Expand Your Audio Development Skills with audioXpress March 2025

audioXpress March 2025, focused on Test and Measurement and audio electronics, explains how to test Power Amplifiers, and how to measure HDMI Audio. Explore the possibilities of George Ntanavaras' SL-100 Sound Level Adjuster and Tom Perazella's Reinforced Speaker Protection solution. Read the interview with Mike Engelhardt, explaining everything about audio THD with QPSICE circuit simulation. Brian Lowe concludes its article on Op-Amp for Phono Preamps, and much more.

Following the launch of its Utopia Main studio monitors, French manufacturer Focal transitioned to Integrated Systems Europe 2025 to introduce Utopia Cinema, a range designed for private cinema rooms of up to 2153 sq ft (200m²). Focal Utopia Cinema includes the Cinema LCR 3-way loudspeaker and the Cinema SUB subwoofer. According to Focal, these new Utopia products are the result of a meticulous and extensive development phase, in an effort to deliver an unprecedented level of performance and to create a complete modular solution for custom systems.

Because of the movement of its membrane, even a perfectly linear loudspeaker produces Doppler distortion, a.k.a. Phase Modulation, and second distortions from the Nonlinear Amplitude Modulation. This article, originally published in audioXpress, October 2024, characterizes and shows how to eliminate Doppler distortion for a good listening experience.

The 2025 trade show season is in full force, and Lavoce Italiana is crossing the Atlantic after attending the NAMM Show in Anaheim, CA, and now moving closer to home, for Integrated Systems Europe in Barcelona, Spain. There, the company will be introducing three neodymium magnet HF compression driver models: DN07.10LTF with 0.75” exit and low Fs, DN10.20 with 1” exit, and DN20.30TK with 2” exit. These compression drivers join the recently announced CAF series ferrite common magnet coaxials and other new models.

The eagerly awaited Purifi Audio PTT10.0X04-NAB-01 10" Midbass Woofer is the sixth Purifi driver to be examined in Test Bench. This 4Ω woofer features extensive proprietary technology that includes the constant Sd surround, cone edge stiffening ring, and low magnetic hysteresis motor design. The PTT10.0X04-NAB-01 exhibits some very unique engineering that can be finally characterized.

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.

Confronted with the impossibility to conduct reliable measurements in the low-frequency domain for his DIY speaker project, George Ntanavaras explores the alternative of relying solely on simulation software. To validate the design of an open-baffle subwoofer using the AKABAK software, created by German company R&D Team, he also explores the transition from measurements to simulation. His experiments contrast the near-field response measurements of his loudspeaker with the accuracy of the simulation using AKABAK.

Celestion announced that its TFX0412 4-inch ferrite magnet coaxial driver is now available for individual purchase through retailers. Originally introduced in 2023, the TFX0412 features a fully combined LF loudspeaker and HF compression driver that are powered by a common magnet motor assembly, with the same magnet used for both elements. With a rigid pressed steel chassis, the TFX0412 is a very cost-effective and compact option for sound reinforcement applications such as ceiling speakers and cinema audio.

As TIME revealed its annual list of the Best Inventions, which features 200 product, technologies and innovations changing our lives, there was a surprising mention of Brane Audio's Brane X portable speaker as a winner in the Entertainment & Gaming category. As audioXpress and Voice Coil readers learned earlier - and coincidently James Croft writes about in Voice Coil November 2024 - the company's Repel-Attract-Driver (RAD) that is part of the Brane X design, is indeed the first effective embodiment of a negative-spring woofer that bends Hofmann’s Iron Law.

In the fourth article from Claus Futtrup in his series about the invention, concept, and historical perspective of loudspeaker bass reflex alignments, he explores the Critically Damped Fourth-Order (CD4) bass reflex alignment. This alignment remains one of the least known and hasn't been discussed in literature related to loudspeaker design, even though it allows for interesting output properties. This article was originally published in Voice Coil, August 2024.