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About Claus Futtrup

Claus Futtrup received his MSc in ME from Aalborg University in 1997 and has worked in the loudspeaker industry since. From 1997 to 2006, he worked at Dynaudio A/S first as an R&D Engineer, designing loudspeaker boxes and later as a System Engineer for automotive. From 2006 through 2007, he was employed as a Transducer Design Engineer at Tymphany Denmark and, in 2008-2013 he was R&D Manager at Scan-Speak. From 2013 to 2015 he worked as Technical Sales Manager for SEAS, Norway, and in 2015 he was promoted to Chief Technical Officer. From August 2021, Claus moved back to Denmark and started working at DALI as manager of the acoustics team.

All items written by Claus Futtrup

The CD4 Bass Reflex Alignment

October 16, 2024 by Claus Futtrup

The CD4 Bass Reflex Alignment

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.

The IB4 Bass Reflex Alignment

October 9, 2024 by Claus Futtrup

The IB4 Bass Reflex Alignment

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.

The LR4 Bass Reflex Alignment

September 4, 2024 by Claus Futtrup

The LR4 Bass Reflex Alignment

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.

Computation of Bass Reflex Alignments

August 28, 2024 by Claus Futtrup

Computation of Bass Reflex Alignments

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.

Loudspeaker Bass Reflex Alignments

June 5, 2024 by Claus Futtrup

Loudspeaker Bass Reflex Alignments

The use of standard filter alignments represents a foundational concept in the loudspeaker industry, with an impact nearly as significant as the invention of the electro-dynamic loudspeaker principle itself. As one of the creators of Speakerbench, a web-based speaker design tool, in collaboration with Jeff Candy, Claus Futtrup is in a unique position to discuss the evolution of enclosure designs based on this electrical filter theory, including the concept of an alignment chart.