Here is an old thread you may find helpful..
REL Sub Woofer Tweaks
Being the proud owner of two REL Storm III Sub's I have noted the following from previous posts. One recommendation was to get rid of the supplied REL Spikes. I was fortunate to have the practical ability to drill, tap the matching thread per millimeter size, and to insert threaded studs into some Mod Squad Tip Toe's. The Tip Toe's were the perfect size, and I also used adequately sized fender washers as shims between the Tip Toe's and the REL feet for levelling purposes.
The biggest surprise was when I changed the factory supplied REL Power Cord to a Dedicated Audio " Pds " type.
I do not know how or why for the Power Cord but the difference was significant.
I advise all REL Sub owners to try the above changes, and I think you will be very surprised.
Djohn (Threads | Answers)