Experienced box builders please advise!

[cx-7heaven 10+ year member]

I am going to build an enclosure for my 2 AA Havoc 18's in my 07 mazda cx-7. Each will be run off an saz-1500d, prolly strapped. I have a few questions, as I **** at ported boxes.

I have calculated total gross of 12.34 cu ft. I assume this is enough for 2 Havoc 18's?

I actually want to do a "convertable" box. I want to run sealed for daily, and have a port package to run for spl. I am thinking to run with aeroports, as these will work in my mind to be easily removable. Suggestions or ideas?

I want to tune relatively low(in the 20's to 30's) for the ported part of the build. Suggestions or ideas?

Can I use a TL on my setup right now to find my resonant freq and tune the new build accordingly, or does the resonant freq change when my build changes?

Right now, I am running a single Havoc 18 sealed @ 5.69 gross~ approx 4 net. I have major flexing, but doesnt hit a meter worth a crap. Hit 139.7 legal last year. I am hoping to get a ~10db gain by going with this build, am I being unrealistic? My main questions are with the build itself, I know a db gain is hard to estimate, but I figured approx 6db for doubling power and woofers, and another 4 for porting... or am I all screwed up?

Sub Specs:

Re 1.85 per coil

Fs 27.5

Qms 6.75

Qes .61

Qts .56

Mms 375 grams

Sd 1210 cm^2

Vas 182.3 liters

Spl 89.8 1w/1m

Bl 19.8

Xmax 30mm

RMS 1250w

Displacement .25

Sealed 4-IB cu ft

ported 6-10 cu ft

Sorry for the wall o' text guys

Thanks,

Rob

Click to read more...

 

[kovemaster559 5,000+ posts]

do around 30-32-33 dont go so low.

 

[profundus-sanus 10+ year member]

first you say sealed then you say tuned low ported...

unless you meant ported for the spl setup.. in that case your going to want to tune much higher.

to get enough port area w/ aero's for 2 18's you'll spend over 100$ on ports.

i would just do a square port thats removable, somewhat like what meades is like in his tahoe.

 

[Rashaddd 5,000+ posts]

140 db isn't bad at all for 1 18 sealed

Tuning higher (probably 35-40+) will give you a peak which will significantly boost output, especially if you tune to whatever your car peaks at.

With what you're talking about changin to, I think its safe to say you'll be significantly louder, even if you tune to 20-30hz, 10 db's? hard to say.

 

[cx-7heaven 10+ year member]

@ profundus:

Ya, I want to do a removable port for spl. I thought about a removable square port, but the shape of the box will prolly make that impossible for me. Also, I don't mind spending the money on aeroports, I have heard nothing but good things about them.

@ rashadd:

Ok, so how do I know what size port to go with to tune at the mid 30's freq?

 

[cx-7heaven 10+ year member]

This is the size and shape I need to use, due to space restrictions. I want to fire the subs forward, NOT into the glass. Any ideas?

 

[mcsoul 10+ year member]

See if the bottom of this page helps:

http://www.bcae1.com/spboxnew2.htm

 

[liftedcj7on44s 10+ year member]

the specs show the FS around 27hz. i would personally tune higher, like said maybe 38-40hz. with the low fs the subs gonna hit the lows no matter what!