On Fri, 12 Mar 2004, Lon Ponschock wrote:

>
> Looks pretty goofy still, but I now have the tubes coupled
> differently to keep the length of the line but not standing 7 ft high.
>
>
> a.
> |-(
> | -( b.
> | |
> | |
> | |
> |++ |
> ______
>
> So the tall part has the speak in an elbow at a. The sound goes
> down through the pipe, makes an upturn and comes out through another
> elbow at the port end b.
>
>
> The interesting thing here is that the whole assemblage is
> demountable to reconfigure without new construction.
>
> Once you get past the sewer pipe idea it sounds pretty good.
> A question I have for the experts is: should the port more properly
> be placed on the short end and closer to the listener with the 1197
> driver at the higher pipe a farther from the listener? Also, since
> I'm just messing arround with lengths, is there some ideal to
> shoot for?
>
>
> Since these things are on rotateable elbows, the base can be put out
> of the way next to a wall and the elbows turned to focus toward the
> listener.
>
>
>
> The only modification internally is a small piece of pillow
> stuffing directly behind the driver sort of wadded in there.
>
> My leads are soldered onto the driver and the speajer wire
> length is runs from the driver all the way out through the
> port tube. Connection to the speaker leadsis with wire nuts.
>
>
> So far I've only assembled one of these things. There is no stereo
> image but the clarity seems pretty good.
>
>
>
> The organ concert is on tonight... that's the big test.

[Note on stick figure drawing above: The editor does not show
the same image you see, so you'll have to use your imagination.]

>
>
>

Friday night is organ recital night and this is going pretty good.

www.pipedreams.org O410 - March Again.

My goal, aside from not having beaucoup dinero to spend on
either tools or audio goods was to use inexpensive materials
at high efficiencies so as to be able yo get large sound out
of, say, one of those mini units they sell at the Best Buy.

I know this goes contrary to all the theories and conspicuous
consumption that goes on in the audiophile world, but hell, it
keeps this board going, right Wayne? :-)

Thanks for your reply. And yes, I'd like to get the
professional lowdown on this (no pun intended). I don't know
of experiments with PVC that have gone in this direction, or with
as little ado about calculations or internal treatment.

I mentioned those shelf systems to test out high efficiency
speakers but I don't have one. My playback is from a Yamaha
RP U100. The Yam is an integrated peripheral for PC use which
has a USB connection to control the stand alone receiver/amp
from the computer. It works either as stand alone or in conjunction
with the PC. These were on deal with rebates at giveaway prices
at buy.com a few months ago: after rebate $89.00 including shipping.
I should have got more than one and possibly an RP U200 5:1 system
as well. 'Been watching Ebay for these to turn up from bulk
purchases.

So explain a bit more about the harmonics. I am not hearing
any strange disonances from this arrangement. And I haven't done any of the numerous tweaks to the Radio Shack 1197.

Because the RS 1197 is discontinued, I'm anxious to test something in current production from Tangband (to maintain the budget approach) or one of the smaller Fostex'. Please send other suggestions for inexpensive full range drivers I might have missed.

Next listening test is with a VHS video of the Civil War called Gods and Generals. There should be some boomers in that one.

by the time this project gets finalized, I may have a digital camera to show some pix. Stay tuned.

lon@athenet.net

Wayne woke me back up, I drifted off for a while and was busy working on other things (horns!). I am struggling to understand your "sketch", I tried cutting and pasting it into notepad, and changing the font, but I could not get it to line up so I could get a clear picture of you layout. Is there a particular font or application that it will line up all of the typing to form a clear picture for me to see?

Martin

Hello Martin,

Thanks for your gracious reply to a newbie.

The link below you might well be familiar with from James Melhuish'
Full Range Driver site.

I started out with that design. So I had one ten foot length that I was going to cut down to the proper length for 2 speaks with RS 1197 drivers. I didn't know what I was doing so I made some baffles from closet fittings because the cutout was the right size. To get the
fittings attached to the 90d elbow I used a short length of the
4" diameter PVC glued onto a closet flange.

