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Multi-Way Conventional loudspeakers with crossovers

MTM sound characteristics
MTM sound characteristics
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Old 30th June 2020, 03:17 PM   #1
hifijim is offline hifijim  United States
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Default MTM sound characteristics

I have been reading a lot of older threads, and I have run across a number of negative statements about MTM driver arrangement.

I am considering an MTM layout for a future project. It will be a pair of 5 or 6 inch drivers with a conventional dome tweeter (no waveguide), with active crossovers. For the sake of discussion, we can assume I would use LR4 crossovers at 200 Hz and 2000 Hz. I have dual 12 inch woofer cabinets.

I do my serious listening while sitting in a specific comfortable location. I do not need a big "sweet spot".

I am interested in any opinions about the inherent characteristics of the MTM layout, both positive an negative. Obviously the MTM layout has a more narrow vertical dispersion than an MT layout, but beyond that I am interested in any theories about why an MTM layout would have a characteristic sound quality.

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Old 30th June 2020, 03:33 PM   #2
augerpro is offline augerpro  United States
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The weird thing about MTM is that some very highly regarded speakers like the Olson Ariel and Salk Songtower are MTM and highish crossover on top of that. I've personally liked the presentation of MTM in my home before, it had a sort of focused sound that projected to you, instead of splashing around. My hypothesis why this happens so often has to do with typical listening room with low ceilings. I think the MTM reduces reflection from the ceiling (and hard floors) in the midrange, which can be helpful. If all rooms were fantastic treated listening rooms, then probably MTM wouldn't be preferred as often anymore, because they do have very real polar response issues. But those rooms are rare.
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Old 30th June 2020, 06:02 PM   #3
plasnu is offline plasnu  United States
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I used perform a test with WTW speakers switching on/off the top woofer to compare WT and WTW (with level compensation). In my impression, WTW sounds more dynamic and analytical, but less intimate. For home audio, I would choose WT, and for critical listening WTW.
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Old 30th June 2020, 06:08 PM   #4
plasnu is offline plasnu  United States
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BTW, one of the best commercial speaker to compare MTM and MT is, Amphion.
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Old 30th June 2020, 07:26 PM   #5
TNT is offline TNT  Sweden
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MTM has an inherent problem with a none-linear power response. It's off axis FR is krocked and this cannot be avoided. It has do so with 2 drivers playing the same thing that has a c-c distance > 0. And you will listen to the off-axis response as it will mix with the on-axis via reflexions - A. Bose is right - 8/9 are reflected energy. So yes - MTM is faulty at conception. But ohh, don't they look cool. That sells.

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Old 1st July 2020, 01:43 AM   #6
AllenB is offline AllenB  Australia
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MTM sound characteristics
MT as well has a unique set of power compromises. If there is a hole in the reflected response near the crossover, the ceiling reflection can sound treble oriented, like a dis-jointed crossover may sound, which can draw undue attention to it.
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Old 2nd July 2020, 09:08 PM   #7
plasnu is offline plasnu  United States
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TNT is right about the ceiling reflection. MTM is known to be sensitive to ceiling reflection, so it would be better to use them with ceiling cloud or such, like music studios. As I said, I consider MTM for more accurate monitoring, and room has to be treated well anyway.
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Old 2nd July 2020, 09:18 PM   #8
plasnu is offline plasnu  United States
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Anyway, I find a real drawback of MTM is M units do not move exactly the same. Moving detached 2 membranes adds very slight something, makes overall sounds a little less organic and less intimate. I don't know how I should call this effect. It's not as bad as 6 string guitar vs 12 strings, but it's audible. For people who prefer full range to multi units, it's would not be trivial, and it should be considered.
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Old 2nd July 2020, 09:57 PM   #9
Scottmoose is offline Scottmoose  United Kingdom
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Some minor points re the above:

1/ 'As bad as 6 string guitar vs 12 strings'? Since when were they intended (or used, by competent musicians) for the same thing?

2/ I design multiway speakers & single-driver types. I like MTM designs and other types running multiple LF units & do not hear the catastrophic 'non trivial' matters that you appear to be stating is some form of universal fact.

More broadly, the polar response of a multiway loudspeaker system heavily depends upon configuration and the on / off axis radiating characteristics of the individual drive units at the chosen crossover frequency, to say nothing of XO order. The terrible flaws claimed above for MTM type speakers quickly start to disappear when wavelengths become long for a given driver spacing. Most MTMs are crossed too high to avoid at least some issues; that does not mean it is invariable.
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Last edited by Scottmoose; 2nd July 2020 at 10:05 PM.
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Old 2nd July 2020, 10:26 PM   #10
plasnu is offline plasnu  United States
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Scottmoose, I use MTM everyday and it's one of my prefered topology. I was not trying to insist that it's a universal catastrophic fact, but if my post sounded like it, I apologize that it caused misunderstanding. Guitar thing is just an exaggeration, please just forget it.

Have you ever directly compared two units vs one unit? I think you'd hear some difference as I did. I can't tell if it's trivial or not for you, and if you can hear only positive effects from 2 units, that's great.

PS: If you would perform the test, its more obvious doing it with mono speaker, not stereo, but it probably depends on the room or speakers...

Last edited by plasnu; 2nd July 2020 at 10:35 PM.
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