kneadle said:
Somewhat. The only thing I can say is that many resonances, due to unequal pressures, is far more beneficial than one big resonance since multiple resonances have a tendency to be lower in amplitude and to sum up to a relatively even response.
We shall see.
Now I remember some of the details. The centrifugal force causes particles to settle on the outside of the entire spiral. What that means to me is that it's not like introducing radical turns in a pipe. So I guess you could say I'm arguing that a continuous, gentle curve, won't introduce odd diffusion like other twisty-turny type TL enclosures, including the classic folded.
At any rate, if I ventured a guess, the force of the standing wave is being unloaded on the outside of the pipe. I wonder if it's unevenly so? I would further venture to guess that this is a measurable distribution.
The problem for me now is visualization. I wonder how it actually is unloading?
They still sound pretty good.
We're off to the art supply store, now that our half of the blizzard is over.
Dave
At any rate, if I ventured a guess, the force of the standing wave is being unloaded on the outside of the pipe. I wonder if it's unevenly so? I would further venture to guess that this is a measurable distribution.
The problem for me now is visualization. I wonder how it actually is unloading?
They still sound pretty good.
We're off to the art supply store, now that our half of the blizzard is over.
Dave
kneadle said:
Hah! We're stuck in the middle of it right here. Absolutely nobody is going anywhere until sometime tomorrow.
Don't wave theory and particle theory intersect somewhat when it comes to behavior in an enclosure?
Here's what I visualize: the standing wave is being "bent" out of shape according to the shape of the enclosure. It's simply not going to resonate. It's like a slinky. The energy, unlike the commercial (it's lo-og; it's lo-og! It's big/it's heavy/it's wood!), literally flies off in all directions.
Yeah, I think the slinky model works here. If you hold it in your hand in a spiral shape, the energy going every which way.
What think ye?
Dave
Here's what I visualize: the standing wave is being "bent" out of shape according to the shape of the enclosure. It's simply not going to resonate. It's like a slinky. The energy, unlike the commercial (it's lo-og; it's lo-og! It's big/it's heavy/it's wood!), literally flies off in all directions.
Yeah, I think the slinky model works here. If you hold it in your hand in a spiral shape, the energy going every which way.
What think ye?
Dave
Well, not having conducted tests, I honestly don't know. It is your position, then, that the spiral will behave differently from a straight pipe cut at a diagonal?
I am thinking that the diagonally cut pipe will have a resonance that is lower in amplitude but broader in peak than the straight cut pipe. Perhaps this might mean a higher 3 dB down point, but a more gradual rolloff. This would be, I think, a perfectly good response. More gradual rolloffs mean better transient response, and a cleaner sounding bass.
As to what the spiral will do, I can't say.
I am thinking that the diagonally cut pipe will have a resonance that is lower in amplitude but broader in peak than the straight cut pipe. Perhaps this might mean a higher 3 dB down point, but a more gradual rolloff. This would be, I think, a perfectly good response. More gradual rolloffs mean better transient response, and a cleaner sounding bass.
As to what the spiral will do, I can't say.
Dave...
My guess is that the spiral will introduce quarter wave harmonics over a broad spectrum of wavelengths.. a more smeared effect than if you had a straight pipe. But I'm inclined to believe that this will be a good thing...
My guess is that the spiral will introduce quarter wave harmonics over a broad spectrum of wavelengths.. a more smeared effect than if you had a straight pipe. But I'm inclined to believe that this will be a good thing...
kelticwizard said:
YES. That is my position. While Steve raises the issue correctly, I think that what we have is more than the sum of the parts.
But I'm in perfect agreement with your last statement.
Just to expand. If we literally straightened the spiral, we'd have 13 segments strung together with a big hole between their short ends, like so: /__\/__\/__\. My real question now is just geometrical logic. Does it follow that when we put them together, we have a long pipe that has a radical diagonal cut? That's a real question; I'm not good at geometrical logic.
Dave
steve said:
First, this thread goes way too fast, sometimes. I barely have time to check my spelling and grammar before a response comes up.
Second, this is a reasonable insight. And my ears, too, are thinking it's a good thing.
Dave
steve said:
I don't think a Transmission Line introduces harmonics. Harmonics are distortion, and the Transmission Line seems to introduce less distortion than other enclosure types. That is why people go throught the trouble and extra volume to build them.
I'm not sure that harmonics is the correct term.. but transmission line systems are definitely designed to 'distort' the frequency response of the driver... it does this by tuning the length of the pipe to a quarter wave of the free air resonance of the driver.. This reduces the load on the driver at this frequency, which improves the bass response of the system..
