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Do I need a center channel?


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21 replies to this topic

#1 of 22 OFFLINE   Thirsty Ear

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Posted March 08 2009 - 06:58 AM

I have always used 2 channel for watching movies and TV and would like to get into multi channel. I just bought a Onkyo 705 7.1.

I watch movies by my self or with my girlfriend. So I am always in the sweet spot and no one else is sitting outside of the sweet spot. I have done a great job in placement with my NHT speakers and TV. When watching news shows or movies with just dialog it seems as though the TV is a speaker itself and I can not tell the speakers are even working until other sound effects begin playing.

So do I need a center channel? I would like to spend the money I would have used on a center, on a sub instead.

Can my Onkyo play 4.1? and if so will there be any loss without the center?

#2 of 22 OFFLINE   Joseph DeMartino

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Posted March 08 2009 - 07:25 AM

Quote:
So do I need a center channel? I would like to spend the money I would have used on a center, on a sub instead.

Chances are any decent sub is going to cost several times as much as a good center channel speaker, so it isn't like you're going to save enough by skipping one to buy the other. A couple of questions:

1) Are you keeping your current front left and right speaker? If you are, you'll need a center that is timbre matched to them. Same brand, and same line of spearkers at a minimum, preferably a model specifically designed to work with them. If you can't find a match, consider replacing them. The front sound stage is one of the most critical parts of an HT.

2) You can "get by" without a center channel by using the "phantom center" mode supported by most receivers, but you don't get the control you need for true multichannel sound. Right now you're listening in stereo - so yeah, blended sounds seem to be coming from in between the two speakers when that's the desired effect, just as on any two channel analog recording.

But once you have a full 5.1 or 7.1 system running and you're listening to a full digital movie soundtrack, you'll find the experience is very different. If it wasn't, nobody would have or want more than two speakers.

Generally speaking a physical center channel speaker lets you do two things that a "phantom" sub doesn't - angle the speaker down from the top of the TV (or below the screen) to the prime listening area and fine-tune the center channel volume to make the dialogue clearer. On most systems once you've adjusted all the speakers so that you're getting the reference volume at the prime listening position (as measured by a sound pressure level meter) the center needs to be tweaked a bit so that it isn't drowned out by the music and effects from the other channels at times. I don't think you can really do that with a "phantom" center that is being produced by the very speakers that would be in danger of drowning out a physical center.

Regards,

Joe

#3 of 22 OFFLINE   Thirsty Ear

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Posted March 08 2009 - 08:08 AM

I am keeping my left and right channel speakers.

I have NHT classic Three speakers and I can buy the matched classic three center for $400. So I thought I could put the $400 in the pot to help buy a velodyne Sub.

I was wondering how the move to multi channel would be regarding having a center channel or not. I have been down mixing to 2-channel on all movies through my Oppo DVD player. The left and right speakers have been doing all the work so far.

I would like to start enjoying Surround sound as soon as possible. I just don’t have the cash right now for every component. What would be the best order in which to purchase speakers. I would like to buy in this order.

1) left and right main speaker then,
2) Sub then,
3) surround sound speakers then,
4) center speaker

#4 of 22 OFFLINE   Stephen Tu

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Posted March 08 2009 - 08:24 AM

Disagree w/ Joseph. If you are in the sweet spot phantom mode works perfectly fine. Angling the speaker down from the top of the TV isn't something that is desirable, something that you get a center for because you want to do it; it's a hack to compensate for a compromised speaker location. Ideally you want identical speakers across the front with tweeter at ear height, unangled, but with TVs (rather than front projector & an acoustically transparent screen) this isn't possible.

And boosting center channel to attempt turn up the dialog just throws your channels out of balance. If turning up volume enough to hear the dialog makes the explosions too loud for your taste, what you want is to use the dynamic range reduction, "midnight modes" or such on your receiver, not bumping up the center channel.

