Pictures taken at the recent Melbourne Audio Club meeting
At the talk Bill Woodman provided interesting snippets:
Good sound in a stadium is rarely possible with line arrays, far better use directional drive units. The acoustics in the Walt Disney hall in LA caused concerns for Keith Jarrett in a 2003 concert “It was like being in the center of a big bowl, with the sound stirring around and never finding any sort of focus,” Jarrett said of playing in Disney Hall. http://www.lsionline.co.uk/news/story/ATC-for-Walt-Disney-Concert-Hall/YGKL6R
Symmetrical Field Geometry is a big improvement in driver motor design. The hysteresis in the pole price and plate is about 6 to 8mm deep. A ring of small oxide coated particles on the front plate is used to control the eddy current for a ‘super linear magnet’.
Ed May, JBL’s designer uses short voice coils on a long gap for his cones. ATC have long or short coils for the cone drivers, because the 3″ dome is used on the flat part of its curve a short coil is not needed. Short coil drivers have a Q of 0.4 or more, good for reflex boxes whereas long coils work best as sealed boxes. All ATC sub’s are in sealed boxes. Bill emphasises that there should be no leaks, or say goodbye to bass.
Speaker Placement- Bill says across the short dimension of the room, about 1/4 or 1/3 of the way out. Subs should be sealed.
“You need a 2000Watt amplifier if you want to reproduce a piano accurately”. “From the quietest note [PPP] to the loudest is about 130dB[fff}”
As someone who played jazz piano, Bill wanted loudspeaker systems that were good at reproducing piano. His love of jazz, especially piano jazz is a reason for his early career in the loudspeaker business. He played jazz as a pianist on board a ship to the UK.
On his way to England he applied for a position with Goodman’s, he recollects his application Floyd.d he was the best candidate available, and he got the job! He was in the Special Projects department before moving to the laboratory. Amongst the advanced developments they developed edge wound ribbon voice coils,although they did not take this much further.
Bill came toMAC from Castlemaine, everything conspiring to wreck his talk. His car broke down, the new model speakers highly anticated held up by the courier company, the heat wave not helping. Then the Victorian Dealer had a family emergency, George described it as the perfect storm. (With the Hot weather the Willis room air conditioner was very welcome).
Bill’s first job after leaving Bendigo Institute of Technology was with Plessy_Rola, as did so many other Australians who became well known in the audio world.
The first product ATC was a 12″ PA driver, which was used by Martin Audio (founded in 1971 by fellow Aussie David Martin)in their PA rigs, famously by Supertramp and Pink Floyd.
The ATC 75_mm (3″) soft dome midrange is the most well known product. Bill began making it in 1976/77, and he describes the benefits as wide, up to 80° dispersion, high power handling, and with high flux magnets, no falling response, covering a decade from 350Hz to 3500Hz. As well, he claims low level time domain distortion with the soft, damped diaphragm.
“Design a drive unit to have a linear response in the range you want to use it”. The 3″ dome diaphragm is constructed to very high standards. The mass of the diaphragm is the same as the mass of the voice coil, giving the best energy transfer. The 3″ works on the flat part of its curve. A 4″ dome has been developed and tested. Flat response from 200 Hz, not planned to go into production. But a 25mm fabric dome tweeter with a neodymium magnet is in production. The reason it took so long is Bill’s philosophy that “Everything we do has to be as good or better than what’s already on the market”.
When discussing similar drivers to the mid range dome he dismisses most, and says there is only one metal dome or cone that’s any good; the mid on tghe Yamaha NS1000. Years ago when testing more than 20 pairs of NS1000 speakers all were within 3dB!
In 1986 the ATC SCM 50 was supplied to Danish Radio as an outside broadcast monitor. This produced turned out to be a speaker that could be used for hi fi not just professional audio. It was followed by the SCM20 in 1989 with the 6.5″ cone driver based on the 3″ dome, good to over 2kHz.
Melbourne Audio Club has a last minute change to Wednesday’s programme: Bill Woodman the founder of ATC Loudspeakers is giving a talk about the beginnings and design philosophy of his designs. As anyone who has used his drivers, especially the 3 inch dome (75 series) will testify, they are extremly low colouration high definition loudspeaker drivers. Several club members use them or have used them in the past. A memorable use is as a midrange driver on Tannoy HPDs. All who were at the “Yello” night will remember the clarity of sound, and of course the bass that the 15″ Tannoys put out.
Not to be missed, Wed 15 January at the Willis Room, 8pm.
The exchange will be open on Sat 11 Jan as normal, at this stage I have no idea what has come in or been sold.
Join me, it should be fun!