Plugging a port or ports on a speaker, can this damage them?

Discussion in 'Speakers' started by Tony V., Jan 10, 2019.

  1. Tony V.

    Tony V. Moderator
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    A thought that recently came to me, given some manufacturers (SVS comes to mind) supply plugs to block the port giving the speaker a tighter bass output. Can this be done to any speaker that are ported? What are the drawbacks or advantages of doing so?
    Is there a difference between a speaker design that has the port on the rear vs the front?
     
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  2. Kal Rubinson

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  3. Tony V.

    Tony V. Moderator
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    Yes, I read that post but it does not speak to plugging a port on a speaker that dose not come with or say that you can plug the port.
     
  4. Kal Rubinson

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    You are right. For years, people have been advised to "put a sock in it" if they perceived problems with vented speakers placed close to walls. However, I doubt if any competently designed and optimized ported speaker would be improved by blocking a port, whether the company recommends it or not.
     
  5. Kerry Armes

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    There are really only two things that can damage your speaker in a home environment. Either the speaker had a defect from the factory or the speaker has been over-powered. Over-powering can cause damage in two main ways. One is causing a thermal failure of components due to the heat. Typically, this causes the enamel that coats the voice coil wire to get hot enough to melt and then you get a short in your voice coil. The second is by over-excursion. Over-excursion can cause a driver to incur physical damage to the voice coil (knocking wire loose) or the suspension (spider or surround separations).


    In a ported system, woofers unload below port tuning. Unloading is when the box provides no restorative force on the driver and the driver shows extreme excursion. So if you have a ported pox tuned to 50 Hz and played a 30 Hz tone, you would see some extreme excursion from the driver. A sealed box does not do this. It as the woofer tries to move more, which is required to play lower tone, the air inside the box tries to resist that movement and therefore will not see the same excursion. Here are two graphs with a typical 6” woofer (the Dayton RS180) tuned to 45 Hz and at 30 watts input power to illustrate the difference between ported and sealed in the same size enclosure.

    Graph1.gif Graph2.gif

    So the point is that there is that sealing the port will not damage your speaker. In fact, you are probably reducing the chances of damage by sealing up a ported speaker.
     
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  6. Tony V.

    Tony V. Moderator
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    Thank you Kerry, thats the info I was looking for.
    Ive seen that exact extreme excursion you mention on my Mission 765 speakers in my livingroom. They are rated down to 36Hz and using the song Funhouse from Flim & the BBs for example during the part where the train whistle and then door slam is heard the cones move alot but no sound is heard or felt as I am sure the sound is well below its output ability.
    I know a sock was mentioned by Kal but what is your recommendation to use as a plug?
     
  7. Kerry Armes

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    I like socks too if you want to seal it up pretty tight without worrying about it being permanent. They also come in black to match your port ;) You can use foam, but foam won't block as much air so it will act more like an aperiodic enclosure.
     
  8. Kal Rubinson

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    Hmmm. Unless the item is an imperfect plug, it should not make any difference. The socks have unspecified acoustical properties but, if they fit tightly, they should do the job, make no damage and be removable. I do not believe that anyone makes audiophile socks....................yet.

    I like the PSB plugs because they are solid thick rubber with finger grips for easy removal.
     
  9. tesseract

    tesseract Senior Admin
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    The calamity and vibration going on in a ported enclosure is much greater than in a sealed, due to the tune causing resonance.

    I once returned a pair of review speakers with the socks still in the ports. The manufacturer gave me a good ribbing over that one, heh.
     
  10. JStewart

    JStewart Active Member
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    Thanks for a good laugh. :)
     
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  11. Kal Rubinson

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    I'm guessing they were ribbed socks.:rofl:
     
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  12. tesseract

    tesseract Senior Admin
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    @Kal Rubinson :heehee:

    Ha! Well, I told them they were clean, at least. Put me out two good pairs of socks, though.
     
  13. BadJRT

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    Kerry,
    In the graph's you showed I don't see where SPL is depicted. I'm curious as to what effect less excursion had (due to port plugging) on SPL, in that particular test.

    Also, how does plugging a port compare with high passing a ported tower at say 40, 50, or 60 Hz? Isn't a port tuned by a manufacture for maximum spl at a certain frequency and then there's rolloff on each side? So if you high pass a speaker above the ports tuned frequency, what role is the port then playing, acoustically speaking?

    If I were going to run a 2.2 system and high pass the towers, that would allow me to position the towers slightly closer to a wall without plugging the ports? Or could a combination of both plugging and high passing end up being best? Are there ramifications to these tweeks I'm not considering?

    Disclaimer: Keep in mind I'm trying to learn and I'm possibly asking questions that don't fully make sense.

    Thanks, Brian
     

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