If you are able to swap the problem Amp with a working Amp to see if that makes a difference, Thats where I would start. If it sounds normal, there is probably a hardware issue with thew Amp. 

I would recommend giving support a call so that they can take a look at yor diagnostics. 

They may ask you to do a factory reset after that, but do not reset until they ask you to.

Do you use or have you used a subwoofer with this AMP? (Either a SONOS SUB or a 3rd party subwoofer.)

If you are using a bi-wire connection to the passive speakers, check to make sure the woofers are connected.

I do not use a sub.  

I’m going to try swapping out the amp with another to confirm it’s truly the amp and not some connection issue.  

Well, it’s not the amp after all.  I hooked up another amp and it sounds just as bad.  It’s really weird that both speakers would suddenly sound terrible. I can’t believe I blew them both out at the same time….

Maybe a mouse or squirrel liked something about a speaker and went back for seconds.

Seriously, check the first AMP for “DC offset”.

If you have a DC voltmeter, AMP output should be near zero at minimum Volume. If you don’t have a voltmeter, disconnect and reconnect the speakers. At the instant of reconnect a minor “tick” is OK, but a major “thump” is not.

Now pull the speakers and check for any issues. There may be something you can see or it may be a bad voicecoil. Then check the cables. Rodents love to chew through cables with a little voltage running through them.

Ordered a multimeter. 

The speakers are registering at 3.6.  I thought it would be higher.

3.6 Ohms is the DC resistance, not the AC impedance at a frequency. 3.6 Ohms is slightly lower than I expected, but reasonable. (Meters are often not so accurate at low resistance) If all of your speakers are the same, I expect that the resistance will be similar.

Also, measure the DC resistance from the speaker wires to building ground. There should be no conductivity here.

I’m interested in the DC voltage at the AMP’s speaker terminals at zero Volume. Note that the AMP will power down after a few minutes of zero Volume or no input. A small offset voltage is not a speaker damaging issue, but it will result in quiet “ticks”as the AMP starts up and shuts down. Normal room noise will usually mask the “ticks”, but once you notice them, you’ll be poisoned forever.

Let’s not overlook the dumb stuff: If you recently rewired the speakers, maybe they are now out of phase. This will significantly reduce the bass output because one speaker cancels the other’s bass. Simply reversing the phase at one AMP speaker terminal can discover this in a couple seconds.

I opened up the other speaker and found water inside.  I told DefTech and they're sending me a new set of speakers.  

Thanks for all the tips and info.