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 http://www.qsl.net/we6w Santa Rosa, CA My 2 pennies worth is just common cents.