the 15hf uses less windings in order to reduce inductance.
that in turn reduces motor strength and power handling, but may give a more extended top end response.
What is an extended top end response? Beyond 100Hz?
the 15ho works well for movies and music. it doesn't move a whole ton of air, so if only using one,
I will be driving with XLS1500. [525W per ch @
4ohm and 1550W bridged @
4ohm ]
Not sure of my config for now. 18" is quite expensive for me to ship. So my thinking is,
1. If I go 18, then one sub is all I can, for now. Maybe upgrade later (Maybe is not an yes

). Plus, if I do upgrade later, I might need to get another amp. Can the1500 drive 2 18's rated at 900W RMS? New amp is gonna push my costs up again. Secondly power consumption is quite high with these monsters.
2. If I go 15 HF, then I can go two subs, each sub is rated 500W RMS - 4ohm. With 2 of 15HO, not sure if 2 will work with one XLS1500, which is rated 800W RMS - 4ohm. Also, unsure what the output is gonna be like.
I'd probably suggest a cab tuned to around 19-20hz and an enclosure volume of around 5 cubic feet or so. usable excursion on that one is a little higher than the spec, but not as high as the 18ho.
I'm not too interested in ported.
So How do I tune a sealed box to a given frequency?