1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Passive subs/external amps- coming back in fashion?

Discussion in 'Subwoofers' started by nathan_silly, Apr 7, 2003.

  1. nathan_silly

    nathan_silly
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    A few years ago most people had passive subwoofers, and were using a spare amp to drive a passive subwoofer.

    Dolby Digital started to appear- and people upgraded to active subs due to their adjustability.

    However nowadays with better crossovers in the processor (settings of 40,80 & 120hz) you do not need another crossover further down the line (in the sub amp module) So it's more preferable to go for a passive subwoofer with a external amp (otherwise paying for a crossover in a subwoofer which isn't used)

    Also you can change amps easily, and adjust volume from the racking.

    Thinking about a SVS CS-Ultra, as I don't need a crossover, and prefer to get a powerful standalone amp rather being lumped with the built-in amps.

    Comments?
     
  2. deckard

    deckard
    Standard Member

    Joined:
    Dec 4, 2002
    Messages:
    425
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    16
    Location:
    leicester
    Ratings:
    +0
    Sounds pretty logical really if you're using the onboard crossover, I guess the only thing you might miss out on is a variable phase control - you'd just have 0 and 180 deg.

    You'd also need to make sure that the power amp you use has the correct gain for your setup - too much and your processor won't be able to set the volume low enough (even if you set -20dB) too little and the reverse could be true.
     
  3. nathan_silly

    nathan_silly
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
  4. deckard

    deckard
    Standard Member

    Joined:
    Dec 4, 2002
    Messages:
    425
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    16
    Location:
    leicester
    Ratings:
    +0
    Mmmm...

    Soon as you start adding variable gain power amps and other things in the signal chain you start losing the purity which was a good idea in the first place, you may as well buy an active sub with a bypassable crossover.
     
  5. nathan_silly

    nathan_silly
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    If using a standard poweramp-probably best then is to use a cheap adjustable pot, and set the right levels (with the processor set in the middle). Then use a multi-meter to get the value of the pot- then replace the pot with a high quality fixed attenuated resistor.

    Wouldn't use the sub-sonic filter myself.
     
  6. deckard

    deckard
    Standard Member

    Joined:
    Dec 4, 2002
    Messages:
    425
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    16
    Location:
    leicester
    Ratings:
    +0
    Absolutely, but the more 'elegant' solution as I mentioned is to use a poweramp with the correct gain in the first place to allow level setting from the processor. Although I guess that would mean have to home demo the amps to make sure they were suitable.

    As for myself, I've just joined the Velo club with a CHT-15 and, as Nathan has suggested (and is a good idea), bypass the crossover and use my processors' bass management. Personally I don't think I'll ever need any more than 300w of sub amplification so I'm not sold on the 'upgradability' idea.

    Anyone else out there got any thoughts?
     
  7. wookie

    wookie
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    What about EQ??:lesson:
    Closed or sealed boxes need eq boost to give good extension.
    a closed box rolls off steeply @ 24db per octave.
    You would need about +12db at 20hz to get something near a flat response.

    Ideally the eq would be an inverse boost of the subs rolloff response without the eq.

    Example:
    Passive closed box Sub measures -12db @ 30Hz:lesson:
    To get a flatish response you would need a +12db boost @30Hz.

    A high quality car equalizer could be used in line between pre out and power amp input.

    Ported subs can be fiddled with to obtain the sensitivity and output desired.

    I prefer closed box as they are tighter and can slam without farty port noise.:laugh:
     
  8. wookie

    wookie
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    What about EQ??:lesson:
    Closed or sealed boxes need eq boost to give good extension.
    a closed box rolls off steeply @ 24db per octave.
    You would need about +12db at 20hz to get something near a flat response.

    Ideally the eq would be an inverse boost of the subs rolloff response without the eq.

    Example:
    Passive closed box Sub measures -12db @ 30Hz:lesson:
    To get a flatish response you would need a +12db boost @30Hz.

    A high quality car equalizer could be used in line between pre out and power amp input.

    Ported subs can be fiddled with to obtain the sensitivity and output desired.

    I prefer closed box as they are tighter and can slam without farty port noise.:laugh:
     
  9. nathan_silly

    nathan_silly
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0

Share This Page

Loading...