JBL Stage 125C Review (Center Speaker)

[anphex]

They could just make MTM but the left and right woofer should get different frequency ranges. So a 3-way-speaker basically.
Hell for visual reasons the woofers could still be the same for all I care. This would be a great compromise for everyone. If speaker manufacturers would just be honest about this characteristic and tackle it I wouldn't be so annoyed by it.

 

[Dj7675]

I wonder what this would measure like with one woofer disconnected? Would that remove the cancellation causing the narrow dispersion?

 

[stevenswall]

So, in short the MTM design doesn't work for center speaker.
Which is just a confirmation of theory.
@amirm Is that even worth testing more then ?

I think it's still worth it to test something like this:

I'd also like someone to do an infinitely steep crossover and do the bad MTM design like this JBL... "Computer, play any frequency under 1000hz on this output, and zero of anything above it... Now Play anything at 1001hz and up on this separate output." Get rid of the archaic ideas of having any sort of slope.

Those familiar with how things work will likely say it's impossible (and it might be with current technology and software)... But then, people also said you can't address more than 4GB of RAM on a 32 bit computer, which is a lie, that megapixels don't matter for smartphone cameras, which the entire industry does now with binning or multi shot HDR, and that everything that could be invented had.

 

[stevenswall]

I wonder what this would measure like with one woofer disconnected? Would that remove the cancellation causing the narrow dispersion?

Most two way speakers even without an MTM have bad lobes/nulls and narrow dispersion vertically, even if not an MTM design.

Subtracting one side would be like putting a two way monitor on its side and listening to it off axis... Unless it's coaxial, there will be issues.

 

[Alice of Old Vincennes]

Infinity RC263 is most economical 3 way available especially if wait for random sale. Love to see Revel 2 way review.

 

[SwampYankee]

would there be an ideal spacing for using a pair of LSXs as a center channel? or is a single speaker always going to be better?

Sorry if I'm being pedantic. Things are easier if you have seating positions within a narrow arc relative to the screen. If you're close to equidistant from the L/R front speakers, you'll get a pretty effective center image and dialog sounds like it is originating from the screen without a dedicated center channel speaker. With horizontal MTM center speakers the sound levels at specific frequencies will deviate from the original signal and from position to position as the sound waves generated from the separate woofers cancel or augment each other. That's a particular problem with horizontal center speakers that rely on woofers or mid-woofers flanking a tweeter. Using two separate speakers (LSXs or others) to play the same signal doesn't help...it's actually worse. You would be extending the frequencies subject to interference and cancellation by having two tweeters playing the same signal. Better to use a single speaker in that case.

 

[beagleman]

Sorry if I'm being pedantic. Things are easier if you have seating positions within a narrow arc relative to the screen. If you're close to equidistant from the L/R front speakers, you'll get a pretty effective center image and dialog sounds like it is originating from the screen without a dedicated center channel speaker. With horizontal MTM center speakers the sound levels at specific frequencies will deviate from the original signal and from position to position as the sound waves generated from the separate woofers cancel or augment each other. That's a particular problem with horizontal center speakers that rely on woofers or mid-woofers flanking a tweeter. Using two separate speakers (LSXs or others) to play the same signal doesn't help...it's actually worse. You would be extending the frequencies subject to interference and cancellation by having two tweeters playing the same signal. Better to use a single speaker in that case.

Another issue, anyone truly sitting far off axis of the center will effectively be sitting in front of either the left or right mains speaker. That will skew the imaging a huge amount also, even with a dedicated Center.

I think the real solution is to simply not sit too far off axis.

When I am forced to sit at far sides, the center dispersion is the least of the issues.

 

[MZKM]

I think it's still worth it to test something like this:

I'd also like someone to do an infinitely steep crossover and do the bad MTM design like this JBL... "Computer, play any frequency under 1000hz on this output, and zero of anything above it... Now Play anything at 1001hz and up on this separate output." Get rid of the archaic ideas of having any sort of slope.

Those familiar with how things work will likely say it's impossible (and it might be with current technology and software)... But then, people also said you can't address more than 4GB of RAM on a 32 bit computer, which is a lie, that megapixels don't matter for smartphone cameras, which the entire industry does now with binning or multi shot HDR, and that everything that could be invented had.

Tekton has a center using their weird array:

Would love to see one of their designs measured (going off Stereophile, not too shabby, but very limited vertical dispersion).

RBH used to sell probably the worst center channel design I have ever seen:

 

[Dj7675]

Most two way speakers even without an MTM have bad lobes/nulls and narrow dispersion vertically, even if not an MTM design.

Subtracting one side would be like putting a two way monitor on its side and listening to it off axis... Unless it's coaxial, there will be issues.

Take for example the JBL 29AV-1 that Amir reviewed

JBL Control 29AV-1 Review (PA/Outdoor Speaker)

This is a review and detailed measurements of the JBL Control 29AV-1 "PA" Outdoor speaker. It was kindly purchased by a member and drop shipped to me. It costs US $409 (each). In discussion with the owner, we decided to measure and review the speaker without its grill: The grill is metal...

www.audiosciencereview.com

It has a rotatable horn, 8 inch woofer. It seems that a single woofer/waveguide combo should work fine shoudn't it? I guess my point is shouldn't a bookshelf speaker with a proper waveguide work fine laying on its side? I guess if not, I am curious why it wouldn't.

