Center Channel Frequency Response

I'm not an authority, but I don't accept the premise - or at least not fully. A speaker optimized to produce music must produce vocals too. Indeed, few (none) of us would be happy with a speaker that won't produce vocal music accurately. And, it doesn't seem to me that a speaker that reproduces vocal music would be sub-optimized for spoken word.

That said, I guess we do agonize over our speaker selection considering which models are better for vocals vs various types of instrumentals. So if you're fanatical about the vocal reproduction accuracy for your HT viewing, you may have vocals criteria, but I wouldn't go beyond that if it were me.

The initial premise is fallacious. Ideally, all the speakers should be full-range and of equal timbre, distance and level. In practice, smaller speakers can be used with proper bass management.

Poor voice intelligibility is generally due to an inadequate (or poorly designed) center speaker, poor center channel placement and integration with the other speakers and, more often than not, bad room acoustics. There are band-aids for most of these.

Oh and why rely on someone who cannot spell "tailored?"
Kal

>First question: Is the underlying premise correct?

Anecdotally, 60% of a motion picture soundtrack's energy ends up in the center channel. It gets more than its fair share of the musical score and effects.

Thanks, guys. Makes sense to me to have as full-range a center speaker as funds and space permit. And, Kal, yeah -- ditto for "intelligible."

Lou

I thought "taylored" was more egregious. I do not understand anyone posting without an active spell-checker.

Kal

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

I don't have a lot of movie DVDs, but at least one ("The Bridge on the river Kwai") has nothing but dialog in the center channel. And, you can have it in your choice of language.

Anyone who is familiar with my comments will know that I am a strong advocate of having a center channel (and surrounds) the same as the Left and Right speakers, and I attribute much dissatisfaction with multichannel sound to skimping on these "extra" speakers (and amps). My system is equal all around, but then I use it for music.

About spelling...

The European Commission have just announced an agreement whereby English will be the official language of the EU rather than German, which was the other possibility. As part of the negotiations, Her Majesty's government conceded that English spelling had some room for improvement and has accepted a 5 year phase in plan that would be known as "EuroEnglish":

In the first year, "s" will replace the soft "c"-- Sertainly this will make the sivil servants jump with joy. The hard "c" will be dropped in favor of the "k". This should klear up konfusion and keyboards kan have 1 less letter.
There will be growing publik enthusiasm in the sekond year, when the troublesome "ph" wil be replaced with the "f". This will make words like "fotograf" 20% shorter.
In the 3rd year, publik akseptanse of the new spelling kan be expected to reach the stage where more komplikated changes are possible. Governments will enkorage the removal of double letters, which have always been a deterent to akurate speling. Also, al wil agre that the horible mes of the silent "e"'s in the language is disgraceful, and they should go away.
By the 4th yar peopl wil be reseptiv to steps such as replasing "th" with "z" and "w" with "v". During ze fifz yar, ze unesesary "o" kan be dropd from vords kontaining "ou" and similar changes vud of kors be aplid to ozer kombinations of leters. After zis fifz yer, ve vil hav a reli sensibl riten styl. Zer vil be no mor trubls or difikultis and evrivun vil find it ezi tu understand ech ozer.
ZE DREM VIL FINALI KUM TRU

There are several versions of this...

Eye halve a spelling chequer
It came with my pea sea
It plainly marques four my revue
Miss steaks eye kin knot sea.

Eye strike a key and type a word
And weight four it two say
Weather eye am wrong oar write
It shows me strait a weigh.

As soon as a mist ache is maid
It nose bee fore two long
And eye can put the error rite
Its rare lea ever wrong.

Eye have run this poem threw it
I am shore your pleased two no
Its letter perfect awl the weigh
My chequer tolled me sew.

Lhf63...Research on this topic has been conducted mostly in context of noisy environments such as you describe. However, consider that the dialog of a movie is heard against the background of all the other sounds on the soundtrack. This is indeed a very "noisy" environment, even if your kids are tucked away in bed!

By the way, my spell checker thinks that "Lhf63" is a good word.

ware is doug (sedond) when we knead him?

Gee, it took a whole day for this thread to degenerate into juvenile baiting. Why I am not surprised?

Fine, don't use spellcheckers since they can't prevent all errors. Don't use seatbelts either, as they can't prevent all injuries. Only audiophiles could possibly find that logic compelling.

Lhf63...Actually, it was the second post that began the off-topic remarks about spelling. Lighten up. There is more to life than audio.

Lhf63 writes
>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?

You're going to have issues with any speaker in a placement it wasn't specifically designed for which can be worked around with equalization (shelving filters) that may take the form of room correction (Audyssey, DEQX, Lexicon's product, Tact, etc.) that's configured automatically using a calibrated microphone.

There is a lot more going on in the middle these days in film sound tracks than in previous years. It isn’t merely simple dialogue unless you are into vintage films.

Good center channel speakers will prove this out. I’ve seen in various articles regarding loudspeaker makers HT over the top, demonstrations, using all the same loudspeakers…. Fronts, center, and rear! I recall a BW demo where they used all 802Ns. Super.

Discarding momentarily my propensity for being quite anal and looking to the more practical side of life, I am not buying 5 of anything that costs $6.5K each! OK so shoot me. I’ll turn in my card. I won’t even buy 5 $4K speakers! Or 5 $3K speakers. Sorry, just being anal again.

That is the issue. We don’t live in a perfect world and overkill usually isn’t the province of every HT-o-phile.

Truth be told, one doesn’t have to buy all the same speakers to gain a very good to great sounding theater experience. Primarily due to price, and adjacently, space limitations, smaller units for the used to be “oh, by the way” sounds that films asked middle and surround speakers to reproduce for that ‘imersive’ event, are the order of the times. Those BTW sounds are becoming not so by the way sounds any more. Likewise the auxiliary 3 – 5 speakers aren’t as inconsequential as they once were.

The quest then becomes matching them all to timber.

Having a center is better than not having a center unless it is well off the voicing parameters of the ones to either side of it. It can and does work where the center unit compliments the mains versus being identically voiced to them.

I set cut offs accordingly. If center and surrounds in my system are capable of 40Hz… that’s where I’ll set their cutoffs. If it’s 65 or 80Hz, I set them there. Sorry Mr Lucas… you do your thing, I’ll do mine.

Adjusting up the cutoff serves to change the perspective of the films’ soundtrack by migrating the sound fields bass impact geographically.

THX is aimed directly at mass fi buyers. Turn key operators. Plug and players. Folks who use primarily quite limited range loudspeakers.

Bass management is for the more enthusiastic HT’er which requires better performance and has wider range reproducers on hand to cope with in his or her array. If one makes just pretty good choices in speakerage, you’ll be better served by using it to address each speaker’s needs individually. Naturally, one can of course, simply ‘season to taste’, the subwoofers influence.

There is very little if anything in audio and video which is created equally. Top to bottom, front to back… the same goes for sound tracks. I believe the notion is that we enjoy the fruit of our efforts so the consequent journey becomes either shortened or expanded due to our own points of view and levels personal satisfaction.

For the less discriminating yet still prideful owner, equalization will be a great benefit ordinarily. For the picayunish HT aficionado, tone equalization will be less a need and more a choice as closer voicing in speakers will be evident. Only room anomalies will confuse things there afterwards.

Dig what you got, get what you can, and don’t fret over what others want you to have. Adjust accordingly thereafter. You’re likely well ahead of many.

Very good luck.