Real Expert or Just Self Proclaimed

[speakerman19422]

The link Strangiato posted is correct.When the author states using low cost cheap drivers in t-lines he is correct. Not that I would buy one what do you think Bose did in the Wave Radio? Bose used cube drivers in 1/4 wave lenght enclosures. I have done the same thing with the same exact drivers. Maybe this forum isn't for helping each other out. I try to give my fellow man helpful information to improve his listening experience. Many forum users are trying to put themseleves on a pedastool. Martial arts, powerlifting, or becoming a skilled marksmen might be a bit more challenging experience for these people rather then speaker building. I try to learn from other people's postings.. Every one can learn from each other's experiences. Most of my friends in the business stay away from forums. I can see why.

[soongsc]

Originally Posted by speakerman19422

... Most of my friends in the business stay away from forums. I can see why.

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.

[LineArray]

Originally Posted by gedlee

I guess that its my turn. First it is entiorely incorrect to say that a bend causes damping because the wave changes direction. Wave can bounce off of walls, i.e. change direction, without any damping at all.
...

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.

[gedlee]

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.

[Don Hills]

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.

[speakerman19422]

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..