#5 of 22 OFFLINE   Brent_S

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Posted March 09 2009 - 09:49 AM

IMO, the bigger issue with no center or surrounds for DD based audio is the compressed dynamic range. Dolby made it part of the spec when downmixing that the dynamic range be reduced to prevent overloading of the remaining channels. There are extensive threads on this at AVS and HomeTheaterShack if anyone's interested. Apparently, DTS didn't implement any downmix "protection", leaving open the potential for overdriving the DAC stage when channels are combined by downmixing.

While I think you can find an acceptable center channel without necessarily using the same brand/family of speakers, Jack Hidley, former NHT engineer, is selling some NHT surplus. Missing from the site is a kit for the NHT VR3 & VC3 that included everything except the cabinet for $150/each...should be back once Jack & NHT figure out exactly how much inventory they have left of certain drivers. Some of the remaining kits include schematics for building the missing crossover if you want to pick up something like three XdS monitors for $100/each. :-)

-Brent

#6 of 22 OFFLINE   Mendoza

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Posted March 09 2009 - 10:24 PM

You can work around a 5.1 soundtrack coming out of a 4.1 setup the same way you can still function pretty well after a wood-chipper claims one of your thumbs. Save money by shopping around and not by cutting off an entire channel. Just my 2 cents. (My level of technical knowledge is low but I have enough experience to confidently promote the idea of 5.1 soundtracks coming out of 5.1 speakers.)

#7 of 22 OFFLINE   Al.Anderson

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Posted March 09 2009 - 11:02 PM

My opinion on the prefered order of speaker purchase is:
1a) left/right
1b) center
2) sub
3) surrounds

I said 1a/1b because really you want those three at the same time.

Stephen, I respect your opinion, you're a very knowledgable guy, but on this center channel issue I think your emphasis came out wrong. It makes sense that phantom mode works just fine if the speakers are placed well (I confess I've never tried a phantome channel system.) But I can't believe a working phantom setup is better than an angled center channel, which is what you seem to be saying. And as you point out, angling is necessary when you don't have a transparent screen; which is most of the time. Bottom line, I think it's much better to have a center channel (angled or not) that a phantom center channel.

#8 of 22 OFFLINE   Stephen Tu

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Posted March 10 2009 - 06:17 AM

I was mostly objecting to Joseph's statement that a center channel "lets you angle", implying the inability to angle was a disadvantage of a phantom setup. Where in fact the angling is a compensation for the disadvantage of typical center channel location, and it's more "with phantom you don't need to angle up/down" rather than "with phantom you can't angle".

Whether phantom works worse/better (I disagree that center channel is automatically much better than phantom, if you are in the sweet spot) depends on how well your center matches your mains, speaker placement, mains quality, and whether or not your receiver kicks in significant, noticeable DRC for DD as Brent mentioned (defeatable/not present on some receivers).

Try it out sometime, it's easy to switch on/off the center speaker in a receiver. Mendoza, the entire channel doesn't get "cut off", it is redistributed to the left/right speakers.

And I never claimed that phantom was "better", I don't see where you pull that interpretation. I am saying it can be as good, or at least very listenable, when you are in the sweet spot, when compared to compromised center channels.

But for original poster, another issue arises since NHT is going out of business. If you do want a center eventually, you want the matching center while you can still find them. So try to find a good closeout deal somewhere in the near future ...

#9 of 22 OFFLINE   CB750

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Posted March 10 2009 - 07:01 AM

I have a total of 4 TV's. Two of them have 5.1 set ups and the other two are 2.1 set ups with no center channel. I find that both of my 5.1 systems with a center channel are superior for TV viewing than either of the 2.1 systems.

The usual work around with a stereo system is to place the L & R speakers close to the sides of the TV screen. This tends to rob you of the ideal separation you should have with those speakers.

Since you already have a receiver with 7.1 capacity why would you want to rob yourself of the best sound delivery that you can have.

#10 of 22 OFFLINE   Torgny Nilsson

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Posted March 10 2009 - 04:43 PM

I agree with Al on the preferred speaker purchase order. While a phantom center can suffice, it is far from optimal. For movies, you really do need a timbre-matched center as most of the dialogue comes out of the center rather than out your left and right fronts.

