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Old 18th December 2007, 10:07 PM   #1
jwmbro is offline jwmbro  United States
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Default Frequency range of the human voice & full range center channel speakers

Hello,

I just had an interesting idea occur to me. I searched around a bit and found nothing, so I assume that means that the idea is flawed, rather than that an idiot like me thought of some revolutionary concept.

The whole thing is based on the following assumptions, most likely several of them are wrong, but you get nowhere by not asking.
  • Center channel speakers are used pretty much exclusively for dialogue in a Dolby setup - I know the reverse is true, dialogue is exclusively on the center speaker, testable by turning off your center speaker while watching a movie
  • Human voice is mainly made up of the frequency range from 85Hz ~ 255Hz - or so wikipedia seems to be telling me
  • Vertical (or in the case of a horizontal center speaker - horizontal) listening window is caused by the interference between 2 different drivers placed above (next to) one another.

Now vertical listening constraints are no big deal to me, since I place my speakers at head hight - enough said. but with the center channel, which I prefer horizontal, I am concerned about worse sound for people not sitting directly in front of it.

So, now my proposal. Would it be possible to build a full-range center speaker out of a 5 inch driver, such as the Tang Band W5-704D, in a ~1/2 cu-ft enclosure (6"h x 9"d x 15"w or so)?
Since most 5" drivers in Zaph's driver roundup seem to be pretty linear in a range from 80Hz up to way above 255, at least 1KHz, sometimes even up to 4KHz, that should be enough to convey the necessary information right?

Or what am I missing?
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Old 18th December 2007, 10:37 PM   #2
fizzard is offline fizzard  Canada
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Speech is unintelligible without the harmonics.

Any 5” driver that I’ve ever seen is fine up to 3KHz so getting the harmonics isn’t a problem. I would build it the same as the left and right to keep it voice matched.
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Old 18th December 2007, 10:43 PM   #3
jwmbro is offline jwmbro  United States
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Quote:
Originally posted by fizzard
Speech is unintelligible without the harmonics.

Any 5” driver that I’ve ever seen is fine up to 3KHz so getting the harmonics isn’t a problem. I would build it the same as the left and right to keep it voice matched.
OK, I thought the harmonics might be the ticket. But even so, going on the basis of that same wikipedia article, 3KHz should also be manageable fullrange. And above that there are no more components necessary for speech?

hmmm, same as left and right, I was considering using a 7" woofer in a two-way speaker for my left and rights. But going from Zaph's graphs, the 7" should also handle the frequency range from 80~3000Hz fine, but using a full-range 7" seems a little drastic too me - is that a good idea?
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Old 19th December 2007, 12:17 AM   #4
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Your off axis response will be poor on a cone that large.
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Old 19th December 2007, 01:11 AM   #5
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As mentioned the higher frequencies is what makes speech intelligible. In fact I like to tone down the midbass (<250 hz) a couple dB or the speech becomes too "chesty" and harder to understand. Which is way teh oft mentioned "telephone band" is 300-3000Hz.

Also if you want wide horizontal dispersion use a coaxial driver or WTMW or TM layouts with the TM vertical. Like this:

Click the image to open in full size.

You do not want to go fullrange becomes as the woofer gets larger or as you move farther off axis, or both, the high frequencies start to drop off. You need a tweeter.
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Old 19th December 2007, 01:23 AM   #6
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The whole surround sound concept was inspired by following beliefs:

1. Listening rooms are untreated so reverberation from a signal source must be added louder than reverberation of the entire listening room (3, and even 4 extra speakers unneeded when a room is well acoustically treated, also the idea is wrong - reproduced reverberation reverberate in the room).
2. In ordinary listening rooms binaural effect on frequencies below 200 Hz is insignificant so the whole system must be cheaper with speakers that work above 200 Hz with a single box for frequencies below 200 Hz (wrong again, it is well audible).

Later, cinematography started to use presence of extra channels for special effects...

I have central and rear speakers (6.5" coaxials), but never switch them on since full range line arrays and subwoofer (below 42 Hz) sound nice in a room with mattresses on walls in appropriate places.
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Old 19th December 2007, 06:34 AM   #7
Svante is offline Svante  Sweden
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The Wikipedia numbers are probably about the fundamental frequency of the speaking voice. I would widen that range a bit. When I have a cold, my fundamental frequency is about 60 Hz. If you put kids in front of a computer program that measures f0 in real time, they can go well above 1 kHz. Sopranos can also go there.

In addition to this, there are overtones together with the fundamental. In some singing styles there are harmonics visible all the way up to 15 kHz.

But of course, the typical dialogue in a movie has a more limited frequency range.
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Old 19th December 2007, 09:42 AM   #8
Pano is offline Pano  United States
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Trying to get clear dialog I used a pair of TB W3-871 in small sealed boxes for the center channel. Sounded wimpy. One, two, whatever - just didn't have body or "size".

Sure would be nice to find a small center speaker just to punch up the dialog a bit.
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Old 19th December 2007, 04:14 PM   #9
MaVo is offline MaVo  Germany
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The linked picture shows the spectrum of me saying the vowel "ahhh" like the "a" sound in house. alot goes on from 100-1000 hz. above is less. the -40 to -60db stuff will probably be noise from my pc and neighbours.

http://img85.imageshack.us/my.php?image=ahhhqj4.jpg
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Old 19th December 2007, 04:29 PM   #10
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Center channels are there for more that dialog. If you look at the amount of information its about 50% of the total to all the speakers in a surround set-up. Looking at those numbers it should have more power handling capabillity than your L/R and Rears.

A fullrange speaker is not the best choice. You might want to look at a coax driver instead. That way you can avoid any MTM issues that plague most center channel speakers. I use a coax driver for my center and works very well.

Rob
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