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TM, MT, MTM, TMM, MMT - behavior differences?
Hello all!
I am curious about the basic "behavior" (dispersion? imaging?) differences among the following driver arrangements: TM, MT, TMM, MMT, MTM.
I think I understand the basics between MTM and TMM such as what drivers handle what frequencies and why. I get that MTM is more symmetrical, minimizing floor and ceiling bounce.
1. With TM and TMM, why do some people put the bass drivers on top instead of below the tweeter?
2. What is the difference between how the MTM images and the TMM?
3. Which arrangement would be better for near-field listening? Which arrangement would be less sensitive to moving around the room? Laying in the floor?
4. When would one ever want ceiling reflections?
5. Which of these arrangements are more consistent with the point source ideal?
Is this important for imaging?
I will probably have better questions than these later (with some assistance). Thanks guys (and girls)! :)
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
1. With TM and TMM, why do some people put the bass drivers on top instead of below the tweeter?
You have seen a speaker MMT...with tweeter on the bottom? I have seen a MT with the tweeter on the bottom...and i think it is more of a marketing differentiater than anything.
2. What is the difference between how the MTM images and the TMM?
MTM limits vertical dispersion. Not how that would affect imaging...especially if properly designed.
3. Which arrangement would be better for near-field listening? Which arrangement would be less sensitive to moving around the room? Laying in the floor?
For nearfield, you would want the drivers as close together a possible. Probably nothing more needed than a good two-way with a tweeter and woofer like the 170.
4. When would one ever want ceiling reflections?
The MTM, properly designed would limit vertical dispersion.
5. Which of these arrangements are more consistent with the point source ideal?
Is this important for imaging?
Probably a two-way with a tweeter and woofer, and a properly designed crossover like on the Sierra-1. Also a speaker utilizing a coaxial driver. For imaging, I think there are other factors.
Just my thoughts on things, don't take them for gospel as I am not a speaker designer/engineer.
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
Hey Curtis!
I have not actually seen an MMT w/ tweeter on bottom. I think the discussions I ran into may have just reversed the letters of TMM. I vaguely remember one discussion in which someone mentioned MT and literally meant "mid first", and I may have assumed that the order of lettering had stricter meaning. Oh, the Internets!
I have a few ideas floating around in my head including "imaging" "point source" "MTM" and "TMM" that I am trying to fit together with better understanding.
When Dave explained in the tower thread why the tower is MTWW and not TMWW, he said "An MTM design will have greater vertical directivity but will also exhibit off-axis lobing, which is not consistent with mimicking the response of a single point source."
I was just wondering what the value of "point source" is? Near field listening? Imaging? Some type of natural "the singer is here in this room" sound? I'm just really curious. :) I am curious about whether a TMM design would also be considered more "point source" than an MTM. You have the tweeter followed by a single mid. The lower "mid" just helps with the lower bass. I was thinking that since lower bass is harder to localize anyway, it might seem that a TMM would behave more like a TM than an MTM. But, I don't really know.
I'm becoming more interested in speaker design and may play around with building a speaker or two based on preexisting designs. Later. When I have time. And $ :)
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
Ah yes! Dave mentioned that to me as well when I asked about books in an earlier thread. Seems to be a classic. I will definitely check it out. Thanks to you both for mentioning it!
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
This just occurred to me, and I probably should have simply asked this single question:
When would one ever want a 2.5 way TMM design instead of a MTM? I think this question pretty much sums up my curiosity. To conclude that you would never want a TMM I think would be pretty extraordinary. Surely there would be a time when you would want the TMM. Either way, I'm sure the answer will be interesting! I'm in no hurry for an answer. I'm just curious as to what Dave thinks about this. (Please take your time! You must continue in your quest of the holy artifact "Sierra Tu!")
"Sierra Tu, we await thy coming. Oooeeeooooohh." :D
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
Quote:
Originally Posted by
j0nnyfive
Hello all!
I am curious about the basic "behavior" (dispersion? imaging?) differences among the following driver arrangements: TM, MT, TMM, MMT, MTM.
I think I understand the basics between MTM and TMM such as what drivers handle what frequencies and why. I get that MTM is more symmetrical, minimizing floor and ceiling bounce.
1. With TM and TMM, why do some people put the bass drivers on top instead of below the tweeter?
2. What is the difference between how the MTM images and the TMM?
3. Which arrangement would be better for near-field listening? Which arrangement would be less sensitive to moving around the room? Laying in the floor?
