Center channel: performance or placement? Pick one.

[TLS Guy]

There isn't any mechanism that I know of where it would be possible for a stereo pair of wide dispersion speakers to have good center imaging at off-axis listening positions, regardless of any other attribute of the speakers. It would be in defiance of the way human hearing works, at least as far as I understand human hearing.

Well localization is somewhat azimuth dependent depending on frequency. However intensity and phase differences remain important.

I I tested the family room system this morning, even with the screen on and off there is still excellent horizontal localization without a center.

I have to say though that localization by these speakers is extremely good. I suspect that is because the 400 Hz to 4 KHz band is covered by a superb dome mid, unfortunately NLA. Even on the couch over on the left, there is still a solid center image.

Here is a good article on sound localization from the European Annals of Otolaryngology.

I have to say, I agree with the BBC that center speakers produce a very mixed bag of results, and I am of the view that many, and likely most make matters worse.

 

[shadyJ]

Well localization is somewhat azimuth dependent depending on frequency. However intensity and phase differences remain important.

I I tested the family room system this morning, even with the screen on and off there is still excellent horizontal localization without a center.

I have to say though that localization by these speakers is extremely good. I suspect that is because the 400 Hz to 4 KHz band is covered by a superb dome mid, unfortunately NLA. Even on the couch over on the left, there is still a solid center image.

Here is a good article on sound localization from the European Annals of Otolaryngology.

I have to say, I agree with the BBC that center speakers produce a very mixed bag of results, and I am of the view that many, and likely most make matters worse.

The primary way human hearing discerns lateral localization is through ILD and ITD, much as the article you linked explains. The problem for stereo pair speakers and speaker placements with respect to non-sweet spot listening (that do NOT use time-intensity trading) is that there is no way to compensate for ILD and ITD, so any imaging collapses to the speaker that the listener is nearest. Even time-intensity trading is a flawed way to compensate for this, but it is effective. Keep in mind we are only referring to stereo systems here- two speakers. I would guess that if you heard center imaging at non-sweet spot locations from your system when it was running in stereo, you were hearing expectation bias. To know if your system can really do what you claim, you would need to run a blind listening test.

 

[RedHotFuzz]

Another option, admittedly clumsy, would be to put the center on a stand in front of your projector and AV cabinet. You might then need to pull forward your L/Rs. Of course WAF, a small room, and aesthetics might make this impractical.

The room is large, but it’s the primary living space in our open floor plan. The projector nearly 3 feet from the wall will already be a bit of an eyesore. No way could I put a center channel in front of it.

I suppose another option would be to stack the projector directly on top of the center channel, but that might look silly too.

With any luck I can get a satisfactory phantom center working. If not I’ll consider in-wall or the stacking solution.

The marketing nonsense around UST projectors sitting “mere inches from the wall” is absurd. Also, give us some models that either remove the speakers entirely or give us the option to use the built-in speakers passively from the receiver.

 

[TLS Guy]

The primary way human hearing discerns lateral localization is through ILD and ITD, much as the article you linked explains. The problem for stereo pair speakers and speaker placements with respect to non-sweet spot listening (that do NOT use time-intensity trading) is that there is no way to compensate for ILD and ITD, so any imaging collapses to the speaker that the listener is nearest. Even time-intensity trading is a flawed way to compensate for this, but it is effective. Keep in mind we are only referring to stereo systems here- two speakers. I would guess that if you heard center imaging at non-sweet spot locations from your system when it was running in stereo, you were hearing expectation bias. To know if your system can really do what you claim, you would need to run a blind listening test.

Well, I carefully evaluated my in wall system as well. Unless you get right up close to a speaker, less than 3' the center image is as stable as if the center is used, right across the listening area. I sit everyday right in front of the right speakers, and there is zero problem with a stable center image.

Not only that, but the center is a downgrade if you use it with an upmixer of two channel program. There is a slight advantage to using the center channel if the program has a discreet center channel. I stress though the improvement is minimal and my wife can't tell the difference. The reason for this is that the speakers are close together, so if you add the center to 2 channel program the output below the woofer crossover at 400 Hz is too great. So you need to reserve the center for program where dialog predominates. In other words there is too much reinforcement of the lower frequencies.

I tested the family room system again, and it is not bias. Both these systems have a very stable sound field from a wide range of positions on 2 channel program, with excellent localization. So I don't know why your results vary. But that is how my speakers are performing.

In the picture below our daily seating arrangement is for my wife to sit in the chair to the left of the side table and I sit immediately to the right of that table, which is right on axis of the right speaker. I just listened today to Performance Today, on MPR in that seat and never once localized to the right speaker. Imaging across the sound stage remained excellent.

