Erin’s Audio Corner posted his long awaited video on center channel comb filtering a few weeks ago. It’s best to watch the video in its entirety to understand what that means. TL;DR, horizontally arranged drivers of the same size tend to promote comb filtering effects, where sound has amplitude peaks and valleys caused by constructive and disruptive interference. (The vertical effect doesn’t bother us because our ears are horizontally arranged).

He talks about the most common center channel configurations (M = midrange driver, T = tweeter, W = woofer, C = coaxial tweeter with midrange): MTM, MMTMM, WMTMW, WCW, WTTW, WTMW.

https://youtu.be/GZrdsxrcpBw

This topic has been around for decades. Audioholics noted this issue a long time ago:

https://www.audioholics.com/loudspeaker-design/center-channel-speaker

https://www.audioholics.com/loudspeaker-design/comb-filtering

On the other hand, Alan Lofft thought this as inaudible beyond listening to pink noise:

https://www.axiomaudio.com/blog/comb-filtering-popular-misconceptions/

Erin measured up to a 5 dB difference at the seating position, a very noticeable effect. My own center channel, an Angstrom Modular Six, has the worst configuration (TMT) possible for comb filtering, and I can clearly hear the artifacts when listening to pink noise. Here’s the thing: I don’t notice it on music or dialog at all. In fact, it’s a good timbre match for the M5HP mains once I dial away the lifted top end that all my Angstroms have (though it runs out of steam if I push it beyond 75 dB).

So I’m siding with Alan for now. What’s your experience with your center channel setup?

My 150v2 was horrible off-axis. The 160v4 fixed it all. Interestingly enough, I had a $40 Soundstage MTM a long time ago and it had no off-axis problems. My lady-friend has a bottom-of-the-barrel Sony MTM that is also very good with her M5s.

Its one of those compromises you have to take if no other options exist. In general, a matched speaker for the LCR front speaker is best, but hard to accomplish without a projector and AT screen.

That said, new laser projectors work well in lit rooms, and good AT screens can be found on Amazon. So options are better for the DIYer than a few years ago.

I havent met a VP180 or VP150 yet in person. I have met the VP100 and VP160. Both were fine and I didnt notice any problems.

Btw another good thread! I really like Erin’s audio corner as well. Watch them as they come out and working on back videos. Rich with info.

Imagine a setup with Dutch and Dutch 8C all around!! Broke! Lol.

I’ll read those links and get back to you.

I’ve haven’t had any problems with the V4 150 or 180 … but I’ve only listen to content. I have sat in all the seats and these centers sounded great in each. A kind of interesting data point is that to date I’ve haven’t ever experienced comb filtering in any speaker setup … I guess I’ve never gone looking for it. I figure it must be pretty subtle if you need specific content (pink noise) to find it. But that’s just been my experience… your mileage my differ.

With the actives, for both music and movies, I've found a centre to be detrimental at MLP+/- 1 seat.

The virtual center sounds far more natural than the more point-like imaging from a real center. The image is diffuse, large and very natural. It's very interesting how I can hear images not only in the centre but also slightly left and slightly right of centre. With a center speaker, those lateral images collapse to the centre.

There is absolutely no way I am going back to a center speaker.

Mojo, as long as your happy with the LFR imaging window I agree, it's best to go virtual . Once outside that window, a hard center, IMO, ends up being a requirement. The trade off being a fantastic stage for the middle seats or a very good stage for everyone.

I'm also very happy with the phantom center with the LFR Actives. I've also given up on having friends who care about audio enough to notice being outside the sweet spot. I usually only have one person over at a time, and I do give them the center seat for the best experience, but honestly, my social life normally exists outside the house, so 99% of the time it's me and only me enjoying my setup, which means I have no problem having every other seat be compromised.

Then ... Ya good to go CV.

It would be nice to have a few selectable setups for a pre-pro. Then you'd select a virtual center or hard center depending on who's in the room.

Ok. I read all the articles. Based on their information (I should note without citation to any external sources in them) I think the following.

I like Alan.

I would choose higher dynamic capability (more drivers) over less capability with single drivers covering a discrete frequency range.

Higher dynamic capability means having a fixed center channel of same model as L/R channels if possible.

Every setup employing a subwoofer with dissimilar distances between channels and sub(s) results in comb filtering. All setups.

Our hearing mechanism uses comb filtering as a tool to effectively determine direction and distance of sounds. Our ears are a comb filter generator.

Rooms with lower decay times or treated early reflections are more probably affected by perceived comb filtering by test tones or pink noise mono signals. Rooms with strong early reflections and longer decay times are as affected, but less perceivable.

Pink noise signals are used for system setup, tuning and validation. Not enjoyment.

All systems with subs have comb filtering.

All systems with two speakers playing a center panned singer have comb filtering.

Timing masking caused by misalignment of channels to eachother or misalignment of channels to subwoofers is much more detrimental to sound reproduction. And audible!

Dynamic range is far more important in the enjoyment in sound reproduction than debatable sound artifacts due to multidriver designs.

