I promised some DIY projects on here but have yet to deliver. So here we are. This is your only warning, this is a nerd heavy wall of text. Bail now or be prepared to be bored to death!
If you have been to a music festival there is a good chance you already know what a “silent disco” is. For those of you who don’t know, I will explain it shortly. In some ways this is one of my most ambitious projects yet. Not only could the success of the project bring the silent disco to the little guy, it could also rewrite the standard model of operation for silent discos everywhere.
The silent disco is a concert that attempts to eliminate noise pollution by transmitting the sound to the listeners ears via headphones rather than traditional ambient methods. The elimination of noise pollution is beneficial for nearby campers, nearby residents, and is a good way to keep the music going late into the night when excess noise is traditionally unwelcome. The standard model silent disco transmits sound through the use of Bluetooth, FM, or Wi-Fi standards in combination with headphones that receive and then play the incoming signals at the users ears. If you’ve been to one you know that it can be an eerie experience at first. People dance, clap, even cheer, but if you aren’t listening it looks like everyone just ate too much acid. If you’d like to read more on the silent disco head on over the wikipedia page.
Here’s a video that does a pretty good job of illustrating the silent disco.
Why have I decided to tackle the silent disco? Firstly, silent discos are fun and bringing that experience to more people would be a good thing. More importantly, the silent disco will likely play an increasingly important role in the landscape of music festivals in years to come. As there appears to be a boom in small festivals which are outcropping regionally and attract similarly regional attendances there is a growing audience for such technology. As festivals face regulatory challenges, not in my back yard types (NIMBY), as well as a host of other barriers, the importance of the silent disco could rise. Additionally, the high technology requirements of the silent disco make them cost prohibitive at festivals and concerts where funding isn’t overly abundant. That said, the widespread infusion of high technology devices into the general population, specifically smart phones, makes a silent disco possible through the use of consumer grade hardware and software.
Use Apple’s AirPlay standard to transmit sound via Wi-Fi to several users who receive the signal via compatible devices such as iPhones, iPod touch, as well as Android devices thereby creating a “silent disco.” These devices will be operationalized in an environment consisting of consumer grade software and hardware in an attempt to achieve a low cost yet effective silent disco system.
- Budgetary commitment – the lower the better (duh…)
- Interface with DJ/Band setup for broadcasting
- Broadcast to a spectrum of commonly used mobile devices
- Eliminate specialized headphone hardware
- Easy setup and tear down
- Provide a cost free listening environment
- To support 40 listeners at base system
- Provide an easily expandable platform
Hardware (current test bed):
- 2012 Macbook Pro (OS X 10.8)
- Dell Optiplex (Windows 7)
- Airport Express Router (A1392 Gen)
- Airport Extreme Router (5th Gen)
- Netgear Wired Switch
- Three iPhones for testing
- Two iPads for testing
- One Apple TV for testing
- Sony MDR-V6 Headphones
- Dayton Audio D652 Satellites
- iTunes 11 OS X
- iTunes 11 Windows
- Airfoil for OS X
- Airfoil for Windows
- Airfoil Speaker for iPhone/iPad/Android (all version are free)
The cost of the system only includes the hardware required to create a base level system. The cost analysis also makes the assumption that an adequate computer is already available.
- Apple Airport Extreme $200 Retail ($80 used)
- Airfoil for computer $25 (both PC and Mac)
Total cost retail: $225
Total cost used: $105
Configuration was not difficult. Let’s start with the hardware. My Airport Express is only capable of handling 10 devices at a time, that immediately violated one of my design goals. As a result, I purchased a used but “like new” Airport Extreme on eBay for eighty dollars including shipping. This got me up to 50 theoretical users from a single router and supplied better signal range than the Airport Express variant. I powered the router via the supplied power pack and a wall outlet and then hooked an ethernet cable from the port of my Macbook to one of the ports on the AirPort Extreme. The modem port does not get used. The DJ or band need only to produce a single output in 3.5mm headphone jack form that gets plugged directly into the mic-in on my Macbook. Finally, each user will need an Andoird or iOS device as well as a setup of compatible headphones.
Now we are ready for software. I installed Airfoil for OS X on my MacBook. I just downloaded and ran the installer. Each device that I push music to will require an Airfoil Speakers install as well. This is available on both iOS and Android. It is free in each respective app store for download. Again, just download and install.
Once installed I only need to connect my device to the Wi-Fi connection that I created on the port Extreme. To setup my Airport Extreme I used the OS X native Airport Assistant. Windows users will need to download this.
