Center Channel Design Vs Spinorama Data

[luft262]

From reading online here and watching YouTube videos such as Erin's Audio Corner I have learned that center channel speakers should ideally use a coaxial or a 3 way design for better horizontal dispersion. Some people even use a bookshelf as their center channel. They make it sound like the traditional MTM design is horrible....however, if you go on Spinorama.org and look at the highest rated center channels (if you use EQ and subs, which most center channels are used with an AVR in surround sound so that sounds most likely) many of the best models are basic MTM 2 way designs. For example the #1 is the Infinity RC252, which is a 2.5 way MTM and the #3 is the Revel C205, which is a completely traditional 2 way MTM design...

What gives! These supposedly inferior 2 way MTM designs have great spinoramas. Early Reflections, Sound Power, and Directivity Index all look great.

Opinions?

 

[voodooless]

Turn 90 degrees!

 

[luft262]

Turn 90 degrees!

I must be slow... I don't get it.

 

[voodooless]

I must be slow... I don't get it.

Often these measurements are done with the center standing upright. Traditional MTM designs will perform much better that way.

 

[luft262]

Often these measurements are done with the center standing upright. Traditional MTM designs will perform much better that way.

You really think Revel would do that? Seems dishonest, but yeah I guess. There is a Klipsch 2 way measured by Erin's Audio Corner and it's near the top of the rankings. I doubt he would have measured it upright...

 

[voodooless]

There is a Klipsch 2 way measured by Erin's Audio Corner and it's near the top of the rankings. I doubt he would have measured it upright...

Vs

So, yes, what you see displayed in the spin is the vertical orientation.

 

[luft262]

View attachment 265944

Vs
View attachment 265945

So, yes, what you see displayed in the spin is the vertical orientation.

That's crazy! At some point they should re-do the rankings for center channels based on the horizontal data! Otherwise there's no way to sort them practically.

 

[pierre]

What you should look like for center is the dispersion pattern. If the center is under the screen it is usually flat (horizontal). The MTM design produces a pattern
of very narrow horizontal and wide vertical which is likely the reverse of what you want.

As explained above, if you turn them 90 degrees, then they can be very good. The low vertical dispersion can also be beneficial in a classical room. It minimises floor and ceiling reflexions.

Also depending on how far your are and how how off axis you are, you can easily compute if 20 degrees (as an example) is enough or not in your room.

Note: i can recompute the scores for center speakers if you want (give horizontal and vertical views).

 

[Beave]

A key point is being overlooked here.

These spinoramas are based on measurements centered on axis.

They're basically assuming you're going to be listening right on axis.

For a center speaker, that might be the case for one person. But it's quite possible there will be other listeners who are well off-axis. That's where the horizontal MTM design falls short. That's where a vertical MTM is better, and a three way center is probably better still.

An MTM center can be fine for one person sitting right on axis. But it probably won't be as good as a vertical MTM or a three-way center for anybody else in the room.

So instead of looking at the on axis spins, you'd need to look at the horizontal off-axis response. For a horizontal MTM, you'll see large cancellation regions that create large, broad dips in the response as you get farther off the main axis.

 

[voodooless]

A key point is being overlooked here.

These spinoramas are based on measurements centered on axis.

They're basically assuming you're going to be listening right on axis.

No, they are not. That’s only half the story. Sound power gives a very good indication of the off-axis behavior.

 

[Beave]

I have no idea what you're arguing against.

 

[luft262]

Even for standmount speakers they list a CEA2034 spinorama, which is what I think of as the main spin and a horizontal SPL spin... Are you sure that the CEA2034 spins for center channels were all or mostly done with the speaker in the vertical position? That seems crazy because 99% of people use their center channel in the horizontal position. It would be like false advertising. It seems to me you're basically saying the CEA2034 spin is the most valid spin for a vertical speaker, but for horizontal speakers, like a center channel, we have to overlook the CEA2034 and instead look at the SPL horizontal...Am I understanding you correctly?

