Paradigm: plugging ports

Discussion in 'Archived Threads 2001-2004' started by EricHaas, Feb 10, 2002.

  1. EricHaas

    EricHaas Supporting Actor

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    I have Studio 20's for mains. Unfortunately, due to WAF issues, I can only mount them on bookshelves about 2 inches from the wall. Consequently, I am getting a little boominess. My question is this. If I plug the rear ports with something, I presume that will diminish the boominess. But will it also diminish base response? In other words, will the 20's not effectively go as low?
     
  2. Michael Mohrmann

    Michael Mohrmann Screenwriter

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    "If I plug the rear ports with something, I presume that will diminish the boominess. But will it also diminish base response? In other words, will the 20's not effectively go as low?"

    That's pretty close to my understanding. Plugging the ports will cause the speakers to roll off at a higher frequency, albeit at a shallower rate of decrease vs. the "ported" performance. If you are using the crossover in your processor/receiver for these speakers (i.e. 80Hz), then it might work out. However, I couldn't tell you whether plugging the ports will cause the speaker any damage (most accounts I have heard say it won't, but these sources aren't backing your speaker's warranty!).

    Michael
     
  3. Brian Bunge

    Brian Bunge Producer

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    Eric,

    Yes, plugging the ports should diminish some of the boominess. Possibly not all of it though. Actually placing a speaker near a wall (or in a bookshelf) will increase boominess even with a sealed enclosure. It's definitely worth a shot though. I have 3 ACI Emeralds for my L/C/R speakers. They are not even near the wall but I have the ports plugged because I prefer the sound.

    Here are a few general advantages of a sealed speaker. First, you get better transient response (tighter, more accurate sound). Secondly, there is less chance of bottoming out the woofers due the the "air spring" created by a sealed enclosure. And thirdly, you usually have greater power handling. (BTW, these are all things that I noticed by plugging the ports on my Emeralds).

    Brian
     
  4. John Cain

    John Cain Second Unit

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    Finally a question I can help someone with!!

    Paradigm makes a "port Plug" that will turn your speaker into an acoustic suspension version. It is a rubber thingy, I can post a pic if you would like.

    They tell me you will lose only the bottom octave your speaker is capable of producing, however it will sound much better than letting that out of phase stuff bounce back into/onto the speaker without the port plugged.

    I'm gonna be plugging my center speaker.

    -- John
     
  5. elMalloc

    elMalloc Supporting Actor

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    Does Paradigm make any prop up for their center speakers, since laying flat they are aimed up at an angle when they should in most situations be angled forward or down?

    Also do they make speaker stands?

    I have mini monitors and the c-370 and I need speaker stands (it's sitting on top of my entertainment center) and I need the center to aim downwards....I was suggested the rubber door stops.

    -ELmO
     
  6. John Garcia

    John Garcia Executive Producer

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    www.paradigm.ca for the stands, or contact your dealer. I'm using 4 S30s.
    Rubber door stops are a bit too tall for me. I just used some weather striping type foam with one sticky side (actually cleanroom compatible air seal) that I had. Thick in the back, thinner in the front. Has to be somewhat dense, as the speaker will crush it. The stuff I have is able to support the weight.
     
  7. Tom Brennan

    Tom Brennan Screenwriter

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    You can't just stuff a vented box and expect it to work as a PROPER sealed box, you're just as likely to end up with a boombox that way. The "Q" of the sealed box determines transients and response at resonance, a sealed box with a high Q will exhibit poor transient response and a rise in response before rolloff--a boombox. Q is determined by box size for a given driver. I think it highly unlikely that the box volume that gives optimum performance for a given driver when vented would also work well when sealed. And then you've the fact that drivers for vented boxes are different in nature from those for sealed boxes. Worst case with plugging a vented speaker would be a huge decrease in bass extension, an increase in distortion (sealed boxes always have higher distortion for a given F3 and driver size than vented boxes due to the greater excursion of the sealed driver at F3) and boomy, poorly defined bass.
     
  8. EricHaas

    EricHaas Supporting Actor

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    Yeah, I am aware that Paradigm makes port plugs. I don't really understand why I need to buy them though. It would seem that I can fill the ports with putty, clay, etc. and achieve the same effect. I am concerned about losing that bottom octave though. But I guess if it is a choice between having sound in a certain frequency range that is muddy or none at all, I guess none at all. What I am really concerned about is will I lose sound in a frequency range where it ISN'T muddy. I will just have to experiment and find out.
     
  9. Ariel

    Ariel Stunt Coordinator

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    i tried stuffing the port of my studio20 and i didn't like the result. it seemed that something is missing even with the subwoofer. i am using the onkyo575 receiver and from what i know, the crossover freq. of this receiver is somewhere in the 80hz. the freq. rolloff by stuffing the ports is above 80hz when i ran the test tone comparing the result without plugging the ports. just try it and you might get a different result because the room is another major factor to consider.
     
  10. Brian Bunge

    Brian Bunge Producer

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    Tom does make some good points concerning the Qtc of a sealed enclosure. In the case of my Emeralds I know all the T/S parameters of the driver so I was able to get a pretty decent idea of the response curve of the driver in a sealed vs. ported enclosure.

    Most of the time a ported enclosure will be large enough for a given driver that when sealing up the enclosure you usually end up with a low Q design. So boominess is probably not an issue. To me the biggest issue is whether or not the resultant F3 ends up being too high to integrate properly with a subwoofer. This is why some experimentation is necessary before anyone can say for sure that it will or won't work. Emailing Paradigm for their input might be a good idea.

    As far as actually plugging the port, I've used an old mouse pad rolled up. I've also used a folded up sponge wedged into the port.

    Brian
     

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