Monday, October 17, 2016

Halloween Yard Haunt Sound System

I have always had sound for my yard haunts.  Even going back to my childhood I had a basic system - a Halloween record playing through an outdoor speaker.  Over the years it has evolved. 

  • Early 1980s - record player and outdoor speaker
  • Late 1980s - two cassette decks crossfaded using a small Radio Shack mixer and several outdoor speakers.  There were different cassettes for each "scene" that the people would walk through and as they transitioned I would crossfade to the next cassette then change the cassette in the other player.
  • 2005 - A boombox playing a CD that loops and a digital recorder playing back through amplified speakers.
  • 2007 - Sound Cue System running on a laptop connected to a multichannel USB sound card, a couple of stereo consumer audio receivers and several 8 ohm speakers.
  • 2012 - 5 hour, 13-channel recording playing from an Alesis HD24 through a Crown 8-channel 70v amplifier and a 70v transformer on each speaker.

I've seen articles about using radios tuned to a weak FM transmitter, wireless speakers (which need power run to them anyway) or small self-contained sound systems with their own playback and amplifier components.

I still feel that the components used outside in the haunt should be inexpensive and easy to replace if stolen or damaged by weather.  So since 2012 I've been pretty happy with a centralized system. 

I use 70-volt constant-voltage wherever I can.  There are still a couple of channels that drive 8-ohm speakers over heavy cable to reduce loss, but all the 70-volt stuff runs over cheap 18-gauge lampcord.  Any 8-ohm speaker can be converted to use 70-volt by adding a transformer of the appropriate wattage.

This $13 70-volt transformer
is available from Amazon.

To compare standard 8-ohm mode against 70-volt, check out this chart:

Power available to system in watts using 18-gauge cable
 100 feet500 feet
70-volt / constant-voltage95.0878.63
8-ohm / constant-current74.3630.93

70-volt systems are far more efficient.

I purchase the sound effects from - once you own the sound effects you can legally use them in a public performance. 

Nero has a couple of free software utilities that were very useful when putting together the soundtrack.

Nero SoundTrax - great for layering sound effects
Nero WaveEditor - great for preparing individual sound effects

Once the individual tracks are completed they are played in a continuous loop while recording to the Alesis HD24.  I bought the HD24 on eBay years ago.  They are probably even cheaper now.

Recording the soundtrack

On the HD24 you can arm individual tracks separately so you can make one pass with the first set, move on to the next set, and so on.  I figured the longest Halloween night could ever run is five hours, so the "song" on the HD24 is that long.

The Alesis HD24

I felt the mix on a couple of the scenes would be best tweaked on site rather than premixed, so I kept those as separate channels and fed them through a Gentner AP800 mixer.  I hacked the Gentner using an Arduino to make a remote mix control.

The Gentner AP800 can be found on eBay for around $25

The output of the Gentner and the other channels from the HD24 connect to a Crown CTs-8200 8-channel amplifier. 

The Crown CTs-8200 can be found on eBay for around $400. 
That's $50 per channel!

Each pair of outputs on the Crown can be set to run in 70-volt or standard 8-ohm mode.

I found it handy to keep track of the patch and levels to make future setups easy.
System Configuration Record
How the sounds are used:
  1. Crickets - there are three speakers on the left channel and three speakers on the right channel, hid at ground level in ivy and bushes.
  2. Regular & Spooky Wind - balanced via the Gentner, there are three speakers on the left channel and three speakers on the right channel set along the edge of the roofline all across the front of the property.
  3. Tree Critters - one speaker per channel, hidden up in trees at the far left and right of the yard haunt.  The tracks cycle through things like bats, owls, birds, and other spooky sounds with a bit of silence in between each one.  They also alternate which side they play on.
  4. Zombie Scene - a story in sound about two zombies.  The speaker for this has a 12" woofer for good bass and is hidden at the rear of the scene area.
  5. Atrium Wind & Music - balanced via the Gentner, there are one to two speakers on the roof facing the atrium area.  The wind in here is different because it is an enclosed space.
The system fits into a 19" rolling rack:

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