I am going to hook up 2 8 ohm mtx thunder 3000 12's in parallel bridged on my 2 channel jensen amp. How many ohms would this make? Would series be better? The amp is stable down to 4 ohms bridged and it puts out 300x1 watts rms and 600x1 watts peak bridged at 4 ohms. The subs run at 200 rms and 400 peak. thanks in advance!

 

I dont think you can do that set up with that amp.


Nate

 

That's exactly the subs I had before I blew one up. I now have one.

Yea that'll be a 4 ohm load. Your amp will be fine, it's the speakers you gotta becareful with, as I found out. I pushed mine the night before an SPL contest just to see if I would blow any fuses. The amp started clipping enough to just fry the voice coil in one of the subs.

If all your subs are the same impedence, then just divide the impedence by the amount of speakers you have and voila.

Your subs would be 8 divide by 2 = 4 ohms.

But say you had three 8ohm subs.
Then it's 8 divided by 3 = 2.67 ohms.

The correct formula for calculating resistance for speakers that are different ohm below. Like two 8ohm subs and one 4 ohm. Not that you'd do that anyway, but now you know how. A scientific calculator makes easy work of this. But if you don't have one then just sharpen your pencil. :

1/x + 1/x = 1/x or

1/x + 1/x + 1/x...etc (depending on how many subs you have) = 1/x

AJ

[This message has been edited by AJ_92RS (edited November 11, 2001).]

 

Running your speakers parrallel will put you at 4 ohms. If your amp is stable at 4 ohms I woould do it that way for more power. The formula you use to get resistance is multiply R1(8)and R2(8)= 64 and divide that by R1(8)+ R2(8)which = 16 (64/16=4ohms)
Running them in series will put you at 16 ohms. Your amp will run clean but not nearly as much power.

 

hey thanks for the help everyone. I can't wait to get my box built so i can hook it all up!

 

By the way aj_92rs....what sort of an enclosure did you have your thunder 3000's in. Was it sealed or ported? How many cubic feet was it? How did it sound and what sort of a box do you reccomend i build?

 

You don't wanna do what I did. I gotta plate, aka baffle board, aka crap, according to a lot of others on this web site.

I hit 135.5db in that comp with the one 12". Not bad for a clean 100 watts, huh?

As far as the enclosure size goes, I roughly calculated it to be ~2 ft.cu. That's kinda big for just one of those speakers. But it's got good lower bass.

If you want to look into reader's rides, there's a pic in there. I had them isobaric, aka face-to-face. Again something else a lot of others on here don't like, but I didn't build my system for them to listen to.

I personally would recommend a sealed encloser. I prefer sealed myself. It's not as efficient as a ported box, but to me, it sounds cleaner. Just a matter of personal choice.

I would put a sealed box in my car, but I don't want the added weight. I can't argue that my system would sound better (and probably louder) if I had one, but to me, it sounds really damn good now. And my car doesn't look like it's squating and taking a ****. A common problem with 175K miles on the springs.

AJ

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92 RS w/t-tops 305 TBI Auto.
175K miles and don't burn a drop o'oil
-K&N Truck filter #1500 w, open ele.
air cleaner
-Dynomax 2 1/2" cat-back
-B&M TransPak
-Jet Stage2 Chip
-180* T-Stat w/ 185* Fan Switch
-JVC CD--Alpine speakers & 4ch. amp
Rockford Punch 100. 1 - MTX 12" sub