But what's your take Trevor? Or are you sayin' "it depends"

If you have a closed room that is perfectly treated and all speakers are correctly time aligned, and subwoofers are equidistant to mains, and phase and time aligned at the crossover, it may be something to worry about… During intent listening of pink noise while rocking your head back and forth!

At the end of the day, I trust an Axiom product to do its job without fear of design neglect. All horizontal centers, even the best ones, are compromises. If worry is beyond abatement, choose a matched speaker with an AT screen.

I think for CV and Mojo to experience center channel content adequately they need an LFR as a center channel, and a db boost to it vs LR channels, as is the case when a mono signal sums to create a phantom center vocalist. For matched LCRs the center channel should be louder than an auto setup routine would decide.

A point source center speaker vs LFR L/R would no doubt sound unnatural. Integration of the front soundstage would break during pans in content. I would assume the effect would be like a star collaping into a black hole and then exploding again. (Hyperbole of course!)

For 1 or 2 listeners, it makes no financial sense to make this investment. Cheaper way is to use a large QRD diffuser on the front wall behingpd the center channel. Again, an AT screen is needed for this to perform correctly.

My take is non issue in practical applications. Millions are happy with soundbars. “Combfilters R Us”

I think I'd agree with that ...

My biggest question is the behind the screen QRD filter with LFRs (my use case). Would it effect their widened image in 2 channel? I'm hoping it's not an issue.

It's an experiment ...

Mojo, what size screen and how far apart are you're speakers that you can identify the pan so precisely?

Two issues come to mind:

• if the speaker spacing is much more than the width of the screen then the dialog does not come from where the image is when far right or left. A pan across the screen is unnaturally wide ... it's unsetting ... it actually sweeps though the screen as you watch the actor walk 1/2, 1/3, or 1/4 the distance.
• if the screen is small and the speakers are on either side ... then to detect a change in angle becomes difficult.

12' apart. MLP 14'. 5' screen. Backs of LFRs 2.5 feet away from front wall. LCD screen hanging on the wall.

My impression is that when audio comes from on-screen objects, that audio is localized in the center - most of the time. I've noticed in wide angle shots, sometimes there's an explosion away from center and for a critical listener like me, I do see the audio-visual discord but it doesn't bother me.

The best way I can describe it is that the centre image fills the area of my 5' screen. It really does sound like the image source is at the screen center and expands from that point. The 160 did that but it was less diffuse, more focused, less natural. And not always, but quite often, I hear voices to just right or left of centre. For example, when two people are sitting at a table talking to each other. I never heard that from a physical centre speaker.

I don't find the pseudo center image wanting. Volume is ideal. With the 160v4, it was too focused relative to what I have now and sometimes I had to bump up the center gain. Not nearly as much as with the 150v2 though. I have never found the pseudo center image to be too quiet even in older movies.

Well, I think it's fair to call this a non-issue.

I'm disappointed that EAC, Audioholics, and ASR ought to be on the front lines of sweeping away audio myths, but are just perpetuating another set of myths to a newer generation who doesn't know any better. I'm sure I'd enjoy a Dutch & Dutch 8C, Genelec 8361A, or Revel Salon 2's in my living room too, but I think they grossly overstate the increase in marginal utility because Erin and Amir have the bias that if it doesn't rock 105 dB, then it's a compromised design. (I live in a duplex, so that's not a performance target I value)

The only place I get reliable information nowadays is from Andrew's Axiom Audio YouTube channel. I sort of laughed when I rewatched the video on DAC's and he was trying to subtly hint that they're excess unless you're streaming from a computer. He walks that fine line of trying not to offend the hard core audiophile, but I don't even think that's Axiom's target market. If it were, their marketing would look more like Bryston's.

I've tried this with two difference screens with my LFRs about 12' apart.
With my 27" monitor (was using it to setup the 8805). Playing a movie on a 2' wide screen and having the sound stage at 12' was disturbing. Then I hung an old 46" TV which made the setup almost viewable but not realistic if the sound was not somewhat centered.

I wouldnt hold anything against Amir or Erin. They are doing their best and their work is invaluable!!

They just dont or cant present audio as a holistic approach. Honestly, their content would not be as digestible if all factors were covered with as much oversight. Too much to sift through.

I should make an opinion thread with my ranked factors of sound reproduction. Frequency response would not rank as high as I used to believe. My DIY towers are junk by Amirs standards. Junk! Lol.

Honestly ...
if you started in with it's possible to hear this but in most cases you won't notice it ...
Your mail box will fill with all the people who will tell you they would notice (probably with a few words rating your intelligence )
But you can say that you never noticed it ... then they will be ok with it because you just have a hearing problem

I've been in this hobby for 3 decades. The more I research, the more I think the future of home audio is wireless sound bar systems. I did an experiment to see the minimum width a 3 channel bar had to be to be perceived as a soundstage rather than a mono point source from my 8 foot seating position. It's 40 inches, and a neutral frequency response goes a long way in making it a viable alternative.