But I disagree somewhat with Stephen; I think an angled center can work just fine. It may not be optimum, but it seems to be the best solution for most people. I also think that, unless your center is identical to your left and right fronts, most people will benefit from turning up their center a couple of dB. Again, perhaps not optimal, but it can result in better overall sound when you have larger fronts and a smaller center, which most people seem to have.

#11 of 22 OFFLINE   Stephen Tu

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Posted March 10 2009 - 05:18 PM

People seem to be completely misunderstanding me, you are reading in totally extraneous ideas that are not at all present in my statements above. I did not say anywhere above that angled center is bad or cannot work fine! If you have a center that's not on plane with your mains of course you should angle. I am just saying that *phantom center can also work fine, if you are in sweet spot*. And that *one gets a center channel to anchor sound for off-axis listeners*, that the purpose of the center is not the angling, the angling is just something you do to compensate for placement, not why you get the center in the first place. The angling is not the advantage of center vs. phantom as the post I was responding to implied.

You should adjust your center such that the test tone is even with the output of your mains. I don't agree with running it hot. Use sound meter / receiver auto-calibration tools. The receiver may well end up boosting the signal a few dB higher than what is sent to your mains but your target is even output.

#12 of 22 OFFLINE   Brent_S

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Posted March 11 2009 - 11:00 AM

Quote:
Originally Posted by Stephen Tu
{snippage}
...and whether or not your receiver kicks in significant, noticeable DRC for DD as Brent mentioned (defeatable/not present on some receivers).
{snippage}

I brought this particular point up because it's a little known "feature" that's not user defeatable with DD and, presumably, DD+ and TrueHD. Dolby made this mandatory in the decoder anytime downmixing is engaged. It's not the same as the user selectable "night mode" and there is no indication to the user that it's happening. The degree of compression is a function of metadata embedded in the bitstream. I once found the document on Dolby's site where the spec was outlined, but didn't save it.

If you want to see it in action, IIRC from the HTS/AVS threads, one can get an idea of the amount of compression by just using an SPL meter to measure the peak SPL in a scene then rerun the scene with the center disengaged without touching the master volume. If the phantom center were truly distributed evenly to the left/right fronts, then the overall peak SPL should stay the same. Memory says the "Master and Commander" SD DVD had some particularly aggressive compression engaged when downmixed.

-Brent

#13 of 22 OFFLINE   Stephen Tu

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Posted March 11 2009 - 01:15 PM

Quote:
I brought this particular point up because it's a little known "feature" that's not user defeatable

On some (most) receivers, but not all. Some Denons have a "DRC downmix" option. I think the amount of effect this has depends on the encoding and thus varies from disc to disc. And apparently receivers have a choice on how they implement this speaker management so it's not universal.

relevant threads:
Skip the center speaker? - AVS Forum
Receivers capable of phantom center without engaging Dolby DRC? - AVS Forum

#14 of 22 OFFLINE   Brent_S

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Posted March 11 2009 - 02:46 PM

Quote:
Originally Posted by Stephen Tu
On some (most) receivers, but not all. Some Denons have a "DRC downmix" option. I think the amount of effect this has depends on the encoding and thus varies from disc to disc. And apparently receivers have a choice on how they implement this speaker management so it's not universal.

relevant threads:
Skip the center speaker? - AVS Forum
Receivers capable of phantom center without engaging Dolby DRC? - AVS Forum

Yeah, uhm, well...uhm...but the OP has an Onkyo 705. Posted Image

I had forgotten that some of the Denon's were found to have a kill switch for the downmix protection. I didn't read every thread on the topic, having only discovered the main discussion after it had gone cold. Were any other brands/models found that gave the user an option or otherwise didn't follow the Dolby spec? HTF and AVS are still mutually blocking links and I'm too lazy to manually go search for your threads tonight.

