Front-Ported v Rear -Ported MAINS

Discussion in 'Speakers & Subwoofers' started by Tom McGary, Sep 5, 2003.

  1. Tom McGary

    Tom McGary Auditioning

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    Yesterday I went to my local Hi-end audio store to give some speakers a listen. I auditioned the Paradigm Monitor 11s and also listen (briefly) to some Klipsch RF-7s. The sales associate assisting me was, lets say, very opinionated, and said something that I had never considered or heard before.

    He said a rear-ported speaker will provide a more "3-D" (meaning not just left and right positioning, but also a near and far ambience) image than a front ported. He illustrated this when I was listening to an orchestra with chorus piece when he switched from the front-ported Monitor 11s to the rear ported RF-7s. The spaciouness of the RF-7s did seemed more three dimensional.

    I had always thought that the port was the tuning/breathing apparatus for the woofers, not the tweeter-which is the primary contributer to the "airness" or "spaciousness" to a speakers sound.

    Is this correct? Does anyone know about advantages/disadvantages with front and rear ported mains?
     
  2. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    I doupt that the difference you heard was because of the rear location of the port. There are other differences between the speakers, including of course their position in the room. You are correct that the port has no effect on high frequencies. It extends the low end output of the woofer. Typically, the port outputs significant energy in the 40 to 100 Hz range which is minimally localizable and therefore plays little role in the image. The tradeoff of front vs rear port location is as follows. Front location has the problem of enhancing cancillation between the port output and the woofer output in the range where they are both active. Their outputs are out of phase- ie, the port is sucking while the woofer is pushing and vice versa. With a rear location, the output of the port smacks into the wall behind the cabinet. This is why rear ported speakers should ideally be 3 feet or so away from a wall.
     
  3. Tim Ranger

    Tim Ranger Stunt Coordinator

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    Tom

    You are right and the saleman is either ignorant or intending to mislead. Like said, the port energy is only below 100Hz, more likely only below about 50Hz. Very non-directional.
     
  4. terence

    terence Supporting Actor

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    Tim & Brian are right, I too believe the salesman is lacking in knowledge or he is full of [email protected]#t! I hate it when some sales people will fabricate or just say anything to sell you something because they don't have a clue or they are just not honest.[​IMG]
     
  5. ChrisLazarko

    ChrisLazarko Supporting Actor

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    Yeah it shouldn't make a difference at all. I think the reason it might have sounded so much more "full" is because Klipsch uses Horn Loaded Tweeters which and I think it has something like a 90 degree angle so it should give a little bit more of a 3d feeling to it. Basically the salesman had no idea what he was selling although I love Klipsch myself... That should be a simple question that he should have been able to answer.
     
  6. Tom McGary

    Tom McGary Auditioning

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    Thanks alot for the response! I knew something was not adding up with the salesman's arguement.

    Brian:
    While there is the potential for cancellation with the front ported alignment, are there any disadvantages to the rear port?
     
  7. Bob-N

    Bob-N Supporting Actor

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    The only I would note is what has been mentioned before: rear wall location. I don't have a very deep living room so my mains need to be fairly close to the rear wall. That eliminated a lot of rear ported designs for my situation.
     
  8. Brian Bunge

    Brian Bunge Producer

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    You can also get some midrange bleedthrough from a front mounted port. That's one reason why many designs mount ports on the rear.
     

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