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In Reply to: RE: The MMG Harmonic Distortion Conspiracy Theory...mostly tongue-in-cheek, long posted by JBen on March 20, 2015 at 11:22:35
Right speaker (tweeter in) distortion at 80dB 125Hz 13% Left speaker just 1.6% The distortion is only high at a specific narrow frequency band - So I suspect it is a resonance that is causing it - loose or Delam wire.
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
Follow Ups:
Hi. Bigguy;Thank you for taking the time to look at the measurement chart that JBen so kindly posted for me from my modest measuring gear. I was hoping for a loose wire, but that was not the case. I might have found something promising yesterday, but my plate is full the rest of the work week, so maybe this weekend I will know.
Thanks again....old guy
Edits: 03/24/15
Hey Bigguy! Before I forget, every time I see your Confucius quote it reminds me of Schrödinger's cat.
Anyway, it sounds to me like you are right. If it is narrow band, it could be what you think. Some sweeps that I've done when a wire segment was loose on mine in the past, did show that way. Visually, they spike alone, unlike what we see on OG42's sweeps (a wide range of frequencies.)
Good luck with this.
Oh! If you are going to disrobe that MMG, would you mind counting the staples and letting us know? This would be the total count or, better yet, each row, horizontal & vertical. As part of our diagnostic effort, we found that OG42's MMGs have less staples than mine. At this stage is just a curious thing. Too early to tell but this line of exploration led him to other promising suspects.
For everybody:You actually don't need any fancy test equipment if you really want to audibly experience the distortion these panels can produce. Buy/borrow an audio signal generator with a continuous (manual) adjustment capability. (Something with rotary potentiometer on the front that gives you complete control.)
You'll hear all kinds of various noises/buzzes/resonances you might not have expected to hear. :) It will easily allow to localize delamination or frame buzzes or various other issues.
This is not unusual with speakers of this type. Apogee's and others will do the same thing.Cheers,
Dave.
Edits: 03/23/15
If you have a smartphone and a 3.5mm-to-RCA cable, then you're already there. There are many signal generator apps available.
Yes, understood. I have a setup for my phone too. I still prefer a generator with a knob though because you can narrow the range of interest very quickly and go back/forth conveniently to isolate.My main point was that a person doesn't need any acoustic measuring equipment....microphone....REW.....etc, etc. to identify problems like this. Your ears will work just fine in this application....with the right signal generator.
Dave.
Edits: 03/23/15
Y'r absolutely right, Tom! Many are free, too. Thanks for the reminder!
And if you later add the proper audio software and, ideally, a <$20 calibrated mic, you get a half-decent measuring setup also. One that I like is "Audio Tools", available for Androids & iThings - phones and tablets.
At a grander scale, REW (Room EQ Wizard) is free and a rather impressive audio measurement package for the various PC/Mac. A normal set of audio hookup cables and presto! Signal generator and more. Then, add the same <$20 microphone that I mentioned for the droids/iThings and you're in serious business.
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