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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
 
David,

The IsoAcoustics Gaia footers are rated for speaker weight up to 70 lbs per set. Definitions well exceed that, so the isolating compound may not as effective under greater mass.

An alternative that is effective for me is from Herbie's Audio Lab:

https://herbiesaudiolab.com/collections/loudspeaker-rack-decoupling-and-isolation/products/cone-spike-decoupling-glider?variant=12645103468599

Under Defs you can use either the regular or giant size, and the titanium spike receptor generally sounds best. This simply puts an isolating compound under the spikes.

Phil
temicxoch OP
20 posts
 
Hey Phil, 

I actually have older spike receptors from Herbie's that I've been using with BDR cones, similar but different to the one's to which you linked. But in the interest of trying something new, I've ordered the IsoAcoustics Gaia's. I learned they actually come in multiple different sizes. The Gaia III's can only handle 70lbs per set, but the I's are rated up to 220lbs. I managed to negotiate a good deal from a store I've gotten a lot of pro audio gear from in the past, so I'm going to give them a shot. The manufacturer also agreed to send me the correct thread adapters directly. I'll let you know what I think about them!

David


spiritofmusic
828 posts
 
David, I thought Phil didn't have that right. Yes, the Gaia I's are the ticket. You will certainly hear a different character in the bass. Whether that's ultimately for you...

I did try GSM's subs settings of 46Hz and 9/10 Level, but in the end found I was better off sticking w my current 38Hz and 6.5/10, as guided by Phil.

I may experiment w toe in. I sit 15' from my Zus, and they cross 3' behind me, much flatter than I initially had them, or the Def 2s before.
temicxoch OP
20 posts
 
Hi Marc, when I spoke with Sean yesterday, he also said he generally liked a lower setting around 38-42Hz as well, depending on the setup and type of music (lower for music with deep synth bass, for example). He said he has never had a need to push the crossover higher than 50Hz. I was cranking it up as far as 90Hz to get the bass I wanted, but obviously that began to smear the lower mids.

I'm hoping the adjustment in amp gain, the upgrade to the Lundahl transformers, and the increased gap height from the Gaia's will all yield improvements (Sean did say gap height could slightly increase the bass output). The toe-in may be quite significant as well. You are lucky to have 15 feet, which I'm sure lets the low frequency waves unfold more. I am 9 feet tweeter to ear, pretty nearfield and hard to get a deep soundstage dialled in, though it does make for a very immersive experience. Like front row seats!

Well, lots of positive developments here. I'm not sure why I expected the upgrade from the Mk1.5's to the Mk4's would be easy and instantly gratifying. I should know by now that, as with everything in this hobby, it's a learning curve and a journey to get to musical nirvana...

Cheers,
David
spiritofmusic
828 posts
 
David, it's totally reasonable not to feel so challenged you can't get it right. I'm envious of those Def4s owners who got things right on the first day, kicked back and relaxed.

Indeed, I've been running my 4s for just over 6 yrs, and in concert w my analog reinstall coming up trumps, I'm FINALLY properly dialling in my Defs.

For me, they've taken big strides re room position, footers, Duelunds and Lundahls upgrades, power cords, fuses, grounding (Sean installed ground posts for me), balanced pwr to subs.

Updated Lundahls, Gaias footers and careful attention to subs settings and toe in could provide big upsides.
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