Re: progress report
i think the mozart might be the best 'test' music because the piano is a more accessible reference...but the led zep is probably more fun to listen to. half vote for each.
wow, great pics. i've been telling my wife about your project. i guess she kindof wonders why i'm at all interested - same as your wife did. anyway, once the project is done i want some good 'show and tell' pictures to present to her; maybe she'll ask me to make some speakers for OUR baby's room....😎
/andrew
kneadle said:
i think the mozart might be the best 'test' music because the piano is a more accessible reference...but the led zep is probably more fun to listen to. half vote for each.
wow, great pics. i've been telling my wife about your project. i guess she kindof wonders why i'm at all interested - same as your wife did. anyway, once the project is done i want some good 'show and tell' pictures to present to her; maybe she'll ask me to make some speakers for OUR baby's room....😎
/andrew
is there any way you could give a comparison of the sound as the tee is mounted on the spiral, vs. if you take it off? i'd be interested to know the effects...
/a
/a
Just a construction note
Noodling around with these things...I can get stuffing in any part of the enclosure even though it's fully assembled. As you see pictured, it has a whole bag of polyester blanket stuffing in the very middle turn; I put it there after I propped it up.
That's Presence 1 1/2, Mozart 1.
Dave
Noodling around with these things...I can get stuffing in any part of the enclosure even though it's fully assembled. As you see pictured, it has a whole bag of polyester blanket stuffing in the very middle turn; I put it there after I propped it up.
That's Presence 1 1/2, Mozart 1.
Dave
faustian bargin said:
The unmounted tee, with all the electronics and speakers, sounds only a little better than if the speakers and x-over weren't mounted on anything. I even put the tee mount flush on the carpet floor with the speakers pointing straight up.
The difference when mounted onto the spiral is phenomenal.
I keep forgetting that these are still TAPED TOGETHER! It's that good. I figure that if I mount the speakers onto the tee with more than tape, use a thicker material to close the top of the tee where the x-over is housed (it's a thin cardboard circle now), and actually GLUE the peices together, my bass response will improve vastly.
And look, you've got to believe me when I say that it's at the tweakable stage RIGHT NOW!
Right now, the midrange up is crystal clear.
Dave
that's great to hear! thanks for the comparison.
BTW mozart only has half a vote, unless someone invisible gave him another half. 😱
/a
BTW mozart only has half a vote, unless someone invisible gave him another half. 😱
/a
faustian bargin said:
you should be familiar with my math skills by now.
😉
That's Presence 1 1/2, Mozart 1/2
Have you noticed a theme in the objects used to prop up the enclosures? I just now did. I was using whatever was handy.
Dave
Dave
I guess "Presence" would get my vote by default, even though I'm not that much of a Led Zep fan. I like their first album and not much since. I traded their second album for Nick Drake back in 1972 and never regretted it. But since I'm not much into the alternatives-maybe Miles a little-they get the vote.
Speaking of the "heavy" sound which Led Zep pioneered-well, maybe co-pioneered with Iron Butterfly, who flew off into oblivion rather quickly-that also applies to the record itself. Vinyl records got physically lighter in the seventies than before. Years later, friends who put the record on the turtable were astonished how much it actually weighed.
I noticed that you put the Vifa 6.5" into a different end of the Tee than we envisioned. We were going to put it in the middle aperture. Doesn't really matter, though. This is one of those things that are definitely improvised to taste.
I am a little concerned about the bottom part laying on the ground like that. That wasn't the way Andrew's plan went. Are you sure all the pieces are fit together right?
It is going to be mounted, which will raise the height to whatever you want. The only really non-negotiable requirement of this was that it be a spiral, and it most certainly is that. So even if it stays the way it is, it looks perfectly fine. But I must wonder why it isn't going exactly according to plan.
How high off the ground is the bottom of the top pipe?
Speaking of the "heavy" sound which Led Zep pioneered-well, maybe co-pioneered with Iron Butterfly, who flew off into oblivion rather quickly-that also applies to the record itself. Vinyl records got physically lighter in the seventies than before. Years later, friends who put the record on the turtable were astonished how much it actually weighed.
