Full range line array in a tube

[carpenter]

I'm experimenting with something new, affordable, and best of all--sounds good.

I purchased a pair of 8" diameter x 48" long cardboard tubes from Home Depot (they're used for forming up concrete piers) and stuffed them with twelve 3" M&K drivers. I ported the array (by standing the tube on some quart sized paint cans ) to increase bass extension and basically wired it up to run as a 4 ohm load.

I'm very impressed! The cardboard is only 1/8" so I expected the possibility of vibration and resonance, but guess what? Due the the fact that the tube is round, there's strength and very little reflection to cause standing waves. The sound is pure--almost uncanny.

I spent $3.75 apiece on the M&K drivers and the tubes cost $7.00 each. There's no crossover, so the overall expense for this project is basically peanuts. There's no way I expected this thing to sound so good.

Of course, my little class A amp has something to do with the sound, but an amp can't do much without decent speakers.

Just had to share...

[picowallspeaker]

Well done. You can put some caps across the lower drivers to obtain a gradual rising response of the highs from the upper ones .

[carpenter]

Originally Posted by picowallspeaker

Well done. You can put some caps across the lower drivers to obtain a gradual rising response of the highs from the upper ones .

Could you offer more details? Sounds interesting.

[picowallspeaker]

Hi Carpenter . It just acts as a series crossover . The speakers placed at ear height will reproduce full band ,the lower ones only bass . Depends how you did the serial parallel connection between them .For example you've got 3 stacks of paralleled drivers ,the 2 lower ones will have 1 cap each (for example :100 uF ;50 uF ).
See also Parts Express: Project Showcase
(just to see the EQ needed )

[Trapshooter]

Very cool!

Have you given any thought to stuffing the tubes?

[carpenter]

Originally Posted by Trapshooter

Very cool!

Have you given any thought to stuffing the tubes?

I have thought of stuffing, but the sound is resonate free, so I can't see any reason for the additional dampening.

I'm guessing the little M&K drivers (which are really tiny and have small motors) have a fairly high Qts. They feel/sound right at home with the volume I gave them, and also may account for the extended bass response in the relatively large tube. These most likely are not bass drivers, so it's pretty cool to be getting full spectrum.

The most important thing to me is keeping the delicate nature of sound that emanates from the cone of a small speaker. Large cones sound just a tad clunky in comparison. I'm getting plenty of texture, nuance, etc that a large driver masks.

There's a line array drawing on my web site if anyone is interested--just click on my name above the avatar.

[carpenter]

Originally Posted by picowallspeaker

Hi Carpenter . It just acts as a series crossover . The speakers placed at ear height will reproduce full band ,the lower ones only bass . Depends how you did the serial parallel connection between them .For example you've got 3 stacks of paralleled drivers ,the 2 lower ones will have 1 cap each (for example :100 uF ;50 uF ).
See also Parts Express: Project Showcase
(just to see the EQ needed )

Gotcha. I was over analyzing your original remark--now I understand completely. Thanks for the advice.

[jrenkin]

Awesome! I have though of, but never done, a speaker using these tubes. I too thought there would be vibration, so my imaginings were with two sono tubes, 8" and 10", concentric with sand or concrete between them. Just a thought.

[carpenter]

Originally Posted by jrenkin

Awesome! I have though of, but never done, a speaker using these tubes. I too thought there would be vibration, so my imaginings were with two sono tubes, 8" and 10", concentric with sand or concrete between them. Just a thought.

That's a terrific idea, jrenkin!

I decided to allow the enclosure to do whatever it wanted as an experiment in minimal design. I've read of speaker enclosure that are designed to resonate in order to enhance the speaker. Seems, in this case, it hasn't done any harm.

I'll have to give your idea a whirl.

[jrenkin]

Let me know how it comes out. It certainly will make it more complicated....