[bradbrad]

Hi,

I'm working on a pair of A/V-3s, and will soon start on A/V-Os.  I'm trying to figure out the best way to attach the floor base to the cabinets.

I'm planing to use hardwood for the base, as I don't think MDF will have the integrity needed to really support these cabinets.  Do you screw the base into the bottom of the cabinet, or just glue?  I would think that screws might work loose over time.  Do you maybe use hardwood as the very bottom piece in the cabinet to provide a better material to screw into?

Regarding the "Os", does the crossover compartment idea work well for everyone?  On this cabinet, you would surely have screw the base into the cabinet bottom without the use of glue, if you wanted to ever access those crossovers.  Do people put the crossovers toward the top of the cabinet somehow?

thanks for your help.

P.S. - I ordered a dust collector last week.  The dust plumes that form while routing MDF are nasty.  I'm working in by basement  near my furnace.  I'm going to have this dust all over my house in no time without a collector.

[Danny Richie]

I'm planing to use hardwood for the base, as I don't think MDF will have the integrity needed to really support these cabinets.

Actually the MDF works fine and has plenty of strength.

Do you screw the base into the bottom of the cabinet, or just glue?

If you glue it then you won't be able to remove it, and then can't access the crossover.

I would think that screws might work loose over time.

Recessed drywall screws will hold it tight from now on. No worries there.

Do you maybe use hardwood as the very bottom piece in the cabinet to provide a better material to screw into?

Nope, MDF. It screws really well into it and holds well. The drivers are screwed into it too.

Regarding the "Os", does the crossover compartment idea work well for everyone?

Actually this is by far the best and easiest to get to location. I have since used this typology on other speakers.

On this cabinet, you would surely have screw the base into the cabinet bottom without the use of glue, if you wanted to ever access those crossovers.  Do people put the crossovers toward the top of the cabinet somehow?

Yes the bottom "A" brace gets screwed into the smaller brace "B's" on each side. Use dry wall screws there and counter sink the heads. Then screw the base onto the bottom brace "A" in the same manor.

This makes the crossover easy to get to. Putting it up top can cause internal surface reflections and would block air flow in the box to the port.

[BrianH]

Hi,

P.S. - I ordered a dust collector last week.  The dust plumes that form while routing MDF are nasty.  I'm working in by basement  near my furnace.  I'm going to have this dust all over my house in no time without a collector.

Any standard bag for a dust collector won't deal with all aspects of mdf dust. MDF dust has two separate problems, one is the urea formaldehyde released when machining it, the other problem is that the dust generated (I read somewhere once that mdf generated 27 times as much dust compared to pine) some of it might not stay in the dust collector but just get recirculated. If you can get the 1 micron hepa bags for it, thats what I would use for working with mdf.

I strongly recommend using a charcol respirator (not a cheap dust mask) when working with mdf. Personally I prefer plywood over mdf but thats me and my experiences as a woodworker, a standard dust collector and a good quality dust mask is fine for wood I believe. Also keep in mind the dust particle size is proportional to the grit you use when sanding. You need to circulate some fresh air to the area as well for the fumes.

Be careful no matter what though, when working with any of this stuff, even worse for your health than mdf are some of the exotic woods ... so if you work with them be extra careful (like fine sanding some exotic veneer for instance). Also the actual formula of mdf (and plywood for that matter) varies by type and manufacturer, some are better, some are worse for health. Google is your friend, read up on the hazards and safety precautions for whatever you are working with, I would advise as I expect all here would. Fumes from glues and cement are no joke either.

Finally, MDF does not have the general strength of either wood or plywood, so you can't use it interchangeably with wood. My experience is that mdf doesn't tolerate assembly and disassembly very well, plywood is better, soft wood (pine etc) is better yet, and hard woods (oak etc) are best for screws. As long as your expectations are in line with whatever material you choose's characteristics, you won't be disappointed.  Tips ... they make screws especially for use with mdf, always predrill mdf with a bit same size as shank of the screw you will be using, drill a hole deeper than the screw, coun tersink ... and screwing into the end of mdf is to be avoided bigtime.

Thats what I can offer from my 40 odd years of messing with wood  hope it gives you some food for thought anyway.

Any day now I should get the parts to make my AV3's, Danny just sent me an email saying they are on the way!! I have chosen to use 13 ply actual Baltic Birch (all 13 plys are slow growing birch from northern europe)

Brian

[Hank]

Brian, good advice about controlling MDF dust.  I've always used it, but am considering trying Baltic Birch.
What is your source for the good stuff?

