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Category Archives: Low Frequency Optimization

The Schroeder / Transition Frequency Explained

Brent Butterworth, a writer over at Sound & Vision, has written a very easy to understand explanation of what the ‘Schroeder’ frequency is. The Schroeder or ‘transition’ frequency is a critical concept to understand because it explains a lot about how sound behaves in rooms, how we measure / analyze them and how we treat […]

Two channel amplifiers with bass management and room correction!

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

Using multiple subwoofers to improve bass: The Welti / Devantier and Geddes approaches

This article continues the theme of the last two blog postings in whic we outlined some ways in which subwoofers can be used to improve sound quality. Last week’s installment ‘Using Subwoofers to Improve Sound Quality: Part 2 Room Modes‘ outlined a technique whereby two subwoofers are positioned within a room to destructively drive a particular room mode, nullifying its frequency response peak and time domain ringing. This week we introduce the Welti / Devantier and Geddes multi-sub methodologies. Both involve using multiple subwoofers as a way to smooth bass response and reduce the impact of modal resonances.

Using subwoofers to improve sound quality: Part 2 – Room Modes

Room modes are caused by perfect constructive interference between a sound wave traveling between two boundaries. This article provides a high level overview of room modes and their impact on sound quality. Two examples of how to use subwoofers to reduce the impact of these modes on sound quality are explained – placing the subwoofer in a pressure null and destructively driving a mode with two subwoofers.

Using subwoofers to improve sound quality: Part 1 – 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 article introduces SBIR and explains how these deep nulls can be ameliorated through use of a subwoofer.