I am a novice and I have heard it discussed about "tuning" to 30-35 htz.

How is this accomplished?

With a port with a specific length & area.

It tunes the rear wave within the enclosure to a certain frequency.

To expand on that for a moment...

The tuning frequency is a function of it's cross sectional area, it's length, and the volume of the enclosure. The port is, in fact, another speaker, but in a different form. If you look at your typical speaker, it's mass on a spring that is driven by the an oscillating voice coil in a magnetic field. In a bass-reflex enclosure, the air in side the port is the mass, the air in the enclosure is the spring, and the speaker itself is the motor. The mass in the port can easily be excited at a resonant frequency, much like a speaker is at Fs (it's resonant frequency). This resonant frequency is the "tuning frequency".

When it comes to the tuning frequency, you can make a few general assumptions:

1. Tune lower and you will net greater low end extension and sacrifice some upper frequency sensitivity.

2. Tune higher and you will net greater upper frequency sensitivity, but lose some low end extension.

3. Tuning lower requires a longer port, assuming the same cross sectional area of the port and net volume of the enclosure.

30-35 Hz is a common tuning frequency in vehicles because, with music, it serves for the best compromise between low end extension and upper frequency sensitivity.

If this is something you're wanting to achieve, perhaps post what products you are using now and we could help determine the best net volume of the enclosure as well as the dimensions of the port. You might find playing with programs like WinISD or UniBox to be beneficial in your understanding of the concept.

For not feeling well today...

Thanks for expanding on my few words

Hey, when you're at home, you've got time for verbal diarrhea.

I could go several different ways.

My current speakers are (2) Volcano CDS 12's DVC 4 ohm and Dual Spider:

fs qms vas qes re power rms

34 9.1 2.7 .45 3.6 400 watts

I could purchase (3) Volcano C 12's SVC 4 Ohm:

fs qms vas qes re power rms

34 9.1 2.7 .45 3.6 400 watts

and a possible purchase would be either (2) or (3) Napalms:

fs qms vas qes re power rms

34 7.36 2.6 .45 4 1000watts

This is from the Manufacture email regarding the possible purchase of the 12c's or napalms:

"I would recommend either in 2 cu ft tuned to 30-35hz. you could be a litter smaller with the Napalm. it has considerable more mms than the 12c"

I told the manufacture when I was on the phone with them that I was going to put my current speakers in a 16"x35"x16" sealed box and he said to build that box and I started to try to get suggestions for something else and he said that was a perfect box.

I have 16" top to bottom and 35" side to side clearance. That would get you to the very back of the back seats.

Any help is appreciated.

i have the winisd program and it is awesome to use. it works better if u have all the perimeters for ur subs