Welcome to Acoustic Frontiers Blog

Creating a system you love shouldn't be difficult. The Acoustic Frontiers blog is here to help.

Using subwoofers to improve sound quality: Part 1 - Speaker Boundary Interference

by Nyal Mellor October 19, 2010

An introduction to speaker boundary interference

Deep nulls in the frequency response in the bass region can be caused by phase cancellation between the direct sound wave from a sound producing device and the indirect sound wave that has reflected from a nearby boundary such as the floor, ceiling or walls. This phenomenon is called speaker boundary interference or SBIR for short. This measurement shows an example of SBIR effects:

<p>The frequency of the SBIR dip changes according to distance from the boundary according to the formula:</p>
<p>Frequency of cancellation = speed of sound / (2 x path length difference)</p>
<p>This relationship between cancellation frequency and path length difference can be exploited to remove SBIR effects.</p>
<h3>How using a subwoofer can reduce speaker boundary inteference</h3>
<p>A simplified example and picture will help illustrate both SBIR and how using a subwoofer can reduce its effects.</p>
<p style= /></span></p>
<p>Take the common situation of a speaker which is placed 4ft out from the back wall as in the diagram. Using the formula introduced above we can calculate a cancellation at 71Hz due to a path length difference between the direct and indirect sound of 8ft. Now a sub is introduced into the system and a crossover point of 80Hz selected. The sub is placed 1ft from the back wall. Calculating the theoretical cancellation frequency for the sub, we see that this is at <span style=141 282Hz. Since the sub is crossed over at 80Hz there is only limited cancellation at 141 282Hz since the frequency response is many dB down as a result of the rolloff of frequencies above the crossover point. The cancellation caused by the main speakers being 4ft out from the back wall is also reduced since the crossover is attenuating frequencies below the crossover point.

What do you think about this cunning subwoofery?

Nyal Mellor
Nyal Mellor


Also in Low Frequency Optimization

JL Audio show the E112 - a new lower cost 12" subwoofer - at CES

by Nyal Mellor January 22, 2012 0 Comments

JL Audio, the manufacturer of the superb Fathom F110, F112, F113, F212 and Gotham subwoofers showed their new E112 subwoofer at CES. I have seen this sub before, at CI Expo, a custom integrator event that was held in Berkeley this year. But this is the first time I had my camera with me to take some photos!

JL Audio E112 subwoofer

Continue Reading

Subwoofer setup and integration 101: sub crossover frequency, slope and phase for two channel systems

by Nyal Mellor October 11, 2011 0 Comments

Continue Reading

Two channel amplifiers with bass management and room correction!

by Nyal Mellor May 13, 2011 0 Comments

Recently I have become aware of a new class of product: two channel amplifiers WITH bass management AND room correction. Why is this cool? Well until this new class of products came out the only way to do this type of thing was with a home theater receiver or a separate preamplifier such as a DEQX or TacT and a power amplifier. Two channel systems benefit just as much from subwoofers and equalization as home theater systems. Many two channel speakers, even high end ones, cannot reproduce low bass below say 30-40Hz with low distortion. A JL Audio F112 can play down to 19Hz at a -3dB point! Using subwoofers also allows for cunning room mode cancellation and avoidance of speaker boundary interference.

Classe CP-800

Continue Reading

Contact Us About This Product


Nyal Mellor, Founder, Acoustic Frontiers

  • (415) 524-8741
  • Serving USA & Canada
  • Fairfax, Northern California, USA

ask us a question about this product