Frequency range of the human voice & full range center channel speakers

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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 :D
  • 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?
 
fizzard said:
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?
 
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:

IMAG0066.jpg


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.
 
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.
 
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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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.
 
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:)
 
FWIW Hearing aids (which by design are to help you hear speech better) only amplify from 200Hz - 8000Hz (with some now reaching 10,000Hz).

Also note that everyone older than 50 will develop a hearing loss from 4000Hz and up.

And if anyone cares noise induced hearing losses affect you from 3000Hz and up.

I state this as people with age-related hearing loss always report difficulty understanding speech especially females and young children. Studies show that hearing loss from 4000Hz and up causes great difficulty differentiating words that sound similar, for example: Hit Sit Fit.

As well studies have shown that 2000Hz has incredible impact on ones ability to understand speech.

I only mention this as I feel it is tremendously important that center channel speakers deliver sounds above 3000 Hz.
 
OK, thanks everyone for the help.

I guess that means I misunderstand the concept of the vertical detioration. I always assumed it had to do with interference of the waves, but how come an WTW wouldn't present with the same problems as a WT?

Would it be reasonable to consider using the same speaker, just on its side for the center, as for the fronts? (maybe the 7" - 1" two-way from Zaph) Or should I try to add a second woofer on the other side of the tweeter to make it symmetrical - would that really help?

I'm kind of confused right now, since I think I got the whole vertical distortion thing wrong.

And as for the voice stuff - thanks for the info, that's also usefull.
 
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Robh3606 said:
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.

IMO the best centre is no centre... proper seating placement and good LR that image with a virtual centre is my preference, (and my preferred LRs are FR)

dave
 
planet10 said:


IMO the best centre is no centre... proper seating placement and good LR that image with a virtual centre is my preference, (and my preferred LRs are FR)

I have the same conclusion (consensus of listeners who were my guests when watching movies), also line arrays help to spread "proper seating placement" over the entire listening room.

Yeah, and speaking of fullranges, I made woofers in composite boxes today, to go from 40 Hz to 160 Hz where line arrays start working. Very heavy boxes... One of components is Portland Cement... While checking Fs (it is 36 Hz) from output of a functional generator with 51 Ohm resistor in series I mentioned ringing in oscilloscope on the table... The box on the floor produced very quiet and clear tone. Though, decay without electrical damping on 36 Hz is about 200 mS, but it will be connected to a hybrid amp with negative Zo, and will work from 40 Hz and above (18 dB / oct crossover)


woofer-12inch-2.gif
 
IMO the best centre is no centre... proper seating placement and good LR that image with a virtual centre is my preference, (and my preferred LRs are FR)

Agreed. The centre channel was invented to achieve a wider listening-ares than just using stereo front-channels.
You end up with a larger usable linstening area - traded in for a mediocre sweet spot.

Edit: And yes, is seems as if all those MTM developers just copy each other without lateral thinking.
This is how centre channels could look also (almost every professional monitor by PMC is available in a special centre-channel config) :

http://www.pmc-speakers.com/docs/145af94f7f3cb7_TB2-C.pdf


Regards

Charles
 
phase_accurate said:
This is how centre channels could look also (almost every professional monitor by PMC is available in a special centre-channel config) :

http://www.pmc-speakers.com/docs/145af94f7f3cb7_TB2-C.pdf

So this is neither inferior nor superior to the typical symmetrical WTW/WWTWW/WMTMW type center speakers that everyone makes?
How about just using a normal 2way speaker on its side?

And as to everyone saying no center speaker is the best center speaker - that's an interesting theory, I am currently using 4 speakers myself, but when i use ProLogicIIx, dialogue becomes inaudible, because there is no center, and the pro logic wants to send all the signals to the center.

I haven't been able to try Dolby yet, because my TOSLink cable hasn't arrived.
 
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