John Sayers' Recording Studio Design Forum Archive

Hello

I've got 5 questions that hopefully you can help me with:

1.) I've seen quite a few pictures of flush mounted speakers like in the link below. From construction posts I've read, you have to put hangers up behind/beside the mounted speakers etc etc. The pic I'm looking at doesn't seem to have that type of construction. What is the best way to construct the frame etc to flush mount a speaker like in the pic?

http://johnlsayers.com/phpBB2/viewtopic.php?t=2065

2.) Is there a difference between a "flush" mounted speaker and a "soffitt" mounted speaker? (Or is the "flush" mounted speaker simply put in a "soffit?)

3.) Is there anywhere to go to get info on the distance you need to be from a speaker? (like the JBL 6332)

4.) How is the speaker secured? (I know you're suppose to make a box for it and fill it with rockwool, but if the speaker is "angled", how is it that the vibration from the speaker simply won't make it "fall out"?

5.) Any suggestions on brands and model types for a passive 3-way 12" speaker?

Thanx!

Have you bothered to read the titles of the stickies on this forum?

I think this answers all your questions.

Andre

Greetings Andre,

Yes I did/do read the stickies. I did find answers to some of the questions after re-checking some of the post again, but I still haven't found an answer to the #1 question I asked along with getting suggestions for a good passive 3-way 12" speaker cabinet.

The type of cabinet/frame I would like to build will be horizontal, suspended from the ceiling, and tilted down and angled. The cabinets will be about 10 ft. from the couch "sweet spot". My ceiling is about 8' 7" high from the ceiling joist to the floor. I am aware that the frame/cabinet will sit somewhat low, but if at all possible I'd like to build them this way due to overall space in my control room.

As I stated, in looking at the basic speaker designs, there are sound absorbing hangers usually made under the speaker cabinets, and possibly what looks like large baffles in the front around the speaker.

How are the speakers built (the way I'm seeing in the (link) picture and the sample picture in this post) other than making a cabinet for the speaker, leaving an air space behind the speaker, using the correct materials (plywood, insulation etc etc)? How does not having the sound absorbent hangers effect the speaker performance? From your estimation, was there something about the designs for the (link) speaker picture, and the picture of the studio I submitted in this post that will still make them efficent?

I plan to have my drywall up, then build a frame to support and house the speaker and the flush-mount soffit box. The frame will be built flush with the drywall, and will have drywall put up around the frame except for a baffle front. (And BTW, is there a minimum size for the baffle?)

Is there a MINIMUM amount of space needed surrounding the cabinet on all sides where the insulation will goes? I will have ample depth space in the rear of the speaker for insulation-air space etc, but I won't have a lot of space on the top, bottom and sides of the frame surrounding the cabinet.

I've read that it's recommended to turn the speakers vertically, have the tweeter at ear height and have a solid stand for them to rest on, but I hope you can help me on any info other than the things I've mentioned that will make this a reality.

I made a 3-D drawing of basically how I plan to position the speakers using SketchUp that I hope will help.

Thanx for any and all help!
Stan

It is difficult to answer your questions clearly because, well, the aren't clear.

Perhaps this Genelec soffit tutorial will help. Also any of teh mid and high end monitors from Genelec include instructions on sofit mounting in their manuals, which are available from Genelec'c website also.

There is confusion in answering the questions because many go into different aspects of control design, not just speaker mounting. For example:

Camistan wrote:Is there a MINIMUM amount of space needed surrounding the cabinet on all sides where the insulation will goes?

Where in the referenced thread it is written:

1. Create an opening that is large enough to accommodate your monitor or any monitors you might potentially use in the future, plus some extra room for sound absorption material. Building a larger space than what you presently need gives you the flexibility to upgrade. Avoid building any structures that directly couple the inner and outer framing.

If you read the thread and studied the drawings you would note that the space around the mounted speaker is basically mechanical space for the straps, varible height shelf, etc. No there is no "minimum" becasue it construction requirement, not an acoustic one.

