A bit of a noob question...

[stickfigursicid]

Hi guys,

I was wondering if you could help me out in understanding a concept. What is the purpose of porting in speaker cabs? I think it is to increase the amplitude of the bass frequencies, but I'm not quite possitive. Also, HOW does it actually go about doing this? :confused:

Thanks for any help!
Marc

[jmail]

It's been so long since I was read-up on it, so forgive me if I mis-state something, but...

The port is used to "re-inforce" a given frequency spectrum. It can be tuned to let the sound from the rear of the speaker out, in phase (supposedly), with the front. The "tuning" of the frequency & its width is accomplished by the size of the hole, along with the length and "shaping" of the "tube" used. One older "classic" use of a port is the "folded horn" enclosure, such as Ampeg had in a few of their bass cabinets years ago. I can't remember if it was a 15" or 18" front-firing speaker, but the bulk of the cabinet was account of a folded horn port, that *really* took the sound down low...

There are possibly some good books available at the local library. You'd be looking for Audio Speaker Enclosure Construction, or some combination of those or similar words to search on. There is a very scientific method to calculate the port's dimensions. Confuses the *fire* out of me... lol About like Ohm's Law... lolol Some folks tune "by the ear"... I've got a tin ear, tho...

[130dB]

Parts Express has a good speaker building forum. Unfortunately, it is old fashioned forum software and not the easiest to search. Its been quite a while since I've frequented there, but there used to be some very knowledgable and friendly folks there.
http://www.pesupport.com/cgi-bin/config.pl