Assistance in selecting a driver

[kinser]

Hey all,
got a new project in mind, and have a choise between two drivers, car drivers, since i was inspiered by the "car sub for home theater" thread..
so my two choises are:
1. Rockfored P212S4
2. JBL GTO1204D

Here are T/S specs for both subs..

Rockford:
NOMINAL IMPEDANCE: 4 Ohms
VOICE COIL INDUCTANCE: 2.6mH
Re: 3.6 Ohms
Fs: 27 Hz
Qms: 7.55
Qes: 0.58
Qts: 0.53
Cms: 2.17E-04 m/N
Vas: 80.6 L
Mms: 153.3 g
SPL: 87dB (1W @ 1m)
BL: 12.9 T-m
SD: 510 cm^2
Xmax: 11mm
Pe: 200 Watts

JBL:
NOMINAL IMPEDANCE: 2 or 8 Ohms
VOICE COIL INDUCTANCE: 1.1mH
Re: 1.93 Ohms
Fs: 24.5 Hz
Qms: 6.97
Qes: 0.52
Qts: 0.48
Cms: 233.7 m/N
Vas: 94.47 L
Mms: 181 g
SPL: 93dB (2.83V @ 1m)
BL: 10.17 T-m
SD: 530 cm^2
Xmax: 12.5mm
Pe: 300 Watts

Been Simulating both on WinISD, JBL performs better, but what i would really like is to simulate them on WinISD Pro, so that i can apply Low Pass, High Pass & Linkwitz Transform, but I have problems when loading the T/S specs...

So i would like to know what will perform better in a sealed box after Linkwitz transfor has been applyed, in a 3.5mx3.5m room..

Thanks
David Resnik

[richie00boy]

I would go with the JBL.

lower resonance frequency
lower inductance
more excursion
more power handling
reasonable Qts
reasonable Vas
can be wired as 8 ohms (nicer load)

[kinser]

Had the same thing in mind.. and the JBL is more sensitive, so it will be easier to drive, right?

Thanks,
David Resnik

P.S.
The power rating that are stated are not Max power handeling, but are RMS power ratings..

[richie00boy]

I would ignore the efficiency rating, they are usually 'made up' like power handling ratings. Also they are irrelevant to a sub-woofer as response is dominated by the resonance characteristics.

Max or RMS it doesn't matter as long as both are max or both are RMS.

[kinser]

understood!
so ill be going this week to pick up the sub, box will be next week..
thanks for the help! =]

David Resnik

[haemphyst]

Not to mention the fact that the Rockfords usually sound like malfunctioning farm equipment. Generally not good sounding woofers. Stick with the JBL. It will be faster, have better output for a given power input, and go deeper in a smaller cabinet.

JBL, hands down :P

[kinser]

okay, so i got the jbl paramaters into WinISD Pro, and i have been playing around with some diff' volume boxes.. but whenever I apply linkwitz tranform, excursion jumps way over the limits right after the F3 point.. can some one help me with finding the right sized box and filtering..? i was thinking something like 40-50 L internal volume..

Thanks,
David

[richie00boy]

What F3 did you want and what final Q? You maybe have too much input power in the simulation. My advice is to ignore the LT simulation stuff and just look at the power handling and excursion graphs.

[kinser]

F3: 28Hz
Q: 0.7

with a 42L box, the roll-off starts at 45Hz.. thats a little high...=\
do you have any other suggestions to get a lower roll-off point? should i go with a bigger box? (id rather not)

Thanks,
David

[richie00boy]

With the 42 litre box, what is the Qtc? You are not wanting to get silly low and have a not too bad starting F3, so I think you will be OK.