# Calculate a PVC Pipe speaker with 3.3" driver

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#### Arne

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?

#### Nenola

So basically you wan't a specific volume, and need to figure out the pipe measurements? There are equations for it, but fastest is one of the many online calculators, like this one: Volume of a Cylinder Calculator - Omni

#### Arne

Well, I need to figure out what the pipe measurements are, but I don't know what volume I should have yet. Or what the length of the pipe should be if looking at a TL setup to maximize bass for instance.

I did find the driver in the Loudspeaker database

#### GM

With a simple TL, can't go wrong with an IB's 10x Vas with a < 2.0 Qts', just might be bigger than necessary. Pipe tuning cut length ROT = ~0.707x [Fs/Qts']. Damp to 'taste'.

Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design

GM

#### Arne

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. )

#### Galu

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.

#### GM

Hey Mike,

This is strictly a tapered [TQWT] calculator, so not applicable for his simple pipe TL, though it does do a good alignment based on a HR sim, so apparently based on MJK's.

GM

#### hitsware

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 ....

#### Galu

Hi hitsware!

Presumably by 2" you mean the radius?

The 3.7" overall width driver would need at least a 4" diameter pipe (outside diameter 4.5").

#### hitsware

No ... I mean diameter ...
It would need some type adaptor .
A 4 inch pipe needs a driver with Fs ~ 150 Hz

#### hitsware

The suggested Visaton could be 35 Hz @ 96 " with 4 " diameter .
I was limiting @ Home Depot 4 ' pipe lengths .

#### freddi

hey hits - if I put things right (???), tuning with this stuffing density is about 70Hz

would it look like so if a straight pipe?

#### hitsware

Freddi : )

????

For ' system volume ' I get
area of 4" pipe = pi * r^2 = 12.56 sq in
so for 96" length volume = 12.56*96 ~ 1206 cu in
convert to liters :
1206 * 0.016 ~ 19 liter

Sonic Pi for synth .... Imagine for slideshow .... My wife singing : )

#### hitsware

gotcha freddi .... your sim is the 2 " pipe ......

#### Arne

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?

#### hitsware

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 "

#### Attachments

• pipesize.png
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#### Arne

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.

#### hitsware

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