I'm looking to get the best sound from ceiling speaker installs with out using subwoofers.

A lot of manufacturers offer a back box of some kind but I'm more interested in a proper custom built enclosure. Something that could be put in place during construction, or even retrofitted if you have attic access.

For example, I was looking through KEFs lineup and they actuallly have a chart of recommended enclosure volumes for all of their speakers. I'll use the CI200QR for this example.

[Link: us.kef.com]

They rate the frequency response at down to 35hz +/-6db with an open back. I'm guessing -6db at 35hz.

They offer a back box which measures about .5cuft. However in their enclosure chart:

[Link: kef.com]

They list 1.24cuft for "reasonable low frequency response" and 2.12 cuft for "ideal".

Far from the .5cuft back box and much smaller than an attic.

If the ceiling was 2x4 trusses on 24" centers then in theory I could put in two 2x4 braces about 48" apart, glue/screw a 2'x4' piece of plywood on top and voila. 2.12cuft enclosure. This would take very little time.

It would be even easier in a 2x10 floor. Blocking about 28" apart and your done.

With published enclosure volumes it seems like a no brainer to get the best sound possible. Does anyone do this?

Thanks.

Craig.


Edit: in this case the speaker is just over 4" deep when installed so the 2x4 truss enclosure just got slightly more complicated but nothing that couldn't be fixed quickly with some ripped plywood strips or 1x2/2x2.

If you have the QTS,VAS,and FS specs,you can optimize the sound output of the driver but I doubt that you will ever get good low end(subwoofer style) from a 6.5" full range driver in the ceiling.

It would be better with out a doubt and something to consider for improved sound given the amount of work involved.

Just don't expect a huge subwoofer sound overall.

Most in-ceiling speakers won't fit in a space defined by 2x4s, so you'll need to make some kind of enclosure that could be described as a 'saddle', which rests on the top of the bottom chord of the trusses. What spacing- 16"? Why not just make an enclosure that fits within the truss and cap the ends wherever needed?

Sounds like you have a plan that would work. I would just build two boxes without a face with dimensions that would allow one side to sit against truss so you can screw the truss and box together and cover speaker obviously. Bead of caulk on perimeter just before setting box in place.
A full enclosure would be better so you could mount the speaker onto a better and more stationary surface than drywall. The best speakers have cabinet fronts that offer no flex when driver is moving.

Thanks guys.

I usually use 8" but what you say still rings true, re not to expect subwoofer like bass. My thought here is just to get maximum performance without including a subwoofer.

Previously I thought it wouldn't be much use as I thought most in-wall/in-ceiling speakers were designed as infinite baffle (with the exception of higher end speakers that have optional full enclosures to be installed during rough in), but with a manufacturer publishing recommended enclosure sizes for an entire line of speakers, that changes things. KEF even offers the same for their more value oriented speakers.

In the case of the 2x4 truss, fitting an enclosure in between the trusses is a great idea as I could make them in an assembly line fashion (at home or on site) vs custom fitting each one. Give my self a 1/4" of room for variance and used wedges to fit.

Adding a rigid baffle would add time as now I have to cut circles, but, would also eliminate the need for a new construction ring so the time spent would be saved there. I think that's a good idea.

Also the enclosure idea eliminates any complication added if resilient channel is used.

I just finished my last two distributed audio system for the year so I won't have an opportunity to try this out soon,but I'm planning to add two ceiling speakers in my kitchen when I can and I have attic access so I think I'll do a before and after type test. I can even run some sweeps with Room EQ Wizard and post results.

I'll revisit this later.

Thanks for your input.

Craig.

We get a local car stereo shop to build a facsimile these for us:

[Link: sonance.com]

This seems like a lot of work and cost for speakers that won’t be placed in the optimal positions for optimal listening, and will most likely be just background music.

If you are that concerned, use box speakers and put them in the proper spots for listening instead of in the ceiling.

This or

Triad

Or

Stealth Acoustics

I agree. By the time you actually put all of the time required to make this happen and all of the labor effort and all of the engineering, you probably could’ve just sold a better speaker that has its own enclosure in the first place.

Doesn’t Totem line the inside of the boxes on their architecture speakers with wood to get more like a box speaker quality?

Some of the back boxes I have seen are so lacking in cubic volume that I have to ask why? Think of a sub/satellite system, where the sats are really speakers in boxes that are too small to extend the LF range. You know what kinda bass they put out - none, which is why a sub is required. If there is not enough volume inside the enclosure, the resonant frequency goes up, up, up, to where there will be no improvement in the bass, no low end at all. In that case, an infinite baffle is way better, and is not really that bad.

For experimental purposes, I would start simple. Cut some 2 x 4 or 2 x 6 at 14–1/2 inches and just frame in the cavity to get the proper cubic volume. Caulk all the seams to prevent leakage. You should get a pretty good approximation of whether it is going to be worth your trouble to start building back boxes.

I would agree with other posters that most rooms are background listening and not critical listening rooms, so you will be putting in a lot of effort, without a lot of return.

For those rooms where are more critical listening is desired, it will be a big jump upwards in trouble and in the budget as well.

1) Craig, where are you working that they are using 2x4 for rafters? Standard construction for ceiling rafters is 2x6 not 2x4. Pretty sure even in Canada that is the case.
​Otherwise how are in-ceiling speakers suppose to work at all. They build them that depth for a reason, although you can get special 'shallow' mount ceiling speakers for that rare occasion.

​2) Building back boxes for in-wall / in-ceiling speakers is quick and easy during construction. I do it all the time. I'm perplexed by the others that say how time consuming it is?
​Simply cut 2x4 or 2x6 blocks (depending on wall or ceiling), the scrape wood is usually laying around the jobsite. Slap a 1/4 sheet of ply or OSB on top of ceiling locations (wall locations will automatically be sealed by the other side). And I use liquid nail around all the seams - you could also use silicone but liquid nail dries faster and not as much odor.

​3) The main purpose for doing this, actually has nothing to do with bass. What we are concerned with, is unequal airspace between 2 speakers. Causing a slightly different frequency response from each. That will hurt stereo imaging and sound continuity. Building back boxes insures the same frequency response from each speaker. Also allowing consistence bass response, instead of multi resonant bass frequencies. This actually is more important for in-wall applications, as most ceiling locations tend to be infinite baffle as far as VAS goes.
​But another good purpose for back boxes is sound transmission to other unintended areas - which actually becomes more important with ceiling locations sometimes.
​And yet another reason is for fire block rating. If you already are use to making back boxes for all your in-wall / in-ceiling speakers; then when you run into a need to have to make them for firewall ratings, it is not a big deal.

Brad, you are accurate and insightful as always. Only statement I disagree with is the imaging part. It is independent of back boxes, as it is strictly a tweeter function.

Keep it simple. I would use the existing joist cavity, and just block it in, if you have attic access.

And, I wouldn't even try to come close to KEF's provided 'optimal' back box volume. Whatever is good, for background music.

This does not make sense. You are trying to extend the low frequency bass response. You're going to the trouble of building a box and sealing it. But you are going to ignore the manufacturer specs and just build a random box? The volume of the box has everything to do with getting the resonant frequency lower than in free air. Why not use the specs and use the right cavity, to get the most out of your efforts?