Transitional Bass Reflex Alignments

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.

Before computers were broadly available for loudspeaker bass reflex box simulations, engineers relied on "Alignments" for their designs. Such box alignments are typically named after equivalent filter functions that the high-pass response of the box was aligned after — for example, Butterworth (B4) and Bessel (BL4) — to name a few. This article, the third in this series, explores the rarely talked about Inter-Order Butterworth (IB4) alignment, mentioned originally by Richard Small and Neville Thiele.

Norwegian company Arendal Sound launched its latest creation, targeting both stereo and home cinema applications. The new Arendal Sound 1528 speaker series redefines high-performance loudspeaker design at fair prices, merging sonic precision, striking power, and elegant aesthetics. A custom carbon-graphene mid-range driver joins an exclusive lithium magnesium tweeter in the biggest ever speakers from Arendal Sound.

There's a new Danish hifi speaker brand in the market, part of the expanding audio universe created by Peter Lyngdorf, the founder of HiFi Klubben, and co-founder of Purifi Audio. The project was inspired by Henrik Reinholdtsen, the CEO of Nordic Hi-Fi, a direct-to-consumer business that is also part of the HiFi Klubben universe. Radiant Acoustics is now on the market with the Clarity 6.2 passive speaker, using a 6.5" Purifi woofer and a new AMT tweeter, with a custom-designed waveguide, developed by Lars Risbo.

Before computers were broadly available for loudspeaker bass reflex box simulations, engineers relied on "Alignments" for their designs - typically named after equivalent filter functions that the high-pass response of the box was aligned after — for example, Butterworth (B4) and Bessel (BL4) — to name a few. In this article, Claus Futtrup now focuses on the Linkwitz-Riley (LR4) Bass Reflex Alignment.

The first in a series of great value for speaker designers, this article provides an updated approach for the mathematical presentation of the various alignments, applicable to all computerized development tools. This is effectively an explanation of the code available in the Alignment Chart of the Speakerbench web application that Class Futtrup developed in collaboration with Jeff Candy.