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Old 31st May 2012, 09:43 PM   #11
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Default Firstly, Thanks all for the kind words. And now speakers again!

Well I got my card tubes back home today!

They are 1.2m long by 3" ID, walls about 15mm thick perhaps.

The way I figure, the pipe resonance occurs at:

{(1.2/342)/4}^-1 = ~71 hz

the Fs of the W3-1285SG is quoted as 100 Hz, I figured a longer tube may compensate a little for the CSA of the pipe being 7 sq.inch, but probably not enough for the A5

The Tangbands were sealed into the end of the tube, using plasticine.

Very ringy, pipe like sound.....strangly.....haha

filling lightly with some rolled up 1/2" PU foam, and a little felt took the vast majority away.

so basically what I have is a horizontal 4ft long pipe with a driver in it, 'Bazooka' perhaps?....

*Since the bass rear wave is displaced 4 ft behind the front radiating surface, the sound varies alot around the 'side' of the speaker*, and the bass output from the open end is really very surprising, not as clean as a larger speaker, but most definitely there. Considering the almost dipole behavior, and all else, im rather pleased in what sound is produced by these drivers.

I was also going to try the Alpair 5s but the supporting members of the driver chassis are a fraction wider than the internal diameter of the pipe. Perhaps some 'machining' of the card will follow....
I am however, expecting the Alpairs to better the TBs in THD, and ultimatly perhaps general sound quality, BUT, I dont think the tuning will work well with the A5s, since the pipe volume is low.

But thats the next experiment. probably a number of sketches later...

*Aside: Regarding the 4ft front to back vent displacement almost dipole effect....
In a way I think id love to put a shallow fraction of a sphere as a baffle, even better an ellipse, maybe 5x3 ft...if I had the room......good experiment though.*
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Last edited by mondogenerator; 31st May 2012 at 09:58 PM. Reason: typos
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Old 1st June 2012, 10:50 AM   #12
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Default seeking opinions.

id starting to wonder if it may just be simpler, smaller and just as satisfying to build them in a vented box rather that the tube?i am planning to fold the tube twice, so that desktop use is possible either way.
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Old 3rd June 2012, 04:19 PM   #13
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I understand the ringyness you speak of.

Im reminded of hollering into storm sewers as a kid and more recntly singing into cardboard tubes from wrapping paper. As i sang up and down a scale some frequencies would bounce right back down my throat and the whole tube would viberate. Pipe resonance yes?

The stuffing you did, i believe, would stop the certain frequencies from doing this and slamming back into the driver.

A question just occured to me, what is the dimension of the stuffing you used, and at what position along the pipe from the driver was it placed?

Perhaps you could find the smallest(shortest) plug and slide it along the tube to eq out the pipe resonance?

Other resonances would travel right through the plug and would require other plugs along the length of the tube?
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Old 3rd June 2012, 04:34 PM   #14
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Haha yes, I was expecting the pipe sound I have to say, but the addition of stuffing did help.

The sound is far from perfect however, but interesting in its nature. using it horizontally, it reminds me of a shotgun mic, hence the 'bazooka' at the start lol.

Im wondering if its behavior, is somehow similar to a shotgun mic, as well, and if that can be used to a home hifi advantage, if you will.

I placed some fairly dense PU foam, in 'sticks' of maybe 1" square by 10" long around 2/3rds the way down the tube, and added a loose roll of felt in the driver end. I had thought that if i could make a cone of foam, then I could use the large end of the cone at the open end of the tube. In this way the area of the tube would be tapered, or maybe not... maybe the foam is almost invisible to the sound.....either way, I could reduce the vent area in this way anyway, and the foam would damp the 2/3rd position still.
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