How high are you right now?

[mobileaudio]

I realize that each room is different, and I'm not looking for "exact" but I'd like to get a feel for what a pair of IB318's can do, so here are my thoughts mixed with questions: 

• How high can/should a pair of 18's be crossed over?
• Do IB only preform well under ##Hz? (e.g., 50, 60, or 80 hz)?
• My main speakers are crossed at 100 hz. Can I get the IB's to meet them?
• How high can they go before IB setups begin to break down? (Break down = Loss of SPL, Loss of Low end bass)
• Where do you guys crossover you mains and IB setup?
• Is there a general crossover "sweet-spot" that will provide high SPL while still covering a wide range?
  
  (My mind tells me 80 Hz is the sweet spot) But 80 hz would seem to leave a hole in my setup where I crossover mains at 100hz.

I guess in a nut shell:
 Are IB's only for the ultra low bass, and do people generally need a 10", or 8's in their mains to help blend?

Sorry it's a mess of questions but I did not see much in the FAQ about this specifically. 

[ThomasW]

With regard to playing higher frequencies, IB drivers are no different than the drivers used in any other sub.

Any sub crossed over at 100Hz requires the sub to be on axis with the mains otherwise there will be a smearing of the stereo image.

To see the anechoic frequency response of a given subwoofer in a 'box', download a sim program such as Win ISD Pro. With it you'll be able to model the performance of any particular driver in a box. To sim an IB enter the largest box size the program allows.