[BrianH]

In the Phoenix metro area ... Woodworkers Source stocks imported Baltic Birch in the 5' x 5' Europe size which should work for all but the tallest enclosures. The deal with the imported BB is that all layers are birch so the density is consistant, thats what you are paying a little extra for.

Appleply is also made very well and it normally comes in 4' x 8' sheets, it's the USA rough equivilent to BB. It should be less costly than the imported stuff. FYI trivia ... the Appleply name is a take off on "as American as Apple Pie" its a US made plywood rather than imported form europe.

http://www.statesind.com/prod/ind_2a2.html is a link to Appleply.
http://alliedveneer.com/what-is-baltic-birch.html is a decent overview of BB.

When I lived in the SF area McBeath carried wood of about every kind you would want.  What I would do if you are in a different area, look for an exotic wood store, sometimes called Fine Woodworking supplies, something like that, I would be very surprised if they wouldn't stock it. Most wood stores can probably order in Appleply at least if they don't stock it.

Also you might call around to a custom cabinetmaker, I would expect them to have something they use that should be equivilent, they will know what you are talking about and can suggest where to get it if they can't get you some. I am just talking about the two kinds I am familiar with, I think Daygloworange said they used something very similar as well but he didn't mention the name of his. We don't care about the brands anyway just the characteristics of the wood.

If you are curious about price, in Phoenix anyway, 5' x 5' BB goes for ~$50 a  sheet for 5 sheets. So it's really not going to significantly change the total project cost over mdf.

Hope this helps a bit,
Brian

[wmeckle]

In the Phoenix metro area ... Woodworkers Source stocks imported Baltic Birch in the 5' x 5' Europe size which should work for all but the tallest enclosures. The deal with the imported BB is that all layers are birch so the density is consistant, thats what you are paying a little extra for.

    In the Phx. area, Spellman Hardwoods has Baltic birch in both 4 X 8 and 5 X 5 sheets, at less cost than Woodworkers Source.
Spellman also has a wide selection of veneers, MDF core plywoods and regular plywoods in furniture grade sheets.

[Hank]

I didn't know you were in Arizona, but thanks for the reply Brian.  I'll check with one of our fine wood suppliers here in Austin.

[BrianH]

Hank ... you might also want to see if they will rough cut those large sheets for you, those 3/4" sheets are really heavy and a bear to cut. Often they have specially set up cabinet saws to work with the 4x8 sheets.

I'm going to check out Spellman in Phx thanks for the info!!

Brian

[Hank]

Good tip, Brian.  I've been using 3/4" MDF for years and handle it by the full sheet, including running it across my table saw.  Compared to ply, it is HEAVY 
I'm toying with the idea of using a sandwich of MDF and BB.  We'll see.

[gitarretyp]

Hank, if you find a local (austin) source for BB, could you let me know?

[Hank]

Hi J, are those dipoles still singin'?

Baltic Birch shortage!

http://www.finelumber.com/catalog.lasso?categorykey=1&type=1
Fine Lumber & Plywood, 9407 Brown Lane, has always carried it, but I called them today and they said there's a shortage on 1/8" and 3/4" - not enough supply.  They should know, they sell lots of hardwood plywood, molding, hardwood to cabinet and furniture makers.  They have 1/2"  5' x 5' for $34.65 -that price seems to reflect a shortage.

Brazos Hardwoods (used to be Hogan's Hardwoods) on Industrial, has no 3/4" - they referred to the shortage also.  Their 1/2" is $25.00

Bluelinx (used to be Austin Hardwoods) on Goodrich has no 3/4" - also referred to the shortage, has 1/2"

You'd think that with the homebuilding slump in the U.S. there wouldn't be such a shortage.  Go figure.

[ely_az]

Hey bradbrad,

Can you let me know what you think of the A/V-Os when you finish.  I built the A/V-3s some time ago and love them but am still using some cheap Boston Acoustics for my surrounds.  I assume these will be much easier to build than the A/V-3s as well.  I am also a little worried about protecting the driver on top.  Do you have any plans or ideas about a grill for the top?
P.S.
Brian and wmeckle, I'm in the Phoenix area too. Thanks for the info on Spellman Hardwoods. I usually go to Woodworkers Source but they can be pretty expensive.

Here is a crappy pic of my A/V-3s without the drivers.