MTM horizontal center channel speaker vs vertical TM center channel speaker

[jronne]

I am pondering my center channel options

they are as follows
1) phantom center channel speaker (my current state, not optimal)
2) MTM horizontal center channel speaker (M=midrange, T=tweeter)
3) vertical TM center channel speaker

nousaine.com on the web regarding center channel issues

audioholics.com dicusses Vertical vs Horizontal Center Speaker Designs
education/loudspeaker-basics/vertical-vs-horizontal-speaker-designs

There is an oft quoted fact that 60% - 80% of the sound energy is delivered to the center channel (probably transient in nature but no one has posted the details on line)

Also the surround sound specs assume identical speakers for all positions (L/R/center/rear) which may exist in the theater but is impractical for homes. These speakers ideally would be full range towers with the center located behind a transparent projection screen. My reality is 2 TM bookshelves and two MFM 15s on their way crossed over at 100hz (yes i would like 80hz but am stuck with 100hz).

the phantom center channel has the issues
a) of a reduced listening sweetspot
b) less power handling as the fronts need to do both front and center channel duty
c) vocal soundstage not strongly anchored at the TV

the MTM horizontal center channel speaker has the sole issue of
a) horizontal lobing with nulls and hot spots
it has the benefits of increased power handling and decreased distortion due to 2M handling the center sound load

the TM vertical center channel speaker has the issues of
a) lack of power handling
b) physical placement is below TV placing the M 6 inches below the MTM midranges as vertical placement is problematic
it has the benefit of no horizontal lobing and minimal vertical lobing between the T and M

I'm interested in reasonably loud sound levels as I'm starting with 2 MFW 15s but may only use 1 MFW for this system depending on the SPL mileage (I currently have 2 DIY 10+ cubic foot sealed long throw 12's that the MFW 15s are set to replace with 1/2 the volume used).

Any thoughts regarding your experiences with regards to a good center channel choice would be highly appreciated.

Are these issues significant or all 3 center channel choices roughly the same ?

I also am curious as to why off axis response issues aren't often discussed with respect to MTM center channel speakers.

There are other choices such a the acoustically transparent video screen and horizontal speakers such as MMTTMM which are economically impractical.

thx in advance, jeff ronne

 

[TLS Guy]

I am pondering my center channel options

they are as follows
1) phantom center channel speaker (my current state, not optimal)
2) MTM horizontal center channel speaker (M=midrange, T=tweeter)
3) vertical TM center channel speaker

nousaine.com on the web regarding center channel issues

audioholics.com dicusses Vertical vs Horizontal Center Speaker Designs
education/loudspeaker-basics/vertical-vs-horizontal-speaker-designs

There is an oft quoted fact that 60% - 80% of the sound energy is delivered to the center channel (probably transient in nature but no one has posted the details on line)

Also the surround sound specs assume identical speakers for all positions (L/R/center/rear) which may exist in the theater but is impractical for homes. These speakers ideally would be full range towers with the center located behind a transparent projection screen. My reality is 2 TM bookshelves and two MFM 15s on their way crossed over at 100hz (yes i would like 80hz but am stuck with 100hz).

the phantom center channel has the issues
a) of a reduced listening sweetspot
b) less power handling as the fronts need to do both front and center channel duty
c) vocal soundstage not strongly anchored at the TV

the MTM horizontal center channel speaker has the sole issue of
a) horizontal lobing with nulls and hot spots
it has the benefits of increased power handling and decreased distortion due to 2M handling the center sound load

the TM vertical center channel speaker has the issues of
a) lack of power handling
b) physical placement is below TV placing the M 6 inches below the MTM midranges as vertical placement is problematic
it has the benefit of no horizontal lobing and minimal vertical lobing between the T and M

I'm interested in reasonably loud sound levels as I'm starting with 2 MFW 15s but may only use 1 MFW for this system depending on the SPL mileage (I currently have 2 DIY 10+ cubic foot sealed long throw 12's that the MFW 15s are set to replace with 1/2 the volume used).

Any thoughts regarding your experiences with regards to a good center channel choice would be highly appreciated.

Are these issues significant or all 3 center channel choices roughly the same ?

