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Thread: How close can CMT340s be to back wall w/o getting boomy?

  1. #1
    Join Date
    Apr 2010
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    Just outside Pearland, TX
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    Question How close can CMT340s be to back wall w/o getting boomy?

    I'm moving to a new office and I'll have space for speakers literally on a bookshelf that's 14.5" deep. Out of respect for the office below me, no sub.

    I'd like to get the 340s, but that's only 4" of clearance behind the speaker. Is that enough or will the bass get boomy or otherwise unhappy? Or are there plugs for the 340s like there there are for the Sierra-1s?

    -Mike

    (P.S. I'd love to do the front-ported Lunas but the budget does not extend that far.)
    .
    Very pleased Sierra-1 NrT and Sierra-1 owner

  2. #2
    Join Date
    Aug 2003
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    Default Re: How close can CMT340s be to back wall w/o getting boomy?

    Quote Originally Posted by SunByrne View Post
    I'm moving to a new office and I'll have space for speakers literally on a bookshelf that's 14.5" deep. Out of respect for the office below me, no sub.

    I'd like to get the 340s, but that's only 4" of clearance behind the speaker. Is that enough or will the bass get boomy or otherwise unhappy? Or are there plugs for the 340s like there there are for the Sierra-1s?

    -Mike

    (P.S. I'd love to do the front-ported Lunas but the budget does not extend that far.)
    I believe I responded in the other thread - but yes, 4" of clearance behind the 340's is fine. Bass does not get boomy due to the port being to close, bass gets boomy due to reinforcement - really no difference for any speaker. The bass wavelengths being produced by the rear port are typically 20 feet and longer - a few inches make no difference...

    The reason you need some clearance behind a rear ported speaker is that the port needs some space so that air can flow freely without being slowed down. In the case of the 340, with a wide diameter port, 4" is fine.

    Hope this helps!
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

  3. #3
    Join Date
    Apr 2010
    Location
    Just outside Pearland, TX
    Posts
    55

    Default Re: How close can CMT340s be to back wall w/o getting boomy?

    Thanks, Dave, very helpful. I really want to get Ascends because I love how neutral they are. Every time I listen to other speakers in a similar price range with something you make, I like the Ascends better. (I have good access to other Ascends since my brother has 340s and my dad has 170s so I have certain expectations at those price points.)

    It'd be great if there were a good source somewhere about handling speaker placement. Not so much "what's the ideal" because a lot of us don't have ideal situations, but "what's going to become a problem and why?" for real spaces. I've heard so many different things about how much space is necessary for front vs. rear port. There's a lot of misinformation out there and I'm not an expert on this issue so it'd be nice if there was a good source of fact-based information.

    For example, elsewhere I think you said the minimum for the 340s was 3" but now it looks like I don't even have that—the office's prior occupant told me the shelves were 14.5" deep but I got in there and measured them myself last week and they're only 13.25" deep. That's not the recommended 3" for the 340s, so now I'm worried. I may be able to build a little forward extension onto the shelf to get the needed clearance, but I'm not sure.

    Another "for example": does the Sierra-1 need more space because it has a narrower port? Since the B-stock Sierra-1s are only $100 more than the 340s I might go that way (above my budget but man I love the Sierras), but not if the space is going to be a problem. (And, just out of curiosity, what about the 170s? In the pics that port looks narrower than the port on the 340s.)

    Just trying to figure out what my options are...
    .
    Very pleased Sierra-1 NrT and Sierra-1 owner

  4. #4
    Join Date
    Aug 2003
    Location
    USA
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    Default Re: How close can CMT340s be to back wall w/o getting boomy?

    Please feel free to contact me directly. It is a bit easier for me to respond by email for technical questions like these as opposed to on the forum.

    Thanks!!
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

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