So what can I do in my car?

[mikee55]

Hi all,I guess I can't stick a di-pole in my car.I have got a 40 pounds sterling ,12"driver from a car accessory shop.I bought it because by visual appearance its got a high x-max.The surround is a bit more,erm! bigger!, than normal subs.It has a dual magnet ring and says on the box it can handle 600w.No T/S parameters printed,just a budget driver that looks like it can shift some air.
I ran it in a sealed box via my 120w RMS Alpine amp in bridge mode,being fed by a 24db Linkwitz Reily xover at 65hz and a Linkwitz Transform after the xover,which I replaced the tuning resistors with pots to try and adjust/tune the Transform by ear.You'd be right in thinking,"cheap speaker,Transform,all with 120 watts!".Yes,under powered and cheap driver etc,well thats all my budget allowed after paying for MOT work etc.It did sound really nice though.It intergrated well with my door speakers.I've tried it in a reflex but it boomed one note,even without Transform and was fatigueing to listen to.I then stuck it in a scoop without the Transform and xover and just used the amps lowpass filter -12db @ 80hz.Ha ha,nice little rumble now and again,start the engine(a diesel) and the low stuff vanished to leave a distorted bass.
I see over on Rod Elliotts site how to measure the parameters of a driver,and am struggling to calculate Vas(reading before trying,so I have no other parameters yet).Could someone explain how to do this?It would be better to stick the speaker in a tuned box rather than my guessed one(appx 14"x14"x16")then I can calculate the transform.Really,I'd also like to run the xover at 40hz to listen below a kickdrum.Would I need gain after the xover and before the Transform to boost xover output?I did run it at 40hz,it was nice and low,so too was the volume.I understand I should provide more watts,but I felt that the gain out of the xover would be lower after applying a -24db cut/roll off.My amp might not have been driven enough to reach full volume.I set my system to hear my music whilst I'm in my car and not so pedestrians can hear it.I used to(ha ha).
So Please,how do I measure my T/S parameters and would gain help after 40hz -24db to drive the Transform and amp better?
Cheers and Happy New 2006.mikee55

[Ron E]

http://www.royalmint.com/RoyalMint/w...CoinDesign.asp

The web page above has a listing of coin weights. Try a combination weighing about 100 grams or so. You want enough to make at least a 30% change in frequency.

Measure the resonant frequency with and wihout the added mass.

find a site that does the calculation for you.

[richie00boy]

Trying to tune a Linkwitz Transform by twiddling pots is a fruitless exercise.

All you need to do is measure Fc and Qtc of the driver in your intended box. There is no need to measure Fs, Qts or Vas unless you want to model the power handling and excursion.

Then you just feed the measured Fc and Qtc into the LT formulas.