open baffle center channel?

**Xander** · 23 December 2008, 12:23 Tuesday

I'd check out the classified section at www.diymobileaudio.com/forum to try to get some Ascendant Audio poly cones. I used to see them around there, might be able to find a couple!

**Face** · 23 December 2008, 17:50 Tuesday

Have you tried running in phantom mode? As long as you have a large "sweet spot", it shouldn't be a problem.

**Undefinition** · 23 December 2008, 22:40 Tuesday

Originally posted by matt12v

hey all! I have searched and searched and i have not found much if any talk of open baffle center channel designs. I wonder if there is a drawback to using an open baffle speaker as a center channel?

First off, those are REALLY beautiful! :T

You know, having done two OB designs, I have quite a few opinions on them. Most of them positive. :W But honestly, their best use is for music. For HT, I think I prefer monopole speakers.

Here's a bit of commentary I posted on Mark K's site...

I have always been fascinated by dipoles ever since my father got a pair of Martin Logan electrostatics. He totally had them set up wrong, but the theory behind them made sense to me in some intuitive way. Even before I got into DIY, I knew that someday I’d have to own a set, and really put it through the works.

I think your idea that most people just parrot what others say about the way dipoles sound is true–especially dipole bass. All the times I’ve heard dipole bass I’ve strained my ears to figure out if the sound really sounds any more “real” than a well-designed sealed, vented, or transmission line enclosure. (And I’ve been a percussionist for 15+ years, playing in every shape and form of concert band, orchestra, jazz combo, rock band, you name it) However, there IS a difference in the midrange. Going back and forth between a monopole speaker and the Aethers or Sunflowers makes me realize that dipoles are sort of “meant for music.” Yes, you can watch a movie with them, and everything about the movie will be clearly intelligible, but there’s just something about the 3-dimensional soundstage of dipoles that’s a bit unsettling about movies (perhaps if we wore 3D glasses while watching the moives :-D)

For music, the 3-dimensional soundstage is a natural match. Yes, the feeling of sounds existing in different spaces of the Z-axis IS an illusion, just as a hologram is an illusion, but my brain finds this novelty very enjoyable. With the exception of a marching band doing a “company front,” most live music is played with musicians standing at various spots within a room, and dipoles sort of bring that feeling back into a recording. Again, it IS an illusion, and it may not even be accurate (for instance, you may hear the flutes behind the trombones), but the “feeling” of depth is a natural fit for my brain.

But they’re not for everyone. Some people spend far more time listening to speakers than live musicians; and the “depth” of soundstage can be confusing or downright offputting. I know they say that the ultimate goal of recorded music is to replicate an actual performance, but for a lot of people, it’s just about having a good time. And who am I to take away their fun?

**matt12v** · 24 December 2008, 03:36 Wednesday

Thanks for the input guys, I still am looking for a couple of the ascendant audio 6.5 polys or a whole new set of matching mids (not sure what yet). I will be checking around that forum though thanks Xander.

I tried running in phantom center mode but I think the sweet spot is a little too narrow to get an accurate image of the dialogue in places.

Paul thanks for the compliment. I like your web site, great speaker designs too! I hear what your saying. I'm thinking the same way. Its not a good idea to mix these speaker design types because it almost produces 2 different dimensions to the sound. I found the problem really gets worse when the speakers are placed further apart also.

Tonight I made a mock up open baffle center channel using an enclosed tc sounds 10", 2 morel 5" with a dayton 3/4" tweet on the baffle just under the screen. After some tweaking and careful positioning I think I got the type of sound I've been missing. The center image is so open and airy now. The front soundstage now feels like a tall wall of sound and blends better overall. I think it could be a lot better though. It doesn't compare to the WWMTWW center I had before. Only in the way the RS52 dome mid had better dialogue and imaging. Every design has its trade-off's I guess.

I have to say I am partial to the dipole sound vs. the enclosed type sound. I have to agree about open baffles, with some movies and the way the sound is mixed sometimes creates a confusing/off soundstage. Then again some movies that are mixed very well are pure magic, and just "come alive" surprising the the crap out of you at times lol! especially while watching in a darkened room. That's the stuff I live for!
-cheers

**dlneubec** · 24 December 2008, 09:24 Wednesday

Have you tried to play with speaker placement? It could be that some changes to placement/toe-in could resolve the issues you are having with the phantom image. Just a thought.

**Curt C** · 24 December 2008, 11:59 Wednesday

In leiu of the AA 6.5” drivers, you might consider a quartet of the TB W6-1721 for a dipole center. Mated with a 40Hz HP filter, a single driver in an open baffle would provide nearly 102 dB SPL at Xmax + 15% at 50 watts.

I’ve not used the TB, but I have used the AA 6.5’s, and I suspect a paper driver like the 1721 would sound similar in voicing. The swept back magnet assembly and 8 mm Xmax suggests it was designed for dipole use.

C

**Dennis H** · 24 December 2008, 13:33 Wednesday

I forget the details but there's a problem playing Dolby 5.1 signals with a phantom center.

Edit: okay I looked it up and dynamic range compression gets engaged with DD and a phantom center. DTS doesn't do it.

**ribd1** · 24 December 2008, 14:00 Wednesday

Hey there,
I see the dispaly of a Behringer DCX2496...are you using this to run your mains? If so, phase could be an issue between the center and mains. Goodluck!

**AJINFLA** · 26 December 2008, 11:06 Friday

Originally posted by Undefinition

All the times I’ve heard dipole bass

Hi Paul,

Hope you (all) had a good Christmas.
Could you be a bit more specific about all these times (system/room/design(er)/etc)? Thanks.

cheers,

AJ

**matt12v** · 05 January 2009, 02:38 Monday

Well the problem with the Phantom center mode was the dialogue still seemed to be blurred even with the decent toe in angle. I think it' because the speakers are now positioned so far apart on the outside edges of the screen.

I did try playing with the phase of the original center channel. I have a couple of dcx2496's controlling all 5.1 channels. It did initially sound kind of like an out of phase issue, but I just can't resolve it. I think I am finally going to conclude that the sound of the closed box design is just too limited as compared to the openness and air of the OB mains.

Curt! I have drooled over the thought of using the new tangband's they look great for OB! I am thinking about using 2 of the 5" W5-1685 Tangband's and a single tweeter for an OB center. Thier xmax is 6.1mm though and I am wondering if a pair of these would cover the duty down to 100hz on a large baffle? Maybe the same as the layout in the attached image?

Attached Files

open baffle center channel?

open baffle center channel?

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment