Multi-Room Audio Systems
Also known as whole house audio, these systems allow you to listen to various audio sources in some or all of the rooms in and outside your home. Typical sources are AM/FM radio, internet radio, MP3 players, music servers, CD juke boxes, etc.
Intercoms, the first multi-room audio systems
From a historical perspective, some of the first
multi-room audio systems were intercoms.
The intercom master
station or base station contained an AM/FM radio, and each room with
an intercom substation, in addition to paging functions, could
listen to the radio station that was tuned by the master/base
station. We still see updated versions of these today but there are better systems
available. Intercoms usually had only one speaker, so stereo
was not available. They usually had very low power, maybe 1
watt, and the speaker was not a high fidelity speaker, so the
quality of music was limited. While later intercoms had inputs
for other music sources, most were limited to one radio tuner only,
and every intercom substation had to listen to the same source.
Speaker selectors and volume controls
The next step to a more advanced system was a stereo amplifier or
receiver connected to a speaker selector. The speaker selector
had on/off buttons for the stereo speakers in each room or "zone".
Electronics in the speaker selector divided the power of the
amplifier among the zones that were selected. Some speaker
selectors also contained individual volume controls for each zone,
but it was more convenient to place the volume control on a wall
plate in the zone. 
The stereo speakers in each zone were much
higher quality than intercom speakers and were usually mounted in
the ceiling instead of the wall. These systems represent the
least expensive implementation of multi-room audio. While this was an improvement
over the intercom system, it still had some drawbacks. The
electronics in the speaker selectors and volume controls degraded
the sound quality significantly, but it was considered acceptable
for "background music". And while you could adjust the volume
in each zone, you could not switch sources, say from CD player to
radio. There was also no control of the source, like changing
the radio station. For anything other than adjusting the
volume, you had to make a trip back to the main amplifier or
receiver and make the changes there. Finally, all the zones
were still tied to the same source, so you could not listen to radio
in one room and CDs in another for example.
Multichannel amplifiers and multifunction keypads
The next leap forward for multi-room audio was the multi-channel
amplifier with keypad controls.
Now there was a dedicated
amplifier for each speaker. A 6 zone system would have a 12
channel amplifier (6 stereo pairs) and 6 keypads, one for each zone.
A typical system would have 4 to 6 source inputs so a variety of
audio sources could be attached. The keypads would allow not
only volume control but source selection as well. Some systems
had IR capability, so the source equipment could be controlled from
the keypad. For example, you could change to the next radio
station, or skip to the next track on a CD. Sound quality was
greatly improved by removing the speaker selector and volume
controls. The new volume controls actually controlled the
amplifier gain instead of just attenuating the speaker level signal.
Some keypads even had displays so you could see what radio station
you were tuned to, or which track on a CD was playing. The
latest versions of this system allow metadata to be displayed on the
keypad, so you can see not only the radio station information, but
also the artist, album, and song name. These newer versions
have iPod integration so you can see playlists, album art, etc.
The most expensive systems had large color touch screens, eliminating
the keypad buttons. While these systems cost more than a simple
speaker
selector with volume controls, they are much more functional
and sound better. The only remaining draw back to sound
quality was the long runs of speaker wire from the multichannel
amplifier to the speakers. For best sound quality, a speaker wire should be as short
as possible. For typical 16 gauge speaker wire, anything
longer than 30 feet starts to compromise the sound quality.
For multi-room audio systems installed in larger homes, 300 foot
speaker wire runs are not uncommon.
Distributed digital audio amplifiers
The development of the digital audio amplifier solved this final
issue with high quality audio in multi-room audio systems.
Digital audio amplifiers are extremely efficient, very small and
dissipate less heat than analog audio amplifiers. This allowed
the amplifier to be distributed right out to the zone. They
are installed on or very near the keypad or touch screen controller
so speaker wire runs are minimized. In some installations the
digital amplifier can be installed right on the back of the speaker.
Quite often these new systems are easy to retrofit. A power
supply replaces the old multi channel amplifier and attaches to the
speaker wires to carry low voltage power to the digital amplifiers.
The
network cable now carries the analog or digital music to the digital
amplifier.
Other Features
We have come a long way since the original intercoms, but the intercom features have been integrated into some of the newer multi-room audio systems. These systems include microphones in the keypads so you can talk to people between rooms. Doorbell microphones let you talk to someone at your front door. When the doorbell is pressed, music is muted in the zones so the doorbell can be heard. Paging is implemented so you can page someone in all the zones at once. Keypads can be very sophisticated, with large color touch screens. These keypads display a rich graphical user interface and can also display video from security cameras.
M31 Inc. is ready to help
From a simple volume control system to elaborate distributed amplification systems, M31 Inc can sell, install and service your multi-room audio system. Give us a call today and let us know how we can help you get beautiful music all around your home!