Measurements that affect vocal clarity

[jsilvela]

Hello, first post here. Recently discovered this awesome site and been learning a lot.

I see many here have the same headache I do: to add or not to add a center channel for increased clarity in movies.
And if deciding to add a center channel, going the AVR route vs. AVP and external amp, or something even more complicated.

After reading Floyd Toole's book on Sound Reproduction (well more like skimming) years ago, I decided a center channel was a good idea and I went the AVR route (Denon), but skimped on the center speaker. (Ascend CBM-170 which amirm has reviewed; not as good as my L-R pair, Ascend Sierra-1's)

Thing is, with much of my learnings from ASR I've been motivated to do some comparison testing with "troublesome scenes" in particular movies, with / without center, or with stereo downmix but only one speaker on to avoid interference, toggling between CBM-170 vs Sierra-1 used for center... And to be honest, the troublesome scenes did not become significantly less or more clear with any alternative.
Been looking at center speaker reviews on ASR, and now I'm wondering if something like one of the Revels reviewed by Amir would make a difference.

Ok, that was setup for the question: are there specific speaker measurements that can give an indication of clarity of vocals?
Is a flat response in the speech frequencies a good proxy? Any other measurements or design parameters to look for?

Do people with a great center channel setup still get movies with muddled dialogs?

 

[solderdude]

Clarity in vocals is in the 800Hz-2.5kHz range.
So any speakers/room with a little boost (just a few dB) in that part of the frequency range will help with clarity.
A recess in that part of the frequency range lowers clarity but can be beneficial for music enjoyment (takes the 'edge' of some recordings).
This is what the 'BBC dip' was all about. A small recess in the 1-4kHz range.

 

[Plcamp]

Clarity in vocals is in the 800Hz-2.5kHz range.

I’ve seen that range quoted as wide as 300 Hz -5 kHz, but the range you quote is closer to that used by telephony, which had its focus on vocal clarity.

In any case, it makes me focus on finding a single driver covering that range, which so far leads me to conclude a horn needs to be involved. You can get point source, low distortion vocals at high spl that way.

 

[jsilvela]

I’ve seen that range quoted as wide as 300 Hz -5 kHz, but the range you quote is closer to that used by telephony, which had its focus on vocal clarity.

In any case, it makes me focus on finding a single driver covering that range, which so far leads me to conclude a horn needs to be involved. You can get point source, low distortion vocals at high spl that way.

Thanks. Any suggestions for products / brands? I've always thought horns == Klipsch.
But also: if the crossover in the vocal ranges is a problem, or THE problem, would this also not muddle vocals in stereo music?

 

[Plcamp]

Thanks. Any suggestions for products / brands? I've always thought horns == Klipsch.
But also: if the crossover in the vocal ranges is a problem, or THE problem, would this also not muddle vocals in stereo music?

Ha! I am having trouble deciding what to do, but the horns at josephcrowe.com … specifically the 600 or 800 Hz ones look great. He also tested the sb acoustic horns one one of the projects he did, and they are inexpensive,

I don’t understand your question about ‘stereo’. Not saying this is THE problem, but I do believe that maximizing vocal clarity will best satisfy what I am after.

 

[jsilvela]

Ha! I am having trouble deciding what to do, but the horns at josephcrowe.com … specifically the 600 or 800 Hz ones look great. He also tested the sb acoustic horns one one of the projects he did, and they are inexpensive,

I don’t understand your question about ‘stereo’. Not saying this is THE problem, but I do believe that maximizing vocal clarity will best satisfy what I am after.

haha. Those look interesting!

So, what I meant: going to center channel would be to get better vocal clarity, for movies that leverage it.
If clarity would improve, as you suggest, with a midrange driver / horn, then the same would be true about all speakers, and stereo too.
I.e. avoiding crossovers in vocals regions would be good design practice for clear vocals (maybe it already is?)

Anyway, to your suggestion on a midrange driver horn, I mis-read that you were making a specific point about avoiding crossover.

 

[puppet]

If this is to enhance dialog in TV/movies why not use any number of full range drivers available for a "in/out switchable" center channel?
I don't believe a full blown (2-3way) loudspeaker solution is needed here. In fact, it might just exasperate the problem.
Here's one example:https://www.parts-express.com/Visaton-FR10-8-4-Full-Range-Speaker-292-513?quantity=1

 

[DVDdoug]

Clarity in vocals is in the 800Hz-2.5kHz range.

