about subwoofers

Tyrone Buk · Post by **Tyrone Buk** » Mon Jan 28, 2002 6:06 am

What would happen if I wire 3 8 ohm subs in parallel to a 2 ohm stable amp in bridged mode. what load will my amplifier see?

SUPER75 · Post by **SUPER75** » Mon Jan 28, 2002 7:24 am

3 8 ohm subs in parallel will give a total resistance of 2.6666666 ohms. You want to bridge your amp, that means each channel will 'see' half the load. So the resistance on each channel will be 1.333333ohms. That should cook your amp pretty good. It will work fine if you use two 8ohm subs. Look at www.jlaudio.com/tutorials/wiring/3svc.html

ddonicht · Post by **ddonicht** » Mon Jan 28, 2002 9:43 am

What if he were to pick up another sub and then not bridge the amp? He could wire it so he has 2 subs on each channel creating a resistance of 4ohms which is what car speakers are at a lot of the time anyway. Just a thought anyway.

Steve

SuperB · Post by **SuperB** » Mon Jan 28, 2002 6:25 pm

If he picked up another sub he could wire two pairs at a 4 ohm load then wire those to sets into a 8 ohm load. Then after he bridged it, it would have a resistance of 4 ohms. This is assuming the fella wanted to keep the amp bridged. It really wouldn't matter if it was bridged or wired to two seperate channels like SUPER 75 described, some peopl just like to bridge amps. The other problem I see though is space. Fitting four subs behind the rear seat in the "luggage" area would be fairly difficult. It could be done with some creativity. Of course I don't know how he planns to arrange the subs. JL Audio sells a sub wired for a specific ohm load (I think it's 6 ohms) that allows the use of three of them wired in parallel to a 2 ohm stable amp. I can't remember what the model is though. Another thought I just had is 2 8 ohm subs wired in parallel would create a 4 ohm load wich would the give the amp a resistance of 2 ohm's bridged right? If I'm remembering right I think you might get more output from this alignment than the four sub idea. The reason I say this is most amps gain power considerabley when the ohm load is dropped. Sorry to run on I just find great joy in trying to figure this stuff out. Let us know what you end up doing and how it worked.

69three@gobot.com · Post by **69three@gobot.com** » Mon Jan 28, 2002 8:46 pm

just to get technical, every time you double the amount of subwoofer cone area, the volume goes up by three decibles.

meaning if you had one sub that made your system 120 db, than two would go 123, four would go 126, eight would go 129. this is of course asuming all subs are in the same size box, are the same spec, etc....

so if it means that you would lose a little watts, usually you will gain it in the long run

Tyrone Buk · Post by **Tyrone Buk** » Tue Jan 29, 2002 4:49 am

Thanks a bunch guys! I think I'll go for 2 8 ohm subs wired in parallel, since I don't know where to put the 4th sub as Steve suggested. As it will be physically impossible to fit 4 10 inch subs INSIDE the luggage area. Thanks Again!

SuperB · Post by **SuperB** » Tue Jan 29, 2002 8:41 pm

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 69three@gobot.com:
<B>just to get technical, every time you double the amount of subwoofer cone area, the volume goes up by three decibles.

meaning if you had one sub that made your system 120 db, than two would go 123, four would go 126, eight would go 129. this is of course asuming all subs are in the same size box, are the same spec, etc....

so if it means that you would lose a little watts, usually you will gain it in the long run</B><HR></BLOCKQUOTE>

Doesn't that hold true with wattage as well? As far as I've understood you need to effectively double the amount of wattage to gain 3db. I could be wrong though, it's been a long time.

Driver Found · Post by **Driver Found** » Tue Jan 29, 2002 9:42 pm

It is NOT impossible to fit 4 10's in the luggage area. Where there's a will, there's a way. You could fit 3 across facing up, and then 1 facing forward. Hell, if you use some subs that need an insanely small amount of airspace, you could fit 6 back there. You'd have to use fiberglass probably though.

SUPER75 · Post by **SUPER75** » Thu Jan 31, 2002 11:05 pm

You could use what is know as an isobaric box. This configuration uses a box with far less volume.