Has anyone tried those in-line FMOD X-overs from PE?

Discussion in 'Archived Threads 2001-2004' started by jeff lam, Feb 13, 2002.

  1. jeff lam

    jeff lam Screenwriter

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    I am wondering if these will work well with the sub output from my receiver to achieve a steeper x-over slope. Is the quality good enough to run with a QSC/Tempest combo?
    I am trying to find a cheaper alternative to buying a seperate crossover. It seems impossible to find a simple low pass filter anywhere. I would love to get a DSP-30 but that would cost more than the amp itself. My other options are BFD and seperate x-over, or these FMOD's. HOw good is the quality of these things?
    http://www.partsexpress.com/pe/showd..._ID=6767&DID=7
     
  2. ThomasW

    ThomasW Cinematographer

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  3. George Martin

    George Martin Stunt Coordinator

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    so whats the differance between car audio use and home theater use on a line level signle? they would do the same thing in either application fliter out the freqs. at a predetermined setting allowing the amp to only amplify those freqs that reach it. Be it low pass or high pass
     
  4. Wayne A. Pflughaupt

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    If this is what I thing it is, those things that plug in-line with the RCA cables?

    If so, they will work fine for what they do. The problem is they have shallow slopes, only 6dB/octave. For subs I think 24dB/octave is best, although most receivers only do 12dB/octave.

    Regards,

    Wayne A. Pflughaupt
     
  5. jeff lam

    jeff lam Screenwriter

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    Well,

    This is what is stated in the item description:

     
  6. Kerry Hackney

    Kerry Hackney Stunt Coordinator

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    Jeff.. The old prologic receiver that I had (Sony) did not feature any type of bass management so the sub out was in effect fullrange. I used a 100hz lowpass FMod for almost 2 years and it worked fine for my application. As far as cascade filtering with an FMod and an internal crossover/bass management, I am not sure of what the resultant slope might be. Beyond that I think it could also play around with the phase angles but I'm not sure. The info on the add is correct in that they are 2nd order 12db per octave. They are so cheap you really don't have that much to loose by trying them.

    Out of curiousity, what is the rolloff point of the existing filter and what FMod were you considering???
     
  7. jeff lam

    jeff lam Screenwriter

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    I believe my Yamaha receiver has a 90Hz 12dB/octave on the sub out. I would get the 100Hz LP FMOD since that's the closest one I found, or maybe I could do the 80Hz.
    Well, I figure I'd try them out. It would be much cheaper than a Crown or QSC Amp-mounted Module or a seperate unit like the Paradigm X-30. If these work out, the BFD and X-overs should run me less than $150. Sweet![​IMG]
    Kerry, You willing to sell me yours if you aren't using them anymore? One question also. Can they be used backwards? Meaning plugged directly into the receivers sub output using the female end as the output? If so, I would only need 1.
     
  8. Kerry Hackney

    Kerry Hackney Stunt Coordinator

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    Jeff,
    I don't think they are directional, but I would still use a patch cord and not plug it straight in... They are kinda long and can easily put a lot of stress on your terminal. Some receivers aren't that great on how strong their RCAs are to begin with. Send me your address and I'm sure we can work something out if you want one of mine. [​IMG] My daughter has claimed my old Sony and my old sub as soon as she saves for a power amp. So, I need to hang on to one of the two I've got...
     
  9. Richard Greene

    Richard Greene Stunt Coordinator

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    I've used FMODS for many years

    for both high-pass filters and

    low-pass filters. At first they were

    going to be temporary until I decided

    what active crossover to buy. But the

    FMODS worked so well I decided there was

    no reason to spend hundreds of dollars on

    a Marchand active crossover.

    The only problem I've found is the fixed

    FMOD frequencies (50, 70 & 100Hz.) may not be

    what you need.

    FMODS are the least expensive method

    to improve a 12dB/octave low-pass filter.

    While it would be nice if there was a

    90Hz. filter for you (or an 80Hz. filter

    that most other people want), your choice

    would have to be a 100Hz. or 70Hz. FMOD

    low=pass filter.

    My instincts would be to get the 70Hz.

    low-pass filter rather than the 100Hz.

    filter so you could reduce output more above

    100Hz. For most audiophiles, 90 and 100Hz. low-pass filters allow too much output above 100Hz. for the subwoofer

    to be sonically invisible.

    For my subwoofer I use two pairs of 50Hz. FMODS for 24dB/octave of low-pass filtering.

    One pair is plugged into the inputs of

    my subwoofer equalizer and another pair

    is plugged into the outputs of that

    equalizer. (If you plug a pair of

    50Hz. low-pass FMODS into another pair

    of 50Hz. low-pass FMODS, the turnover

    frequency seems to go lower -- possibly

    cut in half -- that's why my FMODS are

    not plugged into each other)
     
  10. Peter Jessee

    Peter Jessee Stunt Coordinator

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    I used a pair of 70 Hz FMODS with my Denon AVR1500 for a couple of years. I bought them from Crutchfield (didn't know about PE at the time), and had to buy them in pairs. When I tried a single FMOD, too much high frequency was leaking into my "Subs" (actually a pair of Yamaha NS500 2-way speakers with a ported 10" woofer, powered by an old NAD 3020). I tried two in series and voila, steep enough rolloff so I didn't hear voices coming from the woofers any more.

    I was only using them for bass, so I didn't notice any sonic problems from using them. I'm sure this is not the "audiophile approved" way to low pass your woofer, but it gets the job done when you're on a budget.

    Peter
     
  11. The3dg

    The3dg Auditioning

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    These are great any time you have RCAs in your system. They do say the male end goes toward the amp and stacking them splits the x-over FQ and doubles the roll-off. However, in my exprienc many HT integrated amps have adjustable subwoofer output FQ through hidden menus. Generally their default is set to 80Hz, the standard for THX & DTS. If you looking to get close to that with FMODs, you would need the pair of 150Hz stacked to get a crossover of 75Hz and a 24dB roll-off. I got the 100Hz Harison Labs FMODs from Parts Express and the 12dB roll-off with one isn't quite right and stacked makeing the x-over 50Hz creates a low end spike.
     
  12. The3dg

    The3dg Auditioning

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    I think this information from Harison Labs may be wrong. I think the cut-off FQ doesn't change, just the roll-off does. So I'm thinking about getting the pair of 75Hz low pass filters. Then i can add a third in line to try 36dB roll-off.
     
  13. The3dg

    The3dg Auditioning

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    I feel the best solution and the future of home entertainment systems is a computer based system with a good audio interface like Sound Blaster Omni Surround Sound 5.1, $60 on Amazon. I paid nearly $80 with the S&H for mine but, I found these cards to be impressive for the money. They give you great control over the subwoofer crossover including boost and excellent sound quality unlike the in-line FMODs. With earphones on, I never heard my music sound so good.
     

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