A Guide to Subwoofers

by Andrew Bishop

What makes for a great Subwoofer?

  • Sturdy cabinet construction preferably 18mm 13 laminate air pocket free Birch plywood
  • Ferrite cast alloy basket woofers 12", 15", 18" or 21" generally speaking (dependent on the cabinet design) the bigger the driver the lower the frequency response.
  • Class H or Class AB amplification, especially on the larger woofers when repetitive, quick deep bass is called for on genres such as 'drum n bass'.
  • Positioning - sub bass is not directional and can be enhanced by placing subs in corners.
  • Intelligent and innovative cabinet design such as Para Flex and certain scoop bin designs. There are many to choose from dependent on your personal needs/choice. All designs have their preferred applications.

Subwoofers can be Active or Passive. Active or Powered Subwoofers have Amplifiers built in to them and are typically used for smaller gigs, domestic applications or pubs and restaurants. Volume and frequency are controlled with 2 potentiometers on the rear of the the Amplifier panel. Class D amps are deployed to control temperatures in the sealed amp compartment.

Passive Subwoofers are driven with external amplifiers that are controlled by Speaker Management Processors. Many audio engineers prefer this as control is more precise and some say easier to control in a live situation especially if numerous bands are playing.

Many audio engineers driving twin 18" Passive Subwoofers rated at 3000w RMS (6000w Program prefer to drive these Subwoofers with outboard class H amplification due to the power rating.

What size Subwoofer has the deepest bass and what size hits hardest?

Acoustic engineers report that they get the deepest frequency responses from 21" drivers. For sheer punch most prefer the 18", especially outdoors. For indoor smaller events, 12" and 15" are tight, fast and punchy.

What is the crossover point for a Subwoofer?

A full range professional PA system is considered to be broken down in simple terms to Bass, Mid and Top. Subwoofers take care of everything up to around 105 Hz at which point the mid range speakers take over. The mid ranges speakers hand over to the Compression Drivers for frequencies in excess of 2 or 3,000 Hz dependent on the voicing and tone you prefer. At BishopSound we aim for a full range flat response from our packages from 30Hz to 20,000Hz.

If you have more unanswered questions about Subwoofers contact BishopSound for complimentary expert advice.