Thank You

 

[Beave]

Even for standmount speakers they list a CEA2034 spinorama, which is what I think of as the main spin and a horizontal SPL spin... Are you sure that the CEA2034 spins for center channels were all or mostly done with the speaker in the vertical position? That seems crazy because 99% of people use their center channel in the horizontal position. It would be like false advertising. It seems to me you're basically saying the CEA2034 spin is the most valid spin for a vertical speaker, but for horizontal speakers, like a center channel, we have to overlook the CEA2034 and instead look at the SPL horizontal...Am I understanding you correctly?

Thank You

Erin's tests for MTM center speakers are done with the speakers horizontal, like they would normally be used as center speakers.

 

[luft262]

Ho much should I trust a CEA2034 spin vs a horizontal spl spin? I thought the cea2034 took into consideration off axis listening?

 

[jhaider]

An MTM center can be fine for one person sitting right on axis.

I’ve yet to find one that makes the above a true statement, up to and including Revels with 3” woofers in a toppled MTM.

The mismatch between the direct field and reflected sound is quite jarring, IME.

 

[Beave]

Well, a couple of years ago I bought six center speakers and did level matched comparisons. Four of them were three-ways; two of them were toppled MTMs.

Listening on axis, I didn't notice anything close to "jarring" that I would attribute to the MTMs. They did seem to lack a little of the spaciousness in the mids that the best three way centers had. But that was fairly subtle.

I ended up liking a couple of the three-way centers the most, then the MTMs, and then one of the three-way centers came in dead last.

So I would say a good MTM beats a poor three-way center. A good three-way center beats a good MTM.

This of course was my subjective experience in my room only.

I also did some comparisons where I listened to a toppled MTM versus the same speaker oriented vertically (a vertical MTM). The difference was quite subtle to me.

I'm pretty sure I could reliably pick out the speakers in a blind test. But when it came to the same MTM in horizontal vs vertical orientation, I would be hard pressed to reliably pick out which was which in a blind test.

To me it showed that direct sound dominates, and off-axis response is just the icing on the cake.

 

[luft262]

My thing is if an MTM design, like say the Revel C205 has a better cea2034 spinorama than a coaxial design like the KEF R2c at the very least it should sound better on axis. Unless the mfg was shady and measured it in a vertical orientation the speaker with the better spinorama should be better. I get wanting good design philosophy, but if the spin is showing a better result wouldn't that verifiable data supercede design philosophy? The spin will also take into account some off axis data in the window, reflections, and sound power graphs. But maybe I'm trusting the mfgs too much or not looking at the horizontal spl graphs enough...

 

[Descartes]

Hopefully the KEF R6 Meta performance is good! Had anyone reviewed it yet?

 

[Stiffmeister]

Well, a couple of years ago I bought six center speakers and did level matched comparisons. Four of them were three-ways; two of them were toppled MTMs.

Listening on axis, I didn't notice anything close to "jarring" that I would attribute to the MTMs. They did seem to lack a little of the spaciousness in the mids that the best three way centers had. But that was fairly subtle.

I ended up liking a couple of the three-way centers the most, then the MTMs, and then one of the three-way centers came in dead last.

So I would say a good MTM beats a poor three-way center. A good three-way center beats a good MTM.

This of course was my subjective experience in my room only.

I also did some comparisons where I listened to a toppled MTM versus the same speaker oriented vertically (a vertical MTM). The difference was quite subtle to me.

I'm pretty sure I could reliably pick out the speakers in a blind test. But when it came to the same MTM in horizontal vs vertical orientation, I would be hard pressed to reliably pick out which was which in a blind test.

To me it showed that direct sound dominates, and off-axis response is just the icing on the cake.

What were your findings? As in a list from best to worst?

 

[Beave]

I'm reluctant to make a list like that, as it was all my opinion in my room and may not translate well. Plus, only one of the speakers is still available as a current model. The rest are now discontinued.