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Hilton

in-wall speaker conversion

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Hi

I used to have all my speakers behind my acoustically transparent screen but today I started a project to convert my existing Sony SS-CNX70ED centre speaker to an in-wall speaker to go behind my spandex acoustically transparent projection screen. (the left/right will just come out to the side as per Pic.)

38677656044_35d8598e9d_b.jpgIn-wall speaker conversion by Hilton, on Flickr

The seating distance was a little too tight for my liking so I wanted to move the screen back an extra 50cm (20") to give me just over 3M (10 Feet) seating distance for the 120" screen.

I figured it will match my main Sony SS-X70ED Speakers better than buying an aftermarket in-wall speaker.

24520314667_439dd027b6_b.jpgIn-wall speaker conversion by Hilton, on Flickr

39385872051_ce58202a71_b.jpgIn-wall speaker conversion by Hilton, on Flickr

I've been careful to match the original internal speaker enclosure volume as closely as possible with a custom performance enclosure for the wall that just happens to fit between the wall beams at exactly the right size and position I needed. 

I'm also using a similar internal brace structure as the original enclosure and putting a 90deg bend in for the bass reflex port with a piece of 50mm PVC. 
Fortunately 50mm PVC pipe happens to match the internal diameter of the original port.

This should replicate as closely as possible the original enclosure performance, though I expect quite a different sound with something like an extra 6db of boundary gain in the bass region.


24520317177_74b79fc124_b.jpgIn-wall speaker conversion by Hilton, on Flickr


I've also kept the original speaker alignment and geometry to keep the time and phase alignment of the original design. 

25515986248_823450644a_b.jpgIn-wall speaker conversion by Hilton, on Flickr

Testing fitting in the wall before I assemble it.
I just have to turn the power off tomorrow to remove the power distribution box I found in the wall. It wasn't connected to anything but it is live. Lucky my stud finder alerted me to it's presence!

Tomorrow I'll finish it and let you know how well it works!

38508167115_0876d871e1_b.jpgIn-wall speaker conversion by Hilton, on Flickr

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Interesting project.  Will you be making the baffle bigger than the enclosure to cover the hole in the wall or just putting some trim around it.

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it may just sound so good you'll want to convert your main speakers also!

 

As you mention above, going from full space to half space and not having baffle loss will have an impact on the EQ balance of speakers "voiced" for full space, but well implemented "in wall" speakers avoid all front wall SBIR issues, and have the highest WAF value known to womankind!

 

If you did decide to do the same with your main speakers, an EQ solution might be easier, as it would be the same across all (L, C, and R), and if you use a PC for movies, then most players have EQ available.

 

Great project, and well done - keen to hear how it sounds.

 

cheers

Mike

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Interesting project.  Will you be making the baffle bigger than the enclosure to cover the hole in the wall or just putting some trim around it.
The baffle is made of 6mm MDF and is 30mm wider on each side to mount to the timber frame in the wall. The speakers will mount directly to the box and the internal bracing. They are also recessed another 4mm deeper into the speaker box to match the original time alignment of the factory baffle.

Because the tweeter is to be mounted another 22mm back from the front of the baffle, I have to cutout the baffle the full width of the speaker box in front of the tweeter, and I've given 30mm clearance above and below the tweeter.

I didn't get time to take pictures today but when I get back home Thursday I'll finish and take some pics before final assembly. It will make more sense then!

It's coming together nicely, but I had a 2hr interruption to make a circle jig for my router as the Dremel circle jig melted!

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it may just sound so good you'll want to convert your main speakers also!
 
As you mention above, going from full space to half space and not having baffle loss will have an impact on the EQ balance of speakers "voiced" for full space, but well implemented "in wall" speakers avoid all front wall SBIR issues, and have the highest WAF value known to womankind!
 
If you did decide to do the same with your main speakers, an EQ solution might be easier, as it would be the same across all (L, C, and R), and if you use a PC for movies, then most players have EQ available.
 
Great project, and well done - keen to hear how it sounds.
 
cheers
Mike


Yeah thanks I'm enjoying the process, hopefully it will sound good. Fortunately I don't have to worry about WAF as she's allowed me full reign in my man cave.

I use JRiver Mediacenter 23 so I have DSP at my finger tips. I ran a bunch of room correction filters in the DSP before which will have to be redone now using REW.

I tried to get used to sound coming from under the screen for a few days after I mounted the screen to the wall, but after you've had perfect screen dialogue imaging with speakers behind the screen, you can't go back!

