Which subwoofers have at least a 20k input impedance as required for ARC preamp

thanks al. very good info. i need to do some studying. have passed on arc preamps in the past bc of the dicey nature of the pre driving a main amp plus a subwoofer. 

the nitty gritty. i’m interested in a ref 6 to drive a 20k sub plus either an arc amp w a 300k ohm input impedance or a Dag amp with a 1M? input impedance. Would either work well? Also the 50k JL might work better? Just not proficient enough to decipher. I hope i got the specs correctly. what do you think al? 

(((i’m interested in a ref 6 to drive a 20k sub plus either an arc amp w a 300k ohm input impedance))))

  Why not just hook up a subs at Speaker level like a Rel or pair of Vandersteen Sub 3s?
 Best
 JohnnyR

Or Rythmiks.

@4425, to answer your earlier question 20K in parallel with 300K is 18.75K, and 20K in parallel with 1M is 19.6K. I doubt that there would be a noticeable sonic difference between 20K and 18.75K. However I suspect that 20K already represents a slight compromise (I recall that the specs for some older ARC preamps say "60K recommended; 20K minimum"), and given the caliber of the equipment you are contemplating I would not want to introduce any compromises, however slight they may be.

50K in parallel with 300K is 42.9K, and 50K in parallel with 1M is 47.6K. So the JL Audio Gotham or Fathom subs I referred to should be fine in terms of impedance compatibility, if (and only if) connected single-ended.

Good luck. Regards,
-- Al