Some Colorado Audio
Society members, just like me, have no doubt wanted
to experiment with and get a taste for full-range drivers,
but may not be quite ready to take the plunge into
purchasing those Lowthers just yet. Here’s a
way to sample the full-range menu, learn about speaker
design, and have some rewarding fun. Cost will be about
$50, along with eight hours or so of your time. I think
you will be surprised at the ROI.
I must confess to being a DIY Internet
junkie for speakers and tube amps. I spend a good hour
a day on DIY forums checking out the latest banter and
designs. Talk in the Full Range Driver Forum and elsewhere
on the merits of the Radio Shack (Rat Shack) 40-1354a
driver intrigued me. I have built traditional 2-ways
and subwoofers, as well as push pull EL34 based amplifiers,
but the SET renaissance and heightened interest in full-range
speakers began to pique my interest. And, after all,
is there a better way to spend a weekend than breathing
the MDF dust flying off the old Craftsman radial saw
After reading reports from NY Blast, an
annual single-end tubefest, and then reading Herbert
Jeschke TQWP (tuned quarter wave pipe) article on the
Full-Range Speaker web site, I figured how could I go
wrong at a price of $13 for the Radio Shack 1354a drivers.
(Okay, now that you
have picked yourself up from the floor and stopped
guffawing about the fact we are actually conversing
about a $13 Rat Shack driver, read on.) As further
assurance of this “el cheapo” driver’s
sound quality, a group of audiophile listeners had actually
voted Herb’s speaker best sounding at NY Blast.
We’re talking Rat Shack consensus! So something
must be right in this driver, I concluded.
Some further Internet
snooping scored an excel program by John Rutter that
calculates design parameters for folded TQWPs. Essentially,
in the folded design, one just takes a full-length
pipe like Herb’s and
bends it over onto itself. After a quick download, I
plugged in the parameters of the 40-1354a and had my
design. Internal dimensions are:
37.3” (I rounded to 37)
9.12 inches (I rounded to 9)
1628 cubic inches or 26.7 liters
29.3" (I rounded to 29.25) from the top of the port, or 33” from
the bottom of the speaker.
I was next off to Home Depot for some ¾” MDF to add to the scraps
I already had in the garage. One 4’ x 8’ sheet will do the job
for two speakers (yes I know one side is an extra inch longer).
For a pair of speakers, I cut the following
(4) 6.75” x 37” for
baffle and back
(4) 9” x 37” for sides
(4) 6.75” x 10.50” for tops and bottoms
(2) 5.25” x 29.5” for the inner panels
(2) .75” x 5.25” for throat piece
External volume of the
speaker comes out to 38.5” high, 6.75” wide and 10.5” deep.
This makes for a very attractive sized floor stander.
At 33 inches from the floor (when not using spikes on
the speaker bottom), the center of the driver is positioned
near optimum listening height.
I joined all the MDF panels with standard
wood glue and drywall screws. I wanted to build this
baby in one day so I did not bother with clamps. I ran
the screws into pre- drilled holes and counter sunk them.
About one screw every three inches. While all looked
air tight, I ran a quick bead of some Elmers squeeze
caulk along all the internal corners to make sure.
I did not glue the top or bottom plates,
as I wanted access to fill the line if necessary. To
keep things airtight, I put some gasket material between
the top and bottom panels and side walls and front. When
screwed on, they were airtight.
I routed a flush mount
for the driver on the front baffle. On the back of
the speaker, about 2/3 the way up (makes no real difference
other than how much hookup wire you want to use), I
stayed with the Radio Shack theme and mounted a pair
of RS binding posts. I had to route out a recess to
flush mount them, as their posts are not long enough
for ¾” MDF . My
only variance from the Rat Shack theme was to use some
inexpensive Monster speaker cable I had lying around
for my hookup wire. It was soldered on with RS solder
though, and a very cheap soldering iron to maintain the
no frills, no pedigree, el cheapo approach.
I took Herb Jeschke’s advice and
damped the pipe areas behind the driver. But instead
of his recommended carpet, I used 1/8” thick foam
from my local hardware store for about 12 inches on the
front pipe’s back wall, and for about 12 inches
down the back pipe’s rear wall. Below that for
the remaining length of the back of the front pipe I
glued felt. I also applied felt to the back of the rear
pipe below the foam for another foot or so. No science
was involved here, just what looked good. Total cost
for foam was $2, and felt was about $2.50. 3M spray adhesive
stuck it on nicely.
I stuffed the rear pipe section with some
old fiberglass insulation I had in the garage. Stuffing
was light to moderate. No science, just what kind of
After soldering the hookup wire to the
drivers and mounting them with small drywall screws,
I was ready to rock and roll. I used cheap, adhesive-backed
weather stripping as an airtight seal behind the drivers,
I hooked them up to my home-brew EL34 push
pull amp that runs through a Dyna PAS 3 preamp and Pioneer
DVD player (el cheapo 24/96).
At first, the sound
was a little thin. But as driver break in quickly occurred,
these babies really came to life. I suggest a minimum
of 4-6 hours of listening for break in. So what are
their sound qualities? Quick, tight bass. It doesn’t go to the lowest
octave, but what is there isn’t bad.. Very nice
mids, and the highs are there also. I see no reason (make
that hear no reason) to add a tweeter. Very nice pace
and rhythm. Good detail. Nice layering of textures. A
very lively sound. Virtually no fatigue. They really
make some nice music. For a total of about $50 invested,
these are speakers that deliver. And that is a fairly
ridiculous – if not preposterous -- statement given
the cost of the Rat Pipes.
To verify my ear’s findings, I invited
over my audiophile neighbor who is also a musician. He
has a tube system worth about 20K – C-J amp and
pre, Meridian CD and Project turntable, B&W Matrix
and Theil speakers. He was pretty impressed. But he flipped
when I showed him the box that revealed it was a Rat
Shack $13 driver. “It’s a trick! It’s
a trick!” he exclaimed.
I did not tweak the drivers in any way.
At least not yet. But some treat them with a layer or
two of Damar varnish. Nor have I listened to them on
solid state, an amplification medium not suited to my
I’d have to say if you want total
bang for the buck, as well as a chance to make a go at
DIY speakers and TQWP design, give the Rat Pipes a try.
What have you got to loose? In all candor, I have heard
$1,000 speaker that cannot come close to these little
babies. Will they sound like Ron Welborne’s Oris
Horns or replace your current main system speakers? No!
Nyet! Of course not!!! But for some rock bottom el cheapo
experimental fun, you can’t beat the Rat Pipe.
Praise and thanks to Messers Jeschke and
Rutter, as they are the true design impetus and gray
matter behind the Rat Pipe. I will try and get some photos
posted in the weeks ahead.
So, fellow Colorado audiophiles, throw
some caution to the wind, plunk down your hard earned
$50, break out the circular saw, and crank out some Rat