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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
213cobra
885 posts
 
If I can get detailed answers to the questions I raised a few posts back, I might have more suggestions. -Phil
temicxoch OP
20 posts
 
Hi Phil, 

Here's some answers to the questions you posed:

-- no cable TV in my sources
-- no balanced / XLR cables
-- preamp is a Cary SLP-98 with integrated tube phono stage, no SUT
-- no ground lift switches on any components
-- no passive components
-- cartridge is a Clearaudio Virtuoso v2 ebony, tonearm is a VPI JMW-9
-- there is a lamp situated above the turntable, which was causing buzz when turned on, but that was mostly eliminated by running a ground to the turntable and then preamp. The lamp is off when listening anyway. No other power supplies near the turntable. 

Interestingly, Sean sent me this response about grounding the sub amps in the Definition (I'm sure he wouldn't mind me posting this): "When I rebuild the amps I float the audio ground, that is one of the benefits of the transformer. Another thing I do is to better float the AC transform, much of the hum you notice is coming from the mechanical singing of the AC transform, the power supply is linear so it’s a big piece of the kit in size and mechanical effect. Things should be much quieter when you get them back." 

David
spiritofmusic
828 posts
 
Well based on that reply, I need to contact Sean about solving my subs hum issues as well.
spiritofmusic
828 posts
 
David, Sean has emailed me to say the solutions he has for you may well suit me too. Great customer service.
temicxoch OP
20 posts
 
That's great, Marc! Maybe this thread will end up solving problems for both of us :) 
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