never seen any tapes from the HF boosted 21's. The normal 21's have a very nice high end as it is. very nice and rounded with great color and presence. They can be used in most hockey arena and amphitheater type fob situations with great results...and of course outdoors. From the tapes I have heard and made, I never felt the need for any boost to the HF. If you have a good PA and you aren't too far from the source, You should be fine with the normal 21's, IMO. Location is the key with any situation but it is critical with the 21's, IMO.