Before cutting down the rest to make 2 speakers I assembled
one complete speak with the entire reamining length. This was
a little over 7 feet. Unlike the PVC Periscope, my port at the
base was a 4" tee fitting. So port is the same diameter as
the pipe and faces front.

Listening to this configuration was a gas during the weekly organ
recital on Wisconsin Public Radio. I loved the depth of the sound
rigth away. After all, I had been reading about speaker designs for years but had no listening opportunities. I then tried out some electronic music from Steve Roach and Tangerine Dream too. These
listening tests were also good.

But I still had this Wilt The Stilt speaker nowhere near
ear or listening height. It took me a few days to realize that a second tee fitting at the bottom coupled to the port on the
base would allow me to cut the pipe down while retaining the
overall line length.

To get the idea of what the assembly looks like, imagine you are on the deck of a cruise ship near some stacks that protrude through the deck: one is 5 ft high and there's another 3 ft length in front of it coupled at the base. There's some other flanges and stuff holding the thing upright on some MDF squares with through bolts and t-nuts.

Wayne was wondering how the harmonics would work and I was wondering which is the best way to tweak them. The only interior treatment is a couple 12" squares of pillow stuffing directly behind each driver.

If I had to put a number on it, the length of the boomtoob
from driver to port is about 8.5 ft. Not much sound pressure
at the port end but it is definately noticeable.

A fellow over at the t-line discussion has also done
some assemblage of PVC. Those interested can look for the
piece called "Laying Pipe with Audio Leggo" at the t-line
site.

But I have not seen anything like what I put together.
It may be goofy and impractical to duplicate, but I was looking for something to build with a minimum of tools. I have no shop and live in an apartment. So a hack saw and some other hand tools are all I've used.

I have one of the boomtoobz completed and there is another
of 5 ft. length from the original design so some comparison listening can be done. Perhaps 2 boomtoobz would be too many?

Many questions remain. :-)

lon@athenet.net

• PVC Periscope from Full Range Driver site

About two years ago I bought 10 of the RS 1197 drivers when Radio Shack started dumping them at about $5 each. All of my drivers are the older purple and blue box models. I measured the T/S parameters for all 10 and got the following average values.

fd (Hz) = 84.2
Qed = 0.419
Qmd = 3.578
Qtd = 0.375
Re (ohms) = 7.59
Vad (liters) = 4.87
Sd = 49.5 cm^2
BL (T-m) = 4.95
SPL (dB) = 90.2

I came up with a whole directory full of interesting MathCad designs for the drivers but never got around to building anything. I still have all ten drivers stored in my workshop for a time when I want to experiment.

So if we assume your drivers are similar to mine, then I don't see any reason why a sewer pipe speaker would not be a nice design. Since this is a constant area line I would tune the length to the driver fd.

L = 344 / (4 x 84.2 Hz) = 3 ft 4 inches

For a 3/4 wavelength pipe tuned to the driver fd

L = 3 x (3 ft 4 inches) = 10 ft

and the fundamental tuning frequency would be 28 Hz.

Your pipe is very long! I have never tried a longer pipe like this so I am not sure what to expect. Interesting experiment. What is the inside diameter of the pipe?

I don't see any problem bending it like you did and I also don't see any issue with have the driver in front of the open end or the other way around. At low frequencies these types of separation distances are not important.

Martin

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.

Most of my listening is done with the Yamaha RP U100
receiver. I originally began experimenting with the 1197's
across the room on a bench system. The bench system consists of
a Radio Shack SA155... the smallest and lowest power unit
there is on a commercial basis. I got that used because it has
a built-in phono preamp. On the bench set-up I managed
to transfer a couple phonograph tracks. That was my primary
intention for the bench machine. Somebody donated an old
Pioneer turntable to me and I bought a fresh Grado cartridge
for it.

I figured I could upgrade parts as a I went.

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.

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 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.

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 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?

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.

Which way to go for a driver upgrade or leave well-enough
alone?

lon@athenet.net

"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