Calculate a PVC Pipe speaker with 3.3" driver

Hey guys, I once built a TQWT but with 50's drivers based on drawings based on a slightly comparable driver, the results were not amazing. I now found a couple of Visaton FRS-8's in one of my crates and would like to make another effort building a fun set of speakers. They are meant to be on my desk, next to my screen. I will probably supplement the real low with a subwoofer that I still have lying around.

I would like to use PVC as it is easy to come by and easy to use. However, I have got no clue how to calculate the length of the pipe. Can anyone help me out?
 

Galu

Member
2018-04-17 6:50 pm
Here's a 'no math' suggestion:

Parts Express suggest a suitable sealed volume of 0.06ft^3 (1.7 litres) for the FRS-8.

Obviously, the pipe diameter will have to exceed the driver's overall diameter of 3.07".

Once you've selected the pipe diameter, you can calculate the length required to suit the volume of 1.7 litres.

Start with a longer experimental pipe then shorten it in stages in order to find the optimum length sound-wise.

Stuff the finished pipes with absorbent to kill internal air resonances.
 
Duh ................
That's OK .... I have developed a new (armchair) system for optimizing T.L. s .
Since the driver Fo goes down as the pipe is lengthened ( by the added mass of the column)
AND
The 1/4 wave Fp also goes down ..... My calculator finds the point where the
2 frequencies converge : ) ....... In this case the Visiton FR8-8 needs to be on a 2"
pipe 41" long for Fsys of 82 Hz ....
 

freddi

Member
Paid Member
2005-08-16 4:21 pm
hey hits - if I put things right (???), tuning with this stuffing density is about 70Hz

got any links to your PC music ?

would it look like so if a straight pipe?

4CuuRNz.png
 
The 1/4 wave Fp also goes down ..... My calculator finds the point where the
2 frequencies converge : ) ....... In this case the Visiton FR8-8 needs to be on a 2"
pipe 41" long for Fsys of 82 Hz ....

So, some kind of adapter and then glue that to a 2" diameter pipe that gives it a length completed of 41" and then stuff that thing. Completely open ended, or closed, or perhaps some kind of slot?
 
To make things more manageable :
caps on both ends ....
driver on one end ...... 1" x 4" port on other end
For 8 Ohm model ..... pipe 4" x 13 "
For 4 Ohm model ...... pipe 4" x 27 "

Ok, so when I would use a 4" pipe instead of a 2" pipe, I could almost half the length? And then do a 1" by 4" port at the end? Because I cannot make a 1"x4" port at the end of a 2" pipe. ;)
 
Last edited: