Axiom Home Page Forums General Discussion Home Theater Center channel comb filtering

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"