Outboard DSP: Marani Pro MIR480I Audio System Processor

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

This article reviews a patent awarded directly to inventors Anthony Allen Bisset (Oakland, CA) and Quang-Viet Nguyen (Aldie, VA), for a coaxial horn speaker design. In his review, James Croft looks back at multiple multi-driver horn topologies and compares the unique aspects of the CCPS Horn Speaker System, highlighting the positive attributes and benefits of the invention, to deliver both increased acoustic quality and increased power density.

This latest MR13TX-4 midrange from SB Acoustics is part of the fast-growing Satori line of high-end transducers. A dedicated 5" midrange driver, the MR13TX-4 is the 10th TPCD TeXtreme diaphragm transducer to be featured in Test Bench. In terms of features, the MR13TX-4 is built on a proprietary two-piece cast-aluminum frame, completely open below the BIMAX spider for cooling. The cone assembly consists of a curvilinear inverted single piece "bowl" shaped TeXtreme cone and an inverted NBR surround, driven by a 1.2" diameter voice coil and a neodymium motor.

The B&C Speakers DE640-16 Compression Driver is a 1.4" exit design, which along with the recent DCM414 midrange and the DE360 models represent a line of two-point suspension ring radiator type compression diaphragms. The DE640-16 features a 65mm (2.6") Polymer diaphragm and neodymium ring magnet and is specified for a recommended crossover frequency around 1kHz, and a 140W continuous power rating. For this Test Bench, the DE640-16 was matched with the Eighteen Sound XT1464 elliptical flare horn.

The fifth article by Claus Futtrup in his series about loudspeaker bass reflex alignments explores the concept of transitional alignments, which is helpful in bridging between filter types. The example details a transitional alignment between Butterworth B4 and Linkwitz-Riley LR4. This article series started in May 2024 with “Computation of Bass Reflex Alignments," the series expanded with classical alignments such as the B4, the LR4, the IB4, and most recently, the CD4 vented alignment, in the August 2024 issue.