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Active crossovers and AR 28 LS


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I have a pair of AR28 LS. I am thinking of adding another amp

to my setup and the idea is to have an active crossover before the two amps (the existing one and the one I'll be getting soon).

I need to bypass the passive crossovers in the speakers and feed the amps directly to the woofers and tweeters of the AR. To do this I need to know what are the crossover frequencies of these speakers. Any suggestions?

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The answer is below, but first a question; why?

The roll offs of the drivers are controlled by the crossover network and the mechanical characteristic of the drivers. If you bypass the crossover, you will most likely create an unpleasant dip in the response because most active crossovers have much sharper cutoff than do the passive network in the speaker. Also note that there is a resistor in series with the tweeter.

The AR91 circuit diagram on this site notes that the crossover frequency for the network in the speaker is 700HZ, but if one is using bi-amping with an active crossover, it should be 1000Hz.

The AR30, which has the same drivers and similar cabinet volume to your AR28, the only significant difference being floor vs bookshelf, is list as having a crossover of 1800 Hz.

After you do this, you will need to use a sound pressure level meter and variable frequency generator to find the "right" gain for each driver. You may find that the low pass and high pass cutoff frequencies are different. You will find that the gains are different. And you may have to experiment with relative phase.

Good Luck with you endevor. Do not burn any bridges along the way.


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