I also am curious as to why off axis response issues aren't often discussed with respect to MTM center channel speakers.

There are other choices such a the acoustically transparent video screen and horizontal speakers such as MMTTMM which are economically impractical.

thx in advance, jeff ronne

Jeff,
You have educated your self well, and defined some center channel problems.
The Common horizontal MTM is ridiculous! It has nothing to recommend it. The lobing problem of the horizontal MTM is exactly as you describe. It is a disaster and seriously compromises the HT experience. The array needs to be vertical, then the acoustic center is too far from the TV, unless it a projector with an acoustically transparent screen

Now the center speaker has to be as goos as the mains and take comparable power!

I believe the answer is a good coaxial driver or a good full ranger. The coaxial is an excellent solution, with the cone acting as a tweeter waveguide, interference with the mains is minimized.

The center channel I believe is one of the strengths of my system. This is a TLS with very low coloration. It uses the SEAS coaxial driver. It is diffraction compensated and powered by 250 watts.

http://mdcarter.smugmug.com/gallery/2424008_RKGvb#127077317

When I listen to other systems the severe center channel problems are literally front and center to me.

If you have minimal DIY skills this will be better than any thing else. The problem will be blending it with what ever else you have.

http://www.madisound.com/catalog/index.php?cPath=35_40_402_275

The industry needed to get off this horizontal MTM design a long time ago.

 

[jronne]

TLS Guy thanks for the info.
It seems that the industry in general has prematurely settled and converged on the MTM center speaker design.
Looks like a mistake to me.
I don't understand why alternative designs don't exist when an MTM center speaker has the potential to destroy the HT soundstage.
Why bother with quality fronts when matching them with an MTM center ?
The group think here seems to be pretty universal as market just seems to buy what is built with out question.
For instance I think off axis frequency response graphs for MTM centers are hard to come by because of the embarrassing lobing issues.

these are the two web articles that started these questions, i can't post the urls since i'm on post 2 so the urls are incomplete

at nousaine.com page cen%20chan%201.htm
at audioholics.com page education/loudspeaker-basics/vertical-vs-horizontal-speaker-designs

- jeff ronne

 

[TLS Guy]

TLS Guy thanks for the info.
It seems that the industry in general has prematurely settled and converged on the MTM center speaker design.
Looks like a mistake to me.
I don't understand why alternative designs don't exist when an MTM center speaker has the potential to destroy the HT soundstage.
Why bother with quality fronts when matching them with an MTM center ?
The group think here seems to be pretty universal as market just seems to buy what is built with out question.
For instance I think off axis frequency response graphs for MTM centers are hard to come by because of the embarrassing lobing issues.

these are the two web articles that started these questions, i can't post the urls since i'm on post 2 so the urls are incomplete

at nousaine.com page cen%20chan%201.htm
at audioholics.com page education/loudspeaker-basics/vertical-vs-horizontal-speaker-designs

- jeff ronne

You are right, a center horizontal MTM is a mistake and a big one!

There are coaxial centers around, KEF being the most notable. Tannoy who have made coaxial speakers since the fifties, and now Thiel who have a coaxial center. I'm pretty sure mine is the only TL coaxial. Someone else may have built one somewhere, but I'm not aware of it.

 

[brendy]

Just my experience with using the Infinity TSS-750 system. Switched the MTM center with a matching vertical satellite and heard an immediate improvement in the front soundstage. I will never go back to an MTM center again.

 

[jronne]

Just my experience with using the Infinity TSS-750 system. Switched the MTM center with a matching vertical satellite and heard an immediate improvement in the front soundstage. I will never go back to an MTM center again.

That is the path, I'm considering. I', have ascend cbm -170's (TM, 89db / watt, 200 watts max) for fronts and was considering going with a third one in a vertical orientation.

As a a test I was going to use a KEF bookshelf from the other system as a trail. My system is crossover at 80hz so things are cool as long as the center can handle the SPL load.

Even though MTMs have two midrange the SPL limit might be the single T in terms of distortion. If the T to M crossover point is raised imaing suffers. It is is lowered in the MTM to preserve the point source then the power handling suffers.

I keep coming back to a high quality TM vertical bookshelf or a universal driver such as a coaxial design.

