Does Plugging Bass Port Affect Pace, Rhythm and Timing?

Hi, I recently purchased a used pair of Monitor Audio Silver S1 bookshelf speakers for, well, my bookshelf. :\  As expected, the presentation is a little muddy, and the highs not as extended as they might be otherwise on these speakers known for the quality of their tweeters.  I am about to try plugging the ports to see if any improvement could be had. I was wondering if there is any downside to plugging the ports on a bass reflex design as far as bass accuracy and speed. 
If you want to experiment, go to a fabric shop and buy some Bonded Dacron(polyester batting).   You can then control the vent function, by varying the amount of Dacron(tight or loose wrap/longer shorter roll) in the tube.  1" to 1 1/2"  thick works great and most places sell it by the yard(cheap).
I found out something interesting. The muddiness seemed more than anything else traceable to the fact that the tweeters were a good 12-15 inches above the height of my ears while listening. I tried tilting the speakers down by inserting a shim on the rear bottoms. This helped some - but when I turned the speakers over on their sides - voila! Now that the tweeters are almost even with my ears, the high frequencies and mid-range really came alive.

I didn't realize tweeters of this sort were so directional, but apparently 15 inches off axis is enough to severely attenuate the highs. I still keep the ports plugged due to the closeness to the wall. Pretty well balanced now, although I may have done something to the imaging by turning the speakers over on their sides - more experienced members than myself may be able to chime in on this.
That will do it, and depends how far away.

You could also try turning the speaker upside down. Many are measured on tweeter axis, so this will restore the vertical relationship.

Of course, it only matters if you can hear it.


If you want to tighten up the bass..plug it.
Speakers should not go into "wobble mode"...the bass must be tight and controlled..not doof doof but bang bang!
Good one rwinner..putting the boxes down will help..why your tweeters are directional is a bit disturbing...mids and tops have to point and disperse the audio to your man chair.