The prototype is used for final testing of the drivers
for the crossover design. It is also used to fine-tune the port
size to get the right port tuning. As such, the prototype should
be exactly the same as the final design. The wood can be different
and some niceties can be avoided but
a) the internal volume must be the same
b) the drivers should be recessed into the front panel
so their fronts are flush with the wood
c) the driver positioning in the cabinet should be
the same as final
I used a slightly different wood for my prototype
(I used a medium density chipboard rather than fiberboard) but otherwise
it's the same as the final. Here's a picture of it.
|Click the image for a larger version
You can see the port holes on the right. The drivers
are all flush-mounted and appropriately screwed into the enclosure.
Their positioning agrees with final.
The prototype is used to tune the crossover and to
check the port tuning. As a result, I used a bi-wire type of binding
post on the back of the enclosure (connectors for the woofers and
tweeters are separate). I also used tape to hold the port tubes
in the holes so that they could be removed and resized for tuning.
Unlike the final, the tubes for the ports are not rounded over at
the exit (the side panel) but are left straight. They should be
rounded over to reduce port noise at high volume levels, although
a 2" diameter port is pretty big for the assume volumes of
The other thing I did was to use a solid enclosure
partition (no holes for wiring) at first, to check the internal
volume of the enclosure and to recheck the VAS calculations.
After doing the checks I drilled a hole to run the wires through.