I think I'd be pretty happy with 30Hz too. Maybe I'll try putting a high pass filter at 30Hz one day on my sub and see if I notice any difference with music, but I think my room will gain so much on the low end anyway making the experiment not worthwhile. It means the basshorn will have gain on the low end too though :DHere are the inputs:
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Let me know if you can come up with a better folding scheme!
Adrian