Calculate a PVC Pipe speaker with 3.3" driver

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#22
Arne said:
Thanks GM.

But euhm, can you explain that to me in English? Or point me to a place where I can read up on this in a simple way? (So without some of the massive formula's I have seen on some sites. 😉 )
Click to expand...

Greets!

You're welcome!

While I've posted numerous more explicit write-ups for specific drivers or at least posted a HR sim, I just posted the basic info in the hope that anyone here with some experience would expand on/sim it once it became obvious I hadn't been able to respond in a timely manner.

Anyway, my way makes a bit more efficient alignment [higher power handling] due to using a bigger pipe, but otherwise sims near enough the same as Mike's once both are optimally damped.

A theoretically technically more correct alignment than either of ours would be the Alpha TL and its math is simple enough for even math challenged folks like me. Had I known it was still on-line I would have just posted it: http://diyaudioprojects.com/Technical/Papers/Alpha-Transmission-Lines.pdf

GM
 
#23
hitsware said:
if you drill a 1" hole in a cap .....
one of these :
https://www.amazon.com/10-Pack-Cut-...=2025&creative=165953&creativeASIN=B00LORILBS
will screw in ( some effort and oil needed 🙂 )
since they are 3/4 " they can be ~ 1" long
Click to expand...

And why would you screw this in? Just to elongate that port?

GM said:
Anyway, my way makes a bit more efficient alignment [higher power handling] due to using a bigger pipe, but otherwise sims near enough the same as Mike's once both are optimally damped.



A theoretically technically more correct alignment than either of ours would be the Alpha TL and its math is simple enough for even math challenged folks like me. Had I known it was still on-line I would have just posted it: http://diyaudioprojects.com/Technical/Papers/Alpha-Transmission-Lines.pdf
Click to expand...


Thanks for that article. That should make some good weekend reading. (And calculating) 😉

Lets see what I end up with.
 
#27
hitsware said:
GM .... : )
If you use this formula :
Fb = ( 13500 / 6.28 ) * ( portarea / ( ( Vb * portlength ) ^ 0.5 ) )
to find Fb ....
And the volume of the port becomes substantial ....
Should it become part of Vb ?
Click to expand...

DMB/whoever can solve/manipulate the wave equation would have to answer this the most correctly since every junction has some sort of impedance mismatch, though IME, HR/similar program sims it's frequency dependent, so when it's very close to the same acoustic impedance they act as one, i.e. the box/vent converts from a BR with a 1/2 WL resonator [pipe vent] to a single 1/4 WL TL [what I consider the most technically correct].

FWIW, back before T/S, I used the pioneer's Av = Sd, Fp = Fs, with Vb [box + vent] chosen from published nomographs based on Fs. With tone controls, damping, they all sounded better overall in room than any typical mainstream consumer speakers I was exposed to including many inexpensive multi-ways.

GM
 
#29
Arne,
I just did a quick simulation with the Leonard Audio Transmission Line (LATL) package and I fond the following configuration looked pretty good:
4" Diameter, 24 inches long
4"-2" Reducer
2" Diameter x 4" long port.

Using the 4" to 2" reducer eliminates the need to do any cutting to attach the port.

And the great thing about the PVC route is that you can try different tube and port lengths very, cheaply and easily.

Here's my own PVC MLTL creation. With Pluvia 7.

 
#32
Veleric said:
Using the 4" to 2" reducer eliminates the need to do any cutting to attach the port.

And the great thing about the PVC route is that you can try different tube and port lengths very, cheaply and easily.
Click to expand...

:up: 😀

Indeed! By the mid '60s it was relatively cheap with a large enough selection of sizes, connectivity to allow me and an old one armed DIYer to teach ourselves how to design/tweak intake, exhaust systems, TL speakers, etc., with a lot of help from this doc: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092208.pdf

GM
 
#33
GM said:
FWIW, back before T/S, I used the pioneer's Av = Sd, Fp = Fs, with Vb [box + vent] chosen from published nomographs based on Fs.
GM
Click to expand...
So much for Vb = Vas ..... : )
 

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#34
Ok, so I caught a bit of a flu, so no building yet...
(Did pick up a vintage Cyrus One amp to play with over the weekend with a set of B&W 610i's)

Veleric said:
Arne,
I just did a quick simulation with the Leonard Audio Transmission Line (LATL) package and I fond the following configuration looked pretty good:
4" Diameter, 24 inches long
4"-2" Reducer
2" Diameter x 4" long port.
Click to expand...
Thanks for the calculations. That looks very doable.

Veleric said:
Using the 4" to 2" reducer eliminates the need to do any cutting to attach the port.

And the great thing about the PVC route is that you can try different tube and port lengths very, cheaply and easily.
Click to expand...
My thoughts exactly. I mean, I once built MDF folded TQWT pipes based on a set of vintage Isophone broadband speakers from a historic cinema.

49371556863_4013a5f5a4_c.jpg

That was my attempt.It wasn't quite finished here and I was finding my way around the dampening as well...

49372216852_b31fb2d831_c.jpg
Enough for a mockup with a gasket and some home made clamps to test it on my Quad 34/405-2 combination with an Arcam Alpha CD player. Quite impressed, but in the end their sheer size and the need for a supertweeter and a sub made me decide to sell them. They made their way to Belgium where an enthusiastic builder finished them and told me that playing on them was as if a veil was taken away from all his music. 😀

Veleric said:
Here's my own PVC MLTL creation. With Pluvia 7.

Click to expand...
That looks great. Would love to hear them play. 😉
 
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