Thanks all. Wow 5 subs in a single HT system. Whoa and I thought two was more than most. Yes that can be quite tricky. Bob what I meant by out of synch is that perhaps the two different subs were not in exact phase. Perhaps the drivers could be out of the exact timing being of different types of amps (class B and Class D) and one having a larger enclosure. So here's what I ended up doing. I took home a 2nd ASW610 brand new from my dealer and removed the ASW600.
After many hours of listening and trials, I became convinced this was the right move. I purchased the new ASW610 and redeployed my older ASW600 as a sub for my Dell desktop PC in another room. The two ASW610s work extremely well together being very compatible. The LFE and bass extension is far more tight and focused on the sweet spot. I realized that the older ASW610 produces more rattle and actually more vibrations in other rooms. Now those vibrations have greatly reduced which was also my interest in upgrading. So far, mission accomplished !!
After many hours of listening and trials, I became convinced this was the right move. I purchased the new ASW610 and redeployed my older ASW600 as a sub for my Dell desktop PC in another room. The two ASW610s work extremely well together being very compatible. The LFE and bass extension is far more tight and focused on the sweet spot. I realized that the older ASW610 produces more rattle and actually more vibrations in other rooms. Now those vibrations have greatly reduced which was also my interest in upgrading. So far, mission accomplished !!