Baffle wall with constant directivity waveguide speakers, and toe in - AVS Forum
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post #1 of 18 Old 11-30-2013, 10:05 AM - Thread Starter
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Hi,

I've noticed that not many people have a curved baffle wall or have toed in the waveguide speakers as per some recommendations - Bill Waslo has an interesting paper on the subject:

http://libinst.com/PublicArticles/Setup%20of%20WG%20Speakers.pdf

This paper also mentions toe in on a baffle wall:

http://www.triadspeakers.com/cinemaplus/partners/pdfs/pmi/040601_baffled_again.pdf

Dolby (Atmos) suggests that we can toe in the waveguide but leave the woofer flat on the baffle - part 2.6 Aiming:

http://www.dolby.com/uploadedFiles/Assets/US/Doc/Professional/Dolby_Atmos_Specifications.pdf

As I understand it (what little understanding I have), the 2Pi data of a speaker tells us how it performs in a baffle. Procella speakers work well in a baffle wall and are one of Dennis's recommendations, but he doesn't toe in the speakers as far as I can tell. Is it because the kind of spaces we use at home aren't big enough for it to be that big an issue or something else?

I'm going to attempt a baffle wall at some stage, so would like to get it right if possible - as Dennis has said, once those speakers are in, they're not going anywhere smile.gif

Gary

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post #2 of 18 Old 12-06-2013, 05:23 AM - Thread Starter
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Bump - anyone have any thoughts comments on the above? smile.gif

Gary

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post #3 of 18 Old 12-06-2013, 06:33 AM
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Great topic Gary. While I'm not sure I can offer any info that you should "take to the bank" so to speak, here is where I'm at... The constant directivity style speakers work well, most times in baffle walls...they also seem to benefit greatly from toe in to different degrees based on LP, etc inherent to the design and pattern. I am attempting the same thing with my large SEOS based design. I am enlisting professional help to be sure I don't screw it up too bad though biggrin.gif I think experimenting with toe-in will be a given before wall construction, but the polars, if you have them, on your speakers will help a good deal in giving you a starting point. Dennis is obviously waaaaaayyy more capable, so I'd leave that to him if he's working on your project. Don't take any of my words for gospel, as I'm just learning the deeper end of this stuff and have plenty of help. Right now I'm like a white belt who just learned a new technique and wants to share biggrin.gif Some of my fine details are off though, I'm sure


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post #4 of 18 Old 12-07-2013, 04:41 AM - Thread Starter
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Hi Chopshop.

I'd certainly be interested in what you find and what you end up doing in the end. Is the help you're getting anyone we know from the forum?

There are a lot of people here with baffle walls, so I'm surprised we've not had many more replies yet.

Gary

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post #5 of 18 Old 12-07-2013, 09:00 AM
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You might want to read some of the threads about the SEOS speakers on here - there are quite a few. Some very knowledgeable people are recommending the waveguides toed in quite a bit (up to 30 degrees) iirc to get the imaging correct.
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post #6 of 18 Old 12-07-2013, 09:11 AM
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I will be using JBL Synthesis Array 1400 speakers for L & R. They are constant directivity, but will not be mounted in a baffle wall. They will be located about 13 feet apart (12 ft. wide screen), and Dennis Erskine is recommending 8 degrees of toe-in.


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post #7 of 18 Old 12-07-2013, 09:32 AM - Thread Starter
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Quote:
Originally Posted by mrevo2u View Post

You might want to read some of the threads about the SEOS speakers on here - there are quite a few. Some very knowledgeable people are recommending the waveguides toed in quite a bit (up to 30 degrees) iirc to get the imaging correct.

It was because of econowave and what followed that got me interested in waveguide speakers, and finding Bill Waslo's paper on why toe in is a good thing. As you say, there are definitely some very knowledgeable people here when it comes to that subject. I'm following some of the SEOS/econo threads as well as the DIYSoundgroup stuff.

I wonder if I should post into the speaker forum if I don't get too much feedback here?

I was wondering if anyone had recessed the waveguide only at an angle into the baffle wall so that it was toed in and part of the wall as an extension of the guide. Seems like the only to do it and not have the baffle wall interfere with the guides dispersion pattern. A bit like some recessed surround speakers (bipoles for example).

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post #8 of 18 Old 12-07-2013, 09:37 AM - Thread Starter
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Quote:
Originally Posted by LeBon View Post

I will be using JBL Synthesis Array 1400 speakers for L & R. They are constant directivity, but will not be mounted in a baffle wall. They will be located about 13 feet apart (12 ft. wide screen), and Dennis Erskine is recommending 8 degrees of toe-in.

Not mounting into a bafle wall does have the advantages of freedom of movement of the speakers. Is your screen going to be 16:9?

