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

Definition 4 setup uses less toe-in than Def 1.5 and Def 2 in every room where I have heard both. Particularly in a relatively near-field situation.  Both the Radian supertweeter and the FRD have broader dispersion than the respective drivers in the Def 1.5/2.

You can reduce toe-in with Def 4 without tearing a hole in the middle of the soundstaging. Get some help and adjust toe-in by quarter inch increments of rotation around the inside front foot or spike as the axis of rotation until you hear the soundstage lock in. You can start with no toe-in and incrementally add some or start with the toe-in that worked for Def 1.5s and incrementally reduce it. Trying from both reference points should be revealing because you want to end up in the same place regardless where you start. It helps to use recordings from before the multi-tracks / extensive multi-mics era (pre-1964) or modern recordings known to use simple mic'ing and minimal mult-tracking, to really nail it.

Phil

Also, by the way, David: To remove your sub amps, note that the Speakon connector there is flange surrounding the connector itself. Start by removing the screws from the Speakon flange. The Speakon connector and its wiring harness stay with the Definition. After you've done that, then remove the six screws holding the amp/controls assembly to the Def cabinet. That assembly pulls away and that's what you ship back to Zu.

Phil

David, I'd be skeptical about Sean's advice on simple rubber footers. If you truly need greater bass warmth, trial the IsoAcoustics Gaia footers. I found they were outperformed by the Revopods, but in a situation where bass is MIA, they could be the ticket.

I've managed to remove the sub amps and will send them out today. It was a bit of a challenge pulling them out due to the glue tape! I was surprised how tiny the RCA cables from the speakon inputs to the amps are. Flies in the face of the massive audiophile cables everyone puts on their subs these days. 

Perhaps this is actually an ideal time to play around with toe in, as I'll be without the bass output for a couple of weeks. Based on my listening so far, I thought that the Mk4's in my room would benefit from a bit less toe-in, so it's good to hear your input on that, Phil. I'll try your suggestion of some older recordings. I've got some great jazz from the 50s. Interestingly, I asked Sean about this and he said that the ideal positions he has found in various setups with the Mk4's have ranged from toed-in from as extreme as 2 feet in front of the listening position to some distance behind, usually no more than a couple of feet. He estimated 1/10 times directing the tweeters in front of the listener, 4/10 directly at the listener, and 5/10 behind. I always had the Mk1.5's pointed right at my ears, but notice that these new speakers aren't disappearing as well my old ones in that position, with the frequency spectrum tilted upwards (a little too much high end content in comparison to the mids). 

Marc, I was just looking at those footers! The company is based in Ontario, about an hour from where I live, though I think they're actually manufactured in China. Crutchfield carries them and has an easy return policy, so it's a no risk proposition to give them a go. I'm just waiting to hear back if they have the alternative threads (looks like the Zu's are 3/8"-16, which isn't included in the box). 

David

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