# Home theatre: MTM vs 2-way?



## lunchmoney (Dec 27, 2007)

*Home theatre: MTM vs TM?*

I'm looking to build my own front speakers and center channel for my home theatre... I would very much like for all 3 speakers to be identical.

The two designs I've narrowed it down to are the Parts Express MTM Triune and the Parts Express TM Encore. both designs are known for being great for fronts and center.

MTM Triune: Dual Classic Dayton 5.25's plus Dayton silk tweeter... narrower width will be great for using as a center channel, but is substantially longer than the Encore, and perhaps more precarious when on stands.

TM Encore: Single Reference Dayton 6.5 Plus Dayton Aluminum Tweeter... shorter height than Triune is probably better for stands, but greater width may be awkward for fitting under the TV... better mid than the Triune, but I must admit I'm a little spooked by metal tweeters after a bad experience with metal car audio speakers... but this fear might be unfounded, as I'm quite the noob.

Here's my biggest question: what are the pros/cons of an MTM vs a TM?

Any thoughts on these two speakers?


----------



## ws6 beat (Jul 14, 2005)

look up the natalie p at htguide.com


----------



## Spasticteapot (Mar 5, 2007)

The Triune will be a pretty poor center channel. Because it uses a D'Appolito arrangement, it will have very good dispersion horizontally and very poor dispersion vertically, so that when flipped on its side it won't work properly for anyone not sitting directly in front of it.

The Encores use the Dayton RS52 tweeter, which is very good indeed - I doubt you'll find fault with them. However, perhaps the best and most proven HT design is the Modula MT, which features a Dayton RS180 and either a Dayton RS52 or Seas 27TDFC - a similarly excellent silk-dome tweeter.


----------



## Xander (Mar 20, 2007)

Here's the breakdown of MTM vs MT designs, in a nutshell (if anyone notices anything blatantly wrong here, please let me know, I'm certainly not an expert)

MTMs can usually reach higher volumes with less distortion because the mids don't have to work nearly as hard.

MTMs have a symmetrical dispersion pattern when placed on their side, so it is possible to use them on their side as a center (as you see commercially very often).

It is not recommended to place an MT on its side, as the dispersion pattern will be very different on either side, and there will be many unwanted comb filtering artifacts

On the plus side, MTs are easier to design (generally speaking) and obviously cheaper to build.

You can find a lot more info on the htguide forum, that's where I've learned a lot


----------



## lunchmoney (Dec 27, 2007)

Spasticteapot said:


> The Triune will be a pretty poor center channel. Because it uses a D'Appolito arrangement, it will have very good dispersion horizontally and very poor dispersion vertically, so that when flipped on its side it won't work properly for anyone not sitting directly in front of it.
> 
> The Encores use the Dayton RS52 tweeter, which is very good indeed - I doubt you'll find fault with them. However, perhaps the best and most proven HT design is the Modula MT, which features a Dayton RS180 and either a Dayton RS52 or Seas 27TDFC - a similarly excellent silk-dome tweeter.


I'm assuming that "D'Appolito arrangement" is synonymous with MTM?

So if an MTM configuration ain't so good for a center channel, then what IS a good configuration?... since a TM on it's side is no good... a TM *not* on its side? Got no room for that...

Supposedly the Triune doesn't suffer as much from the MTM-on-its-side problem as other MTM center channels, due to the mids being as close together as possible (smaller drivers than most MTM's being partly responsible), and clever crossover design... supposedly... that's the Triune's claim to fame, anyways.


----------



## lunchmoney (Dec 27, 2007)

Xander said:


> Here's the breakdown of MTM vs MT designs, in a nutshell (if anyone notices anything blatantly wrong here, please let me know, I'm certainly not an expert)
> 
> MTMs can usually reach higher volumes with less distortion because the mids don't have to work nearly as hard.
> 
> ...


Ah... well that answers my "why not pitch an MT on its side?" question... thanks


----------



## lunchmoney (Dec 27, 2007)

ws6 beat said:


> look up the natalie p at htguide.com


okay... looks like another MTM... will this work ok as a center channel? Or are you suggesting it for the mains?

thanks


----------



## Spasticteapot (Mar 5, 2007)

lunchmoney said:


> okay... looks like another MTM... will this work ok as a center channel? Or are you suggesting it for the mains?
> 
> thanks


MTMs, unless specifically designed for center channel use, are often ill-suited to the job. Much better would be a very small MT (such as the Encore) mounted vertically.


----------



## vinny (Apr 28, 2008)

*Re: Home theatre: MTM vs TM?*



lunchmoney said:


> MTM Triune: Dual Classic Dayton 5.25's plus Dayton silk tweeter...
> TM Encore: Single Reference Dayton 6.5 Plus Dayton Aluminum Tweeter...
> Here's my biggest question: what are the pros/cons of an MTM vs a TM?
> Any thoughts on these two speakers?


The primary difference between these 2 will the radiation pattern. In an MTM with a tweeter between 2 mids the radiation pattern is cylindircal where there is little or no difference is the sound as the listener stands up from a sitting position. However it has been found that the sweet spot of many (if not all) MTMs is narrower than MTs. This means for stereo the image will lock in place in a small area. In an MT the image might not lock in place as nicely but the sweet spot covers a larger area.

2 5.25" woofer have a Sd of about 200cm2. A single 6.5" has a Sd of about 150cm2. Hence as far as quantity of bass goes dual 5.25" woofer will provide a bit more bass than a single 6.5" provided their Xmax is the same. If the Xmax of the 6.5" is 25% more than the 5.25" then the max SPL will be the same (provided other T/S specs are the same).

