Mr. Multimedia

In February we talked about Plasma Display Myths. This month we'll discuss whole house music or distributed audio. Since our radio discussions this month are on this, I thought a little more information might be helpful.

There are numerous approaches to distributed audio but basically they break down to 3 categories:

1. Traditional analog sound distribution
2. Hybrid analog/digital
3. Digital networked

We will discuss each of these in turn.

First, let's point out a few facts:

1. All sound is analog when you hear it. We can store it digitally or send it around digitally but when we hear it, it's analog. In the end it has to play through speakers which are motors that move air.
2. Room acoustics, how sound behaves, is just as important to distributed sound as it is to theater sound.
3. There are many common mistakes.
4. Pure analog approaches do not necessarily produce better sound than digital approaches. In many cases the opposite is true.
5. Distributed audio can't be done on the cheap.

Second, let's talk about what and what not to do. Some of this is technical, some is practical.

1. Volume controls
   
   Many people put in whole house music by running speaker wire from some kind of source, say an amplifier, and then put volume controls in the speaker lines. These controls are usually knobs or sliders on a wall. Bad idea. This is done to save money but it is very hard on equipment and sound quality.
   
   The input from a sound source (radio, cd player, media server…) is usually around one volt. It varies a little depending on how loud the music is. The output from an amplifier, driving speakers, is anywhere from 5 to 20 volts or even more. We can control volume from the source with small changes, or we can control it on the way to the speaker with by throwing away lots of energy.
   
   An amplifier expects to see a certain impedance or resistance from a speaker. When it sends energy directly to a speaker it sees that amount. A speaker-line volume control can only cut down on that energy by throwing some of it away. In other words it can only reduce volume. So the amplifier must always play loud. Loud takes more energy (and it can distort the sound). If the volume control changes the impedance, it can actually draw more energy from the amplifier and make it work too hard. The amplifier will cook - burn out. The volume control tries to keep the resistance the same (impedance-matching) but it doesn't work very well. It creates heat when it throws away energy. Just a few weeks ago, we had to repair two amplifiers and eliminate the volume controls from a system in a restaurant. The sound was distorted and the amplifiers kept heating up. Two of three burned out.
   
   The proper way to control volume is by increasing the source voltage when we want more, not decreasing the output voltage when we want less. This can be done with controls in the rooms that connect back to and adjust volume at the source. It can also be done with remote controls.
   
   In-line volume controls are inexpensive, but repairs and replacements are expensive. Distorted sound is not very pleasant. In most circumstances people grow to dislike these systems when they hear others or when the repairs start to add up. There is no cut-rate approach to this.
2. To Zone or Not to Zone
   
   Another common "money-saver" is building a music system that can only play one thing. In other words, you hear the same program in every room. This just never works. The kids want this, the parents want that, Dad wants to listen to the game and it goes on and on. Plan to establish multiple "zones." Each zone can choose its own program. Everyone is happy. No battle of the bands.
3. How do I store music?
   
   There are various ways to access music in a distributed system. Many have a tuner or two for AM/FM/Satellite radio. Most also have a TV input so you can hear what you are watching when you run into the kitchen for a snack.
   
   The major issue is stored music. Some people like to hook up big CD changers. These things can be ganged together to hold up to 1200 CDs, but you can only play one at a time. Also, it can take a long time to load a CD. We generally recommend a media server. There are two that I like depending on the circumstances. Media servers are fast and show information like:
   • Play lists
   • Music by
     • Genre (rock, hip-hop, classical…)
     • Artist
     • Title
   Media servers also can supply multiple outputs, up to 16, in the form of analog audio output cables or digital streams. Your CDs must be transferred to the media server and can be stored in several forms including:
   • Wave files
   • MP3 files
   • CD Audio
   • FLAC
   Wave files and CD Audio take up a lot of space on the server's hard drive, limiting the number of songs that can be stored. The popular MP3 files are compressed. They save space but lose music information. MP3s do not sound as good as the original CD. The greater the compression, the worse they sound. 128mb, the most common form, sounds better than AM radio but is not in the class of a CD. FLAC files are also compressed, albeit not as much as MP3s. But FLAC files do not lose music information. They sound as good as the original and still save space on the hard drive.
   
