Creating ZMA files - AVS Forum
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post #1 of 11 Old 11-06-2013, 04:05 PM - Thread Starter
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I am confused about ZMA files. I believe Omnimic can create ZMA files, however I am using REW. I looked at the REW help file and you can apparently hook the driver directly up to the sound card to record the impedance files, however I doubt that is how it is performed with the omnimic.

I took some gated measurements of my drivers outside, but apparently that only gives me the FRD files. Can I perform the ZMA measurements indoors?

Is there an easier way than REW for getting ZMA and FRD measurements that can use my UMIK-1?

Thanks,
Nathan
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post #2 of 11 Old 11-06-2013, 04:37 PM
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Hi Nathan. You can't get zma files with Omnimic and getting them with REW is a bit of a PITA. This is for your cheap thrills I imagine? Someone can give you the DNA-350 zma (I can) but the woofer, Bill might be able to.

You can't use a microphone. You need to hook up the driver to a separate device. I use a WT3 (now called DATS). There's also a superior WT2 (counter intuitive). Or you can use something called SPL trace if you have an impedance chart. It's really annoying though.

You can do it indoors.
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post #3 of 11 Old 11-06-2013, 04:43 PM - Thread Starter
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Thanks Ryan, yeah it is for the celestion. I have the zma for the dna350. I almost purchased the DATS during my last Parts Express order, but I decided I may never use it.

I may go ahead and rig up the resistors according to the REW help PDF. If I measure the DNA350 and it looks the same or similar, then I guess I did it right.
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post #4 of 11 Old 11-06-2013, 04:46 PM - Thread Starter
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My FRD files that I are coming from REW are large, as in 1.6MB large. I remember reading that there is a program that you can run the FRD file through the clean it up and slim it down. What program is this?
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post #5 of 11 Old 11-06-2013, 04:58 PM
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I think maybe response modeler? Not sure though.
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post #6 of 11 Old 11-06-2013, 05:24 PM - Thread Starter
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That is what I remember reading. Thanks.
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post #7 of 11 Old 11-07-2013, 08:12 AM - Thread Starter
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The REW impedance sweep turned out pretty well I think. It was also easier than I expected. You are supposed to use a "sense resistor", which is just the first resistor in a voltage divider. It is important to measure the real resistance of the sense resistor, however I didn't do that because I don't think my meters are working well right now. I instead just entered the supposed resistance of 100 ohms. Because of that, my measurement may be a tad off, and looking at my comparison from below, it looks to be 5% off. The graph shows my graph of the dna350 vs the one I downloaded. I also overlaid my measurement multiplied by 1.05 and that gets the graph nearly identical. I wonder if I should "calibrate" my resistor value to make it match this graph...

The green line is not my measurement, it is the one I downloaded.
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post #8 of 11 Old 11-07-2013, 08:45 AM
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Close enough to do some modeling. Your tweeter padding will govern things a whole lot more. The woofer will probably be more sensitive to the difference. But still, you gotta measure to confirm the model anyways.
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post #9 of 11 Old 11-07-2013, 10:40 AM - Thread Starter
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I adjusted my calibration inside of REW by 5% and re-measured both drivers (dna350 and celestion buyout). The measurements were taken outdoors with the speaker 5-6 feet up and the microphone 5' away on axis.

Now it is time to play with the modeling software. Here are my measurements for anyone interested.
cheap thrills drivers.zip 72k .zip file
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File Type: zip cheap thrills drivers.zip (72.5 KB, 0 views)
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post #10 of 11 Old 11-07-2013, 11:00 AM
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Did you get an overlay measurment to be able to adjust the acoustic offset in PCD? REW doesn't do that. Maybe you did, I haven't looked at the files.

Good luck.
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post #11 of 11 Old 11-07-2013, 11:33 AM - Thread Starter
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Yes, I did a combined measurement. When I threw it into PCD I came up with 0.017 or so for my offset.
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