Choosing an amp to power a speaker.

Projects General Guidance
1

Hello everyone, I'm currently working on a project and I'm a little bit stuck. In a nutshell I need my arduino to control a linear motor and a speaker, while being controlled wirelessly through xbee.
I have a 12v linear motor and a current-force curve. From there, for the force I need it to exert I conclude that I need about 1A.
The speaker I have is up to 24W, and it's 90 1w/1m db but I need it only to go to about 100db, so about 16w (give or take I don't care), meaning about 8v@2A.
The battery I'm using is 12v, 5Ah.
I want it to connect something like this;
Battery into;
-LM5296 (5v version) into Arduino
-LM5296 (3.3v version) into xbee
-Tip120 into Linear Motor
-some kind of amp into speaker.
Then Arduino is connected into;
-xbee
-adafruit wave shield
-Tip 120 into linear motor

That's pretty much how I planned this with my very limited know-how. I have a couple of problems however.
First, I have no idea how to power up the speaker. I guess, I would need something like this? But I need 16w, not 3.7, also mono is enough for me.
Then, how can I adjust the volume of the sound produced? On the manuals for adafruit wave shield the mechanical potentiometer does this, but I need to do it wirelessly. And indeed, do I even need the said shield? Can I use something like this and read the file myself? I guess the code would be too much of a bother to write and I better use the shield right? (at least that's my reasoning)
And last, is my logic here sound or did I just write a lot of rubbish?
But mostly I guess I need help picking an amp for my speaker.

Thanks guys, I already learned tons form these boards just reading them, and I hope to contribute too, in time :).

2

Sounds like you need something a little more powerful for an amp.
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-553
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-602

3

When battery powering amps go for a class-D amp. The efficiency is much higher so it will preserver the battery.

Something like this will do the trick:
http://www.diodes.com/file_archive/download.php?branchId=2&pointer=PAM8320_NPA%20_RV%2030%20October

There are many more from almost all semiconductor manufacturers. Ans there shouls also be ready bult ones. google..!

4

Yes, those seem exactly like what I need :), thanks. Now, how would I go about wiring that stuff? I assume I would regulate the power from wave shield speaker output (which is up to 5v) to mV levels, and then connect that into an amp? I didn't find the input sensitivity on the PAM8320, but say on the M033N the input is only <80mV.

5

Normally audio line level signals are some 100 mV up to maybe 2V. Very often modules have somewhat higher sensitivity (=lower level for full output) in order to eliminate the need for extra amplification. I see no problem here. The output level of the waveshield is certainly high enough and you can always attenuate it with the potentiometer. Just observe the capacitor on the input.