# AT screen baffle walls & rear firing port speakers



## Blueeyedfrog (Dec 15, 2007)

I've been reading this excellent old thread that describes how to build a baffle wall for acoustically transparent screens: http://www.hometheatershack.com/for...ics/42935-thx-style-baffle-walls-screens.html

I currently have B&W DM602s for L& R,which have front firing ports, with the LRC600 centre which has a rear facing port. In the above thread (post #6) it is suggested that, "any direct radiating sealed speaker will be OK. If there is a port or vent, then it needs to fire out the front. If it fires out the back (behind the wall), it will not be heard in the room and the speakers may even sound 'thin' as a result."

Note, my baffle wall would only be behind the screen with about a 300mm extention past the screen and 1-2 metres gap between the side walls and ceiling/floor.

My question is, could I still use my existing centre speaker in a baffle wall? The centre speaker comes with a port bung - could that fixed the problem? Also, all my speakers are set to small since I have two subs so possibly there will be little, if any, detriment? Could Audyssey correct for any changes due to a baffle wall using the centre speaker with a rear facing port (with/without bung)? 

Cheers.


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## Prof. (Oct 20, 2006)

Sorry for the delay in answering you question..
The person who wrote that post on the baffle wall doesn't seem to be around anymore..

Having built the same design baffle wall that Mark Techer did, I can tell you that even though its not a floor to ceiling baffle wall, a rear ported centre speaker will not perform at it's best..regardless of calibrations.. 

If you're able to close off the port without adverse affect and if this is within the design parameters of the speaker then this would be the only way that the centre channel would be effective..

Ideally..all the front speakers should be either closed design or front ported when fitted to a baffle wall..


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## Zeitgeist (Apr 4, 2009)

I agree with Prof's advice.... If you don't have sealed or front ported, you're going to have a hard time. (IE, it won't work right).

Sealing the port MIGHT work, depending on what impact it has on the FR. You'll loose some bass response and it might be OK, but the only real way is to measure.

Ideally, it's better to have sealed speakers from the get-go, if you're putting it into a baffle wall.


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## Blueeyedfrog (Dec 15, 2007)

Thanks for your reply.

The user manual (LCR600 S3) shows a diagram depicting the change in frequency reponse related to using their supplied bung (see Figure 8 here: http://www.bwgroupsupport.com/manuals/bw-archive).

The bung appears to be made out of a dense foam. Is it safe to assume that it blocks the port - or would it merely attinuate the flow?

I have the opportunity to buy a single DM602 S3 that will match the other DM602 S3s I have for the left/right. Do you think it worth purchasing - keeping in mind that the LCR600 has 2 6.5" bass/mid cones as oppose to the single 7" in the DM602s?


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## Blueeyedfrog (Dec 15, 2007)

ZG - to clarify - are you recommending sealed even over front firing ports?


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## Zeitgeist (Apr 4, 2009)

Blueeyedfrog said:


> ZG - to clarify - are you recommending sealed even over front firing ports?


That's my preference, but I think that either way is practically perfectly fine.


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## Zeitgeist (Apr 4, 2009)

Blueeyedfrog said:


> Thanks for your reply.
> 
> The user manual (LCR600 S3) shows a diagram depicting the change in frequency reponse related to using their supplied bung (see Figure 8 here: http://www.bwgroupsupport.com/manuals/bw-archive).
> 
> ...


I think that Audyssey will be able to cope with it. If it comes with a bung, and they publish the response, I think you're quite safe to do it.

Being dense foam, I'd expect it to block it. It doesn't take much to block the flow, since it's not real high velocity.

You would always swap out w/another speaker if you're unhappy for some reason.


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## Zeitgeist (Apr 4, 2009)

Hmmm. I was looking a the archive PDFs and found the Owners manual/Warranty, but didn't see User's manual? I was trying to find the drawing you mentioned.

Do you have a link directly to it? 

Just curious what the response looks like w/ the bung.


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## Blueeyedfrog (Dec 15, 2007)

Cheers people - will try bung first - now I have to design my wall. Should be interesting - I'm in a rental...


And Happy New Year!


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## Blueeyedfrog (Dec 15, 2007)

Sorry - my mistake - it's the OWNER'S manual you want - scroll down to the 600 series 3 table. The figure is on the first page


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## Blueeyedfrog (Dec 15, 2007)

Here's the direct link:

http://www.bwgroupsupport.com/downloads/manuals/bw/LCR60-LCR600 S3-OM.pdf


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## Zeitgeist (Apr 4, 2009)

Blueeyedfrog said:


> Here's the direct link:
> 
> http://www.bwgroupsupport.com/downloads/manuals/bw/LCR60-LCR600 S3-OM.pdf


Ahhh.. OK, I did see that figure before. I just kept searching for something higher resolution that had a better indication. That graph was kinda dumb since it doesn't show any X/Y axis at all. 

I say, try it! Should be fine -- especially if you're using a subwoofer, and using an 80hz xover.


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## Blueeyedfrog (Dec 15, 2007)

Yes - the figure's pretty dumb without scale indicators - it's a bit like reading published government figures on (un)employment. lol.

Again - thanks for your help. Will 'suck-it-and-see'..


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## Blueeyedfrog (Dec 15, 2007)

Actually - I just found this measured response for the LCR600

http://www.hometheater.com/content/bw-dm-602-series-3-surround-speaker-system-measurements

It appears to be flat to about 100hz. So if we assume that the supplied graph is 20-20k, a guess would be that output will be reduced from 100-1000hz?


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