The overall affect of this distortion on the driver is that the frequency response of the system is improved..
The overall affect of this distortion on the driver is that the frequency response of the system is improved..
Steve:
What it does-and I have never built a Transmission Line-is to damp the resonance of the speaker in the box by making a line one quarter the length of the lowest frequency.
The bass reflex has a similar action. but with Transmission Lines, the length of the line, rather than the volume and the port, is what does the tuning.
The reason the Transmission Line is considered sonically superior by many to the Bass Reflex is that instead of setting up a resonance between the box volume and port to counter the resonance of the driver, the Transmission Line is considered an anti-resonant enclosure. Therein lies the Line's superiority, at least in the mind of the Transmission Line fans.
Both have output at the port that relieves the driver cone from moving as much as a closed box system. The output from the port seems to be deeper in a bass reflex system, (at least around the tuning frequency), while Transmission Lines frequently have port output that extends farther up the scale than the bass reflex.
PS: There are also some kinds of Transmission Lines that have little or no bass output out the port. They are there to smoothly absorb the back wave-that is all. However, we are dealing here with the kind of Transmission Line that has substantial bass output.
What it does-and I have never built a Transmission Line-is to damp the resonance of the speaker in the box by making a line one quarter the length of the lowest frequency.
The bass reflex has a similar action. but with Transmission Lines, the length of the line, rather than the volume and the port, is what does the tuning.
The reason the Transmission Line is considered sonically superior by many to the Bass Reflex is that instead of setting up a resonance between the box volume and port to counter the resonance of the driver, the Transmission Line is considered an anti-resonant enclosure. Therein lies the Line's superiority, at least in the mind of the Transmission Line fans.
Both have output at the port that relieves the driver cone from moving as much as a closed box system. The output from the port seems to be deeper in a bass reflex system, (at least around the tuning frequency), while Transmission Lines frequently have port output that extends farther up the scale than the bass reflex.
PS: There are also some kinds of Transmission Lines that have little or no bass output out the port. They are there to smoothly absorb the back wave-that is all. However, we are dealing here with the kind of Transmission Line that has substantial bass output.
A Little Data
I think Steve has brought up an important detail. Here's some data.
The mathcad worksheets were worked out as though this were a straight pipe 66" long. The tee gives us 6", so I needed 60" of pipe.
I bought 12 feet of pipe. I should say, I PAID for 12 feet of pipe. I never measured it. There was a "sleeve" on the end of it that measures about 6", and I don't know if it counted toward the 12 feet or not. In other words, I could have had anything between 144"-150" of pipe. Let's assume the worst, that it was 144."
I needed two enclosures, which brings the needed length to 120". 144"-120" leaves me with 24" of leftover pipe.
In truth, I have 36" of leftover pipe, which includes the sleeve at the end. That's a rough estimate because there are a few dud segments among the leftovers, which are cut at different angles.
The first question we need answered is: does this actually matter?
If so, then we need to figure what the effects might be. A folded enclosure measures strictly length, but I believe that the volume never changes. We clearly have changed the total volume.
We need a TL expert. Will someone bring this to the attention of Martin King or Planet10?
Dave
I think Steve has brought up an important detail. Here's some data.
The mathcad worksheets were worked out as though this were a straight pipe 66" long. The tee gives us 6", so I needed 60" of pipe.
I bought 12 feet of pipe. I should say, I PAID for 12 feet of pipe. I never measured it. There was a "sleeve" on the end of it that measures about 6", and I don't know if it counted toward the 12 feet or not. In other words, I could have had anything between 144"-150" of pipe. Let's assume the worst, that it was 144."
I needed two enclosures, which brings the needed length to 120". 144"-120" leaves me with 24" of leftover pipe.
In truth, I have 36" of leftover pipe, which includes the sleeve at the end. That's a rough estimate because there are a few dud segments among the leftovers, which are cut at different angles.
The first question we need answered is: does this actually matter?
If so, then we need to figure what the effects might be. A folded enclosure measures strictly length, but I believe that the volume never changes. We clearly have changed the total volume.
We need a TL expert. Will someone bring this to the attention of Martin King or Planet10?
Dave
Are you suggesting that the wedge-shaped cuts of pipe that were made to form the spiral, add up to an additional foot of length, that was omitted from the initial, spiral-length calculation?
In other words, by making the compound cuts, you shortened the pipe by a small amount, and didn't compensate for it?
Do you simply need to add more section(s) to get to this 66" total length?
In other words, by making the compound cuts, you shortened the pipe by a small amount, and didn't compensate for it?
