Rear Ported JBLs... Phil Iturralde??????

Discussion in 'Speakers' started by John*DB, Sep 5, 2004.

  1. John*DB

    John*DB Stunt Coordinator

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    Okay, if any of you have been following my posts lately you can gather I am not a veteran in the world of HT.

    I NEED ADVICE!!

    I am hours away from purchasing 4 JBL E20s (front and rear) , EC35, and E250 sub.

    NOW I see some posts mentioning certain positioning problems for the E20s. I have NO CLUE what rear ported means or how this will effect my set up.

    Help me out. I want 4 of the same so the crossover will be seemless. I like the size of the 20s and dont want to scale down to the E10s.

    All help is appreciated!!
     
  2. DorianBryant

    DorianBryant Screenwriter

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    Rear ported means that the poort is in the back of the speaker. Meaning to acheive proper bass extension/sound you want to avoid placing the E20 directly against the wall. Give them some room to breathe. You will be fine. you may want to play around with the postioning of the speakers in your room to see how the sound varies anyway. Sounds like a good set-up. Glad to hear you will be using the EC35 as well.
     
  3. Tim Stumpf

    Tim Stumpf Stunt Coordinator

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    What Dorian said. I just want to add that you'll want to avoid putting rear ported speakers in an entertainment center or any other enclosed space that would block or muffle the rear ports. Ported speakers rely on the volume of the cabinet to produce bass, so if you block the vent, you'll compromise the performance of the speaker. If you're using an entertainment center, you'd be better using front ported speakers if you want the port option.
     
  4. Phil Iturralde

    Phil Iturralde Screenwriter

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    John, ... the two comments by DorianBryant & Tim Stumpfis are correct and contains excellent advise!

    FYI: The following descriptions will clear up what they mean:

    Ported Enclosure: Type of speaker enclosure which uses a port to allow air to travel from the inside of the box to the outside of the box taking full advantage of a speaker driver’s output and increasing sound pressure (sound output or volume) by 2 to 3 dB compared to a similar speaker with a sealed enclosure (see Bass Reflex).

    Bass Reflex Type of speaker enclosure which uses a port to increase bass output for a given power input resulting in 2 to 3 dB (decibels) more sound pressure than a similar sealed enclosure (also known as an acoustic suspension enclosure).

    ----

    The concern about the rear ports are generally for the surround channels speakers, especially so if they are to be wall-mounted! Note that most wall speaker wall-mounting brackets will provide the proper space (approx. 1-1/2" to 2" min.) away from the wall for the rear port to breath (not an issue for front ported speakers).

    Phil
     
  5. John*DB

    John*DB Stunt Coordinator

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    I sure appreciate your advice. Thank you so much. This is what I was planning on. Please take a minute to let me know if this sounds ok.

    Viewing (front) wall. I have two tall bookcases on either end. In between the tall bookcases is an 8 foot long - 2 1/2 foot high bookcase. EC35 in the middle of 8 ft bookcase. Fronts on a middle shelf of the TALL bookcases on either side. *** If I toe-in the fronts a tiny bit and move them away a "tad" from the back of the book case - will that be sufficiet?

    REAR E20s: Facing eachother approx. 2 ft behind me

    Right rear in a corner book case (will scoot out as far as possible from bookcase (1-2 in. ???)

    Left rear - no problem - will be on some sort of stand (haven't researched what type or how to do that yet)

    Thanks!!!!!!!!!!

    John
     
  6. Phil Iturralde

    Phil Iturralde Screenwriter

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    John - sounds OK, based on what you described above, ... since most bookshelfs/bookcase are approx. 12" deep.

    The E20 cabinet is 8-1/8" deep, and moving the E20 front speaker baffle edge to the front edge (maybe slightly over) of the bookshelf will leave approx. 3-1/2" of space behind the E20 cabinet!

    NOTE: Use the JBL supplied little round rubber bumper pads to isolate the E20/EC35 cabinet from the bookshelf/bookcase surface.

    Let us know how it goes!

    Later,
    Phil
     
  7. PeterK

    PeterK Supporting Actor

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    Just a question john, why did you go with the E20's instead of the E30's they will match your EC35 better as they are a 6" woofer as is your center. The E20's are a better match for the EC25 center channel. Though i am sure the difference is minimal anyway.

    cheers [​IMG]
     
  8. John*DB

    John*DB Stunt Coordinator

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    Money, size, and loudness

    E20 will fit better, not be as big, less powerful for a small room, save a little money for my projector and receiver
     
  9. DorianBryant

    DorianBryant Screenwriter

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    Actually the EC35 does not have a 6" woofer. The EC35 is the same as the EC25 except it has the additional midrange. It will work well with the E20 or E30.

    Very similar to the differences between the N and S center speakers except the S center had a 4" mid and a 1" full titanium tweet.
     
  10. PeterK

    PeterK Supporting Actor

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    oops
     
  11. Phil Iturralde

    Phil Iturralde Screenwriter

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    The same can be said about the 'dedicated' EC35 Center Channel speaker. Mix and match, ... the E-Series speaker lineup with either E-Series Center CH Speaker, ... to your hearts content!

    Phil
     

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