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Thread: Question on integrating passive sub with Sierra 2's

  1. #1
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    Default Question on integrating passive sub with Sierra 2's

    BACKGROUND: Ordered a pair of Sierra 2's for use in a 2.1 system (passive sub) for music only use.
    - The passive sub is an Optimus Pro SW 12 I refurbished and have wired between a HK3485 AVR and the L/R speakers like in the following diagram, except the depicted "in-walls" will actually be Sierra 2's and the sub is NOT an in-wall:

    cx1002wiring.png

    - I replaced the sub's original (lousy ~200Hz) crossover with a better Parasound CX-1002 crossover with the following specs (from Parasound):

    "120 Hz low pass crossover, 12dB/octave
    120 Hz high pass crossover, 12dB/octave

    Oversize inductors for high power handling without distortion
    Low insertion loss to prevent loss of efficiency"

    QUESTION: Should I anticipate any issues with the sub's 120Hz crossover freq and 12dB/octave slope vis-a-vis the Sierra 2's low end capability? In another words, would sending frequencies below ~120Hz for the passive sub to reproduce detract from the overall bass response (Sierra 2's are spec'd down to ~45Hz).

    Buying a new sub is not an option, having just bought the 2's, but other options include:
    1) Not using the passive sub
    2) Replace/adjust the sub's crossover to a lower frequency (such as ??)

    Thanks in advance.
    Last edited by XEagleDriver; 11-23-2015 at 11:00 AM.
    Cheers,
    XEagleDriver

  2. #2
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    Default Re: Question on integrating passive sub with Sierra 2's

    If possible, lower the crossover to 80Hz max. The Sierra-2's will most likely produce a higher quality sound than the sub at those frequencies which are WELL within the -2's range.
    Ed

  3. #3
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    Default Re: Question on integrating passive sub with Sierra 2's

    Thanks, that was what my audio spidey sense was telling me as I wrote the post.
    Cheers,
    XEagleDriver

  4. #4
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    Default Re: Question on integrating passive sub with Sierra 2's

    Quote Originally Posted by XEagleDriver View Post
    Thanks, that was what my audio spidey sense was telling me as I wrote the post.
    120Hz is much too high... I would recommend a 60Hz crossover, but since I have no data about this subwoofer, you are really going to need to do this by ear. There is much more to a subwoofer than just an amplifier and a crossover. Is the sub properly EQ'd for a flat frequency response? Do you have a phase control? Too many variables here to provide you with a definitive answer...
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

  5. #5
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    Default Re: Question on integrating passive sub with Sierra 2's

    Think late 90s/early 00s old school, prior to amplified subs 😆
    - No amplifier (passive); no phase, no EQ, just a fixed crossover at ~120Hz.

    Will try with and without, with the expectation without is probably going to win the day.

    Thanks,
    XEagleDriver

  6. #6
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    Default Re: Question on integrating passive sub with Sierra 2's

    To close the loop . . . the S2's arrived and sound amazing.

    My wife (a singer) and I conducted an initial comparison of the bass response both with and without the passive Optimus sub described in a previous post.

    We used Joshua Bell's At Home With Friends album which has a good mix of instruments, percussion, and vocals.

    Our conclusion was the bass response from the Sierra-2 speakers was much tighter, clearer, and more accurate without the passive sub than with it. In addition, the RAAL tweeter was extremely impressive, providing the best clarity and detail I have heard.
    Cheers,
    XEagleDriver

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