Help me understand how to optimize bass on the Zu Definition Mk IV


I am a longtime owner of Zu Definition Mk1.5 speakers and recently also bought a pair of Definition Mk4's. I based this decision partly on the reviews / feedback posted here on Audiogon in various threads by members such as 213cobra, gsm18439, spiritofmusic and others. I'm really hoping some of you Mk4 owners can chime in and help me out here!

Basically, my issue is that I found the Mk1.5's put out incredibly deep and impactful bass, especially with some of the music I love, like R&B and reggae. And this was with the bass amplitude knob at 12 or 1 o'clock. However, after setting up my new Mk4's, I find the bass underwhelming and anemic, even after fiddling around with various settings and with the volume and PEQ cranked. I have them on spikes into bases on a hardwood floor, with about a 1.5" gap on the bottom. What am I missing here?? Based on the reviews I read, I was expected the bass to equal or exceed the lowly 1.5's. 

Thanks so much in advance for any helpful advice! 


temicxoch
Well based on that reply, I need to contact Sean about solving my subs hum issues as well.
David, Sean has emailed me to say the solutions he has for you may well suit me too. Great customer service.
That's great, Marc! Maybe this thread will end up solving problems for both of us :) 
By the way, I've also installed Isoacoustics Gaia I's to the Definitions. Can't wait to get the amps back to take them for a test drive! Sean said it was about a week turnaround. 
Looks like the sub amps are headed back to me. I'll report back in when everything is up and running. Did you end up deciding to get your amps upgraded to fix the hum issue, Marc?