PC speakers are terrible. You can go out and spend ten
on some cheapies that sound like crud, or you can go out and spend a
couple hundred bucks of a big bunch of cheapies that sound like crud.
Manufacturers making PC speakers seem to think more = better,
regardless of the actual quality. I've also never been a fan of their
aesthetics, old PC speakers were always beige and looked vaguely like
medical equipment, while newer models look more like something you
would use to clean the toilet on a flying saucer.
Honestly, this started out as a way to use some old
interesting parts I had laying around, but as usual I got kind of
carried away. These things are going to be sitting on my desk all day
staring me in the face, I really wanted them to look nice, stately,
elegant, and I also wanted them to sound "pretty good" . I don't listen
to music on my computer that much, but when I do I want to be able to
hear every detail. I also didn't want to spend a lot of money. The
design I eventually settled on is a two-way hybrid sealed box/bass
reflex cabinet made of MDF laminated with a real wood veneer. A nice
extra feature is a headphone jack with a builtin headphone amplifier
with its own volume control.
started out by gluing the veneer (in this case, a very thin lauan
plywood) over a 2×4 foot sheet of particleboard. After I cut out
the panels the outer dimensions ended up being 12" H/4"D/4"W. I mitered
the corners at a 45° angle and glued them with a super strong wood
glue, and added little triangular pieces of particle board to the
interior corners to help stabilize things. Having one of those
ratcheting strap clamps really comes in handy when you're building any
kind of box, since it applies pressure from all sides. I left it
clamped for about 24 hours and went off to work on other things.
front baffle is machined from a solid piece of particleboard. I drilled
out 3" holes for the drivers with a hole saw, then used a router to
smooth down the rough edges. I used the router to chamfer the outside
edge at a 45° angle, since it looks nice that way. I used a router
to carve a 2×3 inch recess about ¼" deep at the bottom of
the right panel where the volume controls and headphone jack will go.
This is also when I painted the front baffle black, to keep it from
showing through the sheer grille cloth.
I salvaged the drivers from a couple of pairs of really
computer speakers, one pair I got from an old Boston Audio set, the
other came from an ancient set made by a company named Labtec. If
you're building a pair of these for yourself I would suggest looking in
to some of the great 3" full-range drivers they have at Parts Express. The drivers I
had didn't come with any kind of mounting holes, so I just glued them
on with a ton of industrial grade hot glue, and since I had the glue
gun out I reinforced the cabinet corners some more.
With the drivers mounted to the front board I could set
grille cloth. The grille cloth I used isn't anything fancy, just sheer
black spandexy type fabric you can find at pretty much any fabric
store. I gave the front panel a quick dose of spray glue to help keep
things in place (protect the drivers with cardboard discs). If you're
using the right kind of spray glue, it should be tacky and hold on to
the fabric, but still allow you to reposition it. The hardest part is
simultaneously stretching the fabric tight and stapling it to the back
of the panel. You have to make sure you get it stretched really tight,
and put a ton of staples in it, or it will
sag eventually and there's no easy way to fix that.
cabinet was done setting and still needed a lot of work. I filled in
any tiny gaps near the corner joints with stainable wood putty and gave
the whole thing a good sanding with 220 grit sandpaper, followed by
#0000 steel wool. I stained it using Minwax 210B Cherry oil-based
stainand let it dry overnight. The next day I applied about four coats
of high gloss lacquer, rubbing it down in between coats with #0000
steel wool to remove the little lacquer particles that harden before
they can stick to the wood, followed by a tack rag to pick up any dusty
residue. Since lacquer dries almost instantly I went ahead and polished
and buffed it with SC Johnson paste wax and an orbital buffer.
final steps involved in putting the cabinet together were gluing the
front panel to the cabinet with more industrial strength hot glue. I
installed a particleboard baffle in the cabinet between the top and
bottom drivers to separate them, since the top driver's enclosure will
be sealed, and the bottom will be ported. The back panel is just a
plain piece of particleboard painted black, sized to fit snugly inside
the back of the cabinet. I drilled a 1" hole about 2" up from the
bottom, this will be the port for the lower driver.
Look at what I found
all my projects, I did this point-to-point on perfboard. There were two
integrated circuits used in this design - a Samsung KA2206 2.6W audio
amplifier for the speakers, and a Samsung KA2209 low power amp is used
for the headphone amp.
Considering I designed these in 2011, that seems like kind of a strange
choice, right? Those chips are both out of production (although you can
cross reference them for other chips quite easily) . Interestingly
enough, it was a "found" KA2206 that started me on this project. Back
in 1989 my parents got me a little Lennox Sound boombox, it was really
nice and I carried it all over the place, listened to thousands of
hours of tapes on it. It went missing some time around 1993 and I
didn't see it again until I was clearing out a backyard brush pile in
the fall of 2008. My poor little boombox, what was left of it, had been
lost in the brush pile for around 15 years (Along
with something else on this site that I
those years of rain and cold and heat didn't do it any good, the
circuit board was cracked in half and the case was full of dirt and wet
leaves. It would never work again, or so you would think.
I salvaged all of the components from it, capacitors, resistors, some
integrated circuits including a Samsung KA2206N amplifier, Daewoo FM IF
frontend, and Sanyo LA3161 tape head preamp, and even the tape head.
Most of the components, save for the potentiometers, still tested
within tolerance and after hosing out all of the dirt they still looked
OK, so I neatly bagged them up to save for a future project. They sat
in my parts bin until 2011 when I was dismantling some broken PC
speakers and noticed they were powered by a KA2206B (same as the N, but
with pins 4,5,12, and 13 fused into a cooling fin). Oh, that's what
I'll do, I'll make some PC speakers with those parts, I thought to
would a 22 year old chip that had spent 15 years out in all kinds of
horrible weather actually work? I went ahead and built the application
circuit with a DIP socket, so I could change out chips as necessary,
and ordered an NTE1667 chip, which is a pin for pin substitute for
KA2206. My circuit turned out alright, and the NTE part was working
fine, I also tried the KA2206 I found in the computer speakers and it
worked fine as well, now for the moment of truth. I plugged in my old
weatherbeaten KA2206 and slowly powered it up, and it actually worked!
In fact, it sounded even better than the new part. The full assembly
included the old KA2206, a few of the salvaged electrolytics and a pair
of salvaged film caps, as well as the headphone jack and power LED. All
of these parts are now 25 years old, 15 of which were spent outside,
and I've been using them every day for the last three years. Is it my
imagination or were things made a lot better in the 80s?
mounted the volume controls, headphone jack and power
indicator on a piece of plexiglass painted black on one side and glued
this into the recess I made earlier. The board containing the amps was
mounted to the inside floor of the cabinet with some plastic standoff
and I wired everything up. I left a flying lead with a 3.5mm plug for
connecting to the computer, and installed an RCA jack for connecting to
the left speaker and DC power jack. I used small self-drilling screws
to secure the back in case I want to make any changes later. The whole
thing runs off of an old Sega Genesis 9V plug-in transformer I had
laying around. I am very pleased with the overall results, and since I
see and use these every day, they've become one of my favorite
projects, and they even hold some sentimental value due to the
provenance of the parts.
Yes, I have at least one orange room in my house. Like you