   Transferring CDs to a media server can be tedious, but your installer may be able to help you out with that. MP3 and wave files can be directly copied onto the server.
   
   A good server will have an internet connection so it can automatically look up title, artist, and other information as well as cover art from most CDs.
4. Wall or Ceiling?
   
   Where do I put the speakers? Simple answer — the ceiling. Ceiling speakers give an uneven distribution of sound (some areas louder, some softer, but they can expose the entire program as people walk around the room.
   
   Wall speakers only work if you, the listener, are seated at a single location like a desk. Otherwise they are subject to interference when someone walks in front of them, fading as you move away, cancellation if they are located across from each other (you can't hear the sound). The only time we use wall speakers is when the listener is in a fixed location or they already exist and we are retrofitting to an old system. Even then we recommend moving or replacing the speakers with ceiling units.
5. Stereo or Mono?
   
   Mono. Everyone has been in the sweet spot between two stereo speakers. The soundstage is perfect. You can tell where every voice and every instrument is located. But, move little to the right and the whole stage shifts. Move beyond one of the speakers and the stage collapses and you only hear one channel. Part of the program is missing.
   
   If you want to hear all the music, put it all in every speaker. Otherwise, one speaker can block another completely.

This is getting long, so let's discuss the different approaches to distributing the music.

1. Traditional analog music distribution.
   
   This is what you find in most existing music distribution systems and is still the most common new installation. It comes in two forms:
   1. Music sent to an amplifier in the room and speakers wired from there
   2. Music coming from a distribution amplifier at a central location and speakers wired all the way from the amplifier.

   I'm going to take a position on this that I will reverse later on the digital network version. Sending music signals (to individual room amplifiers) at line level in shielded cable instead of full volume as with (unshielded) speaker wires makes them more noise immune (i.e. won't pick up interference and have extra sound like static or hum). But, in-room amplifiers are bulky and difficult to place. Most are of low quality. Traditional systems should be built in a central location. Make speaker runs to the room. Still, analog sound quality is distance dependent. The signal gets weaker as the distance increases. There is no ideal solution in this situation. Make sure you use high quality components, use large (low gauge) speaker wire and avoid running the wire next to electric wires or by electronic equipment such as computers.

2. Hybrid analog/digital
   
   Hybrid systems have some analog and some digital characteristics. The control components (volume controls, source selector…) are digital, but the music is still analog from the base all the way to the speaker. The control systems use category 5 wire, the same wire as that used for analog volume controls (the ones that are not in the speaker line). These systems use the same amount and the same kind of wire as that used by the pure analog systems. There is little advantage to these systems over the analog. They are IP addressable so they can participate in a network, but they have little to contribute.
3. Digital Networked
   
   The advantages of this approach are numerous:
   • The music is streamed. It is not analog, it is digital, so it is sent to each room without picking up interference or noise.
   • It uses the same wire as the control systems (volume, selection) so you do not need to run both the control wire and the speaker wire all the way from the source.
   • The speaker wire run is very short, running from a small amplifier by the volume control to the speakers. This is the position reversal I spoke of earlier. For analog run speaker wire from the base. For digital use an amplifier in each room for each pair of speakers. These are very small amplifiers that can actually mount in a wall box just like a light switch.
   • The best of these systems, the one we use, is almost infinitely expandable. It can take as many sources as you want and service as many zones/rooms as you can wire in the network. The wiring is category 5 with extra pair or 2 of wires to power the amplifier. If your network is already wired (Ethernet 10/100) you can power the amplifier and control pads with small power supplies that plug in, but they are unattractive (we call them wall warts).
   • Wireless networking can be used for control but not to actually stream the music.
   • It can be controlled from anything that can run an internet browser and macromedia flash. This includes a PC, laptop, Wi-Fi PDA, wireless pad… So in many cases you don't even have to buy control pads.

Ok, this is a lot to digest but maybe now you understand that doing this right involves a lot of decisions. It's never easy but it is very rewarding. I've never met anyone who didn't love it once they had it. The only exceptions to this of course is when the systems break. That's often how we get business. Someone installed something that wasn't up to par. Do your homework and don't try to find a bargain basement way to do this. There are no shortcuts. There are bad products.

Choose wisely.

As always, feel free to email me at info@infinitesightandsound.com with any questions or to suggest any topic for discussion in this little forum.