Subwoofer doubts: crossover setting for 60hz speakers


Hello there. I’m about to add a subwoofer through “high level” inputs to my stereo system, and I have some doubts. Nominally my speakers (Cabasse Riva) go down to 60hz. According to the stricter books, this means I should set the sub’s crossover to 120hz. Which would be a problem, since -from what I read- sound becomes “localizable” over 80hz, and my only spot to place the sub is a corner of the room. I guess that would severely affect soundstage, which is a deal-breaker for me. 

So my questions: 

1) Would it be ok if I set the sub’s crossover to 80hz? or would I be risking to create some kind of “gap” between sub and speakers? Do rememeber that I’ll hook the sub through “high level” inputs, so there'll be an increasing overlapping of frequencies above 60hz. 

2) Or would I be better off adding 2 subs instead of just one and setting them at, say, 100hz? Many audiophiles on the web advocate for double subs... 

Keep in mind here that my current options are: 1 excellent Velodyne spl1200r (that reaches 20hz), or 2 fairly good Focal sw700w (that reach only 40hz). If the answer to question 1 is "yes" -ie. if I may set the sub's crossover to 80hz without noticeable gap and preserving soundstage- I'll definitely go with the Velodyne.  

Thanks for ANY help -I need to move fast!


fedocable
Thanks a lot, xti16. I'm already free from the annoying idea of setting the crossover as high as 120hz. I'm convinced 80hz or even less will work fine. That means I'm going with the single subwoofer option.
As for it, I just found a third challenger, at a very nice price: a Phase Technology "Power FL-10"; comes with a 10' woofer plus a passive radiator. It goes down to 26hz, decent enough. The seller claims it's new. There are a couple reviews on the web, and they are all very flattering. And, best of all, the price is cheaper than retail in USA! -that is quite extraordinary here in Argentina.
So, new question: has anyone heard of it, or at least of Phase Technology? Thanks in advance!
Fedocable,

Every time I've added a sub, or subs to my system, I've had all sorts of challenges getting them to integrate properly.

My last struggle was integrating a pair of JL subs in a new, larger "man cave", where the room had all sorts of obnoxious resonances.

Using a sound pressure meter and a CD with sweeps I was able to improve things (helped me place bass traps in the room), but the system still didn't sound right.

Then I discovered a program to download, "REW" (Room EQ Wizard) and a " miniDSP UMIK-1 USB Measurement Calibrated Microphone" (thank you Amazon), and with those tools was able to get the crossover point, crossover amount and volume adjusted, and now the system sounds awesome.

You would need a PC (not sure if REW works on a Mac, bet it does, it's a Java app), and the microphone plugs into the standard USB port on the computer.
You would need a PC (not sure if REW works on a Mac, bet it does, it's a Java app), and the microphone plugs into the standard USB port on the computer.

REW works just fine on a Mac.  Absolutely fantastic tool for subwoofer integration.