A subwoofer is speaker designed to reproduce the audio frequencies under 200Hz. These consist of the low frequency effects (LFE) track - the .1 - and bass managed content from the speaker system. Bass management is a function of the home theater AVR or pre-pro, and re-directs bass below a certain crossover frequency - normally 80Hz - to the subwoofer.
The cinematic reference requirement for subwoofer sound pressure level (SPL) output is 85dB program + 30dB headroom. On top of this we need to add some additional output capability for phase coherent bass managed information from the speaker system. Few home theater enthusiasts listen at true cinema reference, so overall output requirements can normally be relaxed 3 or 6dB.
Flat frequency response, with extension to 20Hz at the -3dB point. Once the sub is placed in a room, it's response will be non-flat due to room modes. Using multiple subs is therefore a pre-requisite for smoother and more consistent bass across multiple seats. Typically we will place one sub in each corner, but an engineered answer to the question 'how many and where?' requires design work.
High output to meet SPL requirements. Since it takes two sealed subs to equal one ported in terms of output <40Hz, we recommend ported subwoofers. Typically we will use four 12" or 15" ported subs, but an educated answer requires design work.
Shallow depth to integrate into speaker baffle walls and hide behind stretch fabric. We prefer subs to be <20" including clearance for cable management at rear, which unfortunately rules out most commercial ported subs.
Built in digital signal processing to allow best integration of multiple subwoofers, ideally: level, delay and polarity. With our typical four subs in corners approach, the rear pair need delay and level adjustments.
Triggered turn on / off, so that the sub can start up and shut down with the rest of the system. Some subs only offer auto on / off, which can result in subs turning off during the quiet parts of a movie.
Whilst not class leading in any area, in our opinion SVS offers the best package of attributes at the low-to-mid end of the home theater subwoofer market. Their subs offer high output coupled with great build quality and reliability, and do not audibly misbehave or distort.
The $800 PC-2000's combines a long throw 12" driver with a ported cylindrical enclosure. With most of the cabinet volume in the vertical dimension, the depth is under 17", and unlike conventional box subwoofers, no extra clearance is required for cable management at the rear.
Most of our rooms incorporate a speaker baffle wall at the front of the room and use fabric stretch walls to hide equipment. Commercially available subwoofers just didn't meet our requirements, so we worked with Power Sound Audio to develop an exclusive subwoofer system.
The PRO15.1 / PRO1600 is the result. It's a unique combination of a 800W/ch rack mount power amplification coupled with multiple high output 15" ported "slim" subwoofer cabinets. The 12" deep form factor, with no cable clearance requirement, allows for stealth installations. The rack mount amplifier puts the controls in the rack, not hidden behind fabric.
SVS and Power Sound Audio Pro are our main subwoofer brands, and most of our projects have either 2 or 4 subwoofers. Our projects normally utilize our PRO15.1 / PRO1600 subwoofer system, as recommended above. On occasion, there just isn't space for an in-room subwoofer, no matter how shallow, so we'll use in-wall subwoofers from Triad, JBL Synthesis or JL Audio. One day we'll develop our own high output in-wall, because we're not stoked on any of the commercially available options! If you want 18" or 24" sealed, we offer custom products from Seaton Sound and Deep Sea Sound.
Our Sub Number / Placement Optimization service creates a low frequency model of your room. Different sub number, placement and signal processing scenarios are run to find the smoothest frequency response and most SPL output across the key seats in your room.
The Audio Design service uses the calculated frequency response per seat from Low Frequency Optimization to determine the required output per subwoofer. Using this information we can make sure your subs will have enough output to meet SPL requirements and answer questions like: do I need a 12" or 15" subs?
Nyal Mellor, Founder, Acoustic Frontiers