Low pass filter ICBM bass Management question.

Discussion in 'Archived Threads 2001-2004' started by Paul Hillenbrand, Oct 11, 2001.

  1. Paul Hillenbrand

    Paul Hillenbrand Screenwriter

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    For DVD-Audio, I want to use the Outlaw ICBM in my system for bass management.
    My subwoofers now use the 80Hz 24 dB/octave 4th ORDER Linkwitz-Riley (THX) low pass filter found in THX controllers.
    The ICBM owners manual says they use the "special" 6th order (36 dB/octave) response Low pass filter for THX-certified model subwoofers.
    What audible difference will there be between the two filters and is this going to sound good?
    Thanks for any and all information you can give me.
    Paul
     
  2. RAF

    RAF Lead Actor

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    Paul,
    I was wondering the exact same thing. I'm taking delivery today on an ICBM and I also use THX compliant subs (actually an M&K THX350 and an SVS 16-46PC). My initial thoughts on this are that I will set the ICBM Lowpass Special/Normal switch to Normal and let the current filters contained in the subwoofers take care of business. I don't want to change the settings on the subwoofers themselves for DVD-Audio since the majority of my viewing/listening is still in the digital mode and this would require re-adjusting the subwoofers whenever I switched source material.
    Of course, as the ICBM manual suggests, I'll give the "Special" 6th order setting a listen and let my ears (and other senses) be the final judge.
    I'm going to give Tom V. from SVS a heads-up on this thread. Perhaps he can provide some more technical backup on this matter.
    ------------------
    RAF
    [Demented Video Dude since 1997]
    [Computer Maven since 1956]
    ["PITA" since 1942]
    My HT (latest update 02/05/01)
     
  3. RAF

    RAF Lead Actor

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    **Update**
    My ICBM arrived late yesterday afternoon and I incorporated it into my system. What a nice piece of equipment! It does exactly what it advertises. Low frequencies of significance have returned to my DVD-Audio listening stage.
    I'm currently using 80Hz crossover points for all my speakers (M&K S150s and SS150's) as well as normal settings for the subs (M&K THX 350 and SVS 16-46PC). Since I haven't had much time to do some tweaking and experimenting yet I figured that I would start with some logical settings.
    I did try the 6th order sub setting mentioned in this thread and, from my limited experience at this point, did not hear any audible (or tactile) difference. I'll let you know if I come up with any other settings down the road that improve the sound.
    Remember, everyone's HT environment is unique so what is good for me, might not be so for you. The beauty of the ICBM is that you have so many options to tailor the sound to your particular requirements.
    (Tom V. has agreed to contribute to this thread a little later.)
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    RAF
    [Demented Video Dude since 1997]
    [Computer Maven since 1956]
    ["PITA" since 1942]
    My HT (latest update 02/05/01)
     
  4. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    The main issue is the 24/36dB octave slope on the LP side of the woofage?
    I don't think it's going to make much difference really. On paper...the 36dB slope might lead to less *bleed thru* of voice and stuff. However, if you're having an issue like this with a 24dB/octave slope...something's probably amiss in your components or setup procedures. I think the higher you LP the sub...the more benefit you may realize from the steeper slope though.(if you LP 100hz and up). I suppsoe(and this IS a reach)...if you have some sort of room induced peak in the octave just above the LP set-point...using the steeper filter could tame that a little too?
    The ICBM looks like a cool tweak though...I bet outlaw sells a lot of them!
    TV
     
  5. RAF

    RAF Lead Actor

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    Thanks, Tom, for the input on this. As I said, I didn't notice a significant difference between the two settings so I just kept everything "normal" as I previously outlined.
    And yes, the ICBM does what it is supposed to, as advertised. In my opinion, well worth the money if you have a DVD-Audio or multichannel SACD player that lacks the proper bass management.
    Very impressive and a well built module. (Kinda reminds me of the quality found in the SVS products).
    [​IMG]
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    RAF
    [Demented Video Dude since 1997]
    [Computer Maven since 1956]
    ["PITA" since 1942]
    My HT (latest update 02/05/01)
     
  6. Paul Hillenbrand

    Paul Hillenbrand Screenwriter

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    Many thanks RAF for alerting TV to this thread. It is very much appreciated. [​IMG]
    Thank you Tom for taking the time to post your response. Before this, I didn't have a clue if the ICBM would be compatible with my system. Now I know I can use one with confidence.
    Best Regards,
    Paul
     
  7. John Kotches

    John Kotches Cinematographer

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    The ICBM has two crossover curves, which are symmetric low and high pass.
    The standard curve is 12dB octave, the "other" (sorry it isn't in front of me to get the correct name) is 36dB/octave.
    The 36dB octave crossover is especially useful for THX monitors, which are designed around a -3dB point of 80Hz. Crossing over with a 12dB/octave curve with significant content below 80Hz could (in theory) be damaging to the speaker. In practice, probably not.
    Which to use depends on:
    1) How close your crossover point is to the speakers -3dB point.
    2) Which sound you prefer.
    Regards,
    ------------------
    John Kotches
    Contributing Writer
    Secrets of Home Theater and High Fidelity
     

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