I noticed that you put the Vifa 6.5" into a different end of the Tee than we envisioned. We were going to put it in the middle aperture. Doesn't really matter, though. This is one of those things that are definitely improvised to taste.
I am a little concerned about the bottom part laying on the ground like that. That wasn't the way Andrew's plan went. Are you sure all the pieces are fit together right?
It is going to be mounted, which will raise the height to whatever you want. The only really non-negotiable requirement of this was that it be a spiral, and it most certainly is that. So even if it stays the way it is, it looks perfectly fine. But I must wonder why it isn't going exactly according to plan.
How high off the ground is the bottom of the top pipe?
Listen to your favorite piece... the stuff that you can't get enough of... your going to be playing it over and over ... each tweak will inspire another listening session... it ought to be something you like.... wait hold that thought.... it ought to be something your Wife really likes....
When I was first exploring the idea of using pvc pipe for transmission line speakers I set up a simple proto-type.. I mounted speakers similar to yours on a 6 inch straight pipe.. I also used a tee to mount the speaker.... this straightr pipe... about 3 1/2 feet long sat in a 10 inch pipe... kind of like a flower in a vase.. the 10 inch pipe about 2 1/2 feet long.. Anyway this prototype sounded so good that it sat in my livingroom for almost a year...
When I was first exploring the idea of using pvc pipe for transmission line speakers I set up a simple proto-type.. I mounted speakers similar to yours on a 6 inch straight pipe.. I also used a tee to mount the speaker.... this straightr pipe... about 3 1/2 feet long sat in a 10 inch pipe... kind of like a flower in a vase.. the 10 inch pipe about 2 1/2 feet long.. Anyway this prototype sounded so good that it sat in my livingroom for almost a year...
I misspoke.. I mounted my speaker on the middle opening of the T.. I think I like the way you mounted yours better..
kelticwizard said:
I think the mounting method is according to plan. Isn't that what Andrew's plan assumed? I just double-checked; it is.
I'm glad you mentioned the port config. I think I have the port pieces swapped. They're mounted as labelled, but I think they're on the wrong pipes!
Shoot. It fell down. It's roughly 2 feet from top to bottom.
Miles gets a vote: Presence 1 1/2, Miles 1, Mozart 1/2
And one more thing. Isn't 13 a prime number? If we don't count the tee, this thing has 13 pieces. Cool, huh?
Dave
steve said:
The thing about mounting it the other way, like a periscope, is that you can add length at the very front of the pipe, on top, like moving the speaker down the enclosure, see, without having to re-cut. If anything, that adds volume where the driver is firing, so it could help bass response. We need to call in an expert TL designer on that one.
The way I have it avoids a bend at the very beginning. The air just pushes in one direction till it starts to spiral.
And I can't get over how nice my taped-together PVC pipe enclosure sounds.
Dave
kneadle said:
Hmm...that's not it. I wonder if the orientation of the thing isn't deceiving us. We're certainly perceiving the same thing, though. I'll try turning the thing a little more sharply.
In the paper I'm writing, I have a section called "the human element." It describes a lot of little things that can't be accounted for, like the jig snapping in the middle of a cut, the saw not making "clean" cuts all the way through, the fact that PVC pipe ISN'T perfectly round, etc., etc.
At any rate, it creates a problem when trying to line these things up so they fit together in a spiral. I had to make notes on each pipe where they might need a little extra help, some sanding, and whatever. A half-dozen of these are mostly forced, but as you can see by the picture here, http://www.diyaudio.com/forums/showthread.php?postid=130027#post130027 , I came put-near a mirror image over the course of 26 pieces of 6-inch sewer-grade PVC pipe.
Not without a lot of coaching.
Dave
Kneadle:
I think if you take a look at Faustian's drawing on page 5, post #75, it looks more elongated. Faustian's is the last post on the page:
http://www.diyaudio.com/forums/showthread.php?threadid=10652&pagenumber=5
He said the structure stands 3' 1.5" high. If the bottom of the top pipe is 2" off the ground, that is still a difference.
Regardless, it is a spiral, so you haven't lost. 🙂 🙂
PS: Just one thing-I must have worded my vote incorrectly. I meant to cast it for Led Zep's "Presence", not Miles. Sorry.
