I bought these as part of a package with the PRO 15's. The built in crossover is perfectly designed to use with any other passive HK Audio speakers. I have found that they produce a great full range with the PRO 15's and I should imagine they would also benefit the PRO 12's also. They are perfect for many applications, I have previously used them for DJ's to live gigs. These were once used in a church with a live band as part of a wedding. They produced a great quality sound that would normally get lost with many systems in such a large setting. The balance that the crossover produces is a credit to the system giving great sound in many types of venue. I am sure with multiples of this system you could create a brilliant sound in the largest of venues. The only minor letdown on these speakers the fact you have to purchase the screw on poles if you want to attach the top speakers as a full unit, however this does make the unit has a whole very secure. Fully recommended for all applications.