would pluging the ports on my pair of PL-89 tower speakers an the ports on my Klipsch RB-81 II
with some custom cut thick rubber to sort of make them sealed be ok or would it completly suck im feeding each of them 200watts from a xli 800 ?
iv got a parometric eq to use for room correction
It never hurts to try it!
Often a pair of socks can be stuffed effectively in a port for a quick and easy test.
With one of the older poorly designed subs, you were more likely to notice a positive difference.
Aside from a poorly designed port (where the tuned note of the port is unreasonably dominant), I believe you are essentially reducing the bass similar to the effect you could get from using your parametric EQ. One effect of reducing the ratio of bass to mids and highs (per Josh Ricci) is a perceived added tightness (tightness defined as reducing the overhang of low notes). So you can look at it as finding your optimal point between sufficient bass and proper "tightness".
Of course plugging ports is a on/off switch, where you would ideally want a continuously variable knob, but it may give you a sense of whether you would like to tweak your PEQ.
Also note that if you have subwoofers, but do not have an AVR that would apply a high-pass filter to your speakers, plugging the ports is a fairly effective way to get much of the benefit of high passing the speaker!