Need help with covering for Dueland speaker wire

Well we need more info to be sure it will “work”. Work is a far cry from ideal however.

22 feet may be safe depending on your amp and speaker impedance. But 50 - 70 feet.... no way. The OP is using 16, not 12. 

You will hear a definite loss of signal fidelity with 16 gauge runs of 25-70 feet on a 4 ohm speaker. You just will.

Like most things Audio we read and hear conflicting stuff. All amps sound the same, 100 foot runs of 14 gauge speaker wire is fine .,, etc...

My ears and experience tell me not to use 16 gauge for runs of 20 feet and over. 12 gauge may be fine if your speaker is an easy load. 10 gauge is a better bet.

Here is a decent article. The writer also uses 10 gauge.  The issue is why go up against a spec that is at best is debatable? If The speaker’s impedance load goes below 4 ohms at any point, and many do, then the distances listed are certainly too liberal.  

https://www.audioholics.com/audio-video-cables/speaker-cable-gauge

Thanks for the responses ... you wisely waved me off the idea as I am too inept/lazy to run the PVC under my house.  I failed to mention that I currently use Supra Ply 3.4 wire under the house and am going to stick with it.  I prefer the Ply 3.4 to my former Mogami 3403 wire by a fair margin.    

You might also look into Supra, that offers tin-coated copper wires in a variety of gauges and that come in a "heat and aging resistant PVC jacket."

mitch2 beat me to it. Supra is constructed in a similar way to what you want and is made for walls, under floors, etc. That, and I see you already use it and it does meet all the requirements you need, not to mention, all the codes.

All the best,
Nonoise