I have a pair of JBL LSR2328p monitors.

I've always had them in the upright position but now I want to lay them over on their side.

Would you be inclined to have the tweeters to the inside or outside? I'm sitting about 3' from them.

Please explain your rational for me.

Many thanks.

Came across this article on Presonus.com

But they don't say why.

Ideally, you want the tweeters as close to ear level as possible. 3' is very close, closer than what most call near field listening. So I really don't think it will matter much because of your distance, but I would have the tweeters to the outside to maximize the dispersion and potentially increase the soundstage....but honestly I don't think you will hear any difference.

^This is sound (pun fully intended!) advice.

What I do after something like that is established, is I close my eyes. Sounds dumb but you might find that, despite all logic, your speakers sound best with one tweeter inside and the other outside. I tune my guitar and bass amps and EQ this way; close your eyes and let the ears lead! 

Thanks everyone.

In the past when I've had bookshelf speakers that I wanted to set horizontally I always put the high end out. It just made sense to me. I'm a self taught soundman who never had the benefit of  a formal education in the field. It was baptism by fire the first time I had a 16ch board and 4way PA fired up. God, the first 4-6 months were brutal (1978-79). But then I began to understand the gear and did just that...focused on my hearing.

As has been suggested, I learned to close my eyes and listen.

Final story:

I was hired by Janice Morgan for her band (Network) for a west coast tour. We ended up in Calgary at the Four Seasons for a gig but when we arrived it looked like we had been double booked. The band setting up was Bobby Curtola (famous for his 'Things Go Better With Coka-Cola' ad) They were in the process of doing a sound check and it did NOT sound good. I wondered over to the desk to see if it was a room thing but it sounded the same there. What I found was a guy with a book on acoustical engineering open trying to work a formula for sound absorption coefficients to set his main EQ up. I had never seen anything like it or have since. I think I may have even told him, put the book down and just listen to what's going on.

I once thought that I'd like to  get an RTA, but never did. In the end I just learned how to listen.

You cannot second guess your ears, unless you don't have any  . Its a combination of hearing and technical process, and some understanding of electronics. Gear makers make gear to sound a certain way, its inherent in the designer they will make what sounds good to them, or what they learned in EE school.

Like you said, you learned by listening and tweaking your setup.