 

[Teetertotter?]

More input:
Why need a center channel speaker - Bing

 

[JengaHit]

With any luck I can get a satisfactory phantom center working. If not I’ll consider in-wall or the stacking solution.

This is only anecdotal, but on another forum an owner of the JBL 570s (smaller version of your 590s, with the same waveguide) reports having success with extreme toe-in and time-intensity trading. Good luck!

 

[RedHotFuzz]

This is only anecdotal, but on another forum an owner of the JBL 570s (smaller version of your 590s, with the same waveguide) reports having success with extreme toe-in and time-intensity trading. Good luck!

I wonder what’s considered "extreme."

 

[JengaHit]

The problem for stereo pair speakers and speaker placements with respect to non-sweet spot listening (that do NOT use time-intensity trading) is that there is no way to compensate for ILD and ITD, so any imaging collapses to the speaker that the listener is nearest. Even time-intensity trading is a flawed way to compensate for this, but it is effective. Keep in mind we are only referring to stereo systems here- two speakers.

Any idea how omnidirectional speakers pull off their off-axis center imaging, to get around the ITD/ILD-compensation problem you speak of?

My old Mirage OMD-15s (which Mirage called "omnipolar") would maintain stable center imaging for off-axis listening, but that imaging--even in the traditional MLP--was slightly more diffuse than my earlier conventional NHT 2.5i's. It worked satisfyingly for orchestral, choral, chamber, and jazz, but not so much for 2-ch movie listening. Due to this, I had trouble understanding dialogue with the Mirage's phantom center. I've had no such problem with the Hsu CCB-8s and their razor-sharp imaging.

Interestingly, the more recent Ohm Walsh Talls aren't a pure omni design, but seem to be a hybrid of that and time-intensity trading. They use super tweeters that are aimed to cross their L/R axis in front of the MLP. And Ohm also dampens the rear-firing sound wave of its main driver. The owner of Ohm talks about "time-intensity trade-off" in this interview at the 04:29 min mark.

I haven't heard them, so I've no idea how effective this is. But there are a lot of long-term and loyal Ohm owners.

 

[ryanosaur]

I wonder what’s considered "extreme."

Crossing the streams in front of main LP... Some others can correct if wrong, but for Time Intensity Trading it's something like 1-2' in front of the MLP.
It gets considered extreme because one usually find themselves about 15º off axis with the speakers aimed just to the outside of the ears. (If not keeping them perpendicular to the front wall, that is.)

 

[JengaHit]

I wonder what’s considered "extreme."

With the Hsu CCB-8s you toe the stereo pair in so that their L/R axis crosses several feet in front of your MLP--in my set up it's about 3 ft. The owner of the JBL 570s followed this set up.

 

[mtrot]

Well localization is somewhat azimuth dependent depending on frequency. However intensity and phase differences remain important.

I I tested the family room system this morning, even with the screen on and off there is still excellent horizontal localization without a center.

I have to say though that localization by these speakers is extremely good. I suspect that is because the 400 Hz to 4 KHz band is covered by a superb dome mid, unfortunately NLA. Even on the couch over on the left, there is still a solid center image.

Here is a good article on sound localization from the European Annals of Otolaryngology.

I have to say, I agree with the BBC that center speakers produce a very mixed bag of results, and I am of the view that many, and likely most make matters worse.

Yes, I have tried numerous center speakers, but I just can't get lower male voice reproduction to match what I get out of my mains in "phantom" center mode, no matter what speaker size and crossover settings I tried on both the AVR and on the subwoofer. An example is Russell Crow's voice in The Mummy when he turns into Mr. Hyde. At that point, Hyde is in a huge room and his voice is super deep there.

Now, my Polk LSi M 706c center speaker is pretty good, but it won't match the bass extension and power of my mains. I do have other people watching movies from time to time, so it's nice to have the center channel voices coming from that speaker.

 

[shadyJ]

Any idea how omnidirectional speakers pull off their off-axis center imaging, to get around the ITD/ILD-compensation problem you speak of?

I don't believe that omnidirectional speakers can or do off-axis center imaging. It could be that in some acoustic situations there is so much cross-talk from acoustic reflections from the omnidirectional speakers that the summed sound takes on a monaural-type quality, but that is conjecture on my part. I have heard a lot of omnidirectional speakers, and they weren't able to do center imaging at a non-equidistant point from the left/right, and I have heard some of the highest-end omnis out there including German Physiks, Muraudio, and MBL.