Center channel questions

[enwar3]

I'm a little confused about what the role of a center channel is and what to use for it.

I've heard a lot of people suggest using three identical speakers for L/R/C. I'm fine with this, but I was under the impression the center channel covers a different range of frequencies, since a lot of center channels from manufacturers have mid drivers and such. Would a center channel that is identical to the L/R and cannot physically play any different work for movies and stuff?

 

[Slick5150]

Generally speaking, for bookshelf speakers the matching center speaker will often have the same internals, but is housed in a different body (longer and flatter) so that it fits better under/over your TV. Other times, especially for tower speakers, there will be a "matching" center speaker in the same product line that is designed to timber match the sound from the L/R. It may not have the same power, but it doesn't necessarily need it.

Other times, you can buy 5 identical bookshelf speakers, and that'll work just fine for L/R/C/SR/SL use.

 

[enwar3]

Well I was going to get probably 5 identical bookshelfs, but I was worried I needed a different type of speaker/driver arrangement for the center.

I was going to start with just two bookshelfs, but I'll be watching movies every so often and I hear you absolutely NEED a center for that. Get it, hear? Haha..

 

[Nohr]

Having the same three speakers for LCR is the best solution sound quality-wise if you have the room under/above your TV. What you're mainly looking for is that when sounds pan across in front of you that the center doesn't sound different than the left and right speakers.

Usually getting the matching center speaker from the same manufacturer and series as your left & rights will give you good results and will most likely fit better in the space you have. Horizontal center speakers are a size/space compromise, they're not designed that way for better sound quality or anything along those lines.

 

[Nohr]

Originally posted by: enwar3
I was going to start with just two bookshelfs, but I'll be watching movies every so often and I hear you absolutely NEED a center for that. Get it, hear? Haha..

If no one will be sat far off to the side out of the "sweet spot" you can get away with no center speaker. They call that a phantom center, some people actually prefer it (the overwhelming majority use centers however). I used a 2.1 setup for a couple years and movies were alright, it wasn't like they were unusable or anything. I definitely prefer having an actual center speaker though. Nice to have the dialog locked to where the TV is.

 

[krotchy]

Typically I see the center channel speaker as identical to the bookshelves in a given family, except that it has an MTM configuration instead of simply a TM config. I think the only reason for the MTM is to set the speaker on its side however, so that is can fit under a TV and looks more symmetrical in the system as a whole.

Using a L/R speaker as the C will not hurt anything at all.

 

[enwar3]

Ok. I've also heard that using a horizontal center with two mids causes "lobing"..

 

[PurdueRy]

Originally posted by: enwar3
Ok. I've also heard that using a horizontal center with two mids causes "lobing"..

Anytime you have multiple drivers in a speaker you will have lobing. Generally this is worst at high frequencies which is why few speakers use more than one tweeter. It's not as big of a concern with woofers however, in general, they try to keep all drivers as close as possible to one another.

 

[enwar3]

Thanks guys.

And thanks Purdue... you keep popping up in all my question threads =)

 

[alcoholbob]

With a typical MTM design you are going to have lobing/destructive interferrence where the two woofer's outputs eventually interfere with each other at a certain distance. It's fine for vertical orientation since you generally aren't going to be listening from the floor or the roof.

But for horizontal MTM you will get lobing where you get huge frequency dropoffs. In a typical MTM the crossover is maybe at 2 or 2.2KHz. You lose a lot of the fundamental frequencies of the human voice when lobing occurs in this area.

The only way to have a nice horizontale channel channel and avoid this is a 3-way center channel that has a dedicated midrange driver (to cover 550hz to 2.2KHz). The dropoff will thus occur at 550hz and below.

Of course you could just go with a regular bookshelf or vertical MTM and won't have lobing whatsoever, but most people like their horizontal centers.

 

[enwar3]

I ask this because I'm considering buying three identical bookshelfs for my fronts. Or at least voice-matched bookshelfs. A lot of centers in the line I'm looking at are really big and I'm in a small dorm room, but I do watch movies quite a bit (50/50) so I'd like to have a center.

 

[alcoholbob]

Center channel placement is tricky, especially in a dorm room, and IMO for the same amount of money, 2 quality bookshelves > 3 identical fronts.

Besides if you'll probably want a big quality 3 way center at some point when you have a bigger room instead of having some interim solution. I'm doing fine without a center channel right now (ignore my sig, I ditched the crappy center) and it works great.

