MTM or MT speakers

[maniacdavid]

I would like to build a pair of speakers. I have noticed that most people build just MT speakers. Is there a reason for this quality wise or is it purely financial?

I have done some searching on this site and have been unable to find a good comparison between MTM and MT speakers or why people choose one over the other.

This is the project I'm looking at (with the Vifa tweeters). I plan on building the cabinets myself and buying just the parts.
http://madisound.com/bigavkit.html

Is there a reason why I shouldn't build this speaker and build a MT speaker?

 

[newfinish]

sure you can go tmm ,tm works fine its just you have to also pad the tweeter a bit.so they play the same loudness.but I prefer tm or tmm,mtm would be my last choice check this out
http://www.zaphaudio.com/index.html

 

[planet10]

sure you can go tmm ,tm works fine its just you have to also pad the tweeter a bit.so they play the same loudness.but I prefer tm or tmm,mtm would be my last choice check this out
http://www.zaphaudio.com/index.html

Given 2 Ms + 1 T, i'd be building a 2.5 way with the 2nd M (0.5 one) mounted on the back of the cabinet push-push)

One of the reasons is that with MT on the front you don't have to XO the T as low & as steep.

dave

 

[ocool_15]

I've been looking at doing the exact same thing! 2 woofers will go lower then a single. I have also seen tmm designs that have the 2nd one crossovered alot lower (~200Hz)and there just to extend the low end in a small box. I was looking at doing a MTMW but I think ill end up doing a tmw 1", 2.625" 5.25".

Any advantage in soundstage or upper(650Hz-5kHz) response?

 

[TerryO]

I've been looking at doing the exact same thing! 2 woofers will go lower then a single. I have also seen tmm designs that have the 2nd one crossovered alot lower (~200Hz)and there just to extend the low end in a small box. I was looking at doing a MTMW but I think ill end up doing a tmw 1", 2.625" 5.25".

