THOR: A D’Appolito Transmission Line

One of the most important speaker building projects published by audioXpress, THOR was designed by Joseph (Joe) D'Appolito, who is world-renowned for his pioneering work on MTM-based (mid-tweeter-mid) loudspeaker configurations. The original THOR transmission-line design was published in May 2002. For this online publication, audioXpress kept the original article unchanged, which has since been updated with availability of the original Madisound/SEAS kit and the publication of a complete kit project on the SEAS website. Read the complete article here.

Following the publication of the original Hideaway TL Sub project in audioXpress July 2006, Bjørn Johannesen submitted a follow-up of its “invisible” subwoofer project, using a new updated driver - a Peerless 10˝ SLS 830668 woofer - and a slimmer profile to fit under its new couch, with only 15cm of free space. The article was originally published in audioXpress, October 2007.

This article, a Danish blueprint for an “invisible” subwoofer was originally published in audioXpress July 2006 and it is the first of two by Bjorn Johannesen. In this first article, the author describes a successful transmission line to replace a vented sub, inspired by Rick Schultz articles. A project where the first approach revealed a resonance frequency lower than expected — lower than the driver’s Fs, leading him to study Martin J. King’s quarter wave design.

Inspired by debates on the Internet about quarter wave designs with Tang Band 3˝ full-range drivers, the author decided to design its own quarter wave loudspeakers. This article was published in audioXpress, March 2007 and the results were simply spectacular, generating worldwide interest. Recently, Bjorn Johannesen created a successful business with his own speaker company, called KVART & BØLGE, which means Quarter & Wave in Norwegian and Danish.

UK-based reference monitor manufacturer PMC will be launching a new addition to its twotwo range of active nearfields at NAMM 2015, as well as giving West Coast audio professionals another chance to see the mighty QB1-A large-scale studio monitor, launched in Los Angeles in Autumn 2014.

Do you plan to work with transmission line speakers? Before you begin, consider the effects of stuffing on your transmission line speakers. In this article, you'll learn about the effects, as well as a test setup with mics in a cardboard tube, a preamp, scope, sweep/function generator, and mini receiver.