Attn Audiophiles

[Jake Levin]

I have 3 subs. they are 8 ohms each. Instead of buying a 4 channel amp and wasting 1 channel, I want to wire the speakers in parallel. What will the ohm load be if I wire all 3 speakers?

Now I know that if I wire 2 of the speakers in parallel it will present a 4 ohm load to the amp, based upon the formula (Za*Zb)/(Za+Zb) where Zx=ohms of each speaker, I get (8*8)/(8+8)= 64/16 =4.

If I plug in the 3rd speaker it looks like this:

(Za*Zb*Zc)/(Za+Zb+Zc)=(8*8*8)/(8+8+8)=512/24=21.333.

I'm sure my formula must not be correct and I would think 3 wired in parallel would present a 2 ohm load but I need verification on this from someone who knows.

 

[RAUL AGUILAR]

The formula is

Parallel:



1/R1 + 1/R2 + 1/R3 =1/Rt = .....continued for as many speakers as you have



Series:



R1 + R2 + R3 =Rt .....continued for as many speakers as you have



your case would look like this



1/8+1/8+1/8=1/x X=total resistance

3/8=1/x

3=8/x

3x=8

x=8/3

x=2.6





The two speaker formula looks like this



1/8+1/8=1/x

2/8=1/x

2=8/x

2x=8

x=4 ohms

complicated huh :wacko:

 

[Jake Levin]

between that and work today, I've got a migraine. so now the question is, an amp that is 2 ohm stable should be fine for the parallel wiring scheme of these 3 subs then, correct?:blink:

 

[RAUL AGUILAR]

yes actually you'll be giving your amp a little break in trade for power with the extra .6 ohms in the circuit.

 

[Tony Tassillo]

The formula is

Parallel:



1/R1 + 1/R2 + 1/R3 =1/Rt = .....continued for as many speakers as you have



Series:



R1 + R2 + R3 =Rt .....continued for as many speakers as you have



your case would look like this



1/8+1/8+1/8=1/x X=total resistance

3/8=1/x

3=8/x

3x=8

x=8/3

x=2.6

Couldnt have said it myself.



JLevin, thats what im about to do when i up my woofers from 4 to 6 ill be able to turn my amp up when i do that also. i have to gain it down now.

 

[Jake Levin]

Thanks everyone for the answers. I'll probably go look for an amp that is stable to 1 ohm. Now, can anyone tell me if the power rating changes if the ohms change, and if so how much RMS power should the speakers be able to take if they are rated at 100 watts @ 8 ohms?

 

[Jacob Dryer]

Power rating stays the same on the speakers.



As the load gets lower on the amp it typicly puts out more power.



You don't need a 1 ohm stable amp, it won't hurt but it is not required for your application.

 

[Jake Levin]

Thanks Scott,



I'm currently running 0 gauge wire to the amp I have now for power and ground. The power runs to a distribution block and 4 gauge from there to the amp (plan on adding a second amp for the door speakers at some point) The speakers I'm dealing with aren't rated for a ton of power, (30-130 RMS) so I was looking at an amp that's rated 360 rms @ 2 ohms, 800 max @ 2 ohms. Most amps that I find that are stable at 1 ohm have a much higher power rating then I'm looking for

 

[Joe Kowtko]

I highly recommend JL Audio's new slash series amps. They are stable down to 1.5 ohms and they deliver constant power regardless of input power (11-14.5vdc). The 250/1 delivers 250 watts RMS into 1.5-4 ohm loads. For more information on the 250/1, go to the following link:



http://mobile.jlaudio.com/products_amps.php?amp_id=251



They also have a 500/1 and a 1000/1 if you're really feeling froggy...



Joe