Depending on what the problem is, boosting the higher frequencies may help. Boosting the highs brings-out the "T" & "S" sounds which can help with intelligibility and it "wouldn't hurt" to boost all the way to 20kHz (although that shouldn't be necessary... personally I can't hear to 20kHz and there's probably not much, if any, 20kHz energy in the voice).

I think the root of the problem is the dynamic range in many movies, with the dialog mixed at relatively low levels. Movie theaters are loud enough that you can still hear the dialog. Most AVRs have a "midnight mode" or a "DRC" (dynamic range compression) setting to make it more listenable at lower levels.

 

[jsilvela]

If this is to enhance dialog in TV/movies why not use any number of full range drivers available for a "in/out switchable" center channel?
I don't believe a full blown (2-3way) loudspeaker solution is needed here. In fact, it might just exasperate the problem.
Here's one example:https://www.parts-express.com/Visaton-FR10-8-4-Full-Range-Speaker-292-513?quantity=1

Thanks! I had not considered the DIY route. I'm assuming this in/out solution would not be a "real" center channel from an AVR.
In/out in what way?

 

[jsilvela]

Depending on what the problem is, boosting the higher frequencies may help. Boosting the highs brings-out the "T" & "S" sounds which can help with intelligibility and it "wouldn't hurt" to boost all the way to 20kHz (although that shouldn't be necessary... personally I can't hear to 20kHz and there's probably not much, if any, 20kHz energy in the voice).

I think the root of the problem is the dynamic range in many movies, with the dialog mixed at relatively low levels. Movie theaters are loud enough that you can still hear the dialog. Most AVRs have a "midnight mode" or a "DRC" (dynamic range compression) setting to make it more listenable at lower levels.

I don't expect clear dialog in action scenes.
But there are plenty of mainstream not-so-action movies that have scenes with muddled audio.
I've had problems with sections in "Gran Torino" for example, as well as "The Insider". The problem is diction, if you will. Did this person say this or that?
I'm wondering if a better setup would fix this, or if an upgrade over my decent (so I say) system would give only marginal improvement at best.
That's why I'm trying to find metrics or design parameters for diction specifically.
Many movies play just fine.
I will try the problem movies/scenes with DRC as you suggest. Thanks!

 

[puppet]

Thanks! I had not considered the DIY route. I'm assuming this in/out solution would not be a "real" center channel from an AVR.
In/out in what way?

I had the impression that you use the stereo as double duty ... music and movies. So "IN" when you need the dialog enhancement "OUT" when you don't.

 

[jsilvela]

On the issue of vocal clarity in movies, I think this comment hits the nail on the head:

Upgrade / Comparisons? Ascend Sierra RAAL Towers / Revel F226Be / F228Be

Thanks, I do have sub and I cross over all my surrounds at 100-12Hz and then my center at 100 and my LR at 40, but I do run my subs as mains+LFE kicking in at 120Hz, so no issue me just crossing over fronts at 80 or 100Hx to help beef up the loud on the towers. As an experiment yesterday I ran...

audiosciencereview.com

 

[jsilvela]

And, just for others who may be on the same journey.
One of my "trouble movies" is Gran Torino. Just checked the review on bu-ray.com:

Though generally clear, a few scenes, such as a conversation between Kowalski and Sue in chapter 17, plays almost like it's been filtered through a tin can.

Gran Torino Blu-ray

Gran Torino Blu-ray Release Date June 9, 2009. Blu-ray reviews, news, specs, ratings, screenshots. Cheap Blu-ray movies and deals.

www.blu-ray.com

I think that if a lot of movies are just fine on your system, trouble movies are due to the movie, not sub-par speakers / Amps.

 

[lashto]

Hello, first post here. Recently discovered this awesome site and been learning a lot.

I see many here have the same headache I do: to add or not to add a center channel for increased clarity in movies.
And if deciding to add a center channel, going the AVR route vs. AVP and external amp, or something even more complicated.

After reading Floyd Toole's book on Sound Reproduction (well more like skimming) years ago, I decided a center channel was a good idea and I went the AVR route (Denon), but skimped on the center speaker. (Ascend CBM-170 which amirm has reviewed; not as good as my L-R pair, Ascend Sierra-1's)

Thing is, with much of my learnings from ASR I've been motivated to do some comparison testing with "troublesome scenes" in particular movies, with / without center, or with stereo downmix but only one speaker on to avoid interference, toggling between CBM-170 vs Sierra-1 used for center... And to be honest, the troublesome scenes did not become significantly less or more clear with any alternative.
Been looking at center speaker reviews on ASR, and now I'm wondering if something like one of the Revels reviewed by Amir would make a difference.

