I was talking on the phone with a friend and we got on
the subject of how I handle the driver cutouts -- he
asked, "do you veneer the cabinet before you route
the driver cutouts and recess flanges and, if not, how do
you trim the veneer?" Since my friend is a very
experience speaker designer and builder, I'm guessing
that there are a few more of you out there who might
avoid using veneers because you don't know some of the
tricks... and others of you are applying the veneer
before cutting the driver holes.
I don't like the idea of applying veneer and then
routing the holes and flanges for the drivers. Worse yet,
not flush mounting the drivers can't make an otherwise good
speaker design sound bad, but it might affect the image focus or cause
some objectionable response peaking. So, I almost invariably flush
mount. Also, I like cutting the holes for my
drivers and rabbeting the holes for flush mounting
before I cut any other part of the cabinet. Why? The
sound baffle is the most important piece of the enclosure.
If the driver to driver spacing is not perfect, or the baffle-width
does work well or isn't dead-on, then I cut a new one.
Also, veneer is expensive, while MDF if cheap. If I had
to veneer before I cut the driver holes and the sound of
the enclosure wasn't just right or for some reasons didn't work out
during testing, I'd have wasted a lot of veneer
or I'd have to build cabinets JUST for testing and then
have to rebuild them if I wanted to finish them.
So, here's how to cut first and veneer later. It's so
much easier than you might think that you're going to
kick yourself for not thinking of it already...
Ok. the first step is to apply your veneer to your
cabinet (ignoring the driver cutouts initially). Once the
veneer is applied, cut a small hole with a utility knife
in the center of each driver cutout and using a flush
trim bit, trim the veneer around the driver hole. This
will leave the veneer overhanging the flange, as shown in figure 3.
The next step is the "trick". Change the bit
on your router from the flush trimming bit to the exact
same rabbeting bit you used to cut the flange (or
rabbet) for the driver (see fig. 4). In the case of the
Dayton 275-070 tweeter, I set the rabbeting depth to 3/16" to flush
mount it.
Now, set the depth on the router to about 1/2 the
depth of the rabbet, or less, you cut for flush mounting the
driver. In the case of the tweeter, as I mentioned, the
rabbet is 3/16" deep, so I will set the router depth
for trimming the veneer to 1/16". For the 295-305
woofer, I use a 3/8" rabbeting depth to flush mount
(1/4" for the driver and 1/8" for gasket
material behind the driver) and a 1/4" depth for the
rabbeting bit when I trim the veneer. Now go ahead and
insert the router into the driver cutout hole and follow
the circle around the hole to trim the veneer -- if done
properly, none of the previously cut MDF will be affected
at all. With a little sanding, you should get an
excellent, smooth flush trimmed veneer around the hole.
That's it! Good luck and have fun!
