Am I crazy for doing this?
 

I am putting 2 memphis 12' subs and 6 1/2 diamonds with crossovers and tweets in the car with memphis amps, I wanna keep the factory head unit I don't wanna replace it.Is that gonna really affect my sound?

Yes. The factory HU on the base model is absolute garbaaage. I had it running a loc to an amp and it totally sucked while I waited for my replacement. I have an Osciloscope and can tell you the stock hu will clip at 2/3 volume.

Not true, if he does it right and uses something better than a LOC like the mtx re-q 5. This will clean his signal and flat line it before going to his new amps. I have done this many times with other systems and they sound great. OP do it right and get something better than the cheap LOC's from bestbuy. The JL clean sweep is good as well BUT one big draw back to that is that you have to mount a volume knob somewhere and use that. Which is stupid.

Of course notihg will beat the quality of a new head unit outputting a signal. But to me 2 12's in a z is stupid to begin with.

Why do you say its stupid to have two 12's? My amps are set up for 2 subs unless i can just not use one channel? i know nothing about this stuff.lol you really think one 12 will deliver the deep bass i need? i like loud deep bass

Ask trooper I had to turn his 600 watt amp down it was so loud with one 12 and yes you cam use two channels for one sub

If you crave bass and you have the amps and subs, DO IT.. I absolutely love bass that hits hard and clean in a sealed enclosure. I have a JL 12W6V2 in mine and it is being pushed by the JLHD 900/5 amp. It sounds awesome but I definitely could take even more hard hits with 2 12's.
You can always turn your gains down. Better to have it and not need it, than to need it and not have it.

Get a HU. They do so much more than just clean the line. I love my 5v preouts, customizable EQs, having 12db slope, using time delays, BBC optimization etc.

Also for a car this size, 600rms to a sub is plenty imo. If you want bass get one good sub instead of two weaker ones. You will save weight, room, money, etc.

For the record I have a Pioneer premier 880prs HU and a nine.1 pushing 600rms+ to my 13Ov2 subwoofer (12") in an RSX.

man I can't make my mind up! the weight of the boxes cant be very different, so it would just add the weight of the 2nd sub.and i kinda like the up fire box because it kinda hides the fact that theres subs in it..the box for the one 12inch is very visible..but i also understand maybe 1 is enough..ahhhh what to do what to do
:)

1...vented!

Plus 1 for the vented enclosure. A single 12 in a big ported box will deliver insane low bass! the output would easily exceed 2 12's in a sealed box in the 20 to 30 hz range. I built a system in RX-7 that used a 1.75 cu enclosure tuned to 20 hz using a JL 12W6 (original version) and pushing only 250 watts rms from a Phonex Gold ZX amp. It was louder, deeper, and sounded far better than the pair of 12" kicker comps I previously had in there.

If you go vented only do one because you are not going to have enough space for air to move back there.

^^^ +1 You're looking at close to 1.5 to 2 cu. ft. of airspace needed for a 12" in a reflex enclosure. With a little less than 7 cu ft of cargo capacity... ouch. Where ya gonna put the golf clubs? :D

So if I get a zenclosure box for 1-12inch sub can they port it for me?

every sub needs different spec for the port...you may be better off going custom.

The Zenclosures are little shy on volume for a single sealed 12" sub much less a ported sub. You generally need 30 to 40 percent more volume for a ported enclosure. If you are dead set on the Zenclosure box and want a vented alignment you may have to resort to a single 10" driver.

I have attached a software program that I wrote for calculating sealed and vented alignments and also it will calculate the optimum vented enclosure based on the speaker parameters used.

You will need to find the Thiele Small Parameters of the speaker your are interested in using, they are not hard to find.

You need the following values:

FS
VAS in Cubic Feet (You may have to convert from Liters)
QES
QTS

Also type in the value you wish to use for "Volume of Enclosure" By default I have entered 1

The values will be output to:

FCB
QTC
F3
FRMAX

all of these values will tell you very important information about how the driver will respond. The program will explain the values.

If you have any questions just pm me.

wow! thats above my head :)

Sorry, but really once you understand each of the parameters its not bad. Manufactures always list thier Thiele Small Parameters so you can make a suitable enclosure. What a manufactures suggest for enclosure size is not always optimal but more of a starting point. Its usually better to have too large of an enclosure than too small of one. If you are going sealed its not that big of a deal and you can plus or minus 25% of the recommended enclosure and still be in the park. Vented enclosures need to be much more precise in order to properly tune the enclosure.

down firing subs
 

I am not sure of the acronyms.

Could you please elaborate?

I am contemplating 2-8" down firing subs located behind the metal bar in front of the spare tire well. Not sure whether to do ported or sealed sub box. Any suggestions are welcome.

TS Parameters are simply measurements of a driver that tell us everything we need to know about the specific driver and how it will behave in certain enclosures and it allows us to maximize the drivers performance by designing an enclosure that is optimized for a specific driver. This is why pre-fab boxes are less than optimal for a given driver. You can get away with this for a sealed enclosure but never use a pre-fab ported or bandpass enclosure if you want to get the most out of your subwoofer.

All manufactures of speakers provide all the necessary TS parameters to allow you to custom build your own optimized enclosure. I have attached an example from JL Audio website showing these measurements. In the program I have attached you can just plug in these values and then key in the desired size enclosure and the program will tell you exactly how the subwoofer will perform granted you understand the values. I will be very basic but I will tell you what they mean.

F3 = the lowest frequency the driver can play in the enclosure before it begains to attenuate. (The lower, the better!)

FRMAX = this is the frequency where the woofer plays the highest output in the given enclosure (Again, the lower, the better for a subwoofer)

Q = how tight or accurate the subwoofer will play in a given enclosure. (Anything >1 will be a bit on the boomy - Looser side and anything = or <.6 will be very tight and accurate at the expense of a bit of efficiency.

I tend to prefer a Q of .7 to 1 but anything above 1 is too loose for my taste. Less than .7 is a bit to dry.

BTW I am not sure a pair of 8"s will fit where you want them in a down firing config. I would recommend using (3) 6-1/2 " subs if you are dead set on that location. The JL 6"ers are damn impressive for thier size. Parts Express also has some Tang Band 6" ultra long throw subs that are very good as well and much cheaper than the JLs.

Downfiring boundry loads the drivers and your bass output will be awesome! You will really feel them kick too!

I would port them in order to get lower bass response. These subs would also play some sick midbass duty as well. 200 to 300 watts would the max I would use for them as small sub drivers just wont take a lot of power and they really dont need a lot to do the job.

Don't be intimidated, I have already done all the math equations for you with my software program.

6" JL Sub
 

The car audio store mention 3 - 6" JL subs located in the 370Z hatch area behind the aluminum bar where the foam piece is located. Pricewise 2-8" JL subs appear to be are more cost effective than 3-6" JL subs.

To understand the sub box parameters; would you simply add, either the 3 individual 6" JL sub or 2-8" JL subs specs, in your software?

I am not sure the air space needed in front of the sub in order to downfire either of these subs. The depth is approximately 7" from the bottom to the top of the hatch floor. Any idea of the depth needed in front of the subs to the bottom of the sub box in order to optimize the subs efficiency if the sub box is ported or seal?