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.

 

[xstephanx]

ill take one of them badboys offa your hands if you want

 

[tade]

I dont think i have the cash right now to properly use these pipes. if you think it is worth it to get them to canada, im game!

 

[xstephanx]

ahhh i wish it was worth it but i dont have enough money for another 15, which is really the only reason i would need it.

But thanks for the offer!

you might be able to get a very reasonable price on these in the buy and sell forum, id look into it

 

[ShinOBIWAN]

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...

Your nicking from building sites aren't you?

Theiving pikey

 

[tade]

nicking is such a dirty word. lets call it, being an unpaid intern for city waste management...

 

[xstephanx]

yeah and im a city volunteer for controlling cannabis levels in neighbourhoods

 

[kingdaddy]

I used a 8" X 23" port for a Maelstrom Sonosub, needed that to keep the port noise down. The larger diameter the port the longer it needs to be for the same Fb. I like the sound of larger ports, they seem disappear better.

 

[tade]

I have seen pictures of your sub around, very nice work. what driver was it? and the volume?
thanks.

 

[kingdaddy]

Thanks,

Going from memory here, I think it was 247 L tuned to 18Hz with the Adire Maelstrom Driver, there is an identical twin, but now sadly only a year and a half after finishing the year long construction they are both setting in the game room, not even hooked up.

 

[xstephanx]

ill pay for shipping if you feel like giving one of THOSE away

what was your peak output @ what hz could you get with a pair of those guys?