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

Temicxoch, all this stuff is buyer beware, and critically, room dependent. My old space was a converted industrial loft with a bombproof solid concrete floor overlaid w timber, which meant that the option of Rollerblocks replacing spikes under the Zus was possible, and indeed these did have the edge on stock spikes.

Here, my floor is much more flexy, being an 1861 actual roof space. Even though I didn't realise it to start, the Rollerblocks were deleterious on this floor. I noticed existence of Revopods as I went to trial IsoAcoustics Gaias footers, tried both out, and the Revopods totally ruled. I can't say w any great confidence why this is the case, but for me the Revopods have really pushed my Definitions performance to the next level, incl the ability to get deeper, tighter and more extended subs output, which I know is your ongoing issue.

I'm not going to claim they are your solution, it's room setup and subs settings that needs to be yr current focus, but these footers could then be the icing on the cake.

For the record, the Revopods sit on Panzerholz slabs, themselves on Symposium Acoustics Svelte Shelves.

Thanks for the info! I do realize footers are less important than getting these speakers properly set up at this point. I was just curious to hear about your experience using roller blocks, since I have a couple sets kicking around. I never thought to try them under the speakers. It's a never ending quest, isn't it? :)

Give it a go, I certainly had success to start w RBs. Just take care on physically placing them under the Zus, they're obv not fixed.

Part of the joy of this hobby (or is that pain? LOL) is both incremental impvts, and occasional big leaps. 

For me, the Def4s have so positively responded to the system wide changes I've made, they've justified me not taking the easy option and simply upgraded to pricier, more complex spkrs.

David,

I was able to speak with Sean Casey this morning. Your Def4s definitely are early enough to have to original lower-gain sub amps. You have s/n 007/008; I have s/n 009/010. You have three options, one of which requires you spend some money.

First, you can experiment with the Low Pass Filter frequency. It goes all the way to 110 Hz, so try frequencies above 60 Hz so you are well into overlap with the main drivers' bass response. I don't normally recommend this but it might work for you, and may require experimentation with the other controls to get it to sound right. You can run the level at 9, 9.5 or 10. No harm in trying.

Second, Sean says if you had Def2 and want some of the extra kick-drum slam that the 4x10" array delivered, you will get more of that out of Def4 using rubber feet instead of the stock spikes.

Third, you can simply remove your sub amp modules, return then to Zu for updating which takes about 4 days. The cost is $600/pr. They are not just making a gain change to the amp. The revision also includes Lundahl gain transformers embedded in the module. To arrange this, just call up Zu and talk to Sean or Gerritt. This will get you all the added gain you need, and you still may want to combine it with some measure of the first two options.

Phil

Thank so much, Phil. I really appreciate your help here!

Interestingly, I did try higher crossover frequencies (along with various settings of the parametric EQ) over the weekend and it was definitely an improvement. I'd still like some additional gain for more headroom, but further steps forward. With my ears not so focussed on the inadequate bass I was hearing previously, the upgraded drivers and Radian tweeters really began to shine. 

I wondered, too, if these speakers would benefit from a little less toe in (they are currently pointed directly at the listening position, only 9 feet away), compared to the mk1.5's, which were in the exact same spots. The spray of the Radians is glorious, but perhaps a little too prominent in the mix in this configuration. I haven't yet played with this, as moving these new Zu's is more than a one person job! 

I will make contact at Zu to upgrade the bass modules. I've come too far to stop now :)  

Once I get everything sorted, I'll close the loop and let you guys know how it all turns out...

Happy listening, 
David