Do you simply need to add more section(s) to get to this 66" total length?
x. onasis said:
That, my friend, is the question. The internal length of the pipe, down the middle, as it now stands, taped together, is 66".
I don't actually know if we've changed the internal volume. As Steve mentioned, the thing is 90 inches, measuring all the long lengths of the pieces, then 26 inches, measuring all the short lengths of the pieces. That leaves us a median value of 64 inches, 3 of which are inside the mount. Thus, we have 61 inches of median length, which is pretty much on the button.
I don't know how we managed to do that and have between 8-12" of extra pipe, which turns into 4-6" per enclosure. It COULD be that my pipe was that much longer when I started sawing, and I didn't know it, i.e., I had 156" of pipe to begin with.
Dave
Well, you might not know how long the pipe was when you started, but you know how long the pieces you cut were. For volume purposes, the pieces are equivalent to a square cut pipe of 4.5", and that is that. If you have 13 pieces cut at 4.5", then your volume is 1389 cu in, not including the Tee.
It should be pointed out that if the Transmission Line is anything like the Closed Box or Bass Reflex, you can be off by 10% and there will be little difference. Even having 25% less volume only means that your 3 dB down point will be a quarter octave higher-not that much.
It should be pointed out that if the Transmission Line is anything like the Closed Box or Bass Reflex, you can be off by 10% and there will be little difference. Even having 25% less volume only means that your 3 dB down point will be a quarter octave higher-not that much.
Dave..
I think the wizard is right regarding the volume issue.. I doubt that it is as critical a concern in a transmission line system as in a bass reflex or even a sealed system.. Also, there is another way to deal with the 'length' issue... the 'stuffing' actually influences the effective length of the pipe.. you can tune the pipe by changing the amount of stuffing in the pipe. Add stuffing to increase the effective length of the pipe, removing stuffing decreases the effective length. But unfortunately, the amount of stuffing also affects the overall effectiveness of the line... too much stuffing and the pipe 'chokes'. You'll want to do listening tests with more or less stuffing to see what sounds best..
I think the wizard is right regarding the volume issue.. I doubt that it is as critical a concern in a transmission line system as in a bass reflex or even a sealed system.. Also, there is another way to deal with the 'length' issue... the 'stuffing' actually influences the effective length of the pipe.. you can tune the pipe by changing the amount of stuffing in the pipe. Add stuffing to increase the effective length of the pipe, removing stuffing decreases the effective length. But unfortunately, the amount of stuffing also affects the overall effectiveness of the line... too much stuffing and the pipe 'chokes'. You'll want to do listening tests with more or less stuffing to see what sounds best..
With regard to that, Steve, I think my spiral idea is working like I imagined. I have one that is stuffed and one that is not. Even though they're still in the "taped-together" mode, the bass response is rather equivalent.
I've only sent a few test tones through, but the difference between the stuffed and unstuffed is negligible so far. I'm sure there will be a difference as I go along, but so far...
I have a pro-audio setup here, with SONAR and such hardware and software, but I'm not sure how to apply it to speaker measurement. I think I have an analog synth that will play sine wives at a given amplitude and frequency. That's an issue for later, though.
Oh, another issue for later is how to "upgrade" my Teac AG 380 receiver/amplifier. That's probably for another forum.
Dave
I've only sent a few test tones through, but the difference between the stuffed and unstuffed is negligible so far. I'm sure there will be a difference as I go along, but so far...
I have a pro-audio setup here, with SONAR and such hardware and software, but I'm not sure how to apply it to speaker measurement. I think I have an analog synth that will play sine wives at a given amplitude and frequency. That's an issue for later, though.
Oh, another issue for later is how to "upgrade" my Teac AG 380 receiver/amplifier. That's probably for another forum.
Dave
I spent many hours with a frequency generator and a sound meter.. plotting response curves for the different itterations of my speakers.. I found it very difficult to evaluate the bass response by ear while listening to pure tones.. only by direct a/b comparisons could I percieve easily measurable differences.. this was not the case when listening to music though. While listening to music I could easily pick up subtle differences... diffferences that I was unable to percieve while listening to pure tones.
I'd be very surprised if the stuffing did not influence the bass response of the speakers.. but assuming it doesn't.. I would advocate that less is more... as in I would use as little as necessary. I think this will reduce the load on the driver.. providing a more lively sound..
I'd be very surprised if the stuffing did not influence the bass response of the speakers.. but assuming it doesn't.. I would advocate that less is more... as in I would use as little as necessary. I think this will reduce the load on the driver.. providing a more lively sound..
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