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. 
@prof - That’s actually an often repeated myth.

The overall efficiency is determined by the driver and crossover. The cabinet and port affects the bottom end of the driver’s response. Plugging the port does raise the -3 dB point up to about an octave or so.

I should point out that when I bought MA Silvers they came with factory foam plugs for the bass port, so this technique is quite normal.

@bdp24 - You are kind of right, in that an optimized sealed cabinet is usually quite smaller than an equally optimized ported cabinet, BUT that assumes they are going to be used the same way. If you are going to take a stand-mounted speaker, and then put it on a bookshelf, plugging the port is a very very good way to compensate for the additional bass reinforcement.



Thanks erik,

It's been a very long time since I have been the details of speaker design.  I burned out on the technical side of this hobby years ago and don't follow it near as much (that's one reason it's taking me forever to get around to setting up my subwoofers.  To do it right is such a hassle I never get around to it.  I just sit down and listen to my system as it is...)

I'd always noticed, though, that plugging the ports of a speaker seemed not only to tighten up the lower response, but also seemed to reduce the sense of dynamics, making it a bit more lifeless.  So that seemed to at least subjectively ratify that myth.  Perhaps that was just due to the loss of lower bass...(though I have both the larger and the slightly smaller version of the Thiel 3.7 and 2.7 speakers, the only difference being a 2" smaller woofer on the smaller speaker and not as deep bass, but it certainly sounds as dynamic or more than the bigger speaker with the lower bass....)
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.