You ask:

As I stated, in looking at the basic speaker designs, there are sound absorbing hangers usually made under the speaker cabinets, and possibly what looks like large baffles in the front around the speaker

The absorbers you see are related more to the room acousitcs than speker mounting method. Relatrively straightforwared to answer, Yes? Yes until the latter part of the same paragraph where you wrote:

From your estimation, was there something about the designs for the (link) speaker picture, and the picture of the studio I submitted in this post that will still make them efficent?

Huh? Flat surface soffit mounting INCREASES efficiency. In specific terms, soffit bezels (up to the entire wall) act as 0 phase reflectors of relevant (low) frequencies. The larger the surface the lower the frequencies with improved efficiency.

If you are happy with the efficiency of the speakers you are selecting right now, you will be happy with them soffited. Smoother, tighter and lower distortion bass performance.

I don't mind helping you, but please try and be a clearer with your what you are asking and try to put the questions in such a manner that each can be answered in and of itself.

I made a 3-D drawing of basically how I plan to position the speakers using SketchUp that I hope will help

That will help alot! Written words are a very poor way of communicating ideas. Looking forward to it!

Thanks;
Andre

My apologies for submitting an "unclear post". I went back and re-read what I wrote. I found the way I worded my thoughts may have been confusing. Also, I sent the sketchup drawing with the last post I wrote along with another picture of a studio with overhead speakers. I checked the post after it was written and both pics were there, but when I read your response I didn't see them. Today though, I DO see them (I don't know what happened) Anyway, if you didn't see the sketchup drawing in my last post it's here now.

Let me try this again...

I'm not "building" a speaker cabinet persay. I will (hopefully) be purchasing the JBL 6332 speakers. I will soffit mount the speakers inside an overhead frame I will construct after the control room frame and the drywall have been put up.

I will angle the speakers (along with angling the way the frame is made) to direct the speakers to what will be my "sweet spot" approximately 10 feet away from the speakers.

I assure you, (even though it may not seem to be the case) I DID read Barefoot's design post. I had already been to his post, Genelec's web site, the SAE Institute, Custom Audio design web site, posts from Paul Woodlock, Knightfly and others concerning constructing speaker soffits.
In looking at the drawings I saw in some of the posts, there seemed to be more "construction" to the overall soffit building than the picture(s) I submitted for the way I would like to build my soffits.

Well, my concerns were answered when you said:

If you read the thread and studied the drawings you would note that the space around the mounted speaker is basically mechanical space for the straps, varible height shelf, etc. No there is no "minimum" becasue it construction requirement, not an acoustic one.

The absorbers you see are related more to the room acousitcs than speker mounting method. Relatrively straightforwared to answer, Yes? Yes until the latter part of the same paragraph where you wrote:

Quote:
From your estimation, was there something about the designs for the (link) speaker picture, and the picture of the studio I submitted in this post that will still make them efficent?


Huh? Flat surface soffit mounting INCREASES efficiency. In specific terms, soffit bezels (up to the entire wall) act as 0 phase reflectors of relevant (low) frequencies. The larger the surface the lower the frequencies with improved efficiency.

Your response cleared up things a lot. I was looking at things that were basically an "acoustic" issue.

Now, I plan to contact JBL to try to get some other specifics about the speaker itself.

Later, I may possibly post a design of the frame I plan to build for the soffits, just to get some advice/input.

Hey Andre, don't give up on me...this is all new territory for me. I just want to do things right as much as I can. As I put in my thread, "my mistakes will be someone else's learning tool".

Lesson#1 Communicate my thoughts better/do a better job analyzing info read.

Thanx Man...
GOD Bless
Stan

Thaks fot eh revised post (still no new pictures showing to me though ). The written language is a terible medium, espically for technical communications. I have made many mistakes int he pst, but have learned from people who recognized the errors and I learned by their methodology to improve myself also!

