Sorry about these advertisements too. They come with the territory.

My Subwoofer

1. Adds depth and power to orchestral performances, fullness to string and electric basses, and "reality" to rock performances; and
2. Spares your main speaker system from having to cope with large amounts of deep bass. The main speakers usually cannot produce useful, undistorted sound from the deep bass signal which is fed to them. The cones move, but no sound is produced. This large cone excursion increases the distortion of the bass notes which the main speakers CAN produce, and is therefore detrimental to the overall sound.

The Kit 300/200W Playmaster amplifier incorporates an active crossover which has a crossover frequency of 70Hz (2nd order, adjustable also to 90 and 120Hz). The designs were from Electronics Australia, but similar amplifiers designs are available from Silicon Chip. The crossover board/kit can still be purchased from Dick Smith Electronics. Given the age of this kit, it is probably better to consider purchasing a kit from Altronics (still available) or from Jaycar (currently not available) based on Silicon Chip designs. Of course, now that you know about www.diyaudio.com, you could probably build the amp yourself, or send me an e-mail on diyaudio (GeorgeBoles) and I can provide Australia-centric advice on how to start :) A kit would be best for first timers, I think.

Unfortunately building my subwoofer took a long time, mainly because of my own bizarre methods, especially a frustrating phenomenon known as "paralysis by analysis".  The subwoofer cabinet I made was designed using WinISD and two 12" carbon fibre subwoofer drivers from Jaycar Australia in an Isobarik configuration - reduces distortion and halves the box size ... all modelled in WinISD.

The delay in building my subwoofer was contributed to by the failure of the toroidal transformer, which wasfaulty. I switched on my painstakingly built and checked amplifier, and instantaneously I heard a very quiet "click" ... no smoke, no sparks, just "click".  The primary safety thermal fuse had blown.  I spent ages tracking down the fault, but Dick Smith Electronics did graciously supply me with a new one despite the fact that the kit was truly out of warranty - by about 1 year!

I replaced the faulty transformer with no other changes, but thought I had better test the whole thing carefully.  I directly connected the output of my CD player to the inputs on the MAIN amplifier board, bypassing the crossover, wanting to listen to how the amplifier worked and sounded when it was used as a 20Hz to 20kHz normal amplifier. But there was nearly NO sound ... just the quietest bit of music coming rom the speakers.  I was convinced I had done something else wrong .  My emotional energy was exhausted for a year. Eventually I got started again and, with a friend's oscilloscope, worked out that the electronic crossover was also a pre-amplifier of sorts and that there was insufficient gain in the power amplifier stage to get any sound out!!!.  My worst example of "paralysis by analysis". If I had tested it as per the schematic and not tried to analyze it all so much, I would have been up and going years before! That was a fundamental lack of knowledge, which was cured by browsing www.DIYaudio.com. 

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