How do I install for the lowest of the lows?

Cause Im still kinda confuse on this Hz ****. My box is tuned to 38Hz so what would be the best test tone that would get loud. Above 38hz, 38Hz, or below?

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Not below it, that's for sure. That is what someone above was referring to when they said dont unload your sub. As your signal freq moves further and further below the enclosure's tuning, cone excursion rises, rapidly. You dont have to deviate very far below tuning before your sub will start to bottom out due to this loss of cone control from the enclosure. This is why people use subsonic filters, to block any signals too low for their system's tuning freq.

Generally, most SPL competitors seem to tune about 8-10 hz below their vehicle's resonant freq, then burp at that resonant freq. Talk to an actual SPL competitor to get more details.

Not below it, that's for sure. That is what someone above was referring to when they said dont unload your sub. As your signal freq moves further and further below the enclosure's tuning, cone excursion rises, rapidly. You dont have to deviate very far below tuning before your sub will start to bottom out due to this loss of cone control from the enclosure. This is why people use subsonic filters, to block any signals too low for their system's tuning freq.
Generally, most SPL competitors seem to tune about 8-10 hz below their vehicle's resonant freq, then burp at that resonant freq. Talk to an actual SPL competitor to get more details.

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Cool that makes sence now. How do you figure out your vehicle's resonant freq,?

A mic, a sealed box, a woofer and a plethora of tones.

So it has to be a sealed box? I would ask some of the guys in my area here but you really cant trust em, or they are ass holes

Your vehicle will have a sweet spot where it resonates with the bass. Each vehicle is different. If you want to determine yours, you need to run a signal that outputs equally along the freq spectrum. Use a mic to determine the highest freq, and that's your resonant freq. You must use a sealed box because a ported box has its own tuning freq and therefore wont play a flat signal even with no cabin gain... the peak in your response wouldnt necessarily be from the car's resonance.

Ports just give a boost at a particular frequency. Whatever frequency you choose is what the box is "tuned" for. In home and pro audio applications it is normally tuned to allow your response curved to stay flat to a deeper tone. For example, if your sub would normally be flat down to around 60 hz, then starts falling off and is 6db down at 30 Hz a port might be used at 30 Hz to give the tone a boost in that are making your sub flat down to 30 Hz. First instinct for most is to say "sweet, I will just tune my box down to 20Hz and make anything play down that low!!" It does not work that way unfortunately. You don't want to go very far down below the resonant frequency of your sub or you get really funny looking curves.... man I wish I had a picture of the response from a 6.5" woofer in a large sealed enclosure tuned to 20 hz... funny indeed. SPL competitors will often use ports tuned not to give flat response, but to overexagerate one particular tone. The best "flat response" port for that tuning may be 36 Hz, but they will tune the port up to 60 Hz (or near whatever the resonant freq of the car is) to make those few notes LOUD.

But I am confused. Why do the low lows need so much space?

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Hoffman's Iron Law:

You can only have two of the following three:

1) Low frequency extension ("the lowest of the lows")

2) Small Box

3) Good efficiency

Since we are limited to only having two of the three at any one time, you can see where the problems arise. You can have good low frequency extension and a small box, but it will require more power than the sub will likely be able to handle thermally. So, we can go with good LFE and good efficiency.......but it's going to require quite a large box to accomplish it.

Would that be the "fs" spec on the woofer spec sheet?

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Yes

And personally if we are talking about 20-30hz I don't care about the response being flat as I like 20-30 more than all of the rest.

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If you had a good strong 20-30hz and poor response further up, it will sound very muddy, and you will likely be very unhappy with the overall sound of the bass.

Honestly, IMO, you should try to go infinite baffle.

Infinite baffle with large subs would probably work well for you. What is this going in?

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I just noticed squeak has himself in his own hall of idiots. I feel so **** unoriginal now.

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LMAO //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif Beat ya to it //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

Anyways, a pair Image Dynamics IDMax 12's IB would kick ass aswell

As for IB, I had thought about it but shot down the idea due to several comments about sealing that I felt I may not be able to acomplish. I have been thinking about it again though but with a bit of twist. Basically I was wondering if it would be possible to have say a box with an opening (not a port but a portion of a side missing) X size, maybe with a semi permiable membrane that would or could somehow restrict the maximum volume that the woofer would pereive that it had.

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Simply a box with a side missing would not work since the front wave and rear wave would not be isolated from each other.

However, your idea of having a box with an opening filled with a semi permiable substance would work wonderfully......and it actually has a name //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif It's called an aperiodic enclosure; The box only has to be large enough to house the subs themselves, and no larger. Then, one side is left open (typically the rear of the box) and an "aperiodic membrane" is used to cover the hole (basically, a substance such as fiberglass mat [used in multiple layers] covers the opening to restrict airflow, but still allow air to pass through it). However, the front and rear of the sub(s) still have to be completely isolated from each other (similar to IB). Really, the main difference between IB and AP is that in AP enclosures the membrane is used to help control the cone movement.

If you want to read up on AP, look here:

http://www.elitecaraudio.com/article.php?sid=18

http://forum.elitecaraudio.com/showthread.php?threadid=12522

And search ECA for "aperiodic", "AP", "membrane", or any combination thereof.

As for running IB and sealing; it's really not that difficult. If you have enough room to hang a sub or two from the rear deck, then you just need to seal up the rear deck good (and make it solid as hell as to avoid flexing), and then typically just attaching a MDF board up against the rear of the rear seats (from the trunk) to seal up that area aswell. That's pretty much it.

if you want more info on IBing in a Impala/Caprice, go check the Imp forum, i few people over there have done it so they should be able to help you out

http://www.impalassforum.com