Im glas we got the questions answered. If the answers aren't clear, just jump in with nore quesitons. Answers are cheap, one week old fully built walls with sofits ready for demolition due a design error are not.

Picture of the progress are appreciated (hint )

As far as difering degrees of construction complexity, I think that is more a result of the amount of detail shown, not varyihg amounts of complexity.

Keep us posted!
Andre

There are probably as many ways of building soffits as there are individuals - the main goal (however you achieve it) is to extend the front baffle of the speaker enough to force the lowest reproducible frequency the speaker can put out into "half space" mode (only radiates FORWARD) - according to Barefoot (when he wasn't buried alive ) this requires typically a minimum of 3 to 4 woofer diameters in all directions from the center of the woofer, but should NOT be the exact SAME distance in ANY direction. (This to eliminate any possibility of the same physical "aberation" reinforcing itself due to symmetry of mounting)

The baffle extension (soffit) needs to be in exactly the same plane as the face of the speaker to avoid any diffraction.

The gap between the speaker box's baffle and the baffle extension needs to be as small as you can get it without touching the speaker box - you don't want sympathetic vibrations in the soffit due to contact with the speaker box.

The gap between the speaker box's baffle and the baffle extension should be less than about 3/8", and should be lightly stuffed with insulation kept flush with the faces.

The speaker box itself should be mounted on VERY sturdy pedestals of some sort, NOT resonant at any audio frequency, and the box should be floated (ideally) on elastomeric mounts to isolated boxes from structure (sound travels faster in solids than in air, so it's possible to get "early radiation" from your DESK if there is good coupling between speaker box and structure.)

It's nearly impossible to get sub-audible frequency of m-a-m resonance with this type of mount, the only way I know of is to add more weight to the TOPS of the speaker boxes after they're placed on isolation pads - this increases the effective mass of the speaker box, lowering m-a-m frequency. This weight should be lightly padded (for stability and non-slip) and would need to be calculated relative to the type of elastomer used UNDER the speaker box - the purpose of the elastomer is to be a "spring", as in "mass-spring-mass", and hopefully as damping.

Concrete or steel are efficient "mass enhancers" for the above.

Damping-wise, sylomer or butyl are good choices - size of these would need to be chosen so that the entire weight of all the load (speaker box AND any extra weighting) compresses the material enough so it actually CAN act as a spring (typically 10-20% in most cases) -

Some super high-end studios have gone so far as to pour separate concrete pedestals for speakers that don't contact the rest of the foundation AT ALL - they are their own "islands", bearing directly on earth with NO CONTACT to the building whatever.

If I were an "uber-mathmatician" (I'm NOT) I might be able to give you an actual formula for all this - as it is, the best I can do is point you to this site

http://www.earsc.com/HOME/engineering/index.asp?SID=6

Check out their "white papers" and "online design guides".

Outa time for now, hope this helps clarify a few things... Steve

4.) How is the speaker secured? (I know you're suppose to make a box for it and fill it with rockwool, but if the speaker is "angled", how is it that the vibration from the speaker simply won't make it "fall out"?

Perhaps strapped in like this? http://www.johnlsayers.com/phpBB2/viewtopic.php?t=718

That would be a good way IF the speakers are angled; however, if possible it's better to place speakers so the tweeters are very close to ear level and NOT tilt them - depending on the slope of the console, etc, it's fairly easy to end up with early reflections off the console if speakers are placed at the wrong height.

A simple, inductive test for this would be to place everything in the location(s) it will be, then lay a large mirror flat on the top of the console and look in the mirror toward the speaker location - whatever parts of the wall you can see in the mirror are NOT where your speakers should go.

In a normal height room it's also easy to end up with your woofers at the halfway point between ceiling and floor - another thing to avoid. They should be offcenter vertically by at least 6-8 inches, depending on woofer size. Tweeters don't matter, since they can't reproduce frequencies that are modally important... Steve