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Paul, l I have written about it somewhere: the passive speaker-level crossovers on bass channels are no good. Marko has 250Hz that with 3rd order would be around 10mH and 2mH. With air core then would be very large coils with huge amount of DCR – very negative for bass where .5R of series resistance is well- auditable. If Marko goes for 10ga (I do not think that he will be able to go for 8ga on 20mH) then it will be lover DCR but still substantial. Nevertheless, the 10mH air core with 8ga wire it will be around 50-60 pounds and around $000 each. Is it necessary? The ERSE meal-core coils have very low DCR and for channels that care no HF they will do equally good with air-core. At least in my sub 600Hz channel I saw no difference.  Not to mention that the super large air-cores cones, connected to the driver act a perfect resonance contour and begin to suck AM waves – with high sensitivity speakers all of it will be playing right in your face. If you even built an EMI/RFI shield around 12” air coil then you know how much problems it is.  Even if Marko go for regular first order filter (as he shell do with a single driver) then it will be 5mH against 8R – it will be more manageable but still it will be too large and unnecessary in my view.

There is an additional bitch on passive speaker-level crossovers for bass – it is impossible to calculate them. The driver impedance wares and the Q of the filter is never stable. In addition the coils of the crossover begin to talk with driver inductance and it minimizes the effectiveness of the filter (it would greatly depend from the type of the drivers)…

I was wondering: if Marko has been using active crossover on his bass horns then he has a dedicated amp for that channel. All that he need to do it just to build-in a passive like level crossover into the amp. He would also need to revise that 3rd order filer as I do not think it was right. He has Radian driver sitting in 220Hz horn and he crosses it at 300Hz, first order? That is VERY aggressive!!! I am quite confident that 220Hz Le Cleach horns must not be used with 300Hz 6dB – they should “choke”: (read the quoted section)

http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=5317

I think Marko eventually will move the crossover point to ~500Hz and then drop the sharpens of the low-pass filter on his bass horn. BTW, it would be fun THEN to talk about the modification he did on his Radian driver as the driver will be working in completely different and much less stressful mode.

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