Davis Station Music and Cinema

A couple of days ago I was asked by a friend of mine about the sort of audio we have on the station down here.  It seemed like a great idea for a blog post for a few reasons.  It’s not the first request I’ve had, but there was a blizzard outside yesterday and I’m yet to get clear enough weather to take photos for my other outstanding request.

High quality audio is something close to the hearts (or ears) of many a technician.  Daniel (the ‘requestee’) is one of several ‘techo’ mates with whom I’ve sharedand from whom I’ve poachedaudio ideas.  I’m happy to use his question as the excuse for this blog post.

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The most obvious place to find a good audio setup is in the station cinema.  Every station has one for three main purposes: Video conferences, presentations, and entertainment.  The setup here is quite straight-forward and not too fancy.  There is seating for 25 people in comfort, and the cabinet is mounted behind the door to the left of the screen.

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As with most cinema setups, the heart of it all is a good Audio/Video Receiver (AVR).  This one takes HDMI in from the various devices and outputs sound to the speakers and video to the large projector.  The device names don’t correspond with the input names on the AVR, but the instructions on the door describe which input serves each purpose.

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The sound is provided by a Klipsch 7.1 system, which consists of two main floorstanding speakers (botton left of frame) behind the acoustically-transparent screen, a centre channel on the floor, four dipoles and a powered subwoofer.  Acoustically, the room is acceptable thanks to the carpet tiles, soft furnishings and ceiling tiles.

The speakers haven’t been configured for distance levels or response since it blew its rectifier bridge and was repaired, but the speakers have quite even response and the default distances aren’t too far off the mark.  The subwoofer is running too much gain and the crossover point is a bit high, but most of the movie-goers seem to enjoy the hard-hitting explosions in action scenes so it’s on the bottom of the ‘to do’ list.

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In the Living Quarters (LQ) building, there is a Clipsal C-Bus audio system also running Klipsch speakers.  The audio switcher is setup to take input from either a portable music player or the nearby computer (to allow people to play music from a USB storage device).  The control panel (of which there are many around the LQ) allows choice of input device, volume changing and adjusting treble and bass.

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There are a handful of these speakers spread around the LQ in three zones, and ceiling-mount speakers in the mess.  The lounge, the bar, the kitchen and the mess are separate zones with their own audio levels and adjustment.  All four zones run from the one source.

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As a contrast to the LQ control panel from earlier, these are the two panels to control the lights and audio in the bar area.

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Here you can see a couple of the ceiling-mounted speakers in the mess…

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…and the kitchen.  Neither the slushy nor the chef are expected to work in silence, but that is at the discretion of the ‘slushy’ (we all take turns at being an amateur kitchen hand, see this post for more info).  The slushy for the day has absolute say over the music that is played throughout the LQ.  Not only that, but the slushy’s choice of music is also streamed via the Davis Station website and broadcast via FM radio on 103.5MHz.

This is often listened to in both the station vehicles and in the workshop.  I even build a folded dipole tuned to this frequency (with quick improvised coax coil to get it to 75 Ohms) for the guys in the mechanics workshop as the many layers of steel between them and the radio transmitter dropped the signal too low for the usual ‘piece of wire’ antenna.

And speaking of the audio system, I’d simply assumed that either poor quality compressed music or a hardware issue were causing poor sound quality in the LQ.  When I plugged in my music player (and Android-based phone with some audio software that allows fine control over the inbuilt hardware) and set it to output a typical line level from music that I know sounds good, it gave poor quality audio also.  This prompted me to start troubleshooting with one of the friendly electricians on station.

In the end I discovered that the C-Bus audio switcher only accepts a signal level of 2.8Vpp, whereas the computer was putting out around 3.5Vpp.  Most portable audio devices are around 1-2Vpp when used with headphones, so it was only when I plugged in mine and set it to line level (rather than my usual listening level) that I realised something was amiss.  I ended up building a pair of simple attenuators that I got a bit carried away with:

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They didn’t really need to be engraved, but it was as good an excuse as any to be taught how to use the engraving machine.  The audio quality is now excellent from all zones and the streaming digital audio source.  Unfortunately the FM transmitter is on the blink, but I’ve had a gracious offer from the station’s electronics engineer to help me with troubleshooting in the absence of a schematic.

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Last, and least, is my personal audio gear.  I really didn’t bring anything special with me.  Most of the time I’m content to listen to the IcyFM radio stream (from the LQ) on my Logitech USB-powered speakers.  They produce acceptable sound at surprising volume from the 2.5W they’re provided over USB.

If I’m in need of something that sounds a little better, I seldom travel without a good pair of canalphones.  After having left my old UltimateEars SuperFi5 in a taxi in Bahrain (and they haven’t made the high-end models since Logitech bought them out years ago), I’m now using a pair of Brainwavz B2 canalphones.  They’re not as comfortable as the old UE SuperFi5s, but they have the bass response that my old pair were sorely lacking.  And I recommend using any pair of canalphones with Comply tips as they’re super comfortable and provide superior seal and isolation.  My next project is to build a an acoustic simulator to improve listening comfort using a proven design from Chu Moy of headwize.com.

But enough spruiking about audio.  This post has been a bit more technical in nature that my other recent posts, and I hope you’ve enjoyed the change.  I have an even more technical post yet to publish on the communications gear I work with every day, as promised to a couple of readers.  I hope you’ve enjoyed the post.

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Because I’m enjoying the habit, here’s another ‘bonus’ photo.  It’s not nearly as spectacular as an aurora or an Antarctic sunset, but I still find it interesting.  This is the sort of snow deposition we get on the leeward (down-wind) side of buildings every time there is a blizzard (or ‘blizz’ for short).  It all falls off within days of the wind disappearing, but there’s so much cold air and snow blasted against the building during a blizzard that the quadruple-glazed windows are all covered solid.  It makes for a lot of glare (and this photo is a HDR composite again, otherwise it just wasn’t possible to get the detail out of both the window and the interior).

 

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2 Comments on “Davis Station Music and Cinema

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