Voice Coil Lab Notes: Improved Zobel Network

Passive crossover filter networks for multi-way loudspeakers generally require a resistive termination for optimum performance. The driver itself generally presents a reactive load. Inductive rise with frequency above resonance of the loudspeaker electrical impedance is semi-inductive due to eddy current losses. The L2/R2 impedance model represents the electrical impedance as seen by the amplifier output. An improved compensation network can be realized by using the analogous circuit “dual” of the L2/R2 model. This represents a dramatic improvement to the basic two-component Zobel network and compensates for the non-ideal semi-inductive behavior of the loudspeaker driver across the entire frequency band.

The March 2020 edition of Voice Coil is now available online and in print. In this edition, Vance Dickason gets hands-on with the Audio Precision APx500 Flex Audio Analyzer, Mike Klasco writes about Loudspeaker Enclosure Materials, and James Croft explores a new patent of a novel orientation of a cardioid speaker design. And in Test Bench, Dickason characterizes a home audio transducer from Eastech's Punktkilde line, the cosmetically pleasing AUGWL0016-JN02 6.5” midbass driver.

McIntosh Labs has been perfecting vacuum tube amplifiers since the 1940s and solid-state amplifiers since the 1960s. From that heritage, McIntosh now announced the MC901 Dual Mono Amplifier, a truly one-of-a-kind monoblock that is also two amplifiers combined into one, with each amplifier boasting differing design philosophies including a 300-Watt vacuum tube amplifier attached to a 600-Watt solid state amplifier on one unified chassis.

Sonus faber announced the launch of their Olympica Nova high end speaker collection, with seven completely new models, at the 16th Annual Rocky Mountain International Audio Fest (RMAF). The newly expanded Olympica Nova series embraces the authentic values that inspired the original Olympica line while adding a substantial amount of freshly developed technology, from new drivers and crossovers, to a new cabinet structure and internal volume tuning, and a new exterior look.

MSE Audio will showcase the Induction Dynamics ID1, a switchable four-way tower speaker with dual 10-inch subwoofers, at CEDIA 2019. Designed to respond to both home theater applications and as a stereo music listening system, the new Induction Dynamics ID1 pushes the envelope in audio performance by combining a four-way tower speaker with a subwoofer section via a rear switch with variable crossover frequency.

Do you know what the crossover filters are doing to the response of the loudspeaker system? Some of you might have measured the frequency response of the loudspeaker system to determine what’s happening through the crossover region. However, most designers only look at the loudspeaker’s on-axis response. It’s equally important, or perhaps more important, to know what’s happening off-axis. Let’s see how loudspeaker modeling can be used to help with this. This article was originally published in Voice Coil, August 2017.

In this article published originally by audioXpress in March 2005, Nelson Pass offers a series of tips about designing filter networks for both voltage and current sources. Nelson Pass provides filter examples that can be used equally well with a voltage or current source.