Ok, that was setup for the question: are there specific speaker measurements that can give an indication of clarity of vocals?
Is a flat response in the speech frequencies a good proxy? Any other measurements or design parameters to look for?

Do people with a great center channel setup still get movies with muddled dialogs?

It is probably a miss-conception that center speakers only play dialogue/voices and/or should be optimized for that. Or at least there is no such rule for mixing movie sound. Anything could play on the center, from voices to foley to big explosions.

An EQ bump in the ~300Hz-5kHz vocal range might help and some receivers have "dialogue enhancer" functionality. But if the movie was badly mixed, nothing will give you crystal clear dialogue

Erin has a good video about center speakers but not sure how much of that stuff you should sweat about.
If you are happy with the sound being 'perfect' in just one hotspot, ~any reasonably well built center would be fine.
If you want a THX-level movie room for 5+ people this post/thread is a good start. Also make sure that your bank account agrees...

 

[Keith_W]

I’ve seen that range quoted as wide as 300 Hz -5 kHz, but the range you quote is closer to that used by telephony, which had its focus on vocal clarity.

Correct, while it is true that the frequency range of human speech ranges from 300Hz - 4-5kHz, it is the consonants like P, T, S, and K which reside around the 4kHz range. If that is missing, it will affect speech clarity.

The other known factor to impact intelligibility is excessive reverberation. According to the Law of the First Wavefront (Haas effect) if two or more sounds arrive at the cochlea within 40ms it is perceived as a single sound. Any later than that your brain thinks it is an echo. If your room is reverberant or you have multiple speakers producing the same sound with a lot of echoes it will cause smearing and make it more difficult to understand speech. You can measure reverberation very easily with software like REW, a calibrated USB microphone, and a Windows laptop.

 

[AlzalzS]

hey man, I have to say that after I added my center channel to my already 2.1, to a 3.1. I did not like it all. However once I added the surrounds I noticed full clarity and was pleased. I don’t know if it helped that I stuck to the same brand for all my speakers. Bose btw. I’m guessing different brands have their own sound signature and usually they know how their 5.1 sounds and engineer their products with that in mind. I Hope you enjoy the speakers you have.

 

[GXAlan]

Room correction can improve clarity of the voices independent of frequency response. I find that speakers like the JBL 708P have exceptional clarity in voices. Based upon the measurements, I think the slightly flatter and less downward tilt plays a role but I also find that the sweet spot for the clarity is very narrow. So, dispersion likely plays a big role in intelligibility.

@jsilvela What receiver are you using?

 

[Webninja]

If you can fit it, having the exact same speakers in the center as L and R would be ideal.

For me, it didn’t work with my setup, but I did get the Revel 426, and it is an excellent center. For those poorly mixed movies, I just boost the center via the AVR. Adding 2-4 db usually solves any hard to hear dialog.

 

[Mnyb]

Room correction can improve clarity of the voices independent of frequency response. I find that speakers like the JBL 708P have exceptional clarity in voices. Based upon the measurements, I think the slightly flatter and less downward tilt plays a role but I also find that the sweet spot for the clarity is very narrow. So, dispersion likely plays a big role in intelligibility.

@jsilvela What receiver are you using?

I think dispersion has a lot to do with it not just FR response , badly designed speakers can be helped by EQ in the vocal range it will be more intelligible but it will not sound "rigth".
So Erins video is quite spot on , but any center will help a bad stereo pair ime .

many older 2 way spaers has quite a discontinuity in Di pattern when the tweeter and midbass cross , before DI was understood the classical fix was to move xover frequency closer to 3kHz or some such to make the same driver cover as much midrange as possible . Now we have waveguides and other solutions and yes a classic 3-way with a small midrange driver is also a solution I think ?

 

[tmuikku]

Bad clarity / intelligibility is probably room acoustics in combination with and speaker coverage / DI that is not suitable for it. Bad flutter echo for example would destroy clarity no matter what the speaker system is. Reduced coverage angle by waveguide / big baffle would increase direct to reverberant sound ratio and help some but its perfectly possible you have listening distance far out in too reverberant room and didn't make too much difference. Acoustic treatment along with proper speaker and listening spot placement would be the solution. You could test if its the speaker or room by taking the system outside for a test, if clarity is there your speakers are fine and problem is the room.