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Plug Bass Port?  

post #1 of 9
Thread Starter 
I have the Polk Audio LS90 and they are a little loose on the low end. I would like to tighten them up a little because I have a Velodyne 1500R. Can I plug up the bass port to make it a reflex enclosure to tighten up the bass? Or will this complete distroy the tonal acuracy of these speakers?

And if I can plug them up, then how would you suggest I do it? (I could use a sockhttp://www.avsforum.com/ubb/smilies/smile.gif)

post #2 of 9
Thread Starter 
post #3 of 9
How about a big cork!

On second thought, you better make sure the port is not aiming at you. http://www.avsforum.com/ubb/smile.gif
post #4 of 9
I have a pair of Dynaudio Audience 52's
which come with port plugs, which they
recommend using if used in a bookshelf,
or other hard surfaced enclosure. They
are shaped like a round cylinder and made
out of foam. The foam is grey and appears
to be the same construction as the typical
egg-crate acoustical foam (but solid instead
obviously). I would suggest trying a
craft store for some cylindrical reasonably
dense foam. Cut it to length so that it
fills the port snugly and try it out for
post #5 of 9
Same as above for the twin ports on the Tannoy System 8 Near Field Monitor Mark IIs that I use to mix sound at work. Tannoy supplies a gray closed-cell foam port plug with which to stuff each port to help dry-up the bottom-end when the speakers are attached to a wall (which they are not, here, so I don't use the port plugs.)
post #6 of 9

Unless the speakers were specifically designed so that the ports could be plugged or open they will probably sound worse plugged. Of course you can experiment with a sock or some dense foam, but don't expect an improvement.

Probably the best thing to do would be to adjust your speaker placement. The bass "character" and performance of a speaker is greatly affected by where it is placed in a room (and also where you are in the room).

There are a thousand and one ways to decide on where to place a speaker:
1. Trial and Error - this can take forever.
2. Rules of thumb - the rule of 1/5ths or 1/7ths or whatever, these speed up the trial and error process.
3. Software - these greatly speed up the trial and error process. Do a search either in the archives of this board on a good search engine for "speaker placement software" and find something you like.

post #7 of 9
Thread Starter 
Unfortunately, I have to put one speaker into the corner. So I pulled it out as much as possible and put styrophome blocks behind it.

So I went out and bought some styrophome cones and stuck it into the port (nice fit). It cleaned up the muddiness in the low bass, but it revealed a muddiness in the mid-range - which was covered up by the loose bass. I think its an improvement so far, I haven;t noticed a difference in sonic, detail, or transparency of the music. But the Polk Audio LS90 seal the midrange off from the bass port for the bass drivers.

Here are some pictures:


post #8 of 9
I can't exactly tell from the picture, but it looks like the speakers are sitting directly on the hardwoods. Get some cones and raise those puppies up....it may even clean up your midrange http://www.avsforum.com/ubb/wink.gif
post #9 of 9
Thread Starter 
Yes they are sitting directly on the hard wood floors. There are flat height adjustable feet under all four corners that I use to stablize the speaker. So I should get some cones ... Any particular type or brand of cones?


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