Optimal Toe-In Angle for a Dipole Loudspeaker

I’ve been doing some work on determining the best toe-in angle for a dipole loudspeaker.  The mathematical details are in this draft manuscript, but here is a brief summary.

Attenuating Lateral Room Reflections

By toeing-in a dipole one can selectively attenuate various room reflections by placing them at or near a dipole null (i.e. 90° off-axis).  Shown here are two scenarios for the first lateral reflection paths in a room, with the polar response of an ideal dipole superimposed.  Only the dipole orientation changes, the reflection paths are the same in both cases:

The first case is typical; the side-wall reflection is severely attenuated (about 30dB) since it is radiated near the dipole null.  The front reflection is helped a bit, but it’s only down 3dB (plus about 4dB due to path length).  In practice a mirror placed at the side wall reflection point will show an image of the loudspeaker on-edge. Continue reading

Pluto 2.1 with Software DSP

About a year ago I implemented a software-DSP version of the Linkwitz Labs Pluto 2.1.  My aim was to replace the original analog signal processor (ASP) with a small, standalone PC that can double as a media server: like a Squeezebox that also performs xover/eq duties.

Pluto is an outstanding loudspeaker, and really deserves to be built/heard by more people.  Part of my motivation is to provide a lower-cost, easier-to-build alternative to the ASP.

I own the original ASP version of Pluto 2.1 as well: in several hours of level-matched A/B listening tests I haven’t been able to hear any difference — except that my DSP version currently has a less powerful amplifier on the woofers, which limits the peak output somewhat.

If you want to go the software-DSP route yourself, follow the 2-way crossover instructions in my DSP how-to article.  I’ll post the proprietary Pluto-specific configuration files in the Owners’ area of the Orion/Pluto Forum. Continue reading