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Old 10-14-2008, 03:08 PM   #2
Big Daddy Big Daddy is offline
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Jan 2008
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ACTIVE (POWERED) VS PASSIVE (UNPOWERED) SUBWOOFERS

Advantages of Powered Subwoofers
  • Powered subwoofers are very convenient like receivers.
  • Since everything is already built-in, they are easy to hook up.
  • They can be less expensive just like receivers versus separate components.
Disadvantages of Powered Subwoofers
  • The built-in amps on most, by not all, subwoofers are of lower quality.
  • They are less convenient for subwoofer placement as you need to find a wall AC outlet and run a long subwoofer cable to it.
  • If the amp goes bad (sometimes they do), it is not as easy to replace them.
  • Manufacturers do not always sell parts for older subwoofers.
  • People have reported cases of fire or smoke coming out of their powered subwoofers.
  • Some powered subwoofers do not come on when the signal is low. There are many reports on this, including some on this forum.
With passive subwoofers, you have two options: You can use an external dedicated subwoofer amplifier or use a general purpose amplifier. Dedicated subwoofer amps have a built-in crossover network. For general purpose external amplifiers, you need to add an external powered crossover.

Advantages of Passive Subwoofers (External Amplifier)
  • External amplifiers are higher quality with better power supply and circuits than plate amplifiers.
  • They can produce much more power.
  • A multichannel amplifier can power several passive subwoofers in a home theater room.
  • Passive subwoofers are easier and less expensive to build.
  • The cabinet can be larger and you have much more flexibility in placing the woofer and ports.
  • If the amplifier malfunctions, it can easily be replaced with any external amplifier.
  • There is less danger for fire or smoke.
  • One of the biggest advantages of passive subwoofers is flexibility in their placement. You can leave the external subwoofer amplifier with the rest of your equipment and just run speaker wires to the subwoofer. You do not need a wall AC outlet for them.
  • Long speaker wires are generally cheaper than long subwoofer cables.
  • Speaker wires, particularly flat wires, are much easier to hide than subwoofer cables.
  • A general purpose amplifier can be used to power other speakers in two-channel music when the subwoofer is not used
Disadvantage of Passive Subs
  • More complicated to setup.
  • External amplifiers can be more expensive.

I have a 15" passive subwoofer that I built with a quality driver. It is 4 ohms. The external crossover network cost me $70. I power it with a general purpose stereo Carver amplifier that I bought a few years ago. I have the amplifier hooked up in single channel mode. It supplies up to 1,500 watts of mono power to the subwoofer. It can shake the house. However, I have calibrated it with the rest of my system and set the volume to a reasonable level. The amplifier can easily outplay any plate amplifier.

I also have two modified passive 12" Hsu subwoofers. They are 4 ohms and a monster Cinepro multi-channel amplifier drives both of them. Because they are passive, I have a great deal of flexibility in their placement.

I have another passive DIY 12" passive subwoofer. It uses a 300 watt external dedicated subwoofer amplifier with an external Hsu crossover network. It performs great.

Last edited by Big Daddy; 09-26-2009 at 07:14 AM.
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