The only alternative is to install a "family style" roll bar into your 89.
That allows you to mount the sound bar on the back struts of the roll bar where it is supposed to be in the first place. Instead of on the windshield struts where you have it now.
I tried a sound bar on my 87 sport bar, although I have a 1-piece hardtop, the sound bar was still in the way for me as far as headroom was concerned.
'87 YJ, 4.2L built and bored, 8" of lift, 8.8 rear, AX15/NP 231J, Tom Woods drive shafts, Flat fenders, 12,000LB winch, Custom bumpers, Rattle can paint job. Never completed...