advice on building/finishing speakers

[Rich Wilner]

hi all-- I'm building a set of 5 speaker cabinets for a home theater and i'd like some construction advice, and some advice on what type of finish to apply. The speakers are about 2.5' ft tall by 10" wide by 1' deep. Cabinet material is (not surprisingly) 3/4" MDF. In the past, I've used butt joints. While this method worked fine, this time around I plan on doing all the joints as 3/4 dovetail; i chose this method because i wanted the maximum amount of surface area for gluing, and I figure as the MDF ages, this will provide the most stability with regard to expansion/contraction. I'll also countersink the drivers into the baffle with rabbets; I plan on using a circle-cutting jig attached to my plunge router to cut the rabbets and holes. Are there any other construction tips folks can offer regarding speaker cabinet construction? now, With regard to the finish. I have had problems in the past getting an even finish on the MDF endgrain, and with the dovetail joinery, i will have an odd endgrain pattern. To combat this on the baffle, I was going to rout out 3/4"x1/8" around the outer edge of the baffle and inlay some cherry in that channel. However, I don't want to rout the endges of the whole cabinet on every surface. How does one finish MDF to get a uniform look? I wanted to do a piano black gloss finish for the whle cabinet, but after reading some posts this seems impractical unless I send it someplace. Any idea where I could take the cabinets/what this would cost for 5 speakers (i am in boston, MA)? What alternative finishes are there that are more easily applied? thanks for your thoughts. Rich

[rllipham]

A different choice to dovetails would be a simple butt joint and add

1/2 or 3/4 quarter round to the inside corners. This would save a lot of work and be just as stable. The quarter round would not affect the volume calculations too much.

[Swingman]

Strictly in the FWIW department: In the past I've provided a few mdf cabs for a high end speaker manufacturer when their main supplier, a local cabinet shop with cnc equipment, was swamped. They provided me with the material, dimensions, and specified glued rabbet joints for the box construction. These speakers start around $5K for the pair, so they must feel this a good, perhaps best, method for speaker box joinery.

[Bay Area Dave]

you beat me to the punch re: high end speakers aren't dovetailed. I used to be a dedicated audiophile who can't recall seeing any expensive speaker cabinets with such joinery. Not that they don't exist, but it isn't the norm.

dave

Sw> Strictly in the FWIW department: In the past I've provided a few mdf cabs

[mp]

I'd suggest you try a sample MDF dovetail joint beforehand. You'll probably find that the glue will swell the MDF joint to the point where you won't be able to assemble the joint, even if you work rapidly. Simple dado's are probably your best bet with MDF

Use a particle board edge filler.

I wanted to do a piano black

Try an autobody shop.

[Charles A. Peavey]

Greetings:

[Iraxl Enb]

IMVVHO: The most important part for speaker cabinets is to be air-tight, a function easier to acheive with rabbet joints than dove-tails, especially with MDF (atleast for those of us who arent Frank Klausz-s). Blind dove tails might be okay, but then you mentioned exposed endgrain, so I suppose you were planning on through dove-tails. I would second the recommendation on rabets.

irax.

Sw> Strictly in the FWIW department: In the past I've provided a few mdf cabs

[B a r r y B u r k e J r .]

I've never seen touring stuff dovetailed either. All glued rabbets and dados, with extra internal bracing at high-stress joints.

I have seen the occasional box or finger joint in studios, but usually in furniture quality racks, not speakers.

Barry

[Rich Wilner]

thanks for your replies everyone. I think I will go with rabbet joints as it is a ton less work, and that seems to be the consensus of those that know more than I. charles: can you tell me more about this finish? where can I obtain it? how is it applied (like any other veneer)? how durable is it? etc. thanks Rich