[Steve DeRosa]

Originally Posted by gerardo1000

I bought a pre-owned Loar LH-600 and I wonder which strings you suggest...my ideal strings for this guitar would be strings that do not try to modify the "spirit" of the instrument, but also that can be balanced and loud enough when I play acoustically...

Given your criteria I'd recommend the Martin Retro Monel MM13 set (13-56), about as Jazz-Age period-accurate as you're going to get in a modern string; a couple points based on my own experience:

• The forces that drive the top of an archtop guitar are more akin to a "piston" motion than the torsional forces exerted on a flattop; as such, you'll need a heavier string in general than you might be accustomed to using on your other acoustics - I personally wouldn't go any lighter than mediums on this guitar...
• While monel strings exert more tension than the typical PB/80-20 acoustic set (approximately ten pounds more for a medium-gauge set - exactly what you need on an archtop guitar) they have the paradoxical benefit of feeling "slinkier" and lighter to the touch; until discovering them a couple years ago I used to set up all my acoustic archtops with PB 14's - loads of tension/power to drive the top for unamplified comping, but rough on the fingers by the time that third set rolls around...
• Whatever you do, don't judge their tonal potential until you've played them in for a week or two; FWIW monels settle in somewhat differently, revealing a warm, woody tone with strong fundamentals and less-brash overtones than copper-based wrappings - which IME makes it easier to, in the lingo of the old '30s/40s Big Band guitarists, "coax the velvet out"...
• In the event you decide monels are not to your liking, stay with a strictly acoustic string of appropriate gauge; unless you're going to hang a DeArmond pickup for amplified use the typical nickel-plated electric strings aren't the best choice (I've heard some guys had good results with pure nickel wrap - not too easy to find in the proper gauge, though), and as sweet as flatwounds can sound on an ES-175 or L-5CES, they'll kill nearly all of your acoustic response (Hint: if you like a flatwound-style feel D'Addario Flat Tops - also a higher-tension string by nature - might be a good choice)...

Good luck...