Center Channel Frequency Response

That quote was from me. OK, OK, so I don't always spell correctly. I'm sure you guys never make a mistake.

You guys really need to do some research about reproducing speech for best intelligibility. Much research has been done on this subject, particularly in context of hearing impairment and high noise environments. Note that I referred to dialogue in movies, not singing.

Here is a sample quote from one paper...

"High-quality speech systems need to cover the frequency range of about 80 Hz (for especially deep male voices) to about 10 kHz (for best reproduction of consonants, which are crucial to intelligibility). Response below 80 Hz must be eliminated to the extent possible: not only do these frequencies fall below the range of the speech signal, but also they will cause particularly destructive masking at high sound levels."

"High-quality speech systems need to cover the frequency range of about 80 Hz (for especially deep male voices) to about 10 kHz (for best reproduction of consonants, which are crucial to intelligibility). Response below 80 Hz must be eliminated to the extent possible: not only do these frequencies fall below the range of the speech signal, but also they will cause particularly destructive masking at high sound levels."

So, 80 to 10kHz is necessary, OK. However, eliminating response outside that range is either irrelevant (if there is no signal content outside the range) or a big mistake resulting in loss of program material (if there is signal content outside the range). So, if it is the latter, one may achieve some advantage in voice intelligibility but at the cost of loss of other content. IMHO, a bad trade-off.

Kal

Actually, the idea of a limited HF frequency range does have some merit specifically for movie soundtracks . . . but it is actually my opinion that VERY few "center-channel" loudspeakers have anything near the required performance anyway, so in most surround-sound systems it can be a moot point.

But the main point is one of "X-Curve" compensation. At some point there was a movie-industry standard established for rolling-off the high end in the sound mixing studio, on the assumption that this emulates the typical commercial cinema acoustic that has lots and lots of HF absorption. I'm not sure if all, or even the majority, of film sound studios use this compensation, but it is a major reason why so many movie soundtracks are REALLY bright. And compensation for the X-curve is the cornerstone of home THX signal-processing (that's where "Re-EQ" comes from).

My theater system is in a controlled acoustic environment, and has had parametric EQ applied for really dead-nuts flat frequency response from all channels. For X-Curve compensation, I've found that a modified approach that applies full compensation in the center-channel, slight compensation in the left and right, and no compensation in the surround channels gives the best results on most movie soundtracks, but for the REALLY bright movies I have a preset for full compensation across all three front, and a slight bit in the surrounds. And for older movies or music surround, I usually like it set to flat response.

From this I would infer that in a situation where a center-channel is being used primarily for movie soundtracks without EQ presets or THX signal-processing, it may be indeed be a justifiable approach to modify the center-channel's HF response from what would normally be used for music reproduction.

if you don't have to worry about more people than, say, you and a significant other watching television, i would suggest you try going without a center channel and just sitting in the sweet spot when you can.

people like them for off-axis listening, of course, but i've never liked center channel speakers when i could sit within a couple of feet of the center.

that being said, if you do need one, i agree that it should be as close to full range as you can get. i've heard systems where the center speaker wasn't in the same frequency response league as the L+R speakers and it sounded bad to me. and i would think that even 80 wouldn't be a great low end. i had a center that went to 50 and it didn't seem to be enough to me. tons (too much, if you ask me) of sound is sent to the center channel normally and you'll miss it.

Eldartford: Years ago I actually did do some research on speech intelligibility in high-noise environments, as I was developing a radio communications simulator for military application at the time. I just don't see the applicability of any of that to my living room. I've been in military tanks and helicopters, and my living room isn't that noisy, even with my two sons running around. :)

As to spelling, when you speak as an authority (as seems to be the case here), it would serve you well to run the spell check on your posts.

Kirkus: I tend to agree that some movie soundtracks are overly bright, whatever the reason. I actually like the idea on some speakers of being able to tone things down a bit (James Loudspeakers, VMPS, probably some others). I wouldn't mind having tone controls on my preamp either, but I don't have them right now.

Dcrugby: I've gone without a center for years. With two kids now, plus me and wife, we don't all fit in between the front L & R speakers anymore. That's why I'm considering adding a center channel.

All: Thanks for the responses, whether I agree with you or not.

Final question: Given that a center is useful *for me*, and that broad frequency response is desirable, am I going to have issues with a nearly full-spectrum speaker sitting in a hutch on a shelf above the TV?

Thanks again,
Lou