Rick. Sounds like you had a good workout moving that 100 LB behemoth around the room. Midwall placement is often a great sweet spot for flatter FR especially for single sub placements. A second sub across from that one on the far wall would really flatten it further as well as provide benefits with lower compression and distortion. Its why I always suggest people by subs in pairs. There was a technical paper by Harman that proved that dual subs in midwall placement was an excellent configuration, almost as good as quad subs. http://www.harman.com/wp/pdf/multsubs.pdf
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John