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Help. Is the passive crossover in the PE 250W amp any good, or get active x-over?

Discussion in 'Archived Threads 2001-2004' started by Javier_Huerta, Dec 13, 2002.

  1. Javier_Huerta

    Javier_Huerta Well-Known Member

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    I was wondering about this. Should I use the passive crossover on my PE 250W amp, or should I get an active crossover?

    My system uses MartinLogan Scenarios, an Adcom GFA-5400 amp, Luxman CD player, and a Tempest Adire Alignment sub. I was wondering if I should get an external crossover, and which! I can't find any good ones.

    If there is one, by any chance, can I find it in New York? I'll be there next week...

    TIA!
     
  2. Dan Pawlowski

    Dan Pawlowski Well-Known Member

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    I may be wrong but doesn't the PE amp come with an active Xover???
    Dan[​IMG]
     
  3. Peter Jessee

    Peter Jessee Well-Known Member

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  4. Eric Massey

    Eric Massey Active Member

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    If I read that page right, I think it said this amp has a high pass filter set at 30hz? Is this the "rumble filter" that they talk about on the partsexpress webpage for this amp? If not, does anyone know what frequency the "rumble filter" is set too and is there any way to change it?

    I'm considering using this amp on a sub tuned to 19 hz and it would kind of suck to have a hi pass set on 30hz.
     
  5. Javier_Huerta

    Javier_Huerta Well-Known Member

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    Thanks a lot for your answers! I checked the PDF manual online at PartsExpress and I couldn't find any references to an active crossover on the line-outputs. It's a good thing to know the subwoofer amp actually has one built-in, although a Q of 1.0 isn't exactly what I'd like for my speakers.
    I'll definitely be checking that link, Peter. Thanks for it, although hopefully I won't be needing it, since I'll be using a Behringer UltraCurve to auto-eq my room (still, a Q of 1.0? I don't think I'll be able to leave that alone).
    EDIT - Eric, it seems the amp is rolling off the frequencies below 30 Hz! I see the response at 20 Hz is around F3, which basically sucks, since I'm also tuning my subwoofer at a lower frequency (around 17-18 Hz). Check out Peter's link - it seems the only way to move the rumble filter from that frequency is to change R26 from 18K to 100K ohms. I wonder if I still remember how to solder, because this is the first mod I will attempt. [​IMG]
    Hmm. I just checked the PE manual for the amp. It specifically says it has no active crossover... check it out:
    So, which one is it? Full range output or electronic high-pass filter? [​IMG]
     
  6. Javier_Huerta

    Javier_Huerta Well-Known Member

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    Edit - double post.
     
  7. Baldemar Garcia

    Baldemar Garcia Well-Known Member

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    Guys,
    Trust John K.'s website. There is a high-pass active filter on the low-level outputs. There is a passive filter on the speaker level outputs (single cap, 100Hz/6dBper octave). The active high-pass filter on the low-level outputs is the same circuitry as the 'rumble' filter, so you could easily calculate/modify as you wish. BTW, the 300-794 no longer has a 30Hz,Q=1.6 rumble filter. They now ship with an Fc=20Hz,Q=1.? configuration, so it's not too bad. Still, I'd modify if I were tuning lower than 20Hz.
     
  8. Peter Jessee

    Peter Jessee Well-Known Member

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