Nasty echo in tubular enclosure

[Jim85IROC]

Yesterday I played with my $.87 Onkyo 4" mids and $.24 Onkyo tweeters. Obviously I'm not expecting sonic perfection here, but one thing that was so painfully obvious that even my girlfriend commented on, was the massive echo in the vocals. I suspect this was because I stuck the speaker in the end of a 3' long 4" wide sono-tube that I had some posters shipped in. Since this thing was about 3' long, that would put one full wavelength at around 350hz, and a 1/2 wavelength at 650-700hz, which seems to be where the biggest echo is.

Does anybody care to verify my theory?

Oh, and incase anybody is wondering, these $.24 onkyo tweeters sound horrendous. When I first put in some Norman Brown, I thought the highs sounded pretty decent, although extremely bright. Then I popped in a different cd and I didn't have any highs. My little W3 871s in a cardboard box sounded flawless with all the same music.

I don't care if it takes $50 worth of crossover parts, I'm going to make my $1.11 speakers sound good.

[kneadle]

Originally posted by Jim85IROC

Does anybody care to verify my theory?

I guarantee that if you do some research on transmission line speakers, including these resources,

www.t-linespeakers.org
www.quarter-wave.com

you can make a whole lot out of nothing using just the materials you have, and maybe a simple crossover.

Dave

[tiroth]

In addition to resonance issue, Rod Elliot says:

The absolute worst enclosure is a circular tube (cylinder), with the driver mounted in the exact centre of an end-cap. The response ripples caused by this are extreme, but with most systems this is not an issue, since this would be a very unusual shape for an enclosure. The response in a cylinder shows fluctuations in level that are quite unacceptable, and it is not a shape I would recommend to anyone. A cube is little better, and again the effect is made very much worse if the driver is mounted in the centre. Bacause these shapes are (or should be) avoided altogether, I have not included any response graphs.

http://www.sound.westhost.com/baffle...lestepresponse

[Chris8sirhC]

I'm curious, which onkyo tweeter are you referring to? This is just my personal opinion, but that 2'' extended range sounds much better to my ear than the 4'' one, and it goes relatively high for a .98 cent speaker. Only problem is it has no bottom end (to be expected though)

[critofur]

Originally posted by tiroth
In addition to resonance issue, Rod Elliot says:

"The absolute worst enclosure is a circular tube (cylinder), with the driver mounted in the exact centre of an end-cap. The response ripples caused by this are extreme, but with most systems this is not an issue, since this would be a very unusual shape for an enclosure. The response in a cylinder shows fluctuations in level that are quite unacceptable, and it is not a shape I would recommend to anyone...."

http://www.sound.westhost.com/baffle...lestepresponse

I've actually built several SUPERB (both objectively and subjectively) speaker prototypes using cylindrical enclousures. Also, Ohm Acoustic's "Sound Cylinders" were some of the most highly respected speakers in their price range.

[Jim85IROC]

Chris, here's what I'm using:

$.87 4" midrange: http://www.partsexpress.com/pe/pshow...number=269-570

$.24 mylar tweeter:
http://www.partsexpress.com/pe/pshow...number=269-704

I bought this one on the bracket because it's the same price as the one without the bracket, but the one without the bracket doesn't include the cap. Since this already has the cap for a 6db/octave 6k high pass, it makes a simple add-on to an existing factory car system... which is exactly the environment these were made for in the first place.

I also bought a pair of these: http://www.partsexpress.com/pe/pshow...number=269-776
But I haven't played with them yet.

Oh, and thanks for the info on the tubes & TL's. I don't know if I'm going to build a TL enclosure for a pair of $.87 mids, but at least I'll be able to learn a little bit about why these currently sound so bad. Tonight or tomorrow I'm going to stuff the same mids into a rectangular cardboard box and compare.

These $1.11 speakers are going to give me a great education on acoustics.

[kneadle]

Originally posted by Jim85IROC
I don't know if I'm going to build a TL enclosure for a pair of $.87 mids, but at least I'll be able to learn a little bit about why these currently sound so bad.

Buy some PVC pipe. Measure, cut, damp, mount the drivers, listen.

It's pretty easy.

Dave

[kneadle]

Gosh, I forgot that you had some poster tubing. Just use that, instead of the PVC. You could probably build the whole thing with a steak knife, some glue and something to dampen the thing to keep it from ringing.

Dave

[Jim85IROC]

Maybe I'll fool around with the TL idea. I think right now that might be a bit optimistic considering my skills (or lack thereof). First I'd like to fool with crossovers to get familiar with that whole process before moving on to more complex tasks. These drivers have a nasty peak at 7khz which is probably the reason they have such a harsh sound. If I can smooth that out and then run a 6db low pass at 6k, they may blend pretty well with the tweeters.

[kneadle]

Originally posted by Jim85IROC
Maybe I'll fool around with the TL idea. I think right now that might be a bit optimistic considering my skills (or lack thereof).

OK, you made me do it

Spiral Shaped Transmission Line Enclosure Project Complete

I built that with a handsaw. Very few skills involved. In this thread:

TL Design I can't build

I tested some of the design using cardboard tubing.

Dave