[scorpion]

I can make it easy for me and point to the MJAO G 098 The Anagram thread: http://www.audiocircle.com/index.php?topic=65570.60, showing what it takes to cross Alpha15s passively. Since there has been a lot of debate regarding the Alphas and in combination with various other units. I just want to say, You should take my view here seriously. Using Alphas with a simple crossover will eventually compromise both the Alphas and the other speakers. That's for sure ! So like leaving the Alpha with a single coil it is certain to let the Alphas interfere undiserible with the other speaker. Or by iterating 2nd order slopes, that will not also be enough. Crossovers will any way let out too much HF-content. I am challanging MJK's crossover recommendations for his ever popular Alpha Fostex combinations. My recommendation would be to allow both for the simple Zobel and for the parallell notch, and you will get a speaker performing at the best of the units involved would allow.

/Er ling

[gainphile2]

MJK's lowpass XO is quite low and away from the nastiness of Alpha frequency response.

If I recall, to get flat response with high XO (let's say 1kHz like CS2) there was a need for 400Hz notch as well as 2kHz notch. But I used active xo so that was easy.

[scorpion]

Theoretically it is so, but in practice I really doubt it. I have tried a good amount of 2nd order iterations. None has proved perfect on it's own.

/Erling

[holdent]

Scorpion:
MJK's lowpass filter is second order crossover at 200 Hz for the FE103/Alpha combo.  As gainphile2 points out this is quite low.  So I'm not clear what your concern relates to.  I followed the link you included and it sounds like you're crossing over the Alphas very high -- I don't think anyone (including MJK!) would argue that alot of xover work would need to be done to do this.

[scorpion]

Yes, I shall not be categorical. It might well be that a bigger coil takes a better gripp of the Alpha's output. My LP is calculated at 300 Hz so the difference there is not very great but of course I have only 6 dB fall for the MJAO. And also my experiments for the MJAO went from 300 Hz and a bit higher. My recommendation still would be to listen to your crossover's output and dealing with the Eminence Alpha a Zobel filter will not be out of the place.. Sometimes you learn the hard way. 

/Erling