Real Satellites for my Computer System

First Try Finished June, 2008

Second Try Finished July 2008

Third Try Finished September 2009 (go here for the the one that works)

I decided to concentrate on the sound system for my main computer in my study/home office (OK, it's the spare bedroom in my apartment). This computer is set up with two monitors, a 19" LCD and a 32" LCD TV. I place my speakers on either side of the TV. It's a little over the top, but I'm already surprised by the sound quality to be had when a decent sound card is coupled with a decent sound system.

It's a work in progress. Currently, I'm using an old Creative Audigy Platinum sound card with a Logitech Z560 4.1 sound system. I never hooked up the original satellites from Logitech, I started with the Minimus 77 speakers (in a 2.1 configuration). I've since built the satellites I plan to use, but I'm still using the Z560 for power amp and sub duties.

Building the satellites was a great learning experience. It was my first real attempt to use SoundEasy to measure the drivers and design the crossovers. I learned a lot building the three iterations of these speakers;

• 1. The First Try was horrible. I learned the importance of some of the most basic design criteria by running top speed into the problems created when you ignore them.

  2. The Second Try was usable. Over time I realized the systems were actually too bright, and the high crossover point was less than optimal for the W704s. The problems were irritating enough to make me re-think my design choices and try again.

  3. The Third Try was a major upgrade. I switched to Zaph's ZA14 woofers and Seas TDFC tweeters. With more experience using SoundEasy and drivers costing twice what the original W704/ND20FB-4 combo cost, the change was amazing. I'm very pleased with my third try and have no plans to change the satellites.

The system will eventually be a 2.1 set-up with an active crossover between the sub and satellites. The sound card's analog output will go to a conventional stereo preamp for bass, treble, balance and master volume control. The basics of the audio system are/will be:

• 1. A preamp consisting of

     1. A basic stereo preamp (volume, balance, treble, and bass controls)

     2. Switching for two inputs

     3. A stereo 2-way active crossover (LR 4th order) for sub and satellite outputs, and a sub level control.

     4. A subsonic/rumble filter, F3 at about 15 Hz. This will yield a flat electronic response from about 22 Hz up.

     5. The preamp is Rod Elliott's Project 97, the subsonic filter is Rod's Project 99, the XO is his Project 09, and it's powered by Rod's Project 05 ±15 VDC regulated power supply (working on this part now, 03/12/10).

  2. Power amps built into the sub enclosure

• • 1. The satellite amp will be a Project 03A form Rod, on ±35 V rails, for two 60 watt channels

    2. The sub amp will be a bridged P03A on ±35 V rails, for about 150 watts to the sub

• 3. The sub will be a 10" or 12" in a fairly compact sealed cabinet

• • 1. I have one of Rod's Linkwitz Transform cards. If it looks feasible, I may try it on the sub system.

• 4. My current sound card is a Creative Audigy Platinum. I may try an Omega Claro Halo after I finish the preamp/crossover and power amps if I can hear any noise. Right now, the system is surprisingly quiet and yields excellent fidelity. Either way, I'll let the PC handle the digital side of the audio and depend on a high quality sound card to be the primary source for clean, high quality analog audio.

Jay R. Taylor

March, 2010

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