Why do some sub (bass) boxes have a large hole in the front and some dont?
If i was to make a box do i put a hole in the front or not?

Ray

depends on the sub - if its free air it needs the hole, if its designed for an enclosure then no!!

Oooh lordy, this could be answered with pages of guff ;)

In short, the hole is known as a "port". It is not simply a hole, but will be a piece of pipe that extends deep (maybe) inside the box.

The length and diameter of the port tune the box to a particular frequency. At this frequency, the port is actively increasing the output of the box/driver by having the air from the back arrive at the same time as the air from the front. However, below that frequency the port has the effect of removing the suspension for the driver, which is emphatically a VERY BAD THING (tm).

Ports can be great, and can give a better low-down response than you would expect from a sealed box but normally at the expense of something. Most of the times, the linearity of response is compromised, plus you will get noise from the port (a sort of whooshing/whumping noise) though if it's in the boot you may not hear it.

Use a ported box for speakers that are designed for ports (bass reflex may come into the name, such as the infinity BR series of subs, which like ports).

This is just touching the surface. But in short, don't just whack a hole in your subwoofer's box :D

SJ, if it's free air, then it is designed for infinite baffle usage, which means that the air from the back should never come in contact with the air from the front. :) That's something completely different :D

If it's a free air sub then why put it in a box?
I've always built my own boxes, have you ever worked out what size the box needs to be to get the optimum from a FA sub?

'kin huuuuge. Free air assumes that there's effectively no suspension provided to the driver, but as no driver in the world works like this, they work best with some.

Back to the original question: what sub have you got?

just asking because its been bugging me. a mate of mine built his own box out of crappy plywood and drilled a big hole in to the box, his got one of the Sony Xplod subs.

Been looking in the mags but they do not state if the are for free air or enclosure. they just have a model number and the price.

Ray


Thank you Guru Chiark

Majority of subs are for an enclosure, and you're best off assuming that they will need a box. Whether they need a port depends on whether they are designed for sealed box use, or bass reflex (or ported, or first order, or whatever) use...

When the box falls apart, or the speaker self destructs, that's a bad sign. ;)

easy answer, if you like a low booooom bass port it, if you like punch bass seal it.

also if sealed, sub last longer in life. see what speaker is designed for ( sealed or ported )and most of all use the right cubic feet

clint

Have a look at the jl web site - they have a lot of info on box sizes, types and volumes, sealed, ported and bandpass. If you read everything there then you'll definately be all the more wiser.