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Multi-Way Conventional loudspeakers with crossovers

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Old 7th September 2018, 04:48 AM   #21
wintermute is offline wintermute  Australia
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Quote:
Originally Posted by DonVK View Post
Interestingly. The first time I saw the IR for a passive LR4 , I spent at least a week (with DIYaudio help) trying to determine what was wrong with it. It turned out it was suppose to look like that by design. I even measured 4 different commercial speakers that I own (and like) and all of them had very messy IR and steps.
Is that for three ways, or two ways as well? My two way with 4th order bessel acoustic slopes seems to have a pretty reasonable (to my limited understanding) step response....

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Old 7th September 2018, 05:11 AM   #22
DonVK is offline DonVK  Canada
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It was both 2 way and 3 way, but the 3 way was worse. Have a look OmniDirectional - work in progress It was a surprise to me.

The passive LR4 was in my 2 way at OmniDirectional - work in progress
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Old 7th September 2018, 09:21 AM   #23
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Hello Don,


Thanx for the overlays. It now shows the driver plus textbook filter do not enitirely match. That is what the Big Four (Calsod, Leap, SoundEasy& LspCAD) have optimizer s for. Yet, I am positively surprised about the results. Nice work!



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Old 7th September 2018, 10:07 AM   #24
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OK thanks Don, is the dramatic improvement in your before and after shots mainly due to delay bringing the drivers into time alignment? How does such a dramatic difference in objective measurement sound subjectively?

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Old 7th September 2018, 01:48 PM   #25
DonVK is offline DonVK  Canada
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Yes, the phase compensation is mostly time aligning the driver outputs after all the gain EQ and XO induced delays.

The IR and Step of single drivers are relatively good (but not perfect). I implement separate gain and phase compensations even though they could be combined. The gain adjustments are via equalizer and the effects (if >2dB) are easily noticed when you turn them on/off. The phase compensation is unity gain via FIR convolution and can also be separately turned on/off. However, I find the phase compensation effects much harder to describe because they show up in more subtle ways. Acoustic instruments seem a little more real (detail, attack), if that makes any sense. BTW I still like my commercial speakers even after I measured and discovered their "flaw".

I might try moving the speaker sections forward/backward to see if I can "manually" time align the drivers. I see some speakers where they align the voice coils vertically.

Late post : I only have one test speaker now. So I can't comment on other important phase related details like imaging and sound stage.

Last edited by DonVK; 7th September 2018 at 02:11 PM. Reason: left out imaging
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Old 7th September 2018, 02:02 PM   #26
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Yes it would be interesting to see whether physical time alignment will bring the step response close to what you have achieved with the FIR. I've read that to get a step response like your corrected one you need a transient perfect crossover, which I don't think you can do except with first order? So I'm interested to see results of any experiments you do

edit: doing a bit of searching after posting, it would appear that 2nd order LR are actually transient perfect, but higher orders not so.

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Last edited by wintermute; 7th September 2018 at 02:13 PM. Reason: add comment on 2nd order.
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Old 7th September 2018, 02:25 PM   #27
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Old 7th September 2018, 06:16 PM   #28
DonVK is offline DonVK  Canada
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Default driver jenga

I was curious to see if I could effect the same IR & Step cleanup by shifting the drivers to time align them. The problem is a single distance but the wavelength variation is infinite. Pics#1*#2 show the drivers are shifted in the Z-axis only.

Pic#3 is the FR with EQ only, then overlaid with the EQ+PH corrections on. You can see that I can change phase without effecting the FR shape.

Pic#4 & #5 are a comparison with flat baffle vs voice coil alignment. It makes a little difference but not much. I require more phase adjustment than simple driver shifting can provide. It also is causing more diffraction and a bumpy FR from the front steps. Pic#6 & #7 are just some variations in IR and Step from various combinations that I tried. Notice aligning VC's is a move in the right direction but it's not enough and it would only be the right correction for a narrow band(s) of frequencies.
Attached Images
File Type: jpg DSCN5486r.jpg (516.8 KB, 485 views)
File Type: jpg DSCN5487r.jpg (528.3 KB, 474 views)
File Type: jpg Compare EQ to EQ+PH adj.jpg (100.0 KB, 469 views)
File Type: jpg baffle flat, EQ only.jpg (87.8 KB, 448 views)
File Type: jpg Voice coils aligned.jpg (86.5 KB, 442 views)
File Type: jpg Various alignment Impulse response.jpg (99.6 KB, 91 views)
File Type: jpg Various alignment Step response.jpg (110.5 KB, 102 views)
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Old 7th September 2018, 10:47 PM   #29
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Interesting! Could you also post the comparison of the FR with the phase. I'm assuming that with the phase adjusted it is pretty much a flat line across.. Much less of a difference with the time alignment than I was expecting

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Old 8th September 2018, 12:39 AM   #30
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This is the graph for aligning the voice coils and is very similar to the aligned to baffle graph. You can see the amount of phase adjustment required to get back to a min phase response.

The LR4 may be phase aligned, but not in the same cycle. The LP shift is +360deg (4 * 90deg per order) and the HP is shifted -360deg, so there is a 2 cycle difference (-720deg LP to HP), even if they are "in phase".

Interestingly, you can select a distance that causes two drivers to be out of phase at a particular frequency and generate a null. Might come in handy for resonant drivers.

Late post : sometimes REW is off by a cycle, so in the 2nd graph the min phase should be centered on 0deg not -360deg (diff 1 cycle) and same with excess phase is sometimes 360deg (1 cycle) off. Don't know how to adj it, as all the curves move when you "add phase, +/-360deg".
Attached Images
File Type: jpg aligned voice coils FR + PH.jpg (111.1 KB, 130 views)
File Type: jpg aligned to baffle with no PH adj FR + PH.jpg (112.8 KB, 98 views)

Last edited by DonVK; 8th September 2018 at 01:03 AM. Reason: left out a graph, cycle shift corr
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