Crossover impedance

[vetmed]

If you have a 2 way speaker with a crossover between the speakers and the amp, and one speaker is 16 ohms and the other 8 ohms, what impedance does the amp "see"? TIA


Robert Lees

[Paul Joppa]

It sees the woofer and cabinet in the bass, the tweeter in the treble, and only the crossover designer (and possibly God) knows what around the crossover frequency.

[Paul Birkeland]

There's also just a smidge of possibility that a 16 Ohm woofer and an efficient 8 Ohm tweeter would have a single resistor padding down the tweeter a bit, possibly leading to a higher impedance seen at the tweeter frequencies. 

[earwaxxer]

The impedance of many speakers will vary quite a bit over the frequency range. That can make for a challenging load for amps that are not designed for such low resistance. I always like to make sure that the amp that I buy can handle 2 ohms in stereo, 4 ohms bridged. Then again, I have over 2KW of power on hand. I should be covered.

[vetmed]

In light of the responses so far perhaps I should rephrase the question: Having calculated a set of crossover values for a 16 ohm woofer and an 8 ohm tweeter, and having a choice of 4, 8, or 16 ohm output impedances in my Paramount, which one is most appropriate? Appreciate all responses.

Robert Lees

[Grainger49]

We use the word impedance for AC and resistance for DC.  Audio signas get a lot of things done to them by the components they pass through.  Check this thread for a visual of a good, phase correct crossover, speaker system impedance curve:

http://www.bottlehead.com/smf/index.php/topic,3873.0.html

[Paul Joppa]

Most likely the 8 ohm setup will be the best. But you cannot be sure without knowledge of the crossover's actual impedance and the speaker's efficiency as functions of frequency.

[earwaxxer]

Hey Robert - sorry - I understand now what I think you are getting at. If you are trying to select a capacitor to crossover a tweeter and its 'rated' at 16ohms then calculate the value of the cap based on that. If the woofer is 8ohms then select the value of inductor based on its independence (ex. 8ohms). Here are a couple of calculators that I have used determine the right crossover points. - Hope that helps.

http://www.bcae1.com/passxovr.htm
http://www.aikenamps.com/CapConvert.htm
http://www.ajdesigner.com/crossover/crossoverfirst.php