Sensitivity of the speaker depends on the sensitivity of it's drivers, insertaion loss of the crossover, and the degree to which the designer has implemented baffle step compensation. Some speakers will little or no baffle step compensation sound best (and are designed to) against a wall (at the expense of better imaging).

For a center channel I would consider a coax, fullrange/widerange, or even a "W-(MT)-W" where the MT is a vertically array flanked by 2 Ws. For Home Theater it is nice if the front 3 speakers (atleast) have the same sonic signature. Hence why not a "W-MT-W" for the front 3 channels and a WT (the M in a "W-MT-W" is usually too small to have any bass capabilities) for the surround.

I hope this helps and is what you are looking for. We can expand on this if you so desire.


----------



## DS-21 (Apr 16, 2005)

*Re: Home theatre: MTM vs TM?*



vinny said:


> The primary difference between these 2 will the radiation pattern. In an MTM with a tweeter between 2 mids the radiation pattern is cylindircal where there is little or no difference is the sound as the listener stands up from a sitting position.


Not exactly. Yes, it's true that an MTM has restricted vertical dispersion compared to an MT, assuming that the MT does not use a waveguide that restricts vertical dispersion. However, that fact leads to a conclusion opposite from the one you draw: the MTM will sound noticeably different when one stands.

Horizontally (assuming a proper vertical MTM and not that abominable hack the toppled-MTM) both an MTM and an MT will suffer degraded sound quality in room because of the difference in horizontal directivity between the woofer(s) and tweeter in the passband (usually in the midrange) unless care is taken to 
a) restrict the horizontal dispersion of the tweeter via a waveguide or coincidental/concentric loading using the woofer cone as a waveguide, and 
b) design the crossover such that the restricted treble dispersion matches the woofer's dispersion pattern at the top of the woofer's passband.



vinny said:


> However it has been found that the sweet spot of many (if not all) MTMs is narrower than MTs.


I'm not sure I agree with this generalization. I've found that "sweet spot" area depends much more on horizontal directivity control than anything else. With flush-mounted tweeters (180deg waveguide) both MT's and MTM's will have small sweet spots. With more controlled and narrow midband directivity, both MT's and MTM's can have very large listening areas.



vinny said:


> For a center channel I would consider a coax, fullrange/widerange, or even a "W-(MT)-W" where the MT is a vertically array flanked by 2 Ws.


I think that's generally good advice, with one addendum: the three front speakers should be absolutely identical. So a coaxial, wideband driver, or W-(MT)-W center means that the L and R mains should be the same configuration, and mounted at the same elevation on the same type of stand.


----------



## br85 (May 2, 2008)

How about this?

http://www.dnaudio.com/DNA-Sequence-Speakers.html


----------



## DS-21 (Apr 16, 2005)

That's a very interesting speaker I'd love to hear. I think the upper drivers are the horn-loaded Vifa D26 (also used by Von Schweikert in their high-efficiency offering, and others) and the midrange drivers are old-school Peerless CSX's. (Might be a round frame HDS variant now.) Donald North is one of the top guys at Aura, in addition to this side project. He knows what he's doing, and this speaker seems on paper to do a lot of the things that I know from experience to correlate with good sound, such as controlled directivity.

I'd just as soon use a pro-audio DSP crossover than some triode thingy, though.


----------



## br85 (May 2, 2008)

DS-21 said:


> That's a very interesting speaker I'd love to hear. I think the upper drivers are the horn-loaded Vifa D26 (also used by Von Schweikert in their high-efficiency offering, and others) and the midrange drivers are old-school Peerless CSX's. (Might be a round frame HDS variant now.) Donald North is one of the top guys at Aura, in addition to this side project. He knows what he's doing, and this speaker seems on paper to do a lot of the things that I know from experience to correlate with good sound, such as controlled directivity.
> 
> I'd just as soon use a pro-audio DSP crossover than some triode thingy, though.


As would I. Much of the single ended triode 300B tube amps pulling 3000 watts out of the wall outlet to get 10w of actual signal level is just wankery related to the "audiophile snob" syndrome. Easily solved by moving away from stereo playback to something better (mono, ambio, VBAP or logic7 perhaps).

I was just seeing if anybody could see an inherent acoustic problem with the design. I don't know about the open baffled 15" woofer though. I would want to get that a LONG way from any surface that would reflect that out-of-phase bass back into my sound field.

I like the 4 mid/single tweeter array though. I think the design is patented, so any reproduction of such an a setup would have to be private use only.


----------



## backwoods (Feb 22, 2006)

br85 said:


> As would I. Much of the single ended triode 300B tube amps pulling 3000 watts out of the wall outlet to get 10w of actual signal level is just wankery related to the "audiophile snob" syndrome.


tubes are not snobbery. There is a measureable difference between tubes and SS. And many like the tube distortion.



> Easily solved by moving away from stereo playback to something better (mono, ambio, VBAP or logic7 perhaps).


well, that's just personal preference just like the tubes, and I prefer good ole' stereo to all those you listed.




> I was just seeing if anybody could see an inherent acoustic problem with the design. I don't know about the open baffled 15" woofer though. I would want to get that a LONG way from any surface that would reflect that out-of-phase bass back into my sound field.


Actually, open baffle woofers are made to interact with the rear wave. That's the purpose. They sound wonderful.



> I like the 4 mid/single tweeter array though. I think the design is patented, so any reproduction of such an a setup would have to be private use only.


It would be VERY hard to recreate at home. The signal processing would be the most important part to find out the phase modification done just to get the design to work correctly. It's nowhere near as simple as just building the box.


----------

