Speaker box information?? PLEASE HELP

DsquaredTsquared · « **on:** 3 Mar 2010, 01:56 pm »

We are doing our speaker projects for physics class. our group wants to know what is the best material, thickness, and any other helpful info you have for this. also if you could about what price range it would be in. Thank You

DsquaredTsquard.

gerald porzio · « **Reply #1 on:** 3 Mar 2010, 03:45 pm »

3/4" MDF would probably be the most economical. Then think about veneering or painting it. The cabinets also need bracing. There's no substitute for a good book on the subj. Many of your problems to be will have already been anticipated. You might want to start w/ a kit. Xovers are difficult for the experienced to get correct.

konut · « **Reply #2 on:** 3 Mar 2010, 05:39 pm »

Constrained layer damping, and plywood, particularly, void free plywood. See this page at diyaudio.
http://www.diyaudio.com/forums/multi-way/153419-constrained-layer-damping-mdf-ply-2.html

gerald porzio · « **Reply #3 on:** 3 Mar 2010, 07:11 pm »

To do constrained layer damping will require good wood clamps or heavy weights to even out the glue & get a good bond between layers. This also holds true for veneering.

S Clark · « **Reply #4 on:** 4 Mar 2010, 04:44 am »

Gerald and Konut have suggested the most commonly used materials. They are easy to work with and fairly non-resonant. You definitely want to use at least 3/4" material. For the front baffle, it doesn't hurt to make it even thicker. I have laminated 7/16" hardwood plywood to a 3/4" MDF front. It gives me a 1 3/16" thick front baffle that can be finished with a wood stain, and then paint the rest of the box black. It's easy, looks and sounds good, and isn't terribly expensive.

A sheet of MDF will run under $25. Depending on your project, one sheet should be plenty. A sheet of hardwood plywood in 7/16" was $27 at Lowes last weekend. You could split a sheet with another group, as 1/2 sheet is more than enough to finish the front baffles.

DsquaredTsquared · « **Reply #5 on:** 8 Mar 2010, 07:57 pm »

thank you everyone for all the information. also we were wondering about the best ways of bracing and deadening materials. any information on this is appreciated

thank you

S Clark · « **Reply #6 on:** 8 Mar 2010, 11:40 pm »

D^2 T^2,

Another student has asked a very similar question. See http://www.audiocircle.com/index.php?topic=78492.0

Braces can be as simple as bit of MDF scrap, 3/4"x 1"x however long is needed to fit from one wall to the opposite wall. Dowel rods are very good choices since the rounded surfaces should reduce internal reflections. Try to make sure that you brace any span over 12" (10" is better, etc.) As far as deadening is concerned, open cell foam works well- the denser that better. I keep all open cell foam packing that I get in packages, but it is faster to go get some carpet padding. A respected pro, Danny Richie, recommended years ago that you use a layer of vinyl flooring to one side of the foam (the side nearest the wood). Try to use up to an inch of foam, so you may have to double it up to get enough thickness.

planet10 · « **Reply #7 on:** 9 Mar 2010, 05:44 am »

Will take a while to read...

http://www.diyaudio.com/forums/construction-tips/98834-discussion-what-materials-build-speakers-out.html

dave

S Clark · « **Reply #8 on:** 9 Mar 2010, 03:01 pm »

Thanks Dave, and that's an interesting thread over on diyaudio. I am not sure that I agree with the comment about mdf "sucking the life out of a speaker". An important consideration is reducing box resonance. Solid wood is more resonant at various random frequencies due to the nature of repeating grain patterns and even going down to the nature of cellulose fibers. The more random nature of baltic birch plywood or mdf should make for a more acoustically dead box.
However, you seem to have had good results with some solid wood boxes. Can you give us more detail?

Scott

planet10 · « **Reply #9 on:** 10 Mar 2010, 12:52 am »

Quote from: S Clark on 9 Mar 2010, 03:01 pm

However, you seem to have had good results with some solid wood boxes. Can you give us more detail?

Scott,

I've never built out of solid wood (as long as you exclude my 1st build when i was 12, used double layer of wood salvaged from a Mandarian Orange box. A buddy up island has with good results -- but even him, knowing what he was doing, has something like a 25% failure rate in the field,

I've no solid postable data, but 30 years of playing, 1st with HDF, then HDF laminated with plastic laminate, then MDF, then plywood, building identical cabinets with MDF & ply. Listening and examining with mechanics stethescope, reading every study i could get my hands on (few & far between), i've come to the conclusion that MDF oozes a low level time smeared signal that wipes out the downward dynamic range. You can build a good speaker with MDF, you can't build a great one.

dave

S Clark · « **Reply #10 on:** 10 Mar 2010, 02:44 am »