I think if you take a look at Faustian's drawing on page 5, post #75, it looks more elongated. Faustian's is the last post on the page:
http://www.diyaudio.com/forums/showthread.php?threadid=10652&pagenumber=5
He said the structure stands 3' 1.5" high. If the bottom of the top pipe is 2" off the ground, that is still a difference.
Regardless, it is a spiral, so you haven't lost. 🙂 🙂
PS: Just one thing-I must have worded my vote incorrectly. I meant to cast it for Led Zep's "Presence", not Miles. Sorry.
the only thing I can say about its coming up a foot short is "human element." It seems obvious I got the 22.5° right, but the 11° is a little off. I was perfectly consistent, too, however much I was off.
5/8" in inch on the outside of a 6 3/8" sphere is 11°, by my reckoning.
That's Presence 2 1/2, Mozart 1/2.
5/8" in inch on the outside of a 6 3/8" sphere is 11°, by my reckoning.
That's Presence 2 1/2, Mozart 1/2.
Dave.. I think your thoughts about adding length to the pipe... by extending the T on the top may be useful in any tuning that you may have to adjust.. I've never been totally clear on how the spiral would effect the 'length' of the pipe.. I know you determined the length based on the midline of your curve.. but remember that you are interested in the standing wave in an air column.. if you straightened your pipe out it would look like the end was cut at a diagnol.... the short end of this pipe would be less than 26 inches.. while the long end would be over 90 inches. I'm pretty sure that's right. Will the pressure wave unload at the shortest length of the pipe..the mid point..or a little bit all along the length? I sure don't know.
kneadle said:
Actually, Faustian and I came up with that 5/8" figure. So if it's off, it's not your fault. 🙂
As far as the tape being non stretchable, so we know the structure isn't sagging-I am not so sure. It looks to me like the bottom is sagging a bit under the weight-see how the spiral seems to "open up" as you go higher? We won't know until you glue it. I still have a sneaking suspicion that this thing will be higher than 2 feet-that either the joints or the tape is allowing sag that won't be allowed by the glue, once it is set.
Even if the thing only ends up going 6" higher when you glue-that will take it up to 31". Close enough.
Anyway, it's a smooth spiral, and that is what you were aiming for. It can stay the way it is now and you still have a success.
steve said:
I wondered about that myself.
The only thing that I can tell you is that the Transmission Line started life as the non-tapered Acoustic Labyrinth, manufactured by Stromberg-Carlson back when they made consumer hifi in the thirties or forties. Apparently, they went out of the hifi business, though I think that Stromberg is still around making something, and the Acoustic Labyrinth got transformed into the tapered Transmission Line in the 1960's.
With all the people making Acoustic Labyrinths and Transmission Lines since then, using every conceivable type of turning and twisting at all angles to fit the Line inside the box, nobody has mentioned the length difference between each end of the Line as a factor.
I have seen response graphs of Acoustic Labyrinths and Transmission Lines with horrible holes in their response due to a number of sharp 180° bends, but nobody has brought up the length difference yet. So I think it should be OK.
I am thinking if there is an effect due to the length difference, I wonder if it might not be a smoother response over a greater bass range than a conventional Line. That is to say, the Line may give excursion relief to the woofer over a greater range than a straight cut Line would.
steve said:
I see what you're getting at. What we should do, now that it's too late, is figure the math for that.
As a partial answer, and food for thought, I did base this design on a real-live theory, but not wave theory. Particle theory suggests (and is proven in tests) that force is distributed unevenly in a spiral. The effect it has on particles in motion is simply a centrifugal one, but continuously varying. I forget the details, but it was interesting enough.
I borrowed that theory for my pipe. My theory is that force is being unevenly distributed all the way down the pipe, unlike "normal" enclosures. Now, as far as the science of this thing goes, I think I abandoned science when I made the design. however, it stands to reason that a standing wave is having its energy unevenly dissipated--will you guys quit posting so fast?!? That's two since I started this post!--not only within the spiraling shape, but also in the oblong spherical shape that is formed 2-dimensionally.
Do you see what I'm getting at?
Dave
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