02WS6
Gif Guy and Bobby's BFF
TL/DR: 02WS6 did his math wrong. The dual 4 sub will receive 2/3's total power and the dual 2 sub will receive 1/3 total power.
Actually load the amp sees is exactly what impedance is. Load the amp sees is better described as impedance than resistance. We just generally use the term "resistance" because it's easier for people with electronics knowledge to understand and it's much easier to measure/test for. Impedance is a combination of resistance and inductive reactance, and has to be measured by Z = E/I.
The points raised by the elite, all-knowing, super, high-post-count guys haven't mentioned blowing subs. The conversation ranged from a generic "Don't do it. It's bad", to cancellation from running two different subs. Having said that, you are absolutely wrong with your 70-30 statements. Please give me the formula I forgot to mention that you alluded to. Although I didn't mention power levels, because I assumed OP can set his gain levels to avoid blowing either sub, let's break it down so you can learn something (even though I'm a moron because I have under 50 posts):
This will apply to a series-parallel configuration with two 2 ohm loads wired in series, and two 4 ohm loads in parallel with the series 2 ohm loads, so essentially three 4 ohm loads in parallel. I'm not going to use numbers because this doesn't apply to only one scenario, so variables are more appropriate. I'm going to refer to the voice coils as vc2-1, vc2-2, vc4-1, and vc4-2. Vc2-1 and vc2-2 are the voice coils on the dual 2 ohm sub, and vc4-1 and vc4-2 are the voice coils on the dual 4 ohm sub. You should be familiar with the rest of the formula symbols. On to it.
In every parallel circuit, supply voltage is the same across each branch. Vc4-1 is its own branch; vc4-2 is its own branch; vc2-1 and vc2-2 in series represent a single branch.
Therefore, Evc4-1 = Evc4-2 = (Evc2-1 + Evc2-2), or to rephrase, Evc2-1 = Evc2-2 = 1/2(Ecv4-1) = 1-2(Evc4-2)
Current is limited by resistance, and can be different between parallel branches, but is constant in series loads.
Given that I = E/R, and each parallel branch is equal to a 4 ohm load, Ivc4-1 = Ivc4-2 = Ivc2-1 = Ivc2-2
The formula for power is P = I x E.
So, since Pvc4-1 = Pvc4-2 = (Pvc2-1 + Pvc2-2), we can see that power is cut into three, with the dual 4 ohm sub receiving two thirds of total power, and the dual 2 ohm sub receiving one third of total power.
If you want to simplify it, the dual 4's in parallel are a 2 ohm load, and the dual 2's in series are a 4 ohm load.
I think we can all agree that a 2 ohm load draws more power than a 4 ohm load. Roughly twice as much.
I hope that makes sense to you. You can let me know if you have any questions, but you'd probably trust someone with more posts more than you'd trust me.
- Joe
You're still not getting it. Impedance is a measure of resistance for the voice coil not for the entire circuit which is why you can change final resistance it by wiring in series/parallel. Wiring changes what the amp sees not what each voice coil receives. Total circuit resistance is how you wire your speakers together to get a final matched resistance to whichever amplifier you're using. Internal impedance of each voice coil is how the speaker coil itself consumes the power. You cannot externally change this no matter how you wire it up.
Final resistance for the circuit is doubled to 1.3 ohms in your example (which will work for the amp) but this is what each voice coil see's in the circuit.