I might be tempted to do left and right but that's a much bigger project than a simple centre speaker 2 way system.
I also have the same identical floor standing speakers for my other side and rear surround channels for my 7.2 setup so I don't want to change the sound signature too much. But when I start doing Atmos maybe it will be time to change anyway and put the other surround channels to use in other rooms in the house.

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Posted (edited)

A small update before I get stuck into finishing it tomorrow. :)

Bass Reflex Port
39468809071_10b8f5441e_b.jpgIn-wall speaker build by Hilton, on Flickr

The front baffle (note cutout section above main drivers)
39468812001_eeb1bcef9e_b.jpgIn-wall speaker build by Hilton, on Flickr

Speakers recessed to get the right time alignment. (in reference to the tweeter)
39468812971_f4cde94263_b.jpgIn-wall speaker build by Hilton, on Flickr

As good as it gets for today. :P

38760059044_e88a1a69ab_b.jpgIn-wall speaker build by Hilton, on Flickr

Edited by Hilton

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I'm really hoping that gaffer tape is belts and braces right? you used proper plumbing fittings and glue?

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Posted (edited)
3 hours ago, almikel said:

I'm really hoping that gaffer tape is belts and braces right? you used proper plumbing fittings and glue?

Yes that's just holding the 2.40:1 masking panels in place. I'm making some new ones that magnetically attach.

 

Ooops realised you meant the bass reflex port.  Yes it's proper plumbing fittings and it will be glued once I get the length right as I might need to shorten or lengthen it to tune the cabinet.

 

------------

 

I'm having a break and updating with some more pics before I finish off later this evening.

I just have to cut the speaker post hole and mount the crossover and glue it all together and it's done.

 

Here's the router circle jig I made up

24623864937_146fb6f8b8_b.jpgIn-wall speaker build2 by Hilton, on Flickr

 

24623864157_c1d97fd03b_b.jpgIn-wall speaker build2 by Hilton, on Flickr

 

Almost done!

39459939792_138c967f27_b.jpgIn-wall speaker build2 by Hilton, on Flickr

 

24623864767_1a7323fd0a_b.jpgIn-wall speaker build2 by Hilton, on Flickr

 

It turns out the beam above where you can see the cuts in the plaster was a structural beam, so I had to go down the other way. No problem though it's still at just above ear height when sitting and about a third up from the bottom of the screen.

I'll just patch the plaster up and I'll be painting the wall anyway.

24623858297_c650479efe_b.jpgIn-wall speaker build2 by Hilton, on Flickr

 

A bit more spandex speaker cloth stapled to the back to hide the hole for the tweeter. :)

 

39459932082_e6faac0c00_b.jpgIn-wall speaker build2 by Hilton, on Flickr

 

27713901769_df38fbf52f_b.jpgIn-wall speaker build2 by Hilton, on Flickr

 

Now off to finish after this coffee!! :)

 

 

Edited by Hilton

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And.... it sounds great!  I'll do some measurements once I've patched and painted and put the system all back together. :)

 

The hard work is done. My wife's still away up the coast, but she did see the mess before we went away and said it had to be done before she gets back Saturday.
 

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I listened to a few bits of music videos and movies for a last position check. (not that there's much I could do at this stage anyway)  All centre audio is positioned perfectly! ;)

Now to put the screen up and finish tidying up till tomorrow's painting job.

39464574632_011290087a_b.jpgIn-wall speaker position check by Hilton, on Flickr

39494923051_75c3468def_b.jpgIn-wall speaker position check by Hilton, on Flickr

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you've done a great job placing that centre speaker in the right spot - well done!

is there any perceived EQ in-balance with the mains? i wouldn't think there would be??

 

great project and outcome -  enjoy the results!

 

cheers

Mike

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6 hours ago, almikel said:

you've done a great job placing that centre speaker in the right spot - well done!

is there any perceived EQ in-balance with the mains? i wouldn't think there would be??

 

great project and outcome -  enjoy the results!

 

cheers

Mike

Thanks Mike.

 

It was definitely a worthwhile project.

 

The sound stage is definitely a little better with the speaker in the wall and the screen mounted against the wall compared to when I had all LCR speakers behind the screen and the screen about 70cm out from the wall. Even though the screen is acoustically transparent, it still caused some sound reflections when the speakers were all behind it with the screen out from the wall.  The sound stage is miles better though than having the speaker under the screen.

 

The sound is very well blended with the main L/R and a quick whitenoise test on my iphone with sigscope pro showed absolutely no humps or dips on the centre speaker. I'd say it's very well matched as is and may not need any infinite baffle tuning.  I will do so more thorough measurements and testing over the weekend and see what REW says about it. :)   I love it!!!

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