Ask yourself, "What is it that I am trying to accomplish?"
If you think that lemon oil is needed because it will improve, enhance, feed, protect, and/or buff your speakers, you also need to ask yourself this:
Do I want to add a "hydrotreated light distillate (petroleum)" oil to my speakers finish.
That is what lemon oil is.
My mother-in-law, bless her soul, used to use lemon oil on her fine mahogany furniture, like it was going out of style. I asked her why?. She told me, "I like the smell". That is the only reason to use lemon oil.
I'll say it again, Lou's finish is world class. One of best finishes I have ever seen on any piece of furniture. It combines the tactile naturalness of "Danish" furniture with the very sufficient hardness and protection of varnish. I like just touching the wood. As a woodworker, after talking with Lou I began incorporating the same finish on my own handmade furniture.
I'll get off my soapbox and wish everyone a Happy Thanksgiving.