large PVC port

[tade]

I scavenged a piece of PVC pipe 7.5 inched inner diameter and two feet long. Massive, and expensive if i were to buy it myself. so i am stoked, imagind how kick *** a sub port you would put your head into would be.
Is it useable at all?
what kind of monster specs would my driver need?

thanks

[Stocker]

Increasing port diameter is usually done to reduce port noise. Unless you are moving a LOT of air at VERY low frequencies, this will be a pretty nifty enclosure for a small sub, but not a good port for a mid-size sub.

When I say a LOT of air, I am thinking rock-concert loud. Or louder.

[Collo]

It's definitely useable

Be warned, large PVC ports have a seductive nature that can sneak up on you....

You will find that a large dia pipe needs a large box. Here are some figures (sorry about the metric..)

for a port 187.5mm dia and 600mm long:

a tuning frequency of 35hz requires a box size of 111 litres
a tuning frequency of 27hz requires a box size of 154 litres
a tuning frequency of 20hz requires a box size of 300 litres

pipe resonance 286hz

I have built a dual 10inch sub with a pair of 6inch ports in a 130 litre box tuned to 28hz. With 240w applied, this runs with a peak airspeed of a very conservative 8 metres/sec.
A single 7.5 inch port would have run at around 11 m/sec (although it would have needed to be about 1060mm long)

If you flare both ends, I would guess that you could run up to a pair of twelves with about 300w total.
Look for drivers with an Xmax of around 10mm, which will be happy in about 80-150litres each.

regards
Collo

[tade]

collo, seductive in what way?

[Collo]

You have to ask me?
You've only just acquired it, and already you're trying to fit your head into it!
I think it might be too late for you.....

[tade]

haha yeah, though ill have to get my head around it before i can do anything useful.

[xstephanx]

very usefull piece of material if youu have say, a pair of high excursion 15s, and wanna tune em low.

[lynchingacers]

u could try using it as an enclosure for a pair of 8" sealed and sub on each end or u could biuld it like the bazoka subs in car audio

[tade]

i was biking around town again tonight...
scored a piece with an ID of twelve inches and three feet in length. i think this may be obsessive...

[Stocker]

The best way to fight OCD is to deny the urges...

The best way to use that pipe is as a subwoofer enclosure.