Using high-pass filters for connection to sub?

Discussion in 'Speakers' started by Victor Chan, Apr 14, 2003.

  1. Victor Chan

    Victor Chan Stunt Coordinator

    Dec 10, 2002
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    I'm in the market for a subwoofer and recently read up on ACI's website about the use of high-pass filters to filter out bass signals from reaching the mains.

    I can see how this could theoretically clean up the sound of a system by making sure the amp in my A/V receiver doesn't have to devote power to drive low bass signals that will be handled by the subwoofer. But isn't the crossover in my receiver suppose to already accomplish this job?

    I'd be curious to know if any of you have used high-pass filters in your setup and whether or not it improved the sound of your mains compared to the tried and true LFE input to the sub connection method.

    Would something like ACI's high-pass filters help my system at all?

    If it matters, my setup is a Rotel RSX-1055 driving Ascend Acoustics CBM-170s (+/-2dB at 74Hz). Contemplating adding an Adire Rava (possibly an SE, though I'm not sure what the advantages of the Linkwitz-Riley crossover in the upgraded amp are for my setup... If someone could explain THAT to me, it would be greatly appreciated as well).

    Thanks in advance!
  2. Salvatore Restivo

    May 21, 2001
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    In a sat-sub speaker system, somewhere there is a component performing the bass-management function.

    In typical A/V systems, that component is the A/V receiver. The A/V receiver implements a crossover, usually at 80Hz. The high-pass signal gets routed to the satellite speakers, while the low-pass signal gets routed to the powered subwoofer.

    Sometimes, partiulcarly in 2-channel sat-sub systems, the subwoofer performs the bass-management function. The preamp's outputs are run to the subwoofer's full-range inputs. The subwoofer's high-pass outputs are routed to the (external) main amplifier's inputs to drive the satellite speakers. And the subwoofer itself uses the low-pass signal from its internal crossover to drive it's own internal amplifier and transducer.

    Alternatively, a separate bass management component could be used, such as an Outlaw ICBM or a Paradigm X-30.

    In all of these cases, the main amplifiers driving the satellite speakers work less hard because they do not have to push the current that would otherwise be needed by speakers to reproduce the low-frequency part of the signal. When amps work less hard, they tend to sound better. And you can get away with lower power (read: generally lower priced) amps. These are the more compelling advantages of active bi-amping and sat-sub systems in general.

    Linkwitz-Riley refers to the shape and rolloff of the high-pass filter used in the bass-management function.

    That's how I understand it. I hope it's helpful to you.

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