building your own speaker sets? (1 Viewer)

[Brian Bunge]

The resistors are there in order to get the load back to 8 ohms. Although impedance is frequency dependent so just because you measure 8 ohms at 1KHz doesn't mean you'll measure 8 ohms at 50Hz. If you wire up the 3 drivers in parallel you'll have a nominal 2.66 ohm load and will likely fry your amplifier. You really need a crossover specifically designed for the drivers which you plan on using.

 

[GeorgeTW]

Here is a rudimentary set of equations to help.

Your speakers are rated in Watts. Watts is a measure of Power.

Power(in Watts) = Current(I) X Voltage(Volts).

P = I x V

Current is what heats the wire. It has an opposition component that determines how much of it is allowed to flow. This opposition to Current is called Resistance. I am over stating this for a point.

If you limit Current by opposing it (offering resistance), you limit Power, because if P = I x V , then Current and Power are proportionaly related. If one decreases by 10, the other also decreases by the same value.

Since resistance is the opposition to current, we have an handy equation for that too.

Current = Voltage divided by the Resistance, or
I=V/R
Now that R is the denominator of a fraction, you can see that an increase in R makes V a smaller number, making I a smaller value. Even if I didn't know anything about electricity, the math problem would tell me that (R) Resistance and (I) are indirectly proportional. If one goes up, the other goes down.
Current and Resistance are opposite forces.

Now here is the last part.

Resistance is a component of Impedance.

Resistance = Opposition to Current.
Impedance = Total Opposition in the complete circuit.

No matter how simple or complex, Impedance is the combined opposition of ALL resistances, whether they are reisistive, inductive or capacitive. How these resistances are calculated is beyond the scope of this post, but after all the coils and capacitors are vectored together, the total of their interaction is a resistance component in its own right. Impedance is the whole enchilada of opposition. So you can now see why changing one value of a crossover coil affects the Impedance, therefore affecting the Power. Kind of Global, huh?

The relationship to Power is still the same. If Impedance goes up, Power goes down. If Impedance (total resistance) goes down, then Power is allowed to increase.

so Now you have a quick explanation of how the power(Watts) from your receiver is related to that Impedance rating on the speakers you are trying to build.

I am not atttempting to speak down to you, but without knowing your experience, jumping into Impedance/Power relationship without a referance isn't good.