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Multi-Way Conventional loudspeakers with crossovers

Need help interpreting measurements
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Old 30th January 2018, 04:43 AM   #11
montana1 is offline montana1  United States
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Hi mkane77g,
I must admit, it was a comedy of errors prior to capturing my first measurement.

Best,
Rich
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Old 30th January 2018, 06:21 AM   #12
wintermute is online now wintermute  Australia
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As Allen said the smoothing would be questionable. I've tried it and didn't get good results, I went back to gated with spliced in nearfield.

If you go down the splicing route do make sure you apply a baffle step function to the nearfield result to get the most accurate results. Some of Jeff Bagby's spreadsheets will help you out there I can't remember off the top of my head which one, as he has two that I have used.

Tony.
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Old 30th January 2018, 06:54 AM   #13
Draki is offline Draki  Macedonia
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Quote:
Originally Posted by montana1 View Post
Do you also set a gate time in the right window along with the 6 cycle setting?

Best,
Rich
Further to Tony's response: below is one same measurement shown in REW' default left/right window setting of -125 (left) and 500 (right) in IR Windows, and then with right set to 2.3 ms, just before the aprx 2.5 bump visible on the step impulse (due to a very near reflection, to show the point).
When set to 2.3 ms, you can see the dotted line showing the window opening, and its' corresponding FR - no bumps below cca 450 Hz as the range below is smoothed, but 450 and up is correct and a good "far field" data.
Shown also the same in Holm (like Tony), the 2.5 ms peak and the window setting at 2.3 ms visible. The gating mark positioned automatically at abt 450 Hz.
Note: different scales, REW 40dB, Holm 70 dB, thence HOLM looks "better" ..
Attached Images
File Type: jpg REW 500.JPG (116.9 KB, 174 views)
File Type: jpg REW FR 500.JPG (74.5 KB, 170 views)
File Type: jpg REW 2.3.JPG (114.5 KB, 165 views)
File Type: jpg REW FR 2.3.JPG (71.0 KB, 162 views)
File Type: jpg REW HOLM 2.3.JPG (173.3 KB, 161 views)

Last edited by Draki; 30th January 2018 at 07:09 AM.
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Old 30th January 2018, 09:50 AM   #14
wintermute is online now wintermute  Australia
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Thanks for posting those REW screen shots with the settings shown, especially the %fs one!! I've never been able to get meaningful impulse responses in REW before today!

The first pic is after changing to % FS the second is with the default of dB FS. You can see why I thought it was useless as the 2nd one is what I always got!

Tony.
Attached Images
File Type: jpg IR1.jpg (54.2 KB, 89 views)
File Type: jpg IR2.jpg (100.4 KB, 88 views)
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Old 30th January 2018, 10:13 AM   #15
Draki is offline Draki  Macedonia
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Originally Posted by wintermute View Post
Thanks for posting those REW screen shots with the settings shown, especially the %fs one!! I've never been able to get meaningful impulse responses in REW before today!

The first pic is after changing to % FS the second is with the default of dB FS. You can see why I thought it was useless as the 2nd one is what I always got!

Tony.
Nice clean step! 3-way, mid reversed I guess?
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Old 30th January 2018, 11:06 AM   #16
wintermute is online now wintermute  Australia
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Thanks I'm pretty sure it is just my MTM without the 10" woofers as the date on the measurement is Aug 2013 and I don't think I had my active crossover (to add in the woofers) going till 2016.

The Drivers should be close to time aligned, crossover is Bessel 4th order acoustic.

Tony.
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Old 30th January 2018, 02:06 PM   #17
montana1 is offline montana1  United States
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Hi guys,
Thanks for the the Awesome tips! I will post a full array of measurements with new settings in place later today if you don't mind taking a look and making sure I'm on the right track before proceeding to the next step. Also, concerning baffle step what is the rule of thumb for amount to include for a small room? I would assume there is some art involved in the science of it all. With regard to room gain, it would seem the accepted 6db of baffle step is to much for small room. What are your guys thoughts?

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Rich
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Old 30th January 2018, 02:43 PM   #18
AllenB is offline AllenB  Australia
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Originally Posted by montana1 View Post
on the IR there is brief space that is blank before the first reflection arrives. That I would assume is the cabinet effect you mentioned.
That's it. There should be a gap between the speaker and room. Measure your distances (the obvious first reflections in your room) to confirm it on the time scale. The cabinet edges are usually closer to the direct sound but sometimes it isn't clear.
Quote:
Originally Posted by montana1 View Post
Also, concerning baffle step what is the rule of thumb for amount to include for a small room? I would assume there is some art involved in the science of it all.
I'd say there is. If you must include a baffle step in your design then it depends on the choices you make in room placement.
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Old 30th January 2018, 05:49 PM   #19
montana1 is offline montana1  United States
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Guys,
Got some measurements to critique. Hopefully, I'm on the right track and can start on putting files together for xover design. Another question I have is it correct to unwrap phase in REW before export in .frd file? The attached screenshots are with phase unwrapped.

Best,
Rich
Attached Images
File Type: jpg impulseresponse_ss18w-8434.jpg (55.8 KB, 75 views)
File Type: jpg SPL+phase_SS18W-8434.jpg (57.9 KB, 66 views)
File Type: jpg SSd2604-83300_IR.jpg (49.9 KB, 63 views)
File Type: jpg sSD2604_fr+phase.jpg (55.5 KB, 59 views)
File Type: jpg woof+tweeter_IR.jpg (52.1 KB, 56 views)
File Type: jpg woofer+tweeter_FR+phase.jpg (58.2 KB, 51 views)
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Old 30th January 2018, 07:53 PM   #20
montana1 is offline montana1  United States
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^Here is the beginning of xover design from measurements above. I used PCD7 to find correct offsets then imported summed response into Xsim and adjusted delay until lines overlayed perfect (1.71 in.). Hope I'm going about this the proper way. I welcome any comments that will help me learn at little more about measurements and xover design.

Best,
Rich
Attached Images
File Type: jpg 2way_xover.jpg (34.9 KB, 80 views)
File Type: jpg 2way_FR.jpg (101.3 KB, 84 views)
File Type: jpg 2way_Z+phase.jpg (85.2 KB, 75 views)
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