4. When would one ever want ceiling reflections?
5. Which of these arrangements are more consistent with the point source ideal?
Is this important for imaging?
I will probably have better questions than these later (with some assistance). Thanks guys (and girls)! :)
Hey J0nnyfive,
This is rather complex with really no defined answers so I will just try to summarize and/or address a few items for you.
Quote:
I think I understand the basics between MTM and TMM such as what drivers handle what frequencies and why. I get that MTM is more symmetrical, minimizing floor and ceiling bounce.
Driver orientation and which drivers handle which frequencies are not related to each other. In other words, regardless of driver orientation, the tweeter is going to handle the frequencies that it is optimized for and the same for the woofer. MTM provides a perfectly symmetrical vertical dispersion pattern but it reduces floor and ceiling bounce due to lobing. That is, the output from the woofer closest to you will reach your ear before the woofer that is further from you, and thus these frequencies will either be in-phase (amplified) or out-of-phase (reduced) causing a response that looks like a comb (also called comb filtering). TMM will not provide as symmetrical a vertical response but will have far less lobing.
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1. With TM and TMM, why do some people put the bass drivers on top instead of below the tweeter?
All a matter of the designer's taste but depending on where the acoustic center of the drivers is located, sometimes it is a good idea to move the woofer as far away from the floor as physically possible. There are just so many variables to this....
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2. What is the difference between how the MTM images and the TMM?
Imaging is much more dependent on horizontal dispersion, of which MTM and TMM (if that is the only difference) will have basically the same horizontal dispersion pattern...
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3. Which arrangement would be better for near-field listening? Which arrangement would be less sensitive to moving around the room? Laying in the floor?
In this case, the closer to a single point source the better. A TM or MT would be best
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4. When would one ever want ceiling reflections?
Reflections, regardless of where they come from, create spaciousness. If you listened to a speaker in an anechoic chamber, you would find it dull, lifeless and simply not enjoyable. Too many reflections can also be a problem as they will smear detail and clarity.
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5. Which of these arrangements are more consistent with the point source ideal?
Is this important for imaging?
TM or MT....
:)
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
Quote:
Originally Posted by
j0nnyfive
When would one ever want a 2.5 way TMM design instead of a MTM? I think this question pretty much sums up my curiosity. To conclude that you would never want a TMM I think would be pretty extraordinary. Surely there would be a time when you would want the TMM. Either way, I'm sure the answer will be interesting! I'm in no hurry for an answer.
A 2-way TMM compared to a 2-way MTM has considerably wider vertical dispersion. Provided it is a competent TMM design, it will sound quite good when listening above or below ear level. It can also sound more spacious in a room due to ceiling and floor bounce, as well as provide more overall output in the room due to the lack of lobing cancellations. A properly designed 2-way MTM can provide better clarity when listening directly on axis due to the reduction of reflections, but clarity will be lost when listening above or below the speaker...
With loudspeaker design, if one design was flat out better than another, you would never see it ;) It is all about compromise, sacrifice this to gain that...
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
Thanks for the explanation! As for being all about compromise, I believe it (from what little I know)! I have been putting the explanation to the test on the CMT-340 se, moving up and down and listening for changes in the sound. I must not have golden ears because I can't really tell much difference. I can tell some difference, but it still sounds very pleasant. :) Part of me likes the idea of room interaction, but another part of me doesn't. I guess I'll just have to get both types eventually. . . what a disease. . . Thanks. (For the explanation, and the disease!) lol
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Re: TM, MT, MTM, TMM, MMT - behavior differences?
Quote:
Originally Posted by
j0nnyfive
Thanks for the explanation! As for being all about compromise, I believe it (from what little I know)! I have been putting the explanation to the test on the CMT-340 se, moving up and down and listening for changes in the sound. I must not have golden ears because I can't really tell much difference. I can tell some difference, but it still sounds very pleasant. :) Part of me likes the idea of room interaction, but another part of me doesn't. I guess I'll just have to get both types eventually. . . what a disease. . . Thanks. (For the explanation, and the disease!) lol
Most welcome!! The 340's are not your typical MTM as we use an exceptional tweeter that allows for a lower crossover point and that combined with the very tight spacing of the drivers and optimized phase integration in the crossover -- allows for wider vertical dispersion compared to most MTM's. That said, compared to our 170 or Sierra-1, vertical dispersion is considerably narrower.
