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Old 18th March 2014, 03:20 PM   #1
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Default MA driver measurements

Anyone else measure MA drivers and find they don't measure anything like the spec sheet? There's no "built in BSC" and the high frequencies aren't smoothly humped like he shows one the spec sheet. This has been bugging me for a while.

Mark likes to put down the average DIY'er's ability to measure using a typical Behringer or Dayton mic in a domestic setting. But I've personally measured, and seen measurements from very capable DIY'ers, where proper steps have been taken to isolate reflections and the results are very different than Mark's supposedly anechoic measurements.

And I've done enough measurements to compare against other manufacturer's to know my technique is working, as I get very similar results to their spec sheets and other 3rd party results.

Anybody else get some measurements that seemed off? Or is it just me.

Here's an example of my own:

Alpair 6p

Click the image to open in full size.

Last edited by tuxedocivic; 18th March 2014 at 04:27 PM.
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Old 18th March 2014, 03:40 PM   #2
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I've posted measurements of the Alpair 7.3 here: 3"or 4" driver with very good dispersion and high xmax?
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Old 18th March 2014, 03:50 PM   #3
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Interesting. Your measurements do show some resemblence, but I see the peaks at 10 and 13khz are about +5db more than Mark's benign looking peaks and the resonance dip at 1.6khz is quite severe in your results. Also, you're getting the typical crossing of off axis measurements up in the break up region where his are parallel lines.

I had a similar resonance dip on the alpair 6p that I measured here: Fostex FF85wk and Mark Audio Alpair 6p tested against each other
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Old 18th March 2014, 04:17 PM   #4
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Here are more measurements of Markaudio drivers: http://www.brinesacoustics.com/Pages...udio/Main.html
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Old 18th March 2014, 04:34 PM   #5
xrk971 is online now xrk971  United States
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Tux,
Plot your data on the same range as the factory and see if it helps to beautify it: -10 to +110dB vertical range with 10 dB major increments. A lot may have to do with visual impact of the peaks when viewed over a 50 dB span with 5 dB intervals as you have shown. I agree that consumer mics from Dayton, etc can provide very nice measurements. I also think that a mic with a calibrated ADC right at the mic and a USB output really reduces the room for noise pickup and having the user know how to and implement calibration of their ADC.
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Old 18th March 2014, 04:43 PM   #6
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I've done that, it doesn't change the fact that the off axis plot cross paths, there is a resonance dip at 1.2khz, and there are break up peaks and dips that are greater magnitude. It's easy to do by eye, see here: The Madisound Speaker Store

And the underlying concern I have, is that a manufacturer seems to actively discredit DIY'ers abilities in this area.

I posted on the MA forum last night where the discussion about room influence in measurements was taking place. I suggested that DIY'ers don't need to worry about the room, just go outside and raise the speaker up to about 10ft or more. The responses I've measured are essentially reflection free and totally anechoic. He just deleted the post for no given reason. That is counter productive to what DIY'ers need. We need to measure these drivers and get the facts.

Compared to Fostex, which I've found have great spec sheets, it's a different ball game. Even the FE83 which has a VERy course db scale, still was accurate. Measured terrible, but if you look at their graph close, it's accurate. And the FF85 graph was quite accurate as well. IME, you can buy a Fostex product and know what you're getting!
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Old 18th March 2014, 05:15 PM   #7
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Mark has a very aggressive attitude to deleting posts on his forum that are negative towards his drivers in any way. Even if you're just trying to have a civil conversation, or discussion, while being sincere in trying to offer help and advice, or ways in which things could be improved, it doesn't matter - he takes it very personally.

It isn't surprising for manufactures data to be different from what people measure at home, it's unfortunate, but it's expected. The difference here is that most manufactures don't talk with the DIY community and leave it at that, they remain at a distance. On the one hand it is very nice that Mark gets actively involved and tries to create his drivers around what the community wants. On the other, this active approach gets you right in with the nitty-gritty and Mark takes it personally when someone posts threads like this and he then tries to defend his work. This is only natural I suppose, but to try and discredit the measurements of the hobbyist in the way of improving your own reputation isn't a particularly good way to go about doing it.

I too have been in the DIY arena for years and know full well that my ECM8000 is quite accurate. Almost all the measurements that I make match up very well with the datasheets and/or predicted responses provided by simulation. The fact is that where these mics go wrong isn't going to really affect their ability to accurately measure the issues people are talking about. Even if one were to have a 'bad' mic that shows a 3dB rise from 8k-20k, it's still going to show the breakup accurately, as well as any resonance or off axis issues.

The problem with full range drivers it that it's a difficult arena to be in. To get upper end extension relies heavily on exploiting cone breakup. This is an area that is usually plagued by irregularities. The more extension you try and coax out of a driver, the worse the problems can become. The lighter and thinner you try and make the cone, the worse these things become. Adding to this is that the problem gets even harder when you increase the cone diameter as keeping the moving mass low is critical, which thins the cone even more.
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Old 18th March 2014, 05:20 PM   #8
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Are you reopening the Marcus76 thread same subject? If you don't like MA drivers, don't buy them!!

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Old 18th March 2014, 05:40 PM   #9
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fwiw - take them outdoors on a quiet and appropriately warm day - just for comparisons. Power response dips would be expected off axis with single drivers. Its great the community has a transducer engineer like Mark. (I've not used his products - but they do represent an option to the big manufacturers)

Last edited by freddi; 18th March 2014 at 05:45 PM.
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Old 18th March 2014, 05:40 PM   #10
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I don't know what thread you're talking about Bob. The one Marcus linked? My issue isn't with that. My issue is Mark's contempt for DIY measurements, all while I find his own measurements suspect. This contradiction is a problem. It's insulting to DIY'ers who value measurements, and it's not useful for DIY'ers who want accurate data from a spec sheet prior to purchase. If his measurements are accurate, and I'm out to lunch, then I'll re-evaluate my feelings about his views on DIY measurements.

Don't like MA drivers? I liked MA drivers until he started to offend me. This thread is about whether I'm alone in this offense. Am I the only person who finds his spec sheets unreliable? And if not, then I really have to take offense to his views on DIY measurements if he can't even get his straight.
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