Marine Ply or MDF...what is 'best'??

[spa317]

I am about to embark on Dick Olsher's "Basszilla" design, which uses a 15" woofer in a bass cabinet, with a seperate Fostex 8" driver in an open baffle unit on top of the bass cabinet.
I had been suggested that Marine Plywood would be far superior sound-wise to MDF, but my cabinetmaker says there is not much he can do to enhance the final appearance by rounding edges, etc, using the Plywood, as routing will 'eat' into the underlayers and different grain (I was planning to have the cabinets stained in a walnut color).

However, MDF he says is no problem, and this can be easily routed and finished, plus is about a fifth of the cost the Plywood.

Any suggestions as whether the marine plywood is the better option, even if it will look very 'boxy' and have sharp edging all over? This thing is going to end up BIG and HEAVY, so the edges have me worried!

OR, is the likely difference between MDF and marine plywood not that great sound-wise as I may have been led to believe? I have read that most commercial speakers use MDF....I will use 1 inch for whatever I end up using.

Thanks for any feedback/comments!!

[GM]

It takes between 1.125" and 1.25" thick MDF to match 0.75" thick marine grade plywood's stiffness depending on the local grades, so where do your priorities lie?

GM

[JOE DIRT®]

Mark why didnt your craftsman explain the difference between plywood and mdf....

[spa317]

My priorities lie in the best sound.....so maybe the sharp edges and the marine ply are my best bet?


My 'craftsman' is not an audio person, and doesnt know anything much about acoustical qualities, etc.

Maybe I could go the marine ply and have the edges notched out, and quarter rounds inserted? If it were stained, then it would show different grains/colors but might still be aesthetically better than the sharp edges.....

[GM]

Dick doesn't seem to be too concerned since his is all sharp edges IIRC. Anyway, sharp edges are only an audible concern WRT standing waves across the baffle, so if the dims are short WRT the driver's BW then they can't develop. To have a useful radius for long WLs requires that the driver be mounted in a sphere. For instance, a 1" radius round over only affects the BW > ~2158Hz and I imagine my then the mids/HF driver is beaming, and for sure the LF driver is, so it boils down to how much you want to spend on cosmetics.......

GM

[Variac]

Yeah, the bass cabinet would require a very large radius
to be effective, a one inch radius is just decoration.

Which leaves the baffle. The FE208 protrudes out from the baffle considerably and has a raised ridge around it's circumference, so I wonder if the baffle is affecting things that much.

I made my bass box out of ply, but probably a softer wood than the marine ply (there are various types of marine ply I believe also. Made it with 2, 3/4" layers. That sucker is solid but sure eats into the internal volume.

From my boating experience, I believe that marine is void free
and of course water proof glue. There are other premium dense plywoods such a premium birch and what we call appleply in the US that aren't overly waterproof but are void free and possibly denser. and/ or cheaper.

The trendy thing these days seems to be ply. AND for a bass box you are more concerned about stiffness (which I think plywood excels at) rather than damping which is what MDF does well.

Someday I will veneer the whole thing in some fancy veneer
which will look better than almost any plywood. Square corners make veneering pretty easy compared to rounded. So I suggest the ply, with square corners, WHICH WILL weigh about half what an MDF box would!! If you end up loving the Basszilla , then invest in that fancy veneeer later.


I think the bass in plywood and the baffle in MDF is probably the best which is why I do it that way.
I mailed the new design baffles to Dick yesterday so he can begin
developing the new Basszilla based on the Fe208ESigma and the FT 17 tweeter. He said it will be a while so I think proceeding with your existing driver is a good idea.

I have not faceted the new bafffles, they are just flat slabs, in order to eliminate some variables. As in my previous baffles, the tweeter is under, on a vertical baffle and the 208 is in a tilting upper baffle.


Dick has the new drivers in hand, but who knows, maybe he'll hate them!!

Any decision on your bass driver?

[Nuuk]

Rounding plywood edges can actually be quite attractive as the layers are exposed!

If the plywood 'face' quality is good enough, a few coats of varnish will be all that is required to produce a nice looking enclosure.

[Timn8ter]

Use hardwood stock for the corner joints then round off the hardwood, like this.

[Nuuk]

Use hardwood stock for the corner joints then round off the hardwood, like this.

...and tell your mate that if he must be in the picture to buy a new pair of trainers (sneakers).

[spa317]

Variac,
I ended up getting the Audax PR380's from Madisound, plus their
Basszilla crossovers too.
All set to go at last, am a bit worried about their size and weight, but am sure this will not be a concern once i get to listen to them!

Will go with the marine ply and have the edges rounded off..might look OK after staining or painting, plus soften their appearance a little.

Mark.