Cascading crossovers subwoofers etc.

Discussion in 'Home Theater Projects' started by Chris Popovich, Apr 16, 2004.

  1. Chris Popovich

    Chris Popovich Stunt Coordinator

    Oct 18, 1999
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    This was in part spurred by the recent thread about using a Paradigm X-30 in conjunction with the receiver's crossover etc.etc.

    Who here is really happy with JUST a 12dB/Octave crossover? A friend recently built a Tempest clone sub with the parts express 250 watt plate amp and the 12dB/oct crossover and it sounds..........bad unless it's crossed over lower. Why? Box was built well, sub works fine -just too easy to localize. He uses a Paradigm X-30 now (sub crossover turned all the way up) and is thrilled.

    I know in theory it may make the sound muddy to cascade crossovers, but I haven't found that to be true in actuality, at least for sub duty.

    I find that I can easily localize a sub if it's crossed @ 80Hz & 12dB/oct. I cannot even fathom having my sub crossed over at 80 Hz if (and this is a big if) there is no equalization (ala BFD).

    I had been running my Tumult crossed at 35Hz (and the Denon 80Hz crossover), but since the introduction of the BFD, this will probably change.

    What are your thoughts on this? I personally don't like hearing anything out of my sub except the lowest of the lows, and for this to occur, an 80Hz 12dB/oct crossover ain't going to cut it. Am I losing some of that 120Hz LFE info? Probably. But I personally don't care. What I'm losing there is made up for by having seamless deep bass that is not localizeable.

    /end rant
  2. David Gadd

    David Gadd Auditioning

    Aug 15, 2002
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    Chris: I commented in the other thread, but I'll repeat myself here.

    I absolutely disagree with the assertion that it is always (or even typically) better to use solely the crossover in the pre/pro.

    People always seem to assume that all preamps/processors do a competent job at crossing over between sub and mains. Mine certainly doesn't (e.g., 100 hz 12 db/octave low and high pass!?? and no high pass at all on any analog input). In my case, using the processor alone is a massive compromise (unless you like too high & too shallow roll off for the sub plus double bassing mains depending on which input you choose; I don't).

    Also, stereo subs and/or mains that are competent down lower (e.g. 50hz) are often partially or totally compromised by typical Dolby spec. processors with their typical 80hz 4th order low and 2nd order high passes. My speakers are transmission lines with a rolloff that starts substantially below 80hz. So, even if I did have a "good," "normal," Dolby spec. pre/pro., I'd STILL have double base issues from my mains since there is no way to force my mains to roll off at 12 dB/octave under 80hz which is ASSUMED to be the case under the Dolby standard.

    To summarize: I absolutely disagree that it is always better to use the crossover in the pre/pro. In fact, unless you have main speakers that roll off at 12 dB/octave under 80hz, you WILL HAVE midbass bloat and/or cancellation issues that can make your sub/main integration difficult at best. Again, Dolby assumes mains that most people DON'T own.

    I absolutely agree that a 12dB/octave low pass at 80hz or above doesn't cut it for a single sub.
  3. Wayne A. Pflughaupt

    Aug 5, 1999
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    Katy, TX
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    I agree, too. I’m using 24dB/octave filters with Linkwitz-Riley alignment @ 90Hz. Occasionally I can localize it with poorly EQ’s source material ( probably with an abnormal boost at and slightly above the crossover frequency). 80Hz would probably be a better choice.

    I’ve heard that if you match the crossover frequency of two crossovers you get their combined slopes. Don’t know if that’s true, but it makes sense.

    Defeating the unwanted crossover is not even an option for a lot of people. Few subs and receivers come with defeatabe crossovers.

    Wayne A. Pflughaupt

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