Date: Sun, 07 May 2000 13:07:30 -0700
From: Ed Loranger 
To: "Maddog 'n' Miracles" 
Subject: Re: Resonant Speaker

Well, the only problem I read from your report
is with the length of the inner tube.

The inner tube should NOT be flush with the outer
tube.  The outer tube is over 8 inches long and
the inner tube is much shorter than that.  And
it should be centered within the wood disc, and
the wood disc should be about 4.25 inches from the front
of the large tube opening.  

I am sorry about the difficulty of building the
inner disc that supports the smaller PVC inner tube
and also seperates the two forward chambers.  I have
a very easy, simple to build method for you.  THis
is how I built my prototype disc:

Punch out two PC board circles that will fit LOOSELY
inside your large PVC pipe.  Obtain some packing 
foam and cut it to a diameter large than the PCB discs.
Punch a hole in the PCB discs and the foam.  Sandwich
the foam between the two discs and slide you smaller
inner tube into the hole of the disc/foam/disc assembley.
Epoxy the inner pipe to the disc (use duct tape to hold
the disc tightly compressing the foam).  Now the disc
will be inserted into the larger tube and the foam will
provide the 'DRAG' so it will stay where you put it!

You can build the rear 3/4 inch diam tuning plunger using
a similiar sandwich of PC board circles and foam.

Something is wrong if you have a 2X Fo resonance.  I'm 
happy you built it.  Also, if you are plagued with heavy
QRN ringing the tube, you should reduce the speaker volume
somewhat -- this is usually an overdrive problem with the
speaker bottoming out.

Due to the extreme efficiency of this device, I wonder if
such a hi-Q is necessary so I've used the foam style plug
and it is acceptable, though not quite the performer of
a very tight speaker box assembly.

Monty, you can research the acoustics at the IBM patent server.
It is my design so you are indeed talking to the right person :)

Also, I do hope you check on the length of the small inner PVC
tube in the larger pipe.  It should not be near the front of
the tube at all.

Enjoy.  -Ed Loranger WE6W
72/Ed we6w; A-1 OP; SOC#63; QRPL#1068 Santa Rosa, CA
My 2 pennies worth is just common cents.