I'm leaning towards a center indentical to my fronts to get matching timbre and power handling. I'm about 90% of the way convinced despite being ready to buy an MTM 3 weeks ago. It was only in researching the choices that I stumbled upon these not well publized issues.

thanks fo rthe comments, jeff ronne

 

[gene]

The lobing issues of MTM horizontally mounted speakers is a bit overblown. Consider that in most home theaters, the listeners aren't sitting more than 20-30 deg off axis from the center chanel, its unlikely that lobing will present itself into real world listening tests if the center channel is competently designed.

Personally, I almost never recommend a two way or a coaxial design over a well designed MTM. I am also not a fan of the centers that have 2 mid bass woofers and a small mid and tweet vertically mounted.

Some of the best center channels I have heard are still classic MTM designs and if you are looking for good dynamics, I definately recommend them over a two way or coaxial solution.

 

[jronne]

TLS guy, checked out your system.
Lots of very cool stuff (transmission line speakers, reel to reels, ..).
It still seems like the rules of physics still count more than marketing ads.
I did some DIY stuff in the late 70's and early 80's.
Had the tandberg 10" reel to reel, the microsieki BL 51 turntable w/ sme tonearm, grado cartridge, bi amped system with Halfer amps.
The DYI audax/polydax speakers had a cylinder for each midrange with minimal front surface area, with styrofoam cone on the inside back to minimize internal reflections.
The paper cylinders were sealed, wrapped in lead and then covered with felt.
The tweeters where adjusted back to provide phase alignment is the crossover area.
The speakers had two external crossovers one for low power (6db / octave) and one for higher power (18db / octave).
And 2 10 cu foot sealed subwoofers with 3 inch voice coils and 3 lb magnets tuned to 20hz -3/db slow rolloff.
BTW, just ordered 2 av123 MFW-15s to replace these subwoofers, downsizing from 21 cu foot to 11 cu foot and removing the last halfer amp doing subwoofer duty.
My last piece of legacy equipment is the ritcher scale 1/3 octave subwoofer eq which was a necessity with low subs.
Probably going replace subwoofer eq with a multiband Behringer parametric equalizer or equivalent.
It seems that alot of these older audio concepts still exist today.
And the upgrade of my college / post collage budget system is almost complete ...

- jeff

 

[jronne]

The lobing issues of MTM horizontally mounted speakers is a bit overblown. Consider that in most home theaters, the listeners aren't sitting more than 20-30 deg off axis from the center chanel, its unlikely that lobing will present itself into real world listening tests if the center channel is competently designed.

Personally, I almost never recommend a two way or a coaxial design over a well designed MTM. I am also not a fan of the centers that have 2 mid bass woofers and a small mid and tweet vertically mounted.

Some of the best center channels I have heard are still classic MTM designs and if you are looking for good dynamics, I definately recommend them over a two way or coaxial solution.

My HT room is 14 d x 15 w with two couches, one facing the TV and one along a wall.

One commonly used listening position is at 29 degrees off axis.
The three others are at 0 degrees, and two at +/- 15 degrees.

Is the +30 degree limit typically where lobing is apparent ?
It would seem that lobing would be evident at smaller angles if the distance to the listener is increased.
It would seem that the fdistances further away, less of a angle is required to create a NULL or 2x reenforced loud spot.
The frequencies being considered here are typically 80hz to 2 - 4 khz since the T handles everything above this.

 

[mike c]

I am also not a fan of the centers that have 2 mid bass woofers and a small mid and tweet vertically mounted.

can you expound on this or point me to an existing article on why this type of center sucks?

 

[jronne]

can you expound on this or point me to an existing article on why this type of center sucks?

These two articles discuss some of the issues ...

Here is an article from this site

Vertical vs Horizontal Center Speaker Designs http://www.audioholics.com/education/loudspeaker-basics/vertical-vs-horizontal-speaker-designs

and here is another

Center-Channel Speakers: What the Industry Often Refuses to Tell You http://www.nousaine.com/cen chan 1.htm

 

[jronne]

can you expound on this or point me to an existing article on why this type of center sucks?

