Most people in the business do not want to engage in technical discussions because most are unable to explain very clearly in technical terms why they do things the way they do it. This can be very bad for their business if their living depended on it.
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Given a (stretched) pipe with both ends closed and excited at one end,
there will be resonances at 1/2 lambda, 2/2 lambda, 3/2 lambda ...
The closed end will have maximum reflection for wavelengths
causing a pressure maximum to be located at that closed end.
For the same pipe there will be antiresonances at
1/4 lambda, 3/4 lambda , 5/4 lambda ...
Because the velocity maximum is located at the closed end,
there is minimum reflection for the associated wavelengths.
If we now tune the frequency to hit the 1/2 lambda resonance and
now start bending the pipe sharply in the middle where the velocity
maximum is located ... what would you expect to happen ?
I expect the effective cross sectional area to decrease because
the velocity distribution over the cross sectional area will
deviate from the more evenly distribution of the stretched
version of the pipe, if you look at the bend region.
The Q of that 1/2 lambda resonance should decrease IMO,
because what the bend does is pretty much the same like
placing a barrier there.
A bend in the middle of the pipe for the 2/2 lambda
resonance should have less effect, because of minimum
velocity in the bend region.
I don't think that you understand what "damping" is. Where does the energy go just because there is a bend in the pipe? Unless you can identify where the energy goes in your example, there cannot be any change in the "Q" because of "damping". And don't say "through air friction" because then you would have to say 'for high SPLs" because air friction vanishes at low SPLs. Only when the velocities reach high Reynolds numbers is air friction even a factor. It can happen, but you didn't apply this limitation to your claim.
Oliver,
You have just illustrated the problem I (and, it appears, others) had with villastrangiato's claims. He had a less than complete understanding of the physics involved, and thus came to the wrong conclusions.
Regards,
Don.
You have just illustrated the problem I (and, it appears, others) had with villastrangiato's claims. He had a less than complete understanding of the physics involved, and thus came to the wrong conclusions.
Regards,
Don.
Another area that has been neglected are the frequencies that the driver is reproducing . If the driver is being crossed over at 100-200hz the line and stuffing material does not encounter these frequencies at high db. The low pass filter has already been completed. The whole point of the line is to add ripples in resonances. The time delay in sound emerging from line terminus has already been filtered before the back wave of the driver exits line terminus. Having line terminus in front or rear of enclosure is another issue.Taking advantage of these facts are key issues in final design cabinet and crossover design for subwoofers..
Personally, i just liked the part of this thread concerning exhaust manifolds/downpipes......I always liked the minis 3port racing manifold. Elegant. Functional.
All this over the poor naming of TL speakers, or rather the divergence of operation ( with the insight of continued discovery)....crazy.
Its like my post re: Taper in TQWP. taper is always narrowing towards the vent.....the fact that Voigt used it to mean the opposite, doesn't make the use of language correct.
Still, i managed to keep it to 1 (now 2) comments....
This thread should never have got past post#1....������
All this over the poor naming of TL speakers, or rather the divergence of operation ( with the insight of continued discovery)....crazy.
Its like my post re: Taper in TQWP. taper is always narrowing towards the vent.....the fact that Voigt used it to mean the opposite, doesn't make the use of language correct.
Still, i managed to keep it to 1 (now 2) comments....
This thread should never have got past post#1....������
Can someone please clarify one thing I think all beginners have a problem with.
Is it not true that the resonance frequency that the TL is tuned to is the box resonance (with the woofer) and not the woofers Fs it's self.
To find a woofer with a sealed box resonance of less than 40hz is like impossible. Yes I've found a few and think 40hz is ok with room gain but you also need the woofer to fit the volume of the line so it needs to be around 80 liters for .7Q and always ends up about 1.7 meters long,,,am I right? Again I've found a few and would love to use the AE AB10AU but it only needs 60 liters for a Q of .7 so will be very critically damped with 80 liters.
Because Q is a personal thing and changes with more and less volume,,,but not by that much really,,,is it not true you can just about tune to the frequency you wish providing its at a volume workable for the woofer? Is .5 or .6 too damped? Is .8 or .9 not enough. I understand .9 is more damped than just about any ported design. I love reading all your comments and advice out there guys. Thanks, Ron
Is it not true that the resonance frequency that the TL is tuned to is the box resonance (with the woofer) and not the woofers Fs it's self.
To find a woofer with a sealed box resonance of less than 40hz is like impossible. Yes I've found a few and think 40hz is ok with room gain but you also need the woofer to fit the volume of the line so it needs to be around 80 liters for .7Q and always ends up about 1.7 meters long,,,am I right? Again I've found a few and would love to use the AE AB10AU but it only needs 60 liters for a Q of .7 so will be very critically damped with 80 liters.
Because Q is a personal thing and changes with more and less volume,,,but not by that much really,,,is it not true you can just about tune to the frequency you wish providing its at a volume workable for the woofer? Is .5 or .6 too damped? Is .8 or .9 not enough. I understand .9 is more damped than just about any ported design. I love reading all your comments and advice out there guys. Thanks, Ron
If you want a maximally flat response from the knee in the response curve on up in frequency, the TL's 1/4-wave resonant frequency will be tuned to take into account both the woofer's Fs and Qts. With Qts at or near 0.4, the line's 1/4-wave resonance will be pretty much equal to Fs. If Qts is above 0.4, the line's resonance will need to be below Fs, and if Qts is below 0.4, the line's resonance will need to be above Fs. These guidelines have worked very well in all of my designs but that doesn't mean others are excluded.
Paul
Paul
So are you saying to tune to or around (depending on Qts) the driver's Fs and not to worry about the sealed box relationship the line has with the woofer...Fb.
By the way I'm only using the TL up to 100hz.
By the way I'm only using the TL up to 100hz.
I do not understand the personal stuff
but if you need advice or help, this thread title might not be a positive
but if you need advice or help, this thread title might not be a positive
Hello Tinitus,
I'm not understanding what you said there. Am I not to ask for advice?
I'm new and very confused with your statement but do want to know if I've done/said something wrong.
Please clarify, Thank you, Ron
I'm not understanding what you said there. Am I not to ask for advice?
I'm new and very confused with your statement but do want to know if I've done/said something wrong.
Please clarify, Thank you, Ron
Asking advice is great. Nor have you done anything wrong AFAIK. What he means is that this was a very controversial thread that was started by a troll a few years ago, and that until very recently, it was languishing in well-earned obscurity. You might have done better to ask on a different one. 😉 Perhaps the mods could lock this one?
Anyway. Sealed box volume for a given Qtc has no more relationship to a 'transmission line' (insert favoured definition here) than it does to any other vented alignment. Forget it.
Anyway. Sealed box volume for a given Qtc has no more relationship to a 'transmission line' (insert favoured definition here) than it does to any other vented alignment. Forget it.
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K thanks,
I just noticed there were many on here before with great knowledge and was hoping to hook up with them.
Thanks for the advice.
I just noticed there were many on here before with great knowledge and was hoping to hook up with them.
Thanks for the advice.
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