 

[spidey07]

Originally posted by: enwar3
I ask this because I'm considering buying three identical bookshelfs for my fronts. Or at least voice-matched bookshelfs. A lot of centers in the line I'm looking at are really big and I'm in a small dorm room, but I do watch movies quite a bit (50/50) so I'd like to have a center.

You don't have to have a center. I haven't used one in years. If it's a small room and only one or two people two properly placed speakers will work just fine. The key is placement and if done right you won't be able to point out the speakers sonically and vocals and other center channel duties will sound like they are coming from the screen.

 

[PurdueRy]

Originally posted by: Astrallite
Center channel placement is tricky, especially in a dorm room, and IMO for the same amount of money, 2 quality bookshelves > 3 identical fronts.

Besides if you'll probably want a big quality 3 way center at some point when you have a bigger room instead of having some interim solution. I'm doing fine without a center channel right now (ignore my sig, I ditched the crappy center) and it works great.

Depends on the seating arrangement. Considering most people sit directly facing their center channel, lobing isn't as bit of a concern. Now if you have seats all around the TV, then maybe I might look into it a bit.

 

[PurdueRy]

Originally posted by: Astrallite
With a typical MTM design you are going to have lobing/destructive interferrence where the two woofer's outputs eventually interfere with each other at a certain distance. It's fine for vertical orientation since you generally aren't going to be listening from the floor or the roof.

But for horizontal MTM you will get lobing where you get huge frequency dropoffs. In a typical MTM the crossover is maybe at 2 or 2.2KHz. You lose a lot of the fundamental frequencies of the human voice when lobing occurs in this area.

The only way to have a nice horizontale channel channel and avoid this is a 3-way center channel that has a dedicated midrange driver (to cover 550hz to 2.2KHz). The dropoff will thus occur at 550hz and below.

Of course you could just go with a regular bookshelf or vertical MTM and won't have lobing whatsoever, but most people like their horizontal centers.

Lobing typically occurs off axis and is not necessarily a problem only at the crossover frequency. It depends entirely on the listening angle and the distance between the woofers.

 

[alcoholbob]

Yes, lobing is irrelevant if you are doing PC-TV, but that's why I said he should do phantom center and then get a 3-way later for a bigger room. With a 2-way it's not unusual to get -10db output from 550 - 2KHz as little as 30 degrees off axis from the tweeter. So if/when he gets into a living room setup the three-way horizontal center would be ideal.

 

[enwar3]

Well it won't just be me it's more for like a bunch of friends getting together and watching movies/playing games. But if two speakers will work I'll talk yourall's word for it =)

 

[PurdueRy]

Originally posted by: Astrallite
Yes, lobing is irrelevant if you are doing PC-TV, but that's why I said he should do phantom center and then get a 3-way later for a bigger room. With a 2-way it's not unusual to get -10db output from 550 - 2KHz as little as 30 degrees off axis from the tweeter. So if/when he gets into a living room setup the three-way horizontal center would be ideal.

I don't agree with your figures here. Off axis response suffers the most from the tweeter which obviously is above the range you specified. Provided the woofer is crossed low enough to prevent it from beaming it's off axis response is typically enough to get it far enough into the crossover that if you did get a null you would get it at the crossover frequency and it would be very brief.

Now the lobing effect of any multiple driver system cannot be avoided fully. Not even if you add another driver to the mix. It's true that it can be minimized via good use of drivers and a well placed crossover frequency. However, adding a midrange does not magically fix lobing.

 

[PurdueRy]

Originally posted by: enwar3
Well it won't just be me it's more for like a bunch of friends getting together and watching movies/playing games. But if two speakers will work I'll talk yourall's word for it =)

I will agree that 2 speakers is fine. I like a dedicated center better, but spending more money on 2 speakers on a budget is the better option.

 

[alcoholbob]

Yes, you will always have lobing in a hoizontal center. A good 3-way would absolve lobing for the fundamental frequencies of the vocal range which most would consider the biggest drawback of a horizontal center. You can't do too much about the other frequencies. IMO its the best option to remain decor friendly.

 

[alcoholbob]

Out of curiosity what brands are you looking at.

 

[enwar3]

I'm thinking Primus 152s or 162s. Taking into account sensitivity, bass extension, and price, I just can't for the life of me figure out which speakers to get =)