Weird problem noticed today...

This has never happened before but in my Bluesound Node 2i today there is - I can it descrbe is as - bass slap or pop, I think just coming from the left Maggie. I pretty much only play loud. My subs are right behind the Maggie (16" or so) and it's definitely coming from the Maggie. Now the DAC on the Bluesound has a lot more boomy bass than the CD player DAC - Yamaha Aventage BD-A1060. So I am thinks my it's signal-related but perhaps it's the Maggies only they are not being driven hard in those frequencies enough to make that horrible sound. BluOs just did an update that is only major change to system today. I probably hadn't played music on a couple weeks and BluOs asked me to do update then I noticed problem - could be coincidental though could this be an amp or preamp issue?
Also weird is you said that it doesn't do it with CD, right?  Do you have any other source to try?  I'm sure the Node2i and the CD don't have the exact same output voltage, but they should be close.

If you have a sound pressure meter, maybe measure the output with both sources to make sure they are matched.  You might just be over driving the speaker with the Node2i as the source or maybe with the update, they somehow increased the output a little?

Logic tells us, (thanks Spock) that if the only source that is causing this to happen is the Node2i, the issue's gotta be with that source...
I would also add that as with the poster above the recent Node2i update resulted in no negative consequences at this end.
I'll keep all that mind when I get 'round to testing. I think I noticed, after the update, a reverby sound esp to vocals as well. I am worried that - at lower volumes I heard the slap as well but that could be worry playing tricks. Will let all know when I know more.

Cheers for all help so far. 
You by chance don't have a speaker out of phase?

well they sounded perfectly in phase before this happened so I seriously doubt that. and I never heard, in 50 yrs being a budget audiophile of a out-of-phase speaker having a bass slap.