Spikes & Isolation: The Art of Speaker Decoupling for Optimal Audio Performance

This contributed article by IsoAcoustics' founder and president is an interesting piece that sums up his vast experience in the field, working with professional audio engineers, loudspeaker designers, and music lovers all over the world. The article explores how speakers physically interact with their supporting surfaces, the key factors that affect speaker decoupling, and the pros and cons of many common isolation approaches.

This article is another great contribution by Claus Futtrup, this time with direct support from Jeff Candy, the two creators of Speakerbench, the free to use web-based application for low-frequency analysis and design of loudspeakers. Another follow-up article for the Bass Reflex Alignments article series that was published in audioXpress and Voice Coil, this time, the authors discuss the important Quasi-Alignment Families where the fundamental idea is trying to approach a roll-off similar to the Butterworth B4 alignment (a maximally flat response) but compatible with real systems for which the driver Qt will not allow a true B4 alignment.

This Test Bench characterizes a 1" conical exit compression driver from Faital Pro that was measured along with the brand's STH100 elliptical Tractrix flare horn (80° × 70°). Driven by a voice coil wound with aluminum wire on a high Qm non-conducting Kapton former, and powered by a neodymium ring magnet, the HF110 compression driver targets applications such as stage monitors and PA speakers with a 2kHz recommended crossover frequency (second-order or higher high-pass filter).

After seeing many speaker designers returning to trial-and-error approaches that seem to forget the historical work and analytical approach, Lars Risbo decided to explore numerical optimization to synthesize attractive alignments both for reflex and passive radiator box types. This reference article basically expands on Claus Futtrup's "Loudspeaker Bass Reflex Alignments" article series published in audioXpress, and expanded with dedicated articles in Voice Coil.

In his exploration of available Outboard DSP systems, Vance Dickason explores the Marani Pro Audio MIR4801, the company's flagship DSP processor with four inputs and eight outputs. MIR stands for Marani Impulse Response, which refers to the proprietary Marani linear (zero) phase Linkwitz-Riley filter, which is described in a whitepaper titled by Michael Marani and Simone Castrucci, both from SEED Electronics, Guangzhou, China.

The first in a series of reviews of outboard DSP processors available in the market and of interest to loudspeaker engineers, this article explores an extremely versatile and powerful DSP audio processor and DAC, crossover, and control center for any audio system. The dspNexus comes with balanced inputs and outputs, USB, S/PDIF and Bluetooth aptX HD, and processing is handled by a latest-generation Analog Devices SHARC DSP, with Audio Weaver as the programming interface.

In this article, Vance Dickason explores the use of digital signal processing, and specifically Outboard DSP, an increasingly viable solution to create a complete active crossover design, contained in a programmable unit that can be delivered with multiple presets for different usage scenarios or even configured by the user, according to the system in place. This inspired Vance Dickason to begin a series of product reviews of multiple outboard DSP processors, and this article is a preamble for the project.

This article reviews a patent awarded to Paul Wayne Peace Jr. and Derrick Rodgers, on behalf of Harman International Industries. The patent describes a surface-mounted loudspeaker design that mitigates the interference between direct low-frequency (LF) energy and reflected LF energy by breaking the LF energy from an LF driver into multiple paths using one or more of waveguides, driver load plates, and enclosure ports to diffuse the reflected energy and minimize frequency response errors.

After discussing computation of discrete alignments such as B4, BL4, LR4, IB4, and CD4, this new article in the "Computation of Bass Reflex Alignments" article series explores the real-world situation where it becomes impossible to have a system design that exactly matches a certain driver Qt, normally described as an alignment error (or misalignment). The technique presented allows designers to modify tuning towards a desired target response function.

This article reviews a patent awarded to Teppei Yamada, on behalf of Zorzo Co., Ltd. (Tokyo, Japan), describing an original design of a low-frequency enclosure system incorporating multiple woofers inter-coupled in a manner similar to what is known as an isobaric or compound woofer enclosure. James Croft reviews other approaches to the concept, starting in 1954 with a patent granted to Harry F. Olson on a dual, compound woofer system and later "reinvented" and popularized by Linn Corp., in 1975. In the new patent, the inventor uses an enclosure with as many as 12 woofers, all seriously coupled through individual air chambers