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Old 14th December 2004, 06:03 PM   #1
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Join Date: Jun 2004
Location: Adelaide, Australia
Default Line Arrays Down Under

Just finished my line arrays and thought I'd share my journey with you - and hopefully some pics if I can get them uploaded...

I don't know if you noticed a few months ago there were some crates of Audax midranges for sale on ebay. Forty five three inch Audax AP080G0's for around two hundred bucks. So I decided to take a punt, get a crate shipped across the world to Oz and build some line arrays. First I downloaded Dr Jim Griffin's white paper from this forum, and had a friend model the sealed enclosures on Soundeasy. At one litre per driver, they would sound pretty good down to around 130 Hz. Okay, they would need some help below that, but what the heck. This is what I came up with:

- Twenty drivers per side - because I had them! And because I wanted as much height as possible for my 11 ft ceilings (the speakers are over eight ft). The drivers are only 1cm apart, to recuce volume lobing.

- A (3)-5-4-5-(3) series and parallel setup, with the two three's at the ends joined as one series. This gave my 6 Ohm drivers an overall impedance of 8 Ohms, and gave a power rolloff of 25% from centre drivers to the end ones - which is advisable.

- The final spl is around 96 Db, so I decided to match this with a single powerful tweeter, the Audax TW025A26 - itself around 96Db. This will be mounted on a pod halfway up the column later, which won't break up the array, and also means I can adjust/replace it at will. As you can see from the pics, they are currently mounted in makeshift boxes along with ScanSpeak bass woofers. The arrays are running fullrange now but I will put crossovers in later.

Conclusions? If you're even thinking of attempting a project like this, read and digest Jim Griffin's white paper - it guides you on impedance, power rolloff, how to maximise the near field effect, and how driver spacing affects crossover decisions etc. Thanks Jim! The sound is highly three dimensional - there is no appeciable volume reduction over distance, so you feel immersed in the sound stage. Female voice is especially detailed - but so is upper bass - I guess it's a result of so much air being moved. I have to say it would be hard to go back to point source speakers after this experience.
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