Center Channel help: Unique design application

**djg** · 02 July 2008, 08:56 Wednesday

https://www.billfitzmaurice.com

**---k---** · 02 July 2008, 09:15 Wednesday

I think you need to expand on your goals, or you're going to get a lot of recommendations on how to build a theoretically-perfect outdoor theater for 500 people.

I'm assuming you want something cheep and fun. I'm assuming that you're not trying to do surround sound. And you might as well forget about subwoofers. That gets you down to 2-channels.

In that application, you have lots of compromises. I'm not sure a center channel is worth the limits. Center channels are good for anchoring the sound to the center of the image for the off axis seats. It appears most of the people will be sitting directly in front of the screen. If they are all sitting back 15 - 20 feet, I think a phantom center would be just fine.

I think you were on the right path with a pair of line arrays on either side of the screen. Maybe also consider some pro-like speakers. I can't think of good examples of either off the top of my head.

BTW, my wife asked me if we could do something similar last week. So, it isn't so goofy. My plan, if we ever do, is to just grab a pair of old small Paradigm speakers and enjoy being outside more than the sound.

**cjd** · 02 July 2008, 09:55 Wednesday

Remember that technically, out-door screening to a crowd may require a license.

I'm going to disagree and suggest that a center may help - a lot. But I'm also going to suggest you move to an acoustically transparent screen.

Bump the output from ~800Hz - 3000Hz slightly, that may also improve intelligibility. Sometimes understanding how we process sound can help.

What speaker(s) are you using now? That may also help.

**kenallwine** · 02 July 2008, 10:09 Wednesday

I guess I didn't provide a good picture of what I am doing right now. I actually do have a surround sound set up going on right now. That is why I am having an issue with the center channel. The surround decoding is working well as I have gotten complements on some of the program material we have seen.

I am currently using a design I built for the front three speakers off of P.E.: the Golden Boys and they sound terrible for movies. They are a little better than originally designed since I tweeked the cross overs a bit and put in a better mid-range driver. But, off axis response is bad and there seems to be a lot of comb filtering.

I do plan on building the TUBA 24 for the sub system off Bill Fitzmarice's site. I also was thinking about the SLA center channel on his site as well or the Cynosure on P.E. sites (the Tang Band drivers are on back order until sept.) which is longer than I want to wait for a solution.

Here is my construction page on backyardtheater.com so you can get an idea of what I have been up to:
510 Cinema

It is all about having fun outside with a decent sound for a relatively inexpensive price.

**kenallwine** · 02 July 2008, 10:13 Wednesday

Originally posted by cjd

Remember that technically, out-door screening to a crowd may require a license.

.

This is true if it was a public showing. These are "private" showings by invite only. No different that inviting friends over to watch a movie in your living room. Just much bigger and outside. We have been doing this for a few months now and have had no complaints or visits from the local men in blue.

**cjd** · 02 July 2008, 10:16 Wednesday

Um. Changing drivers, tweaking crossover? Those things could actually end up making measurable negative differences, even though your ear might prefer. I don't know your process to say if I'm way off base here, but my first thought is that these changes you made may not be helping things at all.

I was going to suggest the Magna Cum Laude as a budget "outdoor" speaker that might fit the bill perfectly.

C

**cjd** · 02 July 2008, 10:18 Wednesday

Originally posted by kenallwine

This is true if it was a public showing. These are "private" showings by invite only. No different that inviting friends over to watch a movie in your living room. Just much bigger and outside. We have been doing this for a few months now and have had no complaints or visits from the local men in blue.

Oh, I know there is a fine line, and it's unlikely you'll have any issues. But one neighbor that doesn't like it could be trouble.

I have a neighbor that loves to blast his music from his deck (and sometimes movies) - incredibly annoying, he never asks. I sometimes can't even make music in my house with all my windows closed drown out his noise. So I get tempted to call him on public broadcast.

**Mark Seaton** · 02 July 2008, 11:40 Wednesday

Originally posted by kenallwine

The first row of seating is back 15-20feet. Obviously, I am looking for an inexpensive design as this is for an outdoor application and will only be used on 2-3 weekends a month for 6-7 months a year. I couldn't justify the cost of a over built design.

What do you consider inexpensive?

The coverage area is a bigger factor as is aiming of the speakers. I would think you can get some good results with the speakers above the screen and mounted to the railings so long as they were properly angled down. You might want to mount the left and right a little lower, closer to the bottom of the railing.