 

[SwampYankee]

Another issue, anyone truly sitting far off axis of the center will effectively be sitting in front of either the left or right mains speaker. That will skew the imaging a huge amount also, even with a dedicated Center.

I think the real solution is to simply not sit too far off axis.

When I am forced to sit at far sides, the center dispersion is the least of the issues.

That's a great solution if it's practical. A dedicated center reduces the problem of off axis positions to a significant degree when the soundtrack is sending very little of the center signal to the L/R main channels. I find it very distracting when dialog or center effects are clearly coming from the L/R. My center runs 3-4 db hotter than Audessey calibrated settings to further mitigate the issue.

At the end of the day, I want to focus on the movie we're watching and not the HT system that is supporting that. Hearing Scarlett Johansson's voice coming from two meters east of the screen is disorienting...

 

[abdo123]

I guess my point is shouldn't a bookshelf speaker with a proper waveguide work fine laying on its side?

As long as the woofer and the tweeter are not vertically aligned the dispersion will suffer. the speaker you showed has the mid-range and the tweeter vertically aligned.

 

[beaRA]

Infinity RC263 is most economical 3 way available especially if wait for random sale. Love to see Revel 2 way review.

As far as I can tell, the RC263 stock has finally dried up. I can't find it available at any major retailer in the US. The Emotiva C1+ seems like the economical option these days.

 

[3125b]

Why no coaxials as centers?
They don‘t need much bass, a 5“ would do just fine.

 

[More Dynamics Please]

Infinity RC263 is most economical 3 way available especially if wait for random sale. Love to see Revel 2 way review.

RC263 is most economical 3-way center available only when on sale. At its $500 list price several other 3-way centers undercut it. The RC263 does disappear from stock for long stretches causing speculation that it's been discontinued. But it keeps respawning and going back on sale at ridiculously low prices.

 

[Dmitri]

Why no coaxials as centers?
They don‘t need much bass, a 5“ would do just fine.

Kef utilizes them, Vandersteen VCC1 is a single coaxial. I was never very impressed with my Vandy, but that had more to do with its limited dynamic range. Can’t speak for directivity, as it’s just the two of us vying for center position with movies.
Recently replaced with Monitor C350. Just discontinued hence on big time sale 3 way design with a 4” mid...but jury’s still out.

Please god Amirm don’t test and review it. ; )

 

[sword]

So is there *any* horizontal center channel design that works properly? The whole idea seems flawed, but many people need something in that form factor.

3-way are fine. 2-way MTM is only poor off axis. Not everyone sits off axis, and many who do will never know the difference. As usual, this gets blown way out of proportion here.

Note that the Polk S30 measured pretty well and it's recommended, even though it's a MTM design.

 

[mrmoizy]

So is there *any* horizontal center channel design that works properly? The whole idea seems flawed, but many people need something in that form factor.

Absolutely. If the horizontal woofers cross over much lower, say in the 300-700hz range, they avoid "comb filtering" or playing the same beaming frequencies that cancel each other out. To cross a woofer that low typically requires a 3-way design. The mid would handle from 500hz up to the tweeter. Very doable.

The catch with a 3-way design is cost, nigh impossible to make one and sell it for ~$150. You now introduce 50% more drivers, and 100%-ish more crossover components. In a 2-way, you have the low-pass woofer filter and the high-pass tweeter filter, each requiring a handful of components. With a 3-way, you have those two filters, but then you add two more filters just for the mid-range, to fit it in between the woofer and tweeter. I've only ever designed one 3-way crossover filter, it was very challenging and I almost couldn't fit the crossover through the woofer hole into the cabinet.

 

[mrmoizy]

3-way are fine. 2-way MTM is only poor off axis. Not everyone sits off axis, and many who do will never know the difference. As usual, this gets blown way out of proportion here.

Note that the Polk S30 measured pretty well and it's recommended, even though it's a MTM design.

Sorry, didn't see yo

Tekton has a center using their weird array:

Would love to see one of their designs measured (going off Stereophile, not too shabby, but very limited vertical dispersion).

RBH used to sell probably the worst center channel design I have ever seen:

Yikes. Measure this RBH one too!!!

 

[sword]

So is there *any* horizontal center channel design that works properly? The whole idea seems flawed, but many people need something in that form factor.

3-way are fine. 2-way MTM is only poor off axis. Not everyone sits off axis, and many who do will never know the difference. As usual, this gets blown way out of proportion here.

Note that the Polk S30 measured pretty well and it's recommended, even though it's a MTM design

From Spinorama data that is out there, if the tweeter is in a large waveguide (like the the Revel C25 & C205), then the MTM 2-way configuration is not terrible; though I have not seen the horizontal plots for these speakers, so they may still be poor and their stellar vertical off-axis plots may be making the Spinoramas look better than they should.

Here is the Spin for the C25:

Interesting. The $90 JBL 520C uses a compression driver with a large horn that also overlaps the mid drivers.

 

[sword]

They could just make MTM but the left and right woofer should get different frequency ranges. So a 3-way-speaker basically.
Hell for visual reasons the woofers could still be the same for all I care. This would be a great compromise for everyone for all I care. If speaker manufacturers would just be honest about this characteristic and tackle it I wouldn't be so annoyed by it.

That's a 2.5 way design. I've only seen a few.