# TMMMT vs MTM designs



## jr1414 (Nov 28, 2007)

I've recently been scouring the internet for some DIY speaker designs. My search actually led me to look at some existing speakers, and a design from Axiom audio caught my eye. It is a TMMMT arrangement which they say enhances dispersion and leads to less interference form the woofers as the tweeters are only bordered by the woofers on one side.

I would be concerned that perhaps localization might be adversely affected, but perhaps my concerns are unwarranted. I know very little of loudspeaker design, except what I read in the forums, so I'd appreciate any input. I was considering the Nat P's, but perhaps I'll consider a TMMMT design. I certainly like the looks of the array that way.


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## jr1414 (Nov 28, 2007)

No extremely large room or audience to please, so that may be a bit overkill in my room. Besides, I'm already programmed to like slender speakers, must be what we've been marketed for so long that makes me want a longer array.


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## jr1414 (Nov 28, 2007)

Thanks,

The RJB site is one that I've been on frequently lately. I've been looking at the response curves, and this is what was guiding me toward the Nat P. My concern is that I've heard multiple instances where comb filtering has become an issue for a center channel application of this design. Would anyone have a suggestion for a center channel design with the same drivers to match the mains?


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## jr1414 (Nov 28, 2007)

I've listened to quite a few speakers and I know what type of sound I like. That said, much of a speaker's presentation is missed in the graphs and does have to be heard in person to appreciate.

I am certain that most of the MTM designs out there are more than adequate for L and R mains, but I know many who have done DIY MTM's that have been less than pleased with center channel performance at anything slightly off axis. That being said, Tony Gee has many interesting designs on his website, it was a good read. 

I'm leaning towards the Nat P's for L, R, and would be interested in more of an optimized CC with the same drivers.


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## drf (Oct 22, 2006)

thylantyr said:


> Example. This design uses my favorite midrange vendor, not too many
> people use that vendor as the driver costs are little high plus no graphs
> are published, plus if you did find some graphs, they'd look non-ideal,
> yet these are the best sounding mids I've heard. Measured data doesn't
> correlate with me and my liking. /lol


I understand this, After all it is very hard to quantify subjective enjoyment. Though people will try.


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## 1Michael (Nov 2, 2006)

I can highly recommend the NatP having just built the tower version of them. This link also has several CC's that will match the Nat's. http://htguide.com/forum/forumdisplay.php4?f=39
I am building the RS WMTW CC myself but there are others.


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## jr1414 (Nov 28, 2007)

I've been told by several people that a NatP. turned horizontal suffers more from off axis listening then it does in a vertical arrangement. Thus the reason why many suggest using a vertical center, if your space allows it. I believe it has to do with comb filtering horizontally from the mids. Some have mentioned doing them as a 2.5 way (each mid filtered slightly differently) to help minimize these effects. 

rjbaudio.com has a very in depth evaluation of several different crossover designs for the RS MTM, and he has lent his expertise on the subject. He has also designed a 2.5 way MTM crossover which helps to alleviate some of the comb filtering issues.

It was never that they didn't enjoy the sound of the MTM speakers at all, rather that placed horizontally there are different challenges to be met. A vertical application is different than a horizontal application, and I'm looking for a solution to match the Nat Ps for a horizontal application.


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## dlneubec (Oct 9, 2006)

jr1414 said:


> I've been told by several people that a NatP. turned horizontal suffers more from off axis listening then it does in a vertical arrangement. Thus the reason why many suggest using a vertical center, if your space allows it. I believe it has to do with comb filtering horizontally from the mids. Some have mentioned doing them as a 2.5 way (each mid filtered slightly differently) to help minimize these effects.
> 
> rjbaudio.com has a very in depth evaluation of several different crossover designs for the RS MTM, and he has lent his expertise on the subject. He has also designed a 2.5 way MTM crossover which helps to alleviate some of the comb filtering issues.
> 
> It was never that they didn't enjoy the sound of the MTM speakers at all, rather that placed horizontally there are different challenges to be met. A vertical application is different than a horizontal application, and I'm looking for a solution to match the Nat Ps for a horizontal application.


Within a limited horizontal range, a horizontally oriented MTM will work ok. MTM's typically have dispersion characteristics (lobing) that limits their dispersion vertically, when in the normal MTM uprright position. This is generally a good thing for Home Theater, becuase it reduces floor and ceiling bounce issues, thus increasing clarity. Also, you generally listen seated, so reduced vertical dispersion is not much of an issue.

However, when you lay that speaker on its side the lobing is now oriented horizontally, so as you get out away from the center position, you begin to get into the nulls created by the lobing, say more than 30º off axis. Basically, you have to evaluate your CC position relative to your seating and decide if a horizontal MTM will be adequat. If you have seating out 30º off axis and beyond, I suggest you look at a WTMW or WMTMW design, with the TM or MTM oriented vertically.

Good Luck,

Dan N.


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