Sorry for bringing up an old thread but I just wanted to give it a closure.
The dodecasub has been finished for almost half a year and I am finally
finding some time to collect the pictures
and describe the build.
On the equipment side, I ended up with ten Exodus DPL-10 drivers, an
SMS-1 for eq and an EP2500 for power. The drivers were 10lbs each and
the box weighed in at some 40lbs, so the total was a little bit below 150.
As far as wiring goes, the drivers were divided into 2 groups of five. The
fives within each group were wired in parallel giving a nominal impedance of
1.6ohms and putting the 2 groups in series resulted in 3.2ohms. The leads of
the 2 groups were connected to a set of 4 spring-loaded connectors so that
I could easily switch between dipole and monopole (by shorting out different
pairs of connectors) in like a minute.
Fortunately, my pre/pro had balanced sub-out so there were no problems
hooking up the SMS-1 and the amp with XLR cables. The finished sub is still
in its temp location today, but I did eq it for both dipole and monopole
configurations. The SMS-1 came in real handy as it was so simple to
operate and I could just use preset 1 for monopole and preset 2 for dipole
(=> no mix-ups). It also had discrete remote codes so integrating it into the
system was a breeze. BTW, the sub is cross-overed at the customary 80Hz
01 Ten Exodus DPL10s
02 Dodecasub in temp location
As far as performance goes, in dipole, it sounds gorgeous! "Gorgeous" is
because the low bass is just so tight and clean and very non-fatigueing.
There is plenty of bass and no boominess at all. In monopole, though, the
slamming and authority really come in and I could feel the vibration in my
marble coffee table. I've been leaving it in dipole most of the time. For the
occasional gatherings, I set it to monopole as my friends like to see things
get a pounding. Once I've made some room on the left wall I can move it
there and hopefully find the optimal spot to make it sound even better then.
Coincidently, the Exodus DPL-10's have now been lowered to $45 apiece. I
might just build one more for my other room or whoever wants it.
Anyway, I am gonna go ahead and explain how I built the box. To be able to
repeatedly cut 12 identical pentagons with slanted edges I had to device a
jig. The picture below shows what it looks like.
03 Jig on wood to be cut
The jig looks like a pentagon itself but it does not have to be (it was just the
result of my prior failed attempt at cutting a pentagon). Its main features
are the 2 holes (1 at center and 1 at corner) and the guide (the strip of
wood). The wood to be cut will have 1 center hole and 5 corner holes. The
idea is to stack up the jig and the wood, insert a pin (a nail, really) thru the
centers of the jig and wood, a 2nd pin thru the jig's corner hole and one of
the wood's corner holes. Run the stack of jig+wood thru the table saw and
cut a side of the pentagon. Move the 2nd pin to another corner hole and
another side of the pentagon can be cut then repeat the process. The
next shots show the hole markings on the wood and how it's run thru the
04 Nail holes on wood to be cut
05 Cutting the wood
06 Cutting the wood Close-up
To mark the holes on the pieces of wood to be cut you can use a paper
template. How well you draw a pentagon on the paper template will decide
the precision of your work (I actually double- then triple- checked the
markings). Also, jig's guide has to fit the slot on the saw really well so things
won't wiggle when running the wood thru the saw blade.
Well, before anything can be cut the saw blade has to be tilted at the
correct angle. The dihedral angle (the angle between 2 pentagons) is
116.565 deg so the tilt will be 58.28 deg. The next pictures show how that
was accomplished. Notice I use the straight yellow ruler to extend the
radius of the blade, and tilt the blade until there is no gap between the ruler
and the angle paper.
07 Setting saw blade angle
08 Setting saw blade angle Close-up
Once the tilt is set (and tightened really hard) all the pieces should be cut at
once. I cut 2 extra pieces just in case and that was a good thing. It only
took me about 2 hrs to cut 14 pieces.
09 After 2 hrs of cutting
10 The aftermath
Then I proceeded to make the biscuit holes and 30 braces out of 1x4 wood.
The braces were needed during the glue curing process because how the
heck would I clamp this dodecahedron thing? Anyway, #10 biscuits were
about right for this job and 2 were used on each side.
11 Making biscuit holes
12 Biscuit holes and braces
Before the drivers arrived I couldn't help but try dry-fitting everything:
13 Dry fit 1
14 Dry fit 2
15 Dry fit 3
During the wait, I went ahead making the feet, drilling the connector holes
on, and painted the bottom piece. Eventually, it was time to assemble the
box and I enlisted a buddy's help. Within 20mins we had to glue 2 halves
separately and then glue them together. This is what it looked like 12 hrs
16 Box assembled with feet
Honestly, there were some gaps in a few of the seams so I just ran the left
over glue on all of the inner seams to plug the gaps. On the outside I just
used wood filler. The braces were also removed because I reckoned they
would be a liability more than help. The next few evenings and a weekend
were then spent to apply 2 coats of primer, 2 semi-thick coats of paint and
2 very light coat of spay-polyurathane. The sub was going to be used in a
projector/screen room so I wanted an orange-peel look and did not want it
to be shiny at all. Prolly these are the least interesting pictures:
17 Box primed
18 Box painted
I've been thinking about buying/making the grilles for them but not gotten
any good ideas yet. If you know of an economic way of buying/making ten
grilles please let me know.
Again thanks to those that have helped and a big Happy New Year to you all.