Sub configuration?

Discussion in 'Speakers & Subwoofers' started by Justin_collins, Jul 21, 2003.

  1. Justin_collins

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    Hello everyone. I have a slight problem with my current set up. I have: onkyo 878 running paradigm studio cc and two refernce 20's. An adcom 200x2 running my studio 100's. I want to add a sub but also want to use my towers to their full potential. I'm only aware of two methods to connect a sub to my system. One being speaker level and the other line level. Line level is fine but cuts off frequencies below 80hz to my towers, which I don't want. Speaker level requires a lot more expensive speaker cable.
    Can anyone please help me with this problem?
    Thanks for your time
    Any comments are welcome
     
  2. Edward J M

    Edward J M Cinematographer

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    I'm assuming this is a HT rig and you are running the Adcom via the L/R pre-outs on the 878?

    http://www.hometheaterhifi.com/volum...rs-9-2002.html

    This IMO is the seminal article on subwoofer crossover frequency and other related subjects.

    The high pass filter rate in your 878 is probably 12 dB/octave (confirm with Onkyo). If you select a crossover frequency of 80 Hz for all your speakers, the 100's will only be artificially down 6 dB at 60 Hz and 12 dB down at 40 Hz.

    The 100's are only flat to 40 Hz; while they could probably tolerate being high passed at a somewhat lower frequency (say 60 Hz), the bass capabilities of the towers is hardly being wasted even if they are high passed at 80 Hz. They will still be allowed to play pretty deep, and the dynamic range will improve, along with a reduction in THD and IMD since the load on the Adcom will be much lighter and the cone excursion in the 100 woofs will be significantly less.

    If you are dead set against high passing your 100's, then as an alternative, you could set your mains to large, and the rest of your speakers to small with an 80 Hz high pass, and set your subwoofer to on/yes. That will send the 100's a full range signal and send the sub the LFE channel and the low passed bass from the other surround speakers.

    One caveat: The above recommendation to high pass the 100's is only if you will be using a really high quality sub that can play bass better than the 100's below 60-80 Hz and will also extend the overall FR of the system to well below what the 100's can manage.

    Regards,

    Ed
     
  3. Justin_collins

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    Thanks for the info.
    "One caveat: The above recommendation to high pass the 100's is only if you will be using a really high quality sub that can play bass better than the 100's below 60-80 Hz and will also extend the overall FR of the system to well below what the 100's can manage."

    Could you recommend a sub that would be as good for music as well as movies.
     
  4. Edward J M

    Edward J M Cinematographer

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  5. Justin_collins

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    My current room (I'm building a house soon) is an acoustic nightmare. I will be building a theater room in my basement so I don't know how big it will be. I like my HT and music to be loud but crystal clear. I would like to spend no more than a thousand on a sub or subs.
    Ed could you help me understand what you mean by

    "The high pass filter rate in your 878 is probably 12 dB/octave (confirm with Onkyo). If you select a crossover frequency of 80 Hz for all your speakers, the 100's will only be artificially down 6 dB at 60 Hz and 12 dB down at 40 Hz"

    I'm not sure what you mean by this.
    Thanks again.
     
  6. Edward J M

    Edward J M Cinematographer

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    Justin:

    The bass management circuit consists of high and low pass filters. High pass refers to the surround speakers you have set to small. Low pass refers to the subwoofer.

    If you select a crossover frequency of 80 Hz, the AVR will allow the surround speakers to play above 80 Hz, and the subwoofer to play below 80 Hz.

    To smooth the transition between the surrounds and the sub, the AVR will also allow the surround speakers to play below 80 Hz, albeit at a constantly diminishing rate of volume. The rate of volume reduction is known as the "filter rate".

    A typical high pass filter rate is 12 dB/octave. So if you select 80 Hz as your crossover frequency, an octave below that would be 40 Hz. The high pass filter would impose a 6 dB reduction in volume by 60 Hz, and a 12 dB reduction in volume by 40 Hz, as compared to the volume at 80 Hz and above.

    Conversely, the low pass filter rate for the subwoofer is usually steeper, on the order to 24 dB/octave. The reason the low pass filter rate is so steep is to prevent the subwoofer from playing much at all above the selected crossover point which would otherwise allow it to be easily localized and/or play above its design limits.

    If your budget is "around" $1,000 for a subwoofer, take a look at these offerings:

    SVS PB2-Plus $1,200
    SVS PB1-Plus $1,000
    SVS 20-39PC-Plus $825

    Acoustic Visions Kilamanjaro: $1,500
    Acoustic Visions Sadhara: $1,000

    HSU TN1220HO w/500 watt amp: $1,200
    HSU VTF-3: $850

    R.A.D. Tumult based sub (call for price)

    Stryke Audio Thunder 12: $1,200

    Regards,

    Ed
     

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