I would be very surprised if you could get good sound from more than one seating distance with "The Golden Boy" design. There is certainly room for a lot of improvement there.

**Kal Rubinson** · 02 July 2008, 12:46 Wednesday

Use the in-dash speakers. :roll:

Kal

**kenallwine** · 02 July 2008, 13:21 Wednesday

On the center channel, given the wide variance on driver price, I would say I would be willing to spend $200-$300 for an upgrade.

**augerpro** · 02 July 2008, 14:00 Wednesday

I can't think of any designs off the top of my head that would work well, maybe those MAgna Cum Laude. Something use a pro 8" coax and 12" woofer would probably be ideal. B&C makes some nice ones, but that might blow the budget. PAudio makes some cheaper 8" coaxes...I dunno. Hifi speaker aren't an ideal use here. As mentioned you may try bumping up the 800-3000hz area, although the problem is probably those PE speakers you are using now. It will probably take more than $300 to this *well*.

**augerpro** · 02 July 2008, 14:09 Wednesday

I looked into this a little more and B&C makes a 8" coax with a crossover: the 8CX21. Usspeaker has them, verify that it does come with the crossover though. And this is a very high quality coax. Then I would get a cheapish 12-15" pro woofer and use a Behringer CX2310 to cross that to the 8" coax. You could probably do this for $400 or so.

**Saurav** · 02 July 2008, 14:18 Wednesday

What about Eminence? I think they're generally considered pretty good value for money? They have coax drivers too, and crossovers, but I'm not sure how specific the XOs are to a given coax + compression tweeter pair. Should come in at a lower price point than B&C.

**kenallwine** · 02 July 2008, 14:27 Wednesday

Originally posted by augerpro

I looked into this a little more and B&C makes a 8" coax with a crossover: the 8CX21. Usspeaker has them, verify that it does come with the crossover though. And this is a very high quality coax. Then I would get a cheapish 12-15" pro woofer and use a Behringer CX2310 to cross that to the 8" coax. You could probably do this for $400 or so.

Would you really suggest a 12-15" woofer for the center channel? For the short term, I am only looking to change the center channel design. That is what I am willing to spend the 200-300 on.

**mayhem13** · 02 July 2008, 19:03 Wednesday

My Backround is in live sound work so i may be able to help a little here. I'd scour Ebay for used PA gear-powered monitors preferably. Tons of DJs selling off their stuff all the time. Some Bose or JBL units would do the trick with active XO and amps. Even some cheap Behringer units would be OK. Get em off the floor and angle them down towards the seating area for better dispersion. I'd support you on the DIY effort but i don't think anyone makes any active amp/xo modules for mounting in the enclosure.

**Carl V** · 02 July 2008, 19:31 Wednesday

I agree mount them above the screen if possible.
The Concrete will create a multitude of reflections.

The DJ PA speakers is a good choice.
Otherwise Horn speakers.

I did a large Malestrom/HE10.1 combonation.
For a church & School. they ahve been used
both indoors & out-of-doors for films & programs.
It rocked. You could do the same with the
8" or 10" eminence Coaxial with a 12" under.

Nice project....I never heard of that site.

**---k---** · 02 July 2008, 22:23 Wednesday

Originally posted by cjd

Um. Changing drivers, tweaking crossover? Those things could actually end up making measurable negative differences, even though your ear might prefer. I don't know your process to say if I'm way off base here, but my first thought is that these changes you made may not be helping things at all.

I was going to suggest the Magna Cum Laude as a budget "outdoor" speaker that might fit the bill perfectly.

C

Well, it looks like my assumptions were wrong. I'm with CJD. Building a proven design based on real measurements is the best way to go. PE has had other projects with big drivers, but most of the drivers are now discontinued.

One of Bill Fitzmaurice designs or some used DJ gear would probably be a good bet.

**kenallwine** · 03 July 2008, 08:53 Thursday

I am trying to say away from having to get too much additional gear for the system so the DJ equipment would not be 'ideal'. What would you think if I would build two WMTW enclosures and power them with a seperate amp from my reciever's center channel line level output as a single center channel set up?

I would really like to build something for the center channel.

I might do the Magna's over the winter but I need a short time line solution for the center channel.

Center Channel help: Unique design application

Center Channel help: Unique design application

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