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Tuned CW filter made from PVC pipe!

Discussion in 'Videos and Podcasts' started by KE4GBE, May 12, 2023.

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  1. KE4GBE

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    I made this tuned speaker from PVC pipe, a 2 inch speaker and piece of a CD case. I can't post a video here, but you can hear it in action on my YouTube channel - https://www.youtube.com/channel/UCIFyt-tekzTjqfdYexCrl8Q

    It's not an original design, there was a commercial version back in 70's. But I adapted it using 2 inch PVC pipe from Home Depot. It gives at least a 6 db boost at 700-800 Hz. It's really quite amazing the difference it can make!

    The details:

    You'll need a 2" round speaker. I found one online. The bottom PVC piece is an end cap. Bore a hole on the side for the wire connection and seal it. On the top of the end piece, make sure the speaker will fit without hanging over the edge. Then, using a sharp knife, cut a piece the same size out of a CD case. Next, bore a 1/8th inch hole in the middle. You can probably make a bigger hole if you don't have a bit that small, but keep it as small as possible.

    Then, using silicone adhesive, carefully glue the plastic to the speaker and the speaker to the end piece after attaching your input wire.

    The middle piece is a 30 degree angled piece, You should find it in the PVC pipe bins for 2 inch pipe, and it should slide over end cap. Before gluing it in place prepare the final piece, an adapter section you'll find in the same place as the other pieces. It won't slide easily, so you'll have to sand it down a little to fit. You want it to move in and out without binding. It functions like the slide on a trombone.

    Glue the bottom piece to the middle section. Slide the top piece in and plug into your rig. While listening to a station slide the top part to tune. I was amazed at the difference this made over a regular speaker! It's even better than a narrow filter and most times you won't even need to use the narrow filter. Plus, it sounds a lot better too.

    It's an easy weekend project . Let me know how yours works.

    Mike / ke4gbe
     

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    Last edited: May 12, 2023
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  2. WR2E

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    I was fooling around with one that turned out well a couple weeks ago. VERY different design from yours though. I picked up a couple of the "Dayton DAEX13CT-4" transducers for a couple bucks each.

    Experimented with some junk I had laying around and was surprised to find that just sticking a piece of PVC pipe into the can made a HUGE difference in the resonant peak. Tried a few different lengths and found that 10-1/4" of 1" pipe would tune the chamber to 650 Hz. (I like a slightly lower tone) Shorter is higher of course. A piece of 1-1/4" pipe is hot glued to the can, and it's lined with blue painters tape for a 'loose snug' fit. Just enough tape so I could slide the 1" pipe in and out to tune it, but not so loose that it moves too easily.

    I found that the 1" pipe did not need to be centered in the can. It made no difference at all if it was centered or off to the side. Mounting it to the side was so much easier than making something to hold it centered.

    The driver is a peel and stick to the back of the can. Once you peel the paper and stick it, that's it. You don't get another chance, it's on there for good.

    Not only does it peak at 650 Hz nicely, it also cuts out a huge amount of the background noise. S/N ratio is greatly improved.

    I've got this on a shelf between the radios and all you can see is the pipe sticking out.

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    You can turn almost anything into a speaker with those little drivers. I have another one that I wasted a day putting it on anything and everything I could think of. A 3' x 3' piece of aluminum sheet made a surprisingly nice sounding full range speaker! Even banjo music sounds pretty good with that! (Bass is a little lacking of course)
     
    Last edited: May 12, 2023
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