Subwoofer insight.

I don’t listen to any music that has bass any where near 20hz, let alone below 20hz.

These low frequencies are inherent in the acoustic resonance of large spaces. Therefore present in all music that is well recorded in a large space. Its not "music" in the sense of any particular instrument playing it. Although this is definitely the case with a lot of music. But it is also there in a surprisingly large number of recordings of all kinds of music.

In other words its not that its not in the music you're listening to. Rest assured it is. Its just that your system is unable to reproduce it. If it were, you would experience it. Specifically, you would experience it as a heightened sense of envelopment, of being in the recording space, as opposed to merely being in your room. No doubt about it. Read the comments.
https://systems.audiogon.com/systems/8367

I appreciate all the responses. It has been a long stretch of working 10 nights. Now got 5 days off. Plan on trying to tune them in as best I can the next few days. Should be a good time and am excited to simply enjoy the music more than anything (no music except car radio for the last 10 days). Arghh! Might even try some of the alternative recommendations on connections that others have suggested here. Right now have connected as suggested by REL. I have been following this thread and even though it drifted off topic a few times and got over my head with building crossovers and the such, I appreciate everyone’s insight. Stay well.

Am I the only one that thinks this system is underpowered?  86dB 1w/1M on a 75W tube amp in a big space does not sound correct to me; I'd pick a good 200W/ch amp and see how that does.  I may agree with some of the sub comments, but you don't even have your main speakers set up right yet.  You won't know how the speaker really sounds until they are properly powered.

Underpowering speakers is the #1 most detrimental thing you can do to a speaker.  Running very long speaker cable runs is another, as those long cables suck all your power away and drastically decrease dampening factor so you get very poor bass performance.   so with a  75W amp, you don't have much room for error.  Try your speakers on a 1 foot length of 12 gauge OFC and see what happens.  Then borrow someone's big amp and try that, using your integrated as a preamp.  I bet its night and day. 

I work with speakers and amps all the time and I know from the ATC SCM19s i import, putting them on a small amp (say like a modern receiver, Denon, Yamaha, etc) they sound good.  Plenty of folks would be happy.  Put them on preamp with a big 200W or 300W amp (even if its a new Yamaha or Rotel or NAD -something like that) they sound like a different speaker- amazing!  Way more bass, way more dynamics, headroom etc.  If I tried that first, I might not add a sub.       

Brad

These low frequencies are inherent in the acoustic resonance of large spaces. Therefore present in all music that is well recorded in a large space.

Nonsense! It’s only present if the material was not filtered, which was often SOP for records. Any or all of the microphone, input channel, mix output, cutter could have been filtered to make the disk more playable.

OTOH, some unfiltered large space recording have enough sub-audible low end to put a plate amp sub into thermal shutdown. Adding a 12v 100 or 120mm computer fan run on ≈3.5vdc will keep the amp cool and dramatically extend its life.
see http://ielogical.com/assets/WinterBlues/Force_Fan.jpg Airflow is toward plate to force air up the channels.
The fan is held in place with the compliant mounting plugs. Even Saving Private Ryan or Telarc 1812 w cannon won’t shake it loose.

ricred1

I don’t listen to any music that has bass any where near 20hz, let alone below 20hz.

millercarbonThese low frequencies are inherent in the acoustic resonance of large spaces.

Huh? You must be hearing things!
I suggest you try and measure this "inherent" acoustic resonance. Feel free to report back with your findings.