How to tune a 12 sub box 32hz, or where to find?

Question

First let me say I really like this yahoo answer thing, Ive been reading through a few and learned some things :)

OK, I have a 06 Cobalt SS/SC and I am looking to upgrade my sound system. I have a JVC BT1 head unit. I have been looking at the 12 inch Alpine Type R sub. I think I am just going to go with 1. I will use an Alpine 500/1 mono amp @ 2 ohms to power it.

My questions are as follows.

1.) I have read, if you want good bang and good SQ its best to get a ported box tuned at 32hz. My problem is I cant find a 32hz tuned box anywhere :( I have been looking at the boxes on ebay and on some websites, and most dont say if they are tuned at all. Is there a way to calculate that, and or find tuned boxes?

2.) I know the type R says it should be in a ported box from .75 - 1.5, but what would the difference be if I put it in a .75 vs a 1.5?

Answer 1

Yes, i like yahoo answers too.

1) Its false. you have to tune your sub propertly, not to 32Hz. some speakers will play really bad, ugly and not so loud on 32Hz. It is insane to tune all the speakers to some frequency. The tuning frequency depends on speaker box enclosure volume and the basreflex diameter and lenght.  You should know many TS parameters (examle here http://eshop.prodance.cz/DetailPage.asp?...  no matter which language used but see the amount)

to simulate what happens to the speaker when tuned somewhere. To simulate this, you don't need to know all of them but you'll need Qes, Vas, Qts,Qms, Le,Re,Fs and box properties. You can simulate it in LSPLab or WinISD.

Depends even on kind of music you usually listen. most of normal music styles don't need to play lower than 35Hz (tuning somewhere over 35 to up 40Hz).

2) the difference will be

a) bigger volume does lower tuning

b) lower tuning and big volume does higher cone excursion, so you cannot push as manny Watts of power as to some smaller, higher tuned box. you have to decide and find some compromise if you want go deep or loud. Depends on speaker. Some can go down to 20Hz, some cannot go under 30Hz even when 5' box which will make huge excursion to that speaker.

Answer 2

Like the person said above, 32Hz does not work well for all subs.  For the Type-R, however, it is the ideal tuning frequency for what you are looking for.

0.75 cubic foot is really small for that sub.  I would recommend something much bigger.  I would recommend 2 cubic foot @ 32Hz for the sound you are looking for.  I know it is not in the manufacturer recommendation but it will be a great sounding box if built to these specs.

If you do use a 0.75 cubic foot enclosure it is going to be about as large as a 1.5 or 2 cubic foot enclosure.  The reason is that the smaller the enclosure is the longer the port needs to be.  Since you also need to account for eliminating port noise you will have to have a very long port.  

Instead of looking at a prefab enclosure you should have one custom built.  That way you can get an enclosure build to your sub's specs and built to fit in your car.  You can also get the sound you want out of a correctly built enclosure.  Prefab enclosures are built to generic specs so they will not fit well with most subs.  

Another common problem with prefab enclosures is the size of the port.  First, like you said, many do not say what frequency they are tuned to.  This is not good and you should stay away from these enclosures.  Next, the port are not large enough for any powerful sub.  In order to make the enclosures small and save the companies materials they make the ports fairly small.  This is bad because a powerful sub will have a high air velocity through the port.  This means that there will be port noise from the enclosure.  So even if the enclosure is tuned to 32Hz it may not be right for your sub.

The tuning frequency depends on the internal volume of the enclosure (not including the port), the length of the port, and the cross sectional area of the port.

Good Luck!!!