This is a budget conscious speech distribution network for Homeseer Home Automation system.

A similar budget approach can be taken to microphones and voice recognition. But, that is another web page.

We found a nice set of "Asound" Amplified Computer Speakers on clearance at MCM Electronics for $3.95 per set, including power supply and purchased 10 sets.  You can find  these speakers in the $6 to $10 clearance or surplus columns all the time. It really pays to be on the MCM mailing list. 

By using amplified speakers we have volume control and ON/OFF override in each room. To create speaker zones we powered each speaker set with an X10 appliance module. This allows the computer to choose which speakers to turn on for the message it is about to speak. 

Using Homeseer the computer can look at what room lights are on and what PIR signals it has received to determine where people are in the house. If  you have a day sleeper or if you don't want to startle sleeping children, Homeseer can be told not to send X10 "power on" to speakers in specific rooms at specific times or the day.

 

A simple "passive" distribution system

Your typical sound card has a "low impedance" speaker output  and most Amplified Speakers  have a relatively high impedance input  so matching is not very critical. This is not theater sound.

Loading is minimized because you are looking up in impedance from the sound card's 8 ohm speaker output into the yet higher resistive taps and the still higher input impedance of each  amplified speaker set paralleled across the output line from the sound card. 

You can experiment with various values but with 10 speaker sets we ended up using 200 ohm resisters in a "T" pad to split off to each room. This gives you some isolation between each tap and minimal signal loss while not loading the sound card amplifier.

If the sound card line/speaker output is balanced and both sides are floating above ground, place a "T" in the + and - of the left and the right audio line. That's 4 "T" splitters in the drop for every room.

However, if your sound card line/speaker output is unbalanced, one side is
grounded, place a "T" in only the + side of the left and right audio line and tie the grounds together.

Depending upon the sound card output power and how many speakers you use
the resister values can be changed. This is passive line level audio distribution and is very forgiving providing that the final load does not go lower than 8 ohms or the output impedance of your sound card and that you don't drive high volume level for extended periods.

This system can be modified for high level music distribution but, that is material for another web page.

Each "T" tap for left and right speaker output will look like this.  

Use these transformers if you have hum from ground loops that you cannot
resolve or if you are planning to run continuous loud music levels though this system. 

The resister network will still allow music at moderate levels but is designed primarily for intermittent low level speech to text or paging system. This is not offered as a HI-FI stereo system although I have found it more than adequate for low level music distribution around our home.

I like Rick's idea of using an FM wireless system and I gave it serious thought but it added about $40 per room to the total cost of the system.  Aside from the cost, it is an ingenious alternative to running cable.