# RB-Kit in the ceiling - Surrounds



## keelay (Dec 11, 2008)

Here's another of my build threads.

I bought a set of 4 RB-Kit speakers from Madisound. ...Enough to complete my surround speakers. I wanted to test these kits out and see whether I would be pleased with them and whether they would fit in with my Natalie P's mains.

This is my build thread for building and mounting the enclosures in the ceiling.

After modeling the woofer, a 0.5 CF box optimized the bass response with a port tuned to 48Hz. I wanted to put these guys in the ceiling with minimal presentation in the room. That meant that most of the box would have to go in the ceiling.


----------



## keelay (Dec 11, 2008)

The box is designed to be 22.5 inches long, which is perfect spacing between trusses in the ceiling. I plan to mount the speaker to the trusses and have the angled part of the speaker poke through the drywall along with the bass port.


























-Kyle


----------



## keelay (Dec 11, 2008)

So here I am planning for the bass port. I glued a bunch of blocks to gether so I could drill through it for the port. The other little square with the hole in it glued on was an abandoned plan for adding a port, but it was already glued on.


----------



## keelay (Dec 11, 2008)

So here I am getting ready to and drilling the hole for the bass port. This port is 1.5" wide and 2.75 inches long It is all wood and this method was very easy to do. I think this was the easiest method for installing a bass port in a box that I have tried.


----------



## keelay (Dec 11, 2008)

So here are some more photos of the flaring processes. I think you can see the router bit I used to flare the inside and outside of the port. It makes flaring trivial.


























Kyle


----------



## jeremy7 (Feb 7, 2008)

great idea for the port. I never would have thought of that


----------



## dgilme (Apr 1, 2009)

I can't wait to see how this goes. I was thinking of doing the same thing to pair up with my infinity beta 20s.


----------



## filtor1 (Feb 10, 2009)

This is an amazing idea! I was wondering if you could post up an approximate cost of the entire build. I have been pondering how to get the best placement while getting the rears off the ground. As the rears I have now are rear ported, this was never an option. But now I see the error in my thinking. I never considered building similar units to my BA CR85 mains and using the other two elsewhere. 

Good stuff. I will definitely be following this build.


----------



## bonehead848 (Jan 21, 2007)

Im loving this creativity. Keep up the good work!


----------



## keelay (Dec 11, 2008)

filtor1 said:


> I was wondering if you could post up an approximate cost of the entire build.


*
The cost:*
--------------------------------------------------------------------
*RB-Kit* $59.00 x 2 + shipping $15.00 = $133 (Madisound.com)
*4'x8' Sheet of MDF *= $27 (@Lowes)
*1 Large bottle of wood Glue* $4 (Walmart)
*Speaker Wire* $10
*Misc other stuff* (insulation, a few screws, etc laying around) $0
--------------------------------------------------------------------
*Total $174* for 4 Vifa rear surrounds. (So far I've only posted the build for the 2 rear channels)

_NOTE: I'm adding some pics for the other two surround speakers now..._


----------



## keelay (Dec 11, 2008)

So I have completed the surround speakers. I have a few pics from the build. 

I wanted the same internal volume as the back speakers (0.5CF) and the same tuning (48Hz). The shape of the enclosures for these speakers is a little different than the back (rear) channel speakers. Since the room is 13' wide, in order to place these optimally I had to design them to go in the corner of the top of the wall and the ceiling. This made the cabinet shape different. It also contributed to a smaller chamber directly behind the woofer. This was a compromise.

I would have liked to make this chamber bigger and not have an enclosure wall so close to the back wave of the woofer. I do believe I can hear a difference when doing an A/B test between the back speaker enclosure and the surround. It is not pronounced, and will likely never notice it in operation, but I wanted to point this out for the purists. I wasn't able to avoid this unfortunate shape. 

The other difference is the port is a slot port. I am considering converting the round port to slot port closer to the woofer on the back speakers for aesthetic reasons. I'm not sure when I get these done that having a small port hole a foot off from the speaker will look OK. The slot next to a grill seems a little more low key.

So here comes the pics:


----------



## keelay (Dec 11, 2008)

Here is the low profile box. This is also designed to go between the trusses (22.5") and be easy to insulate. In my attic I have blown in fiberglass insulation. I will just dig out the space where the box will go. Cut the small hole for the speaker protrusion part to poke out, screw the box into place, wrap and staple R19 pink fiberglass insulation around the box, and then push back the blown in insulation to fill the gaps. I have some dry wall work on the other side to do after that.









The little blocks are for box bracing to remove resonances. The angled partition also helps brace and creates an internal non-rectangular shape to help remove standing waves.


----------



## keelay (Dec 11, 2008)

Here is the protrusion part with my slot port in progress. The slot port turned out much harder than I imagined it. Luck for my this is going to be drywall textured in the end to blend in with the rest of the ceiling.


















I back chamfered the woofer hole to keep the baffle from impeding the woofer's back wave


----------



## keelay (Dec 11, 2008)

Here are the boxes finished ready for final assembly. I was able to shape the slot port to look decent using caulk and joint compound. I sanded and primed the protrusion part so that it's ready for tape and texture when I mount them:


----------



## keelay (Dec 11, 2008)

bonehead848 said:


> Im loving this creativity. Keep up the good work!


Thanks, 

My goal here was provide a balance between aesthetics and performance. I kind of lean toward designing so that a speaker can be heard but not seen. If you do have to see something it should blend in and be a subtle as possible without affecting performance too much. The 1400 SQ Foot house, 4 young kids, and the resulting WAF has helped me shape my set of compromises.:nerd:

One of the problems with rear channel speakers is that either they are small and therefore frequency range limited, or large and impose themselves in the room. Ceiling speakers are most of the time hard to direct the way you want them and them still suffer from the drawbacks previously mentioned. This route allowed a blend of:

- relatively large enclosure (to maximize frequency response), 
- minimal room imposition (a speaker should be heard but not seen), 
- Easy to insulate (The attic site of the box doesn't stick up into the attic space. It stays relatively close to the height of the trusses)
- Allow for someone to build a custom or reference speaker design(You could also just gut a nice bookshelf speaker and place the drivers and crossover in a new enclosure like this)​
Kyle


----------



## filtor1 (Feb 10, 2009)

keelay said:


> *
> The cost:*
> --------------------------------------------------------------------
> *RB-Kit* $59.00 x 2 + shipping $15.00 = $133 (Madisound.com)
> ...


Man, I really appreciate the information! I am going to run this by the wife. :bigsmile:


----------



## dgilme (Apr 1, 2009)

keelay said:


> Thanks,
> 
> - Allow for someone to build a custom or reference speaker design(You could also just gut a nice bookshelf speaker and place the drivers and crossover in a new enclosure like this)[/INDENT]
> 
> Kyle


Interesting.. with as cheap as beta 20s go on ebay right now I may have to consider gutting some of them..


----------



## keelay (Dec 11, 2008)

dgilme said:


> Interesting.. with as cheap as beta 20s go on ebay right now I may have to consider gutting some of them..


Yeah most bookshelf speakers are designed with out Baffle Step Compensation (BSC) so ceiling mount should work for any of them. Just keep the driver spacing the same. If you don't have any data on the woofer and cant measure any of the Thiele-Small parameters, then keep the box volume and port diameter length the same. Otherwise you won't be able to tune the port correctly. If you can get the woofer data or measure them, then you can get deeper bass potentially by adding some box volume and tuning the port accordingly.

If you're going sealed then simpler still. Just driver spacing and box volume

Kyle


----------

