Axiom Home Page Forums Thread Like Summary - 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?

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.

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 ...

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.

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