Any advantage in soundstage or upper(650Hz-5kHz) response?
~~~~~~~~~~~~~~~~~~~~~~
Hi,
You should be aware that 2 woofers don't actually "go lower" than a single woofer, but you can bring it in, as several have mentioned, to correct for "baffle step". This is actually done to boost the responce at the frequency that the baffle step starts, but it really doesn't go any lower, just louder in the lowest frequencies.
As it's your dime and time, you can do anything you want to, but why are you using a "2.625" as a mid when you're only going with a 5.25 woofer? Seems like you're going to an awful lot of trouble for little, if any, gain. I'd suggest you go with a 2-way with a TW if you're going to use a 5.25 woofer (actually more of a mid-woofer).
Just my opinion of course, but whatever you decide on, good luck on your project.
Best Regards,
TerryO

 

[simon5]

I have a question in line with this topic.

Let say you do 5 MTMs for a home theater. Then you lay the center channel on the side to sit on the TV or something else. You get 5 channels with the same speakers and design so it's perfect.

Then we heard about line arrays which sound good only in vertical lines. Won't that center channel compromise the sound because it's like a small horizontal array vs a vertical array?

I guess a MMTMM would be even more trouble for a center channel?

Thanks.

 

[newfinish]

you have to make it standing up,any kind of center,tm,mt,tmm,mtm,etc....

 

[planet10]

Won't that center channel compromise the sound because it's like a small horizontal array vs a vertical array?

Sideways MTMs don't really work except that that is what the marketing department has pushed to the point that that is what everyone expects.

IMHO, the best centre channel is no centre channel.

dave

 

[francis varkey]

I have a question in line with this topic.

Let say you do 5 MTMs for a home theater. Then you lay the center channel on the side to sit on the TV or something else. You get 5 channels with the same speakers and design so it's perfect.

Then we heard about line arrays which sound good only in vertical lines. Won't that center channel compromise the sound because it's like a small horizontal array vs a vertical array?

I guess a MMTMM would be even more trouble for a center channel?"

Simon5,
When you have two identical sources firing in the same plane and phase, the sound would appear to originate from excatly the centre point between them. When you place the tweeter at this central point, you get something like a point source(High freq has more directivity too).
So MTM will seem to radiate from the T, regardless of the MTM being placed vertically or horizontally. The same is the case with MMTMM.
IMHO, MMTs or MTs will need to be placed all vertical or all horizontal.
Regards,
Francis

 

[newfinish]

http://www.verityaudio.com/
check their site its very detailed on how they do it.

 

[simon5]

Simon5,
When you have two identical sources firing in the same plane and phase, the sound would appear to originate from excatly the centre point between them. When you place the tweeter at this central point, you get something like a point source(High freq has more directivity too).
So MTM will seem to radiate from the T, regardless of the MTM being placed vertically or horizontally. The same is the case with MMTMM.
IMHO, MMTs or MTs will need to be placed all vertical or all horizontal.
Regards,
Francis

You're right that the sound comes from a point source but the MTM layed on the side have serious issues, the same issues you encounter when laying a line array on the side.

Planet10 just confirmed what I was thinking.

With a big vertical center channel, I guess you need to put the speaker behind a white screen, to project the movie on it. Does those screens are transparent to the HF content? I guess not? You would need to have a rising response I guess.

 

[planet10]

With a big vertical center channel, I guess you need to put the speaker behind a white screen, to project the movie on it. Does those screens are transparent to the HF content? I guess not? You would need to have a rising response I guess.

The screen will compromise the speaker somewhat, and the holes in the screen to minimize the degradation of the speaker degrade the image.

Best centre channel is vertical (or non-existant)

dave

 

[simon5]

Let say you have a big 50" TV set and you want to use a center channel, does using two vertical center channel, one each side of the TV, would compromise the sound alot? I guess yes also?

Better to use a single horizontal one in that case?

Audio, a world of compromises hehe!

 

[planet10]

Let say you have a big 50" TV set and you want to use a center channel, does using two vertical center channel, one each side of the TV, would compromise the sound alot? I guess yes also?

I;d say 2 vertical ones would be less of a compromise... but having gone that far, a set of mains that image and proper seating position would do the same thing.

dave

 

[simon5]

Yeah but let imagine here that we got a very large room.

Thanks for your imput!

 

[planet10]

A large room makes this scheme even more workable since you can get more people in the seet spot (which is necessary to turf the CC -- a CC is simply a fix for people sitting in less than optimum seats).

A big theatre with the proper 4-6 screen heights before the 1st row of seats is ideal for eliminating any centre channel)

dave

 

[Landroval]

Best centre channel is vertical (or non-existant)

I have a coaxial 6,5" center (and mains) with Seas T17RECOAX/TV/AG-EH and couldn't be happier. The Imaging is amazing and there are no traditional center channel problems because of the coaxial point source.

Simon5, if the room is big you could add an active bass "module" for the center to give the sound more body.

I would also strongly advice against dual center speakers. It's always bad to play one channel from two different speakers. It's as you would have a 6 feet wide center speaker with two tweeters abd two basses. The interference will be awful.

Madisound carries a couple Seas coaxials, for ex. the T18RE COAX/TVFC. Give it a thought, you wont regret it.
Edit: they actually seem to have a ready box and x-over design for it also.

 

[BobEllis]

Somehow the multitudes of poorly implemented commercial MTM centers have given everyone the impression that the problem is MTM.

If you go back to Joe D'Appolito's original paper, he was looking for a way to reduce vertical lobing (or improve horizontal polar response in a horizontal MTM center). He showed quite even polar response if an 3rd order acoustic slope is used and the crossover frequency is low enough to avoid lobing due to woofer spacing. The response beams when using even order slopes.

If you play pink noise through an MTM with an even order acoustic filter, you will notice a picket fence effect as you move through the sound field in the plane of the drivers. If you have identical odd order slopes you should notice little if any change in response as you move around.

So, IMHO, the keys to horizontal MTM design are:

1. a tweeter that goes low and clean
2. woofer spacing less than 1/2 wavelength at XO freq
3. Odd order acoustic slope filters - this does not mean that the electrical filter is odd order.

As for the necessity of a center channel speaker, I go back and forth. Sure I can get the two people I care about in the sweet spot without a center. However, I like my screen taking up most of my field of view (like slightly forward of center in a theater) and to keep dialog on screen it takes a center channel speaker.

If you have enough room to stay as far back as Dave suggests, you probably don't need a center as long as you keep your seating area fairly tight to the centerline.

 

[planet10]

I have a coaxial 6,5" center (and mains) with Seas T17RECOAX/TV/AG-EH and couldn't be happier. The Imaging is amazing and there are no traditional center channel problems because of the coaxial point source.

If you have to have a CC then something like this or a FR like the CSS FR125 is the way to go.

If you have to have a big multiway then 2 small mids (2-3") with a small tweeter in an MTM, flanked by woofers (with a low XO) would be the way to go.

dave

 

[planet10]

If you have enough room to stay as far back as Dave suggests, you probably don't need a center as long as you keep your seating area fairly tight to the centerline.

Line arrarys dramatically widen the sweetspot as long as you are in the nearfield.

dave