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In Reply to: RE: DIY speaker design comments posted by JLindborg on March 29, 2014 at 06:52:19
What's different about left and right MMG's? Only the tuning button locations, yes?
You just got through saying that "if you are serous about sound you shouldn't use MMG's because they are two different speakers." Did I extrapolate incorrectly?
The tuning is not totally different, it's slightly different. The (multiple) resonances from both left and right actually overlap each other with this configuration.
Your 8 inch and 10 inch woofer analogy is piss-poor. Here's another poor one, but it's much better. The MMG's are like two identical 10 inch woofers except one has a small piece of chewing gum attached to the cone. This changes the bass tuning frequency just slightly, but differences are inaudible unless program material just happens to line up (very rarely does this happen) with a resonance of either panel for a significant time. For non-bass frequencies the tuning difference is a non-issue.
It's difficult to blind test this difference because you can't exactly co-locate the two speakers, but here's a fairly worthwhile test. Put your MMG's near the center of the room and play pink noise alternating between the two speakers. Have an assistant randomly switch locations of the two speakers and see if you can identify either speaker consistently in an un-sighted test.
Regardless, if MMG's are beginners/kids speakers because of this design aspect then other models are as well. Would you agree?
Cheers,
Dave.
Follow Ups:
The whole point is to prevent the accentuation of combining identical L/R speaker resonances, which can get ugly. The asymmetrical tuning buttons aren't a bane; they're an absolute boon. The result is a smoother combined frequency response. Frankly, I think it's a stroke of engineering brilliance.
For those that are interested, this is a good illustration of the tuning dot scheme for MMG's. (Green speaker 1, yellow speaker 2.)
It's easy to see the two panel resonances of the single dot speaker transducer (green) and the four panel resonances of the three dot transducer (yellow.)
Cheers,
Dave.
I don't remember seeing that before. If that doesn't convince us of the judiciousness of the asymmetrical tuning dots, I don't know what can! It's even more critical when one considers that most typical rooms have modal issues in the neighborhood of 70Hz.
I got all kinds of 'em.
Here's one that shows woofer element coupling onto the tweeter. The woofer being actively driven but the tweeter being monitored with an analyzer.
A decent indication of the "mechanical" crossover between electrical elements on the same transducer surface. It's sort of like a psuedo IM distortion measurement.
Dave.
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