The KatKit: An experiment in Transmission Line Portability

[kneadle]

...or something like that.

Disclaimer: this is a compromise project, intended for my sister, who wanted to have a nice-sounding home stereo system to use occasionally as a PA. Construction costs, shipping and a little for me came to right around $200 US.



You can read some details at my website; otherwise, I have two comments:
[list=1][*]I don't understand baffle step loss.
These things, a four-foot long (<1 meter) 4-inch diameter PVC pipe speaker system, with a nice Vifa 4-inch driver mounted directly on the end, really thump down low. If there is baffle-step loss, then... then... then what? How much lower can these things go?

I haven't bothered to measure them, but my ears tell me that the F3 is far lower than I expected. In truth, I didn't expect very much at all in the low end of the spectrum for a number of reasons, not the least of which is the understanding that BS will occur much higher when the driver is mounted directly onto a cylinder.

[*]Transmission Lines sound better with some kinds of music than with others.
I auditioned two CDs, U2's How To Dismantle an Atomic Bomb and an Anda Mozart piano concerto CD. I noticed that all the good parts were there on the U2 CD, but they seemed "smeary." Mozart was heavenly, though.

This is an observation I can say is a common denominator for all three of my TLs, especially for the two which reproduce deep bass frequencies. Rock = smeary, classical = heavenly.[/list=1]

Well, notwithstanding, I'm sad that I have to send these off to my sister because they sound excellent. I'm not going to call up Linkwitz and tell him to forget the Orion, but I am quite pleased with the price/performance ratio. This project pleases me.

I appreciate any comments or corrections.

Thanks,
Dave

[454Casull]

http://www.trueaudio.com/st_diff1.htm

More "angular" enclosures exhibit the underlying 6 dB step along with a series of response ripples that are dependent on the placement of the speaker with respect to the baffle edges. The worst case appears to be placing the driver at the center of a circular baffle so that it is the same distance from all diffracting edges.

[kneadle]

Here's a question: have I actually mounted the driver "in the center of a circular baffle"? Or have I mounted it on no baffle at all?

Dave

[DonoMan]

your baffle is 4"

Your low end response will be 3dB down at 300/ft -> 300/(1/3) = 900Hz.

As for not liking the U2 as much, many more things factor into that, particularly the driver itself.

[PeteMcK]

did you use any stuffing?
how long are the pipes?

Cheers,
Pete McK

[kneadle]

They are around 48" long. They are stuffed to spec using MJKs mathcad worksheets.

I'm listening to them, trying to hear the BS loss. I just don't know what to think.

There's a scoop in the mids, and a nice hump just above the scoop, but it's really a design flaw that serves the function. You know, accidentally on purpose.

I listened to them at comfortable levels all day, and there was no ear fatigue. It's kinda hot toward the upper mids, as mentioned, but they sound nice for a couple of drivers shoved into the end of a four-foot four-inch PVC sewer pipe.

Dave

[planet10]

Originally posted by DonoMan
Your low end response will be 3dB down at 300/ft -> 300/(1/3) = 900Hz.

Using the formula here http://www.t-linespeakers.org/tech/b...tep/index.html i get 1140 Hz...

Another innovative project Dave... what's next?

dave

[kneadle]

Thanks, dave.

Since the caterpillars, I've been spending time experimenting, mostly learning what the squiggles on the modelling software actually sound like in real life. It's ok, I learned, to have some measure of design compromise. You can hear the squiggles, but not all of them are bad. Not all of them are good, either. Which ones can I live with?

I also learned that a 4-inch driver can really rock, if you talk to it the way a 4-inch driver likes to be talked to, you know, flowers, candy, PVC pipe, etc.

At the moment, I'm helping someone make a spiral enclosure with either a Fostex Fe108ez or Fe167e. If he goes through with it--what a committment!--it should be an improvement over the caterpillars, both visually and performance-wise.

What's next for me? A half-dozen chipamps early this season, then, who knows? Something's cooking, I assure you. All these experiments keep coming out pretty good. Not to mention the ones I don't publish, namely some OB/dipole stuff.

Whatever it is, it won't be a box.

I'm so glad someone finally asked.

Dave