What I'll probably do is experiment with my LCR speaker layout and toe in, and see what seems to work the best for the main listening position, and perhaps for both rows, to see if a good compromise can be made. Once I've done that, I'll try to replicate that with the wall. There will be some differences of course, but not having gone this route before, it'll be an interesting learning curve. I think a single skin wall to start with until I'm happy with the results, and then finish it with another couple of layers for the finished item once speaker location has been decided.

I may even experiment with a curved wall and screen.

Gary

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post #9 of 18 Old 12-07-2013, 09:50 AM
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My screen will be 2.35:1 Constant Image Height.


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post #10 of 18 Old 12-07-2013, 09:53 AM
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I think u should post in the DIY speaker section.
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post #11 of 18 Old 12-07-2013, 09:58 AM - Thread Starter
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Quote:
Originally Posted by LeBon View Post

My screen will be 2.35:1 Constant Image Height.

OK - I guessed at 16:9 because I thought you were using an AT screen - I think I assumed that because a baffle wall only works with AT screens and assumed you had one too, and speakers are usually placed outside the of the 16:9 image, but within the edges of the 2.35 image.

I'll be doing CIH again, but this time using an AT screen with the speakers behind and located as per the Dolby image in the doc I linked to.

Gary

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post #12 of 18 Old 12-07-2013, 10:42 AM
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I should have made that clear-- my screen will be AT probably a Stewart Lexus DeLuxe UltraMatte 150 Microperf. The center channel (JBL Array 880) will be behind the screen in line with the tweeter horns on the 1400s.


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post #13 of 18 Old 12-08-2013, 04:13 AM - Thread Starter
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I'm curious - why aren't you putting the left and right speakers behind the screen as well?

Gary

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post #14 of 18 Old 12-08-2013, 04:42 AM
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Personally, I wouldn't put the front right and left speakers behind the screen for multiple reasons. For one, you can move them around to get the best imaging for two channel (for those of us, like me, who value two channel way more than 5+ channel). Because the speakers are into the room, you ban better balance low frequency response (where more drivers = good). Plus, you can get some bigger, taller speakers (depending on the size of the screen, room situation, etc.). And you're not limited to sealed/front ported speakers.

Bob
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post #15 of 18 Old 12-08-2013, 05:41 AM - Thread Starter
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Good point. I was thinking purely from a movie watching point of view as all the documentation show them behind the screen - probably for best imaging and correlation with the soundtrack mastering process.

Having said that, my last set up was a 2.35 non AT screen with the speakers outside of the screen (and toed in), and I can't say that it sounded bad. It's possible that I may find this set up to sound better, but with a big gap between then and now, I won't have an accurate memory of what it sounded like before anyway. With audio unless you do immediate comparisons in the same room/level etc it's often difficult to compare.

My set up will be purely for movies as this will be a dedicated cinema room.

I may just build in some tweeter toe-in to one of the boxes I'll be modifying and see if that makes a difference. A wedge shape for just the tweeter or tweeter and woofer - not decided yet. I'd like some more feedback if possible. M&K build speakers with some toe in so maybe that might work. 8 degrees sounds very do-able.

I'll post this in the DIY speaker forum as well to see what the guys over there have to say. It's purely because people here have baffle walls built and Dennis Erskine deigns them with a high level of technical knowledge that I was hoping to get some good nuggets of knowledge on the subject.

Cheers.

Gary

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post #16 of 18 Old 12-08-2013, 10:00 AM
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My room is fairly wide (19 ft), so we have the flexibility. Also, the JBL Array 1400 is big and funny-shaped with a horn (waveguide?) on top. Dennis E. was mildly annoyed that I wouldn't sell them and buy Procellas (so we could build a baffle wall), but I love their sound, so I am keeping them. But they won't really fit in a baffle wall. His design puts them outside the screen, so I am going with that. They could go behind the screen if we don't like the results of the wider spacing. This is an art, to a great extent...


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post #17 of 18 Old 12-08-2013, 10:17 AM - Thread Starter
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Quote:
Originally Posted by LeBon View Post

This is an art, to a great extent...

I couldn't agree more.

I've looked at what's involved in speaker building, and that alone makes rocket science look like an easier hobby to take up.. smile.gif

Gary

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post #18 of 18 Old 12-08-2013, 10:27 AM
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I am a big believer in Baffle Walls and THX and other designers are well on board with their necessity in an AT screen. Something has to absorb those reflections of the screen's back.

Here's a photo of mine though I will have to have it rebuilt as I am changing out my speaker system to a better, more precision loudspeaker system. I'm ready to consider a move away from horns but want similar dynamics and output. I have a trial pair of Quested loudspeakers coming to me in the next couple of weeks or so. Should be fun.

I looked at Procella. Nice speakers. Heard them at CEDIA.




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