using.
-50dB should not be a problem though, unless you can localize a sub, etc.

Maybe try a slightly gentler windowing algorithm such as Hamming or Hann, and see if it sounds different?
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Old 12th September 2019, 03:01 PM   #2779
mark100 is offline mark100  United States
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Quote:
Originally Posted by pos View Post
frequency-dependent gating certainly is a good way of squeezing more information out of a single measurement, but it often cannot beat several measurements specifically tailored to a given frequency range.
For example you can analyse the lower frequency range of a driver with maximum resolution using a close range measurement, pushing reflections further away, but you will need more distance to get an accurate view of the higher frequency range, depending on the driver diameter.
Have you been able to compare multi-measurement stitching together, to relatively reflection free single measurements?

I use stitching when the weather is bad, but I feel I get more trustworthy measurements outdoors with speaker and mic on ground, at 4m distance.
Indoor close mic'ed sub measurements always seem a bit too good to be real.
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Old 12th September 2019, 08:33 PM   #2780
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Well, of course if you have access to (near) anechoic measurement conditions then things get easier
But then you don't need frequency-variable gating either

Re multiple measurements, to me it is not that much a matter of really stitching them together than it is of relying on one or the other when tackling specific frequency ranges: several measurements with different gating/smoothing processings, at different positions (distance and angles), etc.
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