Quote from: planet10 on 10 Mar 2010, 12:52 am

I've no solid postable data, but 30 years of playing, 1st with HDF, then HDF laminated with plastic laminate, then MDF, then plywood, building identical cabinets with MDF & ply. Listening and examining with mechanics stethescope, reading every study i could get my hands on (few & far between), i've come to the conclusion that MDF oozes a low level time smeared signal that wipes out the downward dynamic range. You can build a good speaker with MDF, you can't build a great one.

dave

So if we have a group of first time speaker builders, what would you recommend? Our local Lowes/Home Depot carry mdf, and we can get Baltic Birch, but those are our only quick options. I'll check around at the smaller lumber yards to see what they have. Am I right that you prefer BB plywood to MDF?
Scott

planet10 · « **Reply #11 on:** 10 Mar 2010, 02:54 am »

Quote from: S Clark on 10 Mar 2010, 02:44 am

So if we have a group of first time speaker builders, what would you recommend? Our local Lowes/Home Depot carry mdf, and we can get Baltic Birch, but those are our only quick options. I'll check around at the smaller lumber yards to see what they have. Am I right that you prefer BB plywood to MDF?
Scott

Scott,

Baltic Birch. It is all we use (well except for an occasional bamboo ply box -- big $$$). We could get almost all the MDF we could use free, we happily pay for BB.

dave

S Clark · « **Reply #12 on:** 10 Mar 2010, 11:00 pm »

This is a crucial topic for any new or novice speaker builder. Perhaps we can get some opinions from more of our professionals. Hopefully Kevin H, Danny R, Jim S, Mike D, etc. will see this and chime in. I'd also like to know more about laminates, liners, coatings, etc.

gerald porzio · « **Reply #13 on:** 11 Mar 2010, 12:25 am »

I would think that you might want to minimize cost w/o making major sonic compromises. There's going to be a learning curve if you wish to continue building speakers. It's tough to design & fabricate a sonic Piccasso on your 1st attempt. Who knows? Maybe you'll get on a DIY spkr. hobby, but this will be a good primer.

S Clark · « **Reply #14 on:** 11 Mar 2010, 01:09 am »

These are questions from high school students that are using drivers donated mostly from our AudioCircle members. I suspect that there will be more difference in their carpentry skill, research and design skill, and the bracing and deadening than in the MDF/BB debate. One thing is for sure, BB is easier to finish than messing with veneer if they try to do something other than flat black.

MDF works well and is cheap. Use Baltic Birch if you want a wood finish. Use MDF and veneer if you want a fancy wood finish. To improve the sound, laminate the front baffle to 1 to 1 1/2" thickness, use an extra brace of two, and put an inch of carpet pad with vinyl backing to interior surfaces.

Duke · « **Reply #15 on:** 11 Mar 2010, 01:52 am »

In my opinion if you're going to laminate the front baffle or enclosure walls anyway, consider doing constrained layer damping.

The idea is you have two stiff layers (MDF or plywood or depleted uranium, depending on your budget) bonded by a glue that stays soft, so that flexture of one layer isn't transmitted to the other layer.

I use a purpose-made glue that I buy in quantity, but I think fabric stores sell glues that stay soft after they dry.

To demonstrate the effectiveness of constrained layer damping, cut four squares of cheap wood, maybe 10" by 10". Glue two of them together with wood glue, and the other two with a glue that stays soff. After the glue dries, hold up each laminated square by one corner and give it a sharp rap with your knuckles or a rubber mallet. The difference will be apparent.

A low-noise enclosure won't make up for major problems like poor crossover design, but it can make a good system even better. You can just glue & screw constrained-layer panels to the inner surfaces; the screws themselves won't transmit much energy. You can take 'em out when the glue is dry if you want to.

Duke

S Clark · « **Reply #16 on:** 11 Mar 2010, 04:56 am »

Quote from: Duke on 11 Mar 2010, 01:52 am

... bonded by a glue that stays soft, so that flexture of one layer isn't transmitted to the other layer...

Duke

Would a tube of silicon caulking work?

Duke · « **Reply #17 on:** 11 Mar 2010, 05:13 am »

I think silicone caulk would indeed work. Nasty stuff to work with; have some solvent on hand to help clean off your fingers. You want the silicone to end up about 1/8" thick or so; in other words, don't super-clamp it. You can use wood screws and just pay attention to avoid overtightening. You don't want the boards to actually touch each other.

rajacat · « **Reply #18 on:** 11 Mar 2010, 05:25 am »

How about 1/16" mass loaded vinyl between the stiff panels? Perhaps use silicon adhesive to hold/bond maybe screws too or pneumatic staples?

-Roy

S Clark · « **Reply #19 on:** 11 Mar 2010, 05:36 am »

I've wondered about that also. 1/2" MDF/Vinyl/1/2" BB ply might be a nice combination.