And thanks for the reminder. I will qualify any future comments about Dolby's downmix dynamic range limiting with a "most" instead of all. Posted Image

-Brent

#15 of 22 OFFLINE   Thirsty Ear

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Posted March 12 2009 - 05:17 AM

If you copy paste the AVS form links into google it is much faster. The top hits bring you right to the wanted links. Its a very good read

#16 of 22 OFFLINE   Thirsty Ear

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Posted March 13 2009 - 02:05 PM

After reading the links and reading through all the information I could find on the web about the benefits and cost to using a phantom center, I have decided to go with and matching center speaker. I can get the classic three center for $399 through closeout deals. The Classic three center was $700 less then and year ago. I have never heard a good 5.1 system and so I will have to just try a hard center for my self and at the very worse I will just disable my center if I do not prefer the sound.


So I have a speaker placement question. Because I had used phantom center I could rase the speakers and lower the TV so the dialogue came straight from the center of the screen. Now with a center speaker should I put the center as close to the bottom of the screen as possible. Then put the left and right channels at the same level as the center or higher up?

Can a viewer sit too close to a 5.1 system as to hear too much form the center speaker?



Also will there be DRC when watching DD movies when I don’t have rear speakers?

#17 of 22 OFFLINE   Mendoza

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Posted March 13 2009 - 11:09 PM

Quote:
Originally Posted by Thirsty Ear
So I have a speaker placement question. Because I had used phantom center I could rase the speakers and lower the TV so the dialogue came straight from the center of the screen. Now with a center speaker should I put the center as close to the bottom of the screen as possible. Then put the left and right channels at the same level as the center or higher up?
That's right. Ideally you should place the center speaker directly below (or above if below is physically impossible for some reason) the TV, center it, and angle it towards your listening position--if necessary. Your front speakers can be anywhere between the height of the center and the top of the TV; if it's convenient to lower and raise them then experiment.

Quote:
Can a viewer sit too close to a 5.1 system as to hear too much form the center speaker?
It's possible, but if you calibrate your receiver properly you should be fine. And of course you can raise or lower the volume of individual speakers if necessary.


Of course, 5.1 will sound incomplete without the surrounds; godspeed. (P.S. Try the T-D/Theater Dimensional listening mode in your receiver.)

#18 of 22 OFFLINE   Brent_S

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Posted March 14 2009 - 04:37 AM

Quote:
Originally Posted by Thirsty Ear
{snip}
So I have a speaker placement question. Because I had used phantom center I could rase the speakers and lower the TV so the dialogue came straight from the center of the screen. Now with a center speaker should I put the center as close to the bottom of the screen as possible. Then put the left and right channels at the same level as the center or higher up?
{snip}
Also will there be DRC when watching DD movies when I don’t have rear speakers?

Per my fuzzy memory of the Dolby spec and some of the user "testing", I'm pretty sure the dynamic range is compressed when any channel needed by the bitstream is missing. IOW, if you're listening to 2.0 DD, which a lot of broadcast TV still is, you're not going to be "penalized" for downmixing. However, if you listen to DD 5.1 with a 3.1 array, then you will experience dynamic range loss.

Ideally, you want the listening axis as close to matched for the front three as possible. However, I would optimize the L/R mains for imaging, soundstage, frequency response and compromise the center as needed. With visual imagery, your brain is good at hearing the sound come from the screen as long as the difference between speaker and screen isn't ridiculous. Angle the center to put it on axis for the main listeners as needed. I mounted my parents' speakers on the angle of a vaulted ceiling with the flat screen above the fireplace...distance is probably 4'+ from screen to speakers, but you never get a disjointed feeling between the two. Audyssey will also help mitigate any time smearing that might happen from using different acoustical axis for the center and mains.

-Brent

#19 of 22 OFFLINE   Matt^Brown

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Posted April 03 2009 - 08:08 AM

I now want to ask the opposite of the first question.

How important is a rear center speaker. I have always ran 5.2 but never went as far as to run 6.2. I could match the front speaker which is a JBL EC35 but I am not sure how necessary every one feels this is currently. I watch no TV on this system and use it 95% of the time for X360 and 5% for movies.
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#20 of 22 OFFLINE   Matt^Brown

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Posted April 07 2009 - 05:17 AM

Bump for the rear center -- Question above.
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