BTW, sucks is a rather defining term.
I'm merely trying to get a feel for the pros and cons.
I think all center channel designs including the virtual or phantom center have drawbacks.
It is up to the consumer to pick your poison.
In audio, perfection is a fools errand but one can make the best use of ones budget.
The industry has settled on the MTM horizontal center as the only defacto choice when other choices may work better for some systems.
I'm leaning towards a high performance matching vertical TM which is not the norm and just wanted some feedback before I committed the purchase.
The choice of a TM vs MTM are mutually exclusive options, and if I change to another option I end up with an orphaned useless speaker (MTM or TM).

- jeff

 

[mtrycrafts]

...
It seems that the industry in general has prematurely settled and converged on the MTM center speaker design.
- jeff ronne

Convenience and necessity in some cases when people want a speaker under a TV or above it and the room is slim to none, limited. So, some in the industry cater to the larger market more so that the smaller one.

 

[mike c]

BTW, sucks is a rather defining term.
I'm merely trying to get a feel for the pros and cons.
I think all center channel designs including the virtual or phantom center have drawbacks.
It is up to the consumer to pick your poison.
In audio, perfection is a fools errand but one can make the best use of ones budget.
The industry has settled on the MTM horizontal center as the only defacto choice when other choices may work better for some systems.
I'm leaning towards a high performance matching vertical TM which is not the norm and just wanted some feedback before I committed the purchase.
The choice of a TM vs MTM are mutually exclusive options, and if I change to another option I end up with an orphaned useless speaker (MTM or TM).

- jeff

actually, I was talking about the WTMW setup and not the MTM or TM centers you are looking at. you see, I have a WTMW center, which is why I was curious about the "limitations" of that design.

i'm also aware of the lobing limitation of the MTM design, but since my HT seats only me and my wife, I don't really care about the dispersion problems.

note: but thanks for the link in which I was able to get this ...
http://www.audioholics.com/educatio...-designs/2500-wtmw-horizontally-oriented.html

 

[TLS Guy]

The lobing issues of MTM horizontally mounted speakers is a bit overblown. Consider that in most home theaters, the listeners aren't sitting more than 20-30 deg off axis from the center chanel, its unlikely that lobing will present itself into real world listening tests if the center channel is competently designed.

Personally, I almost never recommend a two way or a coaxial design over a well designed MTM. I am also not a fan of the centers that have 2 mid bass woofers and a small mid and tweet vertically mounted.

Some of the best center channels I have heard are still classic MTM designs and if you are looking for good dynamics, I definately recommend them over a two way or coaxial solution.

If I listen to a horizontal MTM, I hear no integration of the center at all. The dispersion is ALL vertical, aggravating room and floor reflection. To me, and others I have discussed this with, they stick out like sore thumbs.

A coaxial driver as a point source properly configured makes the MOST IDEAL driver for the center channel. Voices sound natural and coherent. There is good blending with he mains without excessive comb filtering.

This coaxial driver is absolutely world class. With a well designed crossover, it has a very smooth and extended response. Voices are coherent, stable and natural without sibilance. Music reproduction is of the first order. This is by far and away the best OEM driver you can lay your hand to as the basis for a center channel speaker.

http://www.seas.no/images/stories/prestige/pdfdatasheet/h1333_t18re_xfctv2_datasheet.pdf

It is ideal for TL loading, and if you add a second driver without the tweeter connected as the fill driver, you have an awesome speaker. The listening window covers the seating areas well, with very stable imaging. This center speaker is far better than any other I have auditioned, and is a major reason for the outstanding life like performance of this system.

I recommend this SEAS driver as the basis for a center channel speaker without reservation.

http://mdcarter.smugmug.com/gallery/2424008_RKGvb#127077096

 

[User5910]

These two articles discuss some of the issues ...
Vertical vs Horizontal Center Speaker Designs Vertical vs Horizontal Center Speaker Designs | Audioholics
...
Center-Channel Speakers: What the Industry Often Refuses to Tell You http://www.nousaine.com/cen chan 1.htm

Here's a current link for Tom Nousaine's article Center-Channel Speakers: What the Industry (Even the "White Hats") Often Refuses to Tell You. He has similar findings.

See Nousaine's archive for more.