I'm sure this has been discussed innumerable times here, but I've failed to find the answer here or anywhere, so I'll just start a thread.
I've watched a few tutorials on 2 / 3-way crossovers. I think I get the basic idea.
The part that I never see discussed is how do you target an ohm value for the speaker?
Let's say I want to make a 3-way speaker that's 4 ohms. The woofer, the midrange, and the tweeter are all probably 4 ohms individually. So how do you end up with a total of 4 ohms for the speaker?
The only thing I can think of is you'd add a 8 ohm resistor in series to each driver, but if anything like that is discussed in crossover design I've missed it.
I've watched a few tutorials on 2 / 3-way crossovers. I think I get the basic idea.
The part that I never see discussed is how do you target an ohm value for the speaker?
Let's say I want to make a 3-way speaker that's 4 ohms. The woofer, the midrange, and the tweeter are all probably 4 ohms individually. So how do you end up with a total of 4 ohms for the speaker?
The only thing I can think of is you'd add a 8 ohm resistor in series to each driver, but if anything like that is discussed in crossover design I've missed it.
Typical parallel crossovers allow the amplifier to "see" the impedance of each driver only within its own operating bandwidth.
Above and below each driver's operating bandwidth, the crossover raises the impedance much higher.
(Except for below the woofer's resonance, although there are a few exceptions there also.)
So the parallel crossover system impedance curve is typically made up of a curve for each driver (and its related crossover),
and all those individual impedances are in parallel, and they all combine as parallel resistors do.
If you just had several identical drivers all in parallel without crossovers, the impedance would get lower, as you thought.
Above and below each driver's operating bandwidth, the crossover raises the impedance much higher.
(Except for below the woofer's resonance, although there are a few exceptions there also.)
So the parallel crossover system impedance curve is typically made up of a curve for each driver (and its related crossover),
and all those individual impedances are in parallel, and they all combine as parallel resistors do.
If you just had several identical drivers all in parallel without crossovers, the impedance would get lower, as you thought.
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Take a two way crossover. It directs the high frequencies to the tweeter and the low frequencies to the woofer.
The high frequencies only see the tweeter as the load, say 4 ohm.
The low frequencies only see the woofer as a load, say 4 ohm.
So, over the entire frequency range the load as seen by the amplifier is 4 ohm.
Because of the crossover's action, the tweeter and woofer are not electrically in parallel and therefore the amplifier load is not 2 ohm as you might expect.
The high frequencies only see the tweeter as the load, say 4 ohm.
The low frequencies only see the woofer as a load, say 4 ohm.
So, over the entire frequency range the load as seen by the amplifier is 4 ohm.
Because of the crossover's action, the tweeter and woofer are not electrically in parallel and therefore the amplifier load is not 2 ohm as you might expect.