To start audio exchange I just turned the Airfoil software on at both my Macbook and my iPhone/device. At my Macbook it only takes a few seconds for the device to show up as “available.” To send audio from a DJ or band I simply select the line-in option from the top of the Airfoil software on my Macbook. During my tests, I used iTunes audio rather than a DJ or band. Once a device is shown as available on my Macbook I then can turn on the audio stream to that device by clicking the music note to the right of the device name, when the icon is blue it is actively being fed audio. Success!
Two testing configurations were arranged. Both tests were carried out in my small apartment.
Configuration One – My home network is already configured with a Dell Optiplex hard wired to my AirPort Express.
Configuration Two – I used the MacBook Pro connected to the network via ethernet. This time the network consisted of a AirPort Express and Airport Extreme in roaming mode. Both routers remained in close proximity to each other.
Configuration Three (distance testing) – MacBook Pro connected directly to the AirPort Extreme. Used iPhone with headphones to receive audio. The AirPort base station was placed on a second level balcony that is approximately 20 feet from ground level.
Devices – I installed the the Airfoil application on three iPhones and two iPads. For additional load testing I streamed to two Apple TV’s. I used an iPhone with the Sony MDR-V6’s and walked acround both in my apartment and outside of it to test distance capabilities.
Configuration One – Playback worked without connection losses. Sound quality was average or slightly better than average on the Sony headphones and Dayton Audio speakers. There is a detectable latency in play of about 3 seconds. When starting or pausing playback at the Dell Optiplex it took around 3 seconds to affect change at the device. This means that the system is not suitable for use as a live studio monitor. DJ’s or bands will need to figure out live audio monitors on their system separately.
Configuration Two – Playback was again very stable. Sound quality remained average or slightly better than average. I connected seven devices in total to the feed. Playback was consistent and without drops. The approximate three second latency remained.
In both configurations, tests outside a 25 foot radius of the router resulted in signal drops and irregular feed. When traveling outside the signal had to pass through several brick walls and is likely a consequential factor to low signal strength at a distance. Future tests will be performed in the outdoors to evaluate obstruction-less performance.
Update 1 – August, 16
Distance testing – I connected headphones to the iPhone and started walking away from broadcasting station. I was able to go nearly one full city block away from the base station and maintain music without drops. I estimate this distance at around 300 feet. It is important to note that this was with little to no obstruction in the sight-line between me and the base station. Signal dropped dramatically at the one city block distance. Additionally, as the number of obstructions between me and the base station increased there was a noticeable sound performance loss. This was true for connection and sound quality. The obstructions consisted of buildings, both brick and wood. However, obstructions like this are are not something you would typically encounter on a dance floor.
This test also highlights the potential gains that might be experienced from locating the AirPort Extreme base station at a high elevation relative to the dance surface. Mounting the Airport Extreme a few feet over crowd (12 to 15 feet off the ground) should minimize human obstruction of the signal and insure good service for all users.
Caveats and Notes
If at some point I need stronger signal over a larger area, need to support more than the 50 theoretical users, or both, simply applying an additional router in roaming mode (Airport Extreme instructions) should do the trick. In fact, the network should be completely scalable simply by adding routers as throughput becomes too low or user number increases. It should also be noted that this setup requires no outside internet connection or internet service provider as it functions exclusively on the local area network (LAN). Additionally, there are plenty of sources where people have used 8 or more Airport Extreme units to create a large business class network again showing the scalability of the setup.
Router hardware could be an issue as throughput is likely a key factor in reliable playback. Airplay function, while efficient, can be degraded with low signal strength or if outside interference is present. It must also be said that good reliable routers with high output signal is probably desirable. This is why I stuck with the Apple products as I personally have bad great luck with them. That in mind, I suspect that there are a bevy of quality routers on the market that would do the job while being a little easier on the pocket book.
Note (August 16): Roaming mode may not be the best solution when needing greater throughput as devices will likely drop signal when switching from router to another. Instead, leaving each router setup with a standalone SSID might be better. This also could allow for manual allocation of users across the network.
Links and Resources
Apple Airport Express Client mode Help Document – http://support.apple.com/kb/HT2272
Apple Base Station Help Document – http://support.apple.com/kb/HT4145
Apple Airplay Setup Help Docoment – http://support.apple.com/kb/HT4587
Rogue Amoeba Airfol – http://www.rogueamoeba.com/airfoil/
As this project is compiled completely on consumer grade hardware and software I reserve no attachments to the system in any way. In fact, I encourage you to setup your own system and begin sharing the silent dj love. If you do test the system, make alterations in hardware or software, or have information to add I encourage to comment below!