Posted by Martin [ 204.97.174.18 ] on March 19, 2004 at 09:27:14:
In Reply to: Re: Boomtoobz posted by lon on March 19, 2004 at 00:24:44:
Hi Lon,
"My pipe diameter is tandard 4" with the fittings.
I do not have golden ears for listening to what's here..
more like cabbage ears."
So you probably have an S0/Sd of about 1.6 which is a littrle low but not too bad. As a TL's area gets bigger the bass resposne gets better. I have found that this effect starts to reach a diminishing return at about S0/Sd = 3. The classic ruls of thumb recommended S0/Sd = 1.25 which in my opion is too small and chokes the bass response.
"My 1197s are blue box and cost about the same. I read about
them in the forums and so word of mouth sent me to the store
to go see if there were any left."
I did the exact same thing, I hit every Radio Shack I came across in my daily travels. I think my wife even hit the mall stores and scored a couple of the 1197 drivers. I think we have the same versions of the 1197 drivers.
"As part of this dialog I began reading your introductory pages
the t-lines but am not very far with that yet so I don't have any
sensible sort of questions.
I'm moving the 1197's from one project to another. They started out in cardboard boxes."
I bet you are learning a lot and having a great time in the process. If I were to recommend a classic TL per my understanding of the topic, I would recommend the length I preciously posted and a pipe diameter of at least 5 inches. If you could find a way of mounting the driver 20% to 33% along the length you would get additional improvement. Maybe a "T" could be used.
"I had wondered how SPL effects pushing the sound through such a long length... or which of the parameters addresses the issue of
pushing the sound through a long length."
The sound does not really get pushed through the length. The pipe responds at discrete frequencies that are related to the length. At these frequencies the air in the pipe resonates, attenuates the driver's motion, and almost all of the sound comes form the pipes open end. This is similar to a BR but at more frequency values.
"Send me a mail with your address. I will take some snaps
and send them to you. The footprint of these things isn't really
that large. Both toobz sit on a piece of chipboard shelving
I get for $.69/ea. The shelving is 10 1/2 inches by 23 1/2.
I'm reminded of some recent postings in the Full Range Driver forum which related to building with sonotube. More dimension
is available with that and the upshot of the article was that
sonotube sound (which I figure is similar to what I have) sounded
better to the listeners than more expensive rigs in the same room."
I used a sonotube for my test TL and it worked great. I seen many TL designs using sonotube both tall straight ones and folded ones using nested tubes of different diameters. If you can cut cardboard easily and glue joints that are air tight then sonotube would probably be as flexible to use as the sewer pipes. Nothing wrong with cheap and easy.
"I have not found any fault with the boomtoobz except insofar
as announcers on their various mic setups can sound from ok to
peculiar. But those shortcomings are tranparent when listing
to concert performances like Pipe Dreams and other classical
reproductions.
To conclude, you said up there that a 3/4 wavelength pipe
would be a total of 10 ft. What could I expect by adding on
another short length to go the full 10 ft. distance?
Would anything be gained?"
I have no idea how a 3/4 wave pipe would work and if there is an advantage or disadvantage to using one. I always try to keep things small. TL's tend to be big enclosures and I struggle building big boxes and getting up two flights of stairs form the basement to my listening room.
"Since the 3 ft. 4" length for a TL is pretty close to
my shorter tube, I'm thinking that the driver should
be on the shorter length which would be closer to listener's
sitting height and the back tube would be open and may
not even need an elbow for "directionality" if I'm
reading what you're saying correctly. In that configuration
it'd prob'ly look more like a calliope."
I think that this experiment would answer the question above. Try the two different lenght and see what you hear. Maybe one will be far superior to the other. The proof is in the listening.
"Which way to go for a driver upgrade or leave well-enough
alone?"
The two manufacturers that come to mind are Fostex and Tangband (spelling?) for an upgrade that would not cost an arm and a leg. I don't know anything about Tangband and have seen mixed reports on different models. Some appear to be very good and others are reported to be not so good. In my gallery is a back loaded horn using one of these drivers and it is reported to be excellent. I think any of the smaller Fostex drivers would be a step up but at a little more money.
Hope that helps,
Martin