Discover What Is A Passive Subwoofer And How You Can Power It?

If you want to know about what is a passive subwoofer and how to power a passive subwoofer? Do not leave this place unless you are done!

Passive Subwoofer

What Is A Passive Subwoofer by speakerjournal.com

A passive subwoofer is a speaker that is not powered and only contains the necessary components to playback the bass frequencies. It receives wiring instructions from an amplifier, just like any other active speaker.

So, Passive Subwoofers are not self-powered Subwoofers. 

Functionalities Of Subwoofer

  1. Increasing the power of low range audio signals.
  2. Reproducing very low frequencies. 
  3. Enhancing musical sounds and effects in sound stereos or home theatres with excellent frequency responses over a limited range of audio frequencies. 
  4. Creating deep, extremely loud bass sounds that can be felt and heard by the audience in a public address system.

How To Power A Passive Subwoofer?

1) An amplifier is required to power the passive subwoofer. The amplifier sends an audio signal to the speaker, converting it into mechanical energy (sound). 

2) There are various types of loudspeakers like woofers, tweeters, mid-range speakers, horns etc. The loudspeakers used with subwoofers are called Passive Radiators or just plain old woofers.

3) It might be necessary to place a passive subwoofer near an AC outlet so you can plug it into the wall for power when using a home audio amplifier.

4) Using an electronic crossover will ensure that only low-frequency energy is sent to the subwoofer and high-frequency sounds are sent to regular speakers. 

5) Most powered subwoofers have their built-in crossover, so you don’t need to worry about using an external crossover.

6) A subwoofer should be placed in a corner if possible because sound waves will reflect from the floor and ceiling, allowing for maximum low-frequency output. Having it in a corner also reduces standing waves that are produced by the subwoofer’s output interacting with the room’s boundaries. Standing waves can distort the bass response.

7) Subwoofers also have a phase switch that allows you to reverse the output for correct subwoofer placement. The end of the sub where the power cord attaches should be connected to the amplifier’s positive (+) terminal, and the other end (the speaker wire connection) should be connected to the amplifier’s negative (-) terminal.

8) This is called “direct connection”, where the subwoofer is wired directly to an amplifier or receiver. It’s important to keep the amplifier channel and subwoofer in phase with each other for maximum performance.

9) Most powered subwoofers have a built-in crossover, so you don’t need to use an external crossover.

Subwoofer With Crossover

What Is A Passive Subwoofer by speakerjournal.com

Most subwoofers use passive crossovers that divide the incoming signal into high and low frequencies, sending the highs to your full-range speakers and routing the lows to the subwoofer. Passive crossovers are usually located near or inside a subwoofer’s cabinet. 

How Subwoofers Work

  1. Subwoofers work by using a woofer (a speaker that reproduces low-pitched frequencies) to push air and cause pressure waves.
  2. A subwoofer’s woofer is designed as a large diameter driver, capable of moving lots of air and delivering those pressure waves into the listening area more efficiently than any other type of speaker.
  3. Subwoofers can deliver deeper bass than regular speakers, with as much as a one-octave drop in response below the sub’s designed operating range, which is around 50 Hz.
  4. The cutoff frequency of a subwoofer typically starts at about 80 or 100 Hz and goes down to somewhere below 20 Hz.
  5. Subwoofers are commonly powered by an amplifier, which is often built into the subwoofer itself.
  6. The power range varies from about 5 to 500 watts for home subwoofers and up to thousands of watts for large speaker enclosures used in a PA system or recording studio.
  7.  The amplifier for a subwoofer provides enough power to compensate for the lower efficiency of the driver(s) and adds more low-end bass.

Why Subwoofers Are Used

  1. Overcoming the problem of non-directional bass sounds.
  2. To overcome the deficiencies of AM and FM radio, which cannot produce loud, low-frequency sound.
  3. To add more punch to the music in home theatre systems
  4. To extend the frequency range that loudspeakers can hear 
  5. The human ear does not detect high frequencies below 25 Hz, and therefore the quality of bass in an audio system is not much noticeable at the lower end of the audio spectrum. Additional subwoofers are used beyond the minimum two-speaker system (known as dual-subwoofer configuration) to get more bass response.
  6. Some listeners feel that low frequencies are more immersive and visceral than midrange and high frequencies. For this reason, a subwoofer may sometimes be the only speaker in an audio system.
  7. Subwoofers are sometimes used in home cinema to reproduce the low-pitched sounds of an explosion or a bass instrument (e.g., electronic synthesizer or electric guitar).

Difference Between Subwoofer & Speakers

What Is A Passive Subwoofer by speakerjournal.com
  1. Subwoofers can be active or passive, while speakers are active by default.
  2. Passive subwoofer (the most common type) is not powered and does not have a power amplifier.
  3. Subwoofers generally have one driver, whereas a speaker enclosure can consist of multiple drivers arranged to work together in the same enclosure to reproduce the entire frequency spectrum.
  4. Most subwoofers are very limited in power compared to a speaker enclosure with multiple drivers and high power amplification that can deliver much higher sound levels than a SINGLE subwoofer can.
  5. Subwoofers are often limited to one or two frequencies, while most speakers can reproduce audio across the entire frequency spectrum.
  6. Subwoofers typically have a single driver (one that moves back and forth like a piston to create sound), whereas speakers use multiple drivers housed in an enclosure to broaden their effective radiating area. 
  7. Subwoofers are mainly used to overcome the problem of non-directional bass sounds. Subwoofers are also sometimes used in home cinema to reproduce the low-pitched sounds of an explosion or a bass instrument (e.g., electronic synthesiser or electric guitar).
  8. I hope this article cleared all your doubts and was informative. Keep coming for more.