Am I crazy for doing this?

optiontrader

^^^ +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?

__________________

40th Anniversary Z - 3M Paint Protection Film, CA Legal Tint! (70/40)

boomboom

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

90 ST

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

2fast4thelaw

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.

Attached Files

Subwoofer Calculation Software.zip (15.3 KB, 6 views)

__________________
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

boomboom

wow! thats above my head

2fast4thelaw

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.

__________________
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

37Z

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.

2fast4thelaw

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.

Attached Images

TS Parameters.jpg (101.0 KB, 6 views)

__________________
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

37Z

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?