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Multi-Way Conventional loudspeakers with crossovers

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Old 12th October 2017, 02:23 PM   #14791
Pano is offline Pano  United States
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The Faital and JBL impulses are cleaner, just inverted.
Phase is still odd, tho.
EDIT: Never mind on phase, I was looking at the wrong part of the spectrum.
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Old 12th October 2017, 02:42 PM   #14792
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Here are four drivers compared, normalized, 40dB range, +/-5mS
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File Type: png Faital-vs-JBL.png (87.6 KB, 263 views)
File Type: png Alu-vs-Be-Spectrogram.png (87.7 KB, 260 views)
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Old 12th October 2017, 03:09 PM   #14793
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Here they are stacked as an animated GIF
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Old 12th October 2017, 03:45 PM   #14794
BYRTT is online now BYRTT  Denmark
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Nice graphs Pano especially the animation is awesome know its hard to see in published scales but there is error for jbl2450sl in above 4kHz its faster than real time, you can better see this in below scale but its also there into your, asking for minimum phase of amplitude also show problem and in IR/SR window even SR is hurt by that prering, don't know the actual reason but expect more failure is in measurement chain than in REW, waterfall will probably show excellent up there when it has decayed before waterfall begin
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File Type: png 200.png (73.9 KB, 239 views)
File Type: png 201.png (40.8 KB, 30 views)
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Old 12th October 2017, 04:44 PM   #14795
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Quote:
Originally Posted by POOH View Post

The microphone is the Dayton EMM6 with Fast Track Pro and a Yamaha M40 power amplifier. The level has been calibrated. I see what you mean regarding phase - sometimes it seems right and other times not - I imagine something in the settings is wrong? and there is always operator error?

What in the settings/use of REW can cause this?


Here are two more wave files from newer measurements. Do these have the same problem?


Attachment 639905
Attachment 639906


Thanks
Mmmmhhh, for me this looks strange again.

IMHO it could be related to the microphone. Had an UMK1 before which is in the same price class as yours. It was a great microphone for amplitude measurements but not for phase. The phase looked too often questionabe for me. This was the reason why I invested in the Earthworks.

You could test two settings in REW if this helps to overcome this issue:
- Sub-sample timing adjustment
- Allow 96 PPO log spacing

Another test is to measure the amplification chain in REW and post it here. The output of your audio interface drives your power amp terminated with an 8R2 resitor or similar and this output back to the audio interace (microphone input as line input without phantom power). This whole chain can be calibrated inside REW. Here is my chain before calibration:
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File Type: jpg pm40c_fr.jpg (189.1 KB, 38 views)

Last edited by docali; 12th October 2017 at 04:52 PM.
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Old 12th October 2017, 05:32 PM   #14796
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Quote:
Originally Posted by BYRTT View Post
... there is error for jbl2450sl in above 4kHz its faster than real time...
Not sure I see that. Can you point it out? I don't see anything unusual before the start time on the spectogram, but the impulse does look doubled or something.
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Old 12th October 2017, 06:17 PM   #14797
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Quote:
Originally Posted by BYRTT View Post
Year thanks it looks good and at 96kHz so maybe APL_TDA will accept my loop, intend try offline EQ process it tonight.

Haven't looked into IR from POOH myself but you and Pano have pointed out it looks weird in phase, same was my impression when fluid analyzed it in post 14776 where we can see it looks like it had been FIR phase time aligned more than 1800 and that is more than 20th order of minimum phase linearization which is somehow weird, POOH must have a very fast mid or woofer it shall catch up to .
Very good!

And if you work on this I have also the export for the same thing but with ventilation hole closed. May be interesting how this changes LF.
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File Type: zip 745Neo-noVent_CD80x50_35cm_8uF2.zip (299.1 KB, 2 views)
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Old 12th October 2017, 06:33 PM   #14798
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Quote:
Originally Posted by Pano View Post
...Can you point it out...
It looks being in yours too just harder to see because of crude time scale, below should help with a zero time line edited white then follow performance of black dotted peak energy time which very weird show frq 4kHz and up will happen before real time, the one at right better follow book for minimum phase domain.
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File Type: png 3001.png (485.2 KB, 42 views)
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Old 12th October 2017, 07:18 PM   #14799
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OK I see what you mean, where it crosses the 0 time line at 4kHz. Sure.
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Old 13th October 2017, 02:33 AM   #14800
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Originally Posted by docali View Post
Thanks a lot!

I have done another measurement with a different horn which is similar to Beyma TD385. In this case the microphone is 35cm away from the mouth. Some damping material was on the floor. And the measurement was done with 96kHz

This horn needs considerable EQ also in the 1k-2k5 region which might be related to the strange looking mouth area. This horn does not show such a deep hole around 12k. Also attached is an impuls export. I have done the measurement with more power (louder) than before. The impedance curve in this horn was already shown earlier.
Took another approach this time to learn something under process myself so little late because all was manual work but fun and actual predictions are excellent to dream about in real world. To base correction first thing in REW was export MP of raw and import it again, and then to get rid of possible real world comp filter reflection at 19kHz plus 29kHz added FDW 35 width in cycles. Then made curve for synthetic target band-pass in Rephase being a 8th order LR at 800Hz - 2nd order BW at 20kHz, having a downward tilt being 7dB from point 30Hz to point 30kHz, and also added LP 25kHz 2nd order BW for microphone domain and LP 48kHz 24th order LR for digital domain. Then after some offsetting did the math to get difference curve between MP/FDW filtered raw and target curve, and that one was EQed flat over in Rephase to create reverse EQ curve, if you want Rephase settings file to create DSP filter give a note.

Waterfalls this time are much improved to excellent and probably because of the filtering and more care into Rephase task, think only real world setup can tell if they comp filter reflections sits there at 19kHz plus 29kHz and make their noise. BTW I'm away until late Saturday if any questions is asked.
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