Stephen W. Moore

July 13, 2009

Outdoor Dipole Audio

Filed under: Uncategorized — Moors @ 8:15 pm

I was put in charge of providing audio at a local estate party. I thought this was a good opportunity to test some dipole systems I’ve been considering. My home audio system consists of the Linkwitz Phoenix system, which is the DIY version of the Audio Artistry systems.  Home Hi-Fi is not appropriate for outdoor PA usage (“sound reinforcement”) – they have incompatible goals:

  • H-Fi (Home Audio):  accurate presentation, tonal purity, flat frequency response, very low bass response
  • Sound Reinforcement (Pro Audio):  high efficiency, maximum decibels, ruggedness, durability

However, I’ve seen the Linkwitz dipole arrangement used successfully as a PA system. I put together a system using Bose monitors to cover the frequency range above 150Hz and some modified Linkwitz dipole Phoenix woofers for reproduction from 35Hz to 150Hz.  I used the stock Phoenix crossover circuit board with few modifications (resistor values).  The woofer modules used Lambda 12″ woofers (no longer in production, but their descendants can be found here). The Bose monitors were mounted on tripods for the correct height.

Dipole Woofer with Bose Monitor Dipole Woofer with Bose Monitor

The electronics package was transported in an old WWII CY-573 military carrying case for oscilloscope and testing equipment. The case is very rugged, has a waterproof seal, and is generally very cool. The electronics included:

  • Carver TFM-45 Amplifier for the woofer modules
  • Audio Control Richter Scale III crossover module (for Bose monitors)
  • Linkwitz Phoenix crossover and dipole compensation module
  • Numark 4 channel mixer
  • Alesis Compressor/Limiter
  • iPod Nano
  • Hewlett Packard iPaq with WinamPAQ

Electronics

The sound was very good – clear with very rich bass and tone. The dipole woofers functioned beautifully in the outdoors environment. Their “figure 8” radiation pattern was clearly evident, with null nodes at the sides and full bass response directly in front and back. I noticed several partygoers taking advantage of the null nodes for private conversations, and the buffet tables were also placed in the  null node on the other side.

The equipment broke down rapidly for easy transport.
Equipment Transport

With the tremendous success of the dipole woofers, I’m now considering a full system with dipole midranges and tweeters using the Linkwitz Pheonix crossover. Hats off to Linkwitz for sharing his knowledge and talents with us.

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