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Multi-Way Conventional loudspeakers with crossovers

Anarchy 7 - Wavecor MTM Crossover
Anarchy 7 - Wavecor MTM Crossover
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Old 5th February 2019, 09:50 PM   #41
ODougbo is offline ODougbo  United States
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Jon, Tony,

Thank you for helping me out with this:

Phase and Raw drivers (woofers only).
Interesting the phase line are so close at the xo point.

In the second screen shot, green is a 1.5mh baffle step coil (vs. the 1.2mh) but it can be spooled out easily for testing. I though the 90 degree angle was trouble, but now sounds like an acoustical filter.
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File Type: jpg temp.jpg (284.3 KB, 106 views)

Last edited by ODougbo; 5th February 2019 at 09:52 PM.
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Old 6th February 2019, 02:58 AM   #42
wintermute is offline wintermute  Australia
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Anarchy 7 - Wavecor MTM Crossover
OK, looks like the phase is different for each measurement. Holm impulse lets you lock time zero so that your measurements include the relative phase differences. To do this you need to do the following:

Set up with the mic on axis with the tweeter.
Take a measurement of the tweeter.
click on the options button for the measurement and set up as below
Anarchy 7 - Wavecor MTM Crossover-time_zero1-png
Specifically the highligted bits. change the detect time zero to highest positive peak (if your impulse has the biggest pulse negative you probably need to tick the invert recorded signal option in the Device and Signal tab). Click on the Auto Detect button twice (it doesn't seem to always get it right the first time).

Copy the value in the offset samples box.
Go to the Data Anaysis tab and set up as below:
Anarchy 7 - Wavecor MTM Crossover-time_zero2-png
specifically choosing the time zero locked button, and pasting in the offset we copied above.

Now take a measurement of the woofers (without changing any thing else in the setup).

Your woofer and tweeter measurements will now show the relative phase difference between the drivers. and these measurements can be used for simulating the crossover.

For sanity check purposes you can take a third measurement which is with Both the woofers and the tweeter all running (again changing anything else).

You can combine the individual woofer and tweeter measurements in a crossover tool and what you get should match the measurement of all three drivers running together.

If this is the case your measurements should be good for crossover design.

Note I'm on a new machine with a new holmimpulse install so some of the other settings on the data analysis tab may be different to what I would normally use. I'm going to have to check, but the time zero is the most important for measurements that can be used for crossover modelling (alternatively you can work out the driver z offset using the three drivers running together measurement, there is a document on how to do so by Jeff Bagby. But the time zero measurements are probably the easiest to deal with.

edit: as a final sanity check you can take another measurement of the tweeter and it should be exactly the same as the first one. Note I was using 1/8th octave smoothing rather than gating for this measurement as I was looking at the room effects.

Tony.
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File Type: png Time_zero1.PNG (80.7 KB, 205 views)
File Type: png Time_zero2.PNG (41.5 KB, 117 views)
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Last edited by wintermute; 6th February 2019 at 03:08 AM. Reason: add final sanity check.
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Old 10th February 2019, 08:50 AM   #43
ODougbo is offline ODougbo  United States
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Tony,

Thank you for taking the time to post all of this.

I did work on this yesterday, and had some success, but not seeing much in the lower impulse response...will have more time later today/
The phase shift with the mock up xo was getting old and thought it would be a good idea to set them up active. Which sounded very nice and reassuring that the speakers do work well together. Reversed the tweeter, and noticed a dip in the response.
*12db xo slope



2.10.jpg

Last edited by ODougbo; 10th February 2019 at 09:12 AM.
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Old 10th February 2019, 09:53 PM   #44
wintermute is offline wintermute  Australia
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Anarchy 7 - Wavecor MTM Crossover
Hi Doug, can you tick the phase checkbox and post again?

Tony.
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Old 11th February 2019, 03:20 PM   #45
ODougbo is offline ODougbo  United States
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Tony,

Better, much better, although not seeing a lot in the lower window.
No xo's - only a 15uf cap in series with the tweeter + for protection.
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Last edited by ODougbo; 11th February 2019 at 03:35 PM.
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Old 12th February 2019, 02:49 AM   #46
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Anarchy 7 - Wavecor MTM Crossover
Hmmm I think the time zero is off. The cap in series with the tweeter whilst good for protection will affect the phase. You can go into the devices tab and choose sine for testing and set the start frequency to say 200 Hz.

I have robust tweeters so I actually sweep them from 20Hz at times.

I've actually started using REW so that I can get accurate phase (using 2nd channel) It is interesting to import measurements that I took in REW in holm and detect time zero and then set the offsets for both drivers. The phase looks better with the REW imports.

One thing that may be happening is your sound card may not have constant latency. If the latency changes from measurement to measurement you won't get usable phase data with Holm. I think rew with the dual channel setup will cope with latency variances.

First graph is measurement done in holm (both woofers running) second was done in REW (only one woofer)

Tony.
Attached Images
File Type: png holm_settings.PNG (21.3 KB, 9 views)
File Type: png holm_measurement.png (48.3 KB, 7 views)
File Type: png rew_import.png (46.7 KB, 7 views)
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Old 16th February 2019, 11:27 AM   #47
ODougbo is offline ODougbo  United States
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Tony,
Thought it best to try new computer with a fresh download.
Some improvement
both woofers:
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File Type: png woofer 01.png (75.9 KB, 6 views)
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Old 16th February 2019, 12:04 PM   #48
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Anarchy 7 - Wavecor MTM Crossover
Hi Doug, You've got 200 db on the scale there, that is making it look a lot smoother than it really is Try setting it to 60db to get a better idea of what's happening in your room. regardless it is looking pretty good

Tony.
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Old 16th February 2019, 01:11 PM   #49
ODougbo is offline ODougbo  United States
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ok getting somewhere;
mic is 3' from speaker
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File Type: png woofer 01.png (44.7 KB, 10 views)
File Type: png Tweeter 01.png (78.7 KB, 10 views)

Last edited by ODougbo; 16th February 2019 at 01:14 PM.
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