# Testing Crossovers



## Andy (Sep 23, 2007)

I recently got my hands on a pair of Yorkville Elite 401s, to use for parts. One woofer was cooked (I couldn't even get an impedance measurement across the terminals). The other was an 8 ohm, when the crossovers require a 4 ohm woofer. Would this damage a crossover, and how can I see if the crossovers are still good without blowing out a power amp?

Thanks.


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## Hamm Guitars (Jan 12, 2007)

Using an 8 Ohm driver on a passive crossover designed designed for a 4 Ohm load can change the crossover point of the filter, depending on the design. I the simplest design, higher frequencies are shunted to ground through a capacitor and the reactance of the filter will change with the impedance of the driver as its impedance is a component of the filter.

However, I think that the RCF speakers that originally came in the 401's were 8 ohms, so that 4 Ohm rating may be a minimum load as Yorkville may have used the same crossover in the cabinets with 2 15' drivers as well. If you get a hold of Santon Audio (North of Toronto, or on Ebay) you can either get the original driver reconed, or replaced if it has been swapped out with something other than the RCF.


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## Andy (Sep 23, 2007)

Thanks for the info.

I have a pair of eminence 4 ohm drivers that would work perfectly in it. I just checked the crossovers, one specifies an RCF L15K81Y (A 4ohm driver according to Santon Audio), and the other an RCF L15K80Y (8 ohms). So, I guess I'll have one Eminence and one RCF -- these cabs are just for rehearsal.

I assume a 4ohm in the 8ohm crossover would lead to an impedance drop where the low and high drivers meet -- as they'll effectively be in parallel from the crossover frequency to an octave above it.


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## Hamm Guitars (Jan 12, 2007)

Yup, a change in the impedance of one of the drivers might result in either a gap in the crossover points or a summing of the two components producing frequencies in the same region. It won't necessarily be an octave because a doubling of the impedance won't necessarily equal a doubling of the crossover frequency. If the 15 goes too high, it's not that bad, but if the horn goes too low (not as likely as there will be an inductor shunt) you could destroy the hf driver.


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