Subwoofer Box: MDF or Birch Plywood

murphy8166 01-25-2009, 5:21 PM

I am going to be rebuilding my subwoofer box. Which is the preferred material MDF or Birch Plywood?

Ben Kerran 01-25-2009, 6:33 PM

MDF preferably with an epoxy resin coating

(wakeboard19) · (wakeboard19) **Join Date: Apr 2005** 01-25-2009, 6:59 PM

MDF for sure.

(nlindbert) · (nlindbert) **Join Date: Jan 2009** 01-25-2009, 8:48 PM

how does mdf hold up against water?

(jonyb) · (jonyb) **Join Date: Nov 2008** 01-25-2009, 8:57 PM

It doesn't, unless it's coated with resin

(murphy_smith) · (murphy_smith) **Join Date: Dec 2005** 01-26-2009, 6:21 AM

Thanks, orginally my gut feeling was MDF but now I will use MDF for sure.

Thanks again for the quick responses

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 01-26-2009, 7:47 AM

OR youc can have it sprayed with bedliner type material.

(detonate69) · (detonate69) **Join Date: Apr 2001** 01-26-2009, 9:02 AM

Just be sure to have it sealed. Water will DESTROY MDF very easily.

(timmy) · (timmy) **Join Date: Jul 2001** 01-26-2009, 9:12 AM

I tend to build my boxes out of plywood, but that is not typical.

(murphy_smith) · (murphy_smith) **Join Date: Dec 2005** 01-26-2009, 10:31 AM

I am going to seal it with an epoxy resin ans well as silicone the inside joints. My question is more along the lines of performance?

The sub is a JL 12w6 v2.

(05mobiuslsv) · (05mobiuslsv) **Join Date: Apr 2006** 01-26-2009, 10:40 AM

Murphy I've got the same subs. I have the boxes built to spec, internally braced, and line-x's. The boxes are bullet proof. This is the method I suggest, they'll last forever this way. Plus you drop it off, pick it up and it's done.

(hehateme) · (hehateme) **Join Date: Sep 2008** 01-26-2009, 7:56 PM

Why in the world would you use MDF in a boat????????? That thing would be a sloshball after one season!

(05mobiuslsv) · (05mobiuslsv) **Join Date: Apr 2006** 01-26-2009, 8:54 PM

Maybe because 90% of people do Martin

(tuneman) · (tuneman) **Join Date: Mar 2002** 01-27-2009, 6:29 AM

MDF, or particle board, is typically used for speaker enclosures because of the consistent transmission of sound vibrations thru it. Birch plywood is typically used for enclosures that require a thin wall, but knots and grain in the wood can disrupt the vibrations and thus, alter the quality of the sound.

Now, for subwoofers, it's not nearly as critical, so you could use birch plywood with sound loss that only a true audiophile would notice. If you epoxy or line-x the inside of the box, you eliminate the sound quality of MDF and it will sound a bit more harsh. Coating the outside has minimal effect to sound quality.

Hope this helps.

(david_e_m) · (david_e_m) **Join Date: Jul 2008** 01-27-2009, 12:11 PM

MDF is the most consistent and acoustically inert material. Do not use a water-soluable glue, instead use the water-resistent type.

Be careful with plywood. Not all are created equal. Some are constructed with water-based adhesives and are nearly as vulnerable as MDF.

Coat the MDF box with fiberglass resin inside and out and especially around the woofer and terminal cup mounting hole edges.

Resin is micro-porous so its not waterproof but it is water-resistent. A resin-impregnated fiberglass hull will sink without the gelcoat. Paint the cured resin for a better seal. The key is to elevate the enclosure off the carpeted sole so that you don't create a moisture trap where the enclosure wicks up water through the resin. Use 1/2 to 3/4-inch polymer mounting pads to do this.

Polyurethane bed liner is waterproof. You should still resin the inside and edges of holes, especially if its a bass-reflex enclosure.

MEDEX is a highly water-resistent MDF that costs a little more. Its made with solvent-based adhesives versus water-based. Its lasted for years outdoors used as highway signs, stop signs and such. I would still apply the resin.

Thats my story and I'm sticking to it.

David
Earmark Marine

(hatepain) · (hatepain) **Join Date: Aug 2006** 01-27-2009, 12:20 PM

I love having you smarty pants stereo guys on here.

(timmy) · (timmy) **Join Date: Jul 2001** 01-27-2009, 1:11 PM

Just a little more info to throw in the pot...

My boat sub box is nearly all fiberglass except for the speaker rings, which were thoroughly covered in resin.

If you use the good plywood where they fill in the voids, and build a solid box, you won't notice any detriment in sound quality, you'll just have a much more sturdy box that costs a lot more to build. If you use the cheap plywood with voids, you are risking the chance that you'll have a buzz where the void resonates at certain frequencies. My preference for plywood comes from building speakers for PA systems where durability is a factor. MDF isn't going to hold up if you drop the box on the corner.

Bottom line, if you are going to coat it with resin, might as well use the cheaper material (MDF) since you aren't going to be moving it around.