Background
When selecting an amplifier and speaker, you are usually provided ratings or output in watts. For a speaker you get maximum and nominal watts rating, while for an amplifier you get output in watts.
I am confused, because I have read that you want your amplifier to have a higher output in watts than you speakers watts rating, as this means it does not need to work so hard to power the speaker, so will avoid clipping.
I have also read, that you only want to supply the speaker on average its nominal rating, while only supplying its maximum rating in bursts. If you exceed these numbers you will damage the speaker.
Question
So, which is it? Should my amplifier have a higher output in watts than my speakers maximum or nominal power rating? Or should my speakers have a high maximum or nominal rating...and if so, which one, nominal or maximum?
TPA6211A datasheet
Which of these configurations is recommended?
1. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (3W Output)
2. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (2W Output)
3. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (1.5W Output)
4. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (1W Output)
5. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (0.5W Output)
Context
To provide some context, I am designing a solution for a low cost consumer product that does not require high fidelity audio or high volumes. The amplifier will need to run off 3.3v or 5v, which will be provided by an adapter connected to mains power. Audio will be provided by a line-level input, most likely the audio device will be a phone, mp3 player or computer.
I am currently looking at these ICs, as I just need a low cost mono amplifier (class AB) to drive a small speaker (most likely 8 Ohms, unless I can be convinced otherwise)
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You are the best.
Having lower amounts of power will not cause the amp to clip. What causes clipping is when the amplifier gain is turned up to the point of clipping. Now if you are slightly under powering a speaker or overpowering nothing bad is going to happen if the gain is set correctly. The only bad thing that comes from not enough power is low volume and people try to compensate for that by turning up the gain and causing the amp to clip. It's not a exact science. A little less or a little more than the speaker is rated for is not going to cause any issues. Something else to keep in mind is that the max power rating on a speaker or on a amp doesn't mean anything. A company can basically put any number on that as they want. The number your looking for is the RMS or as you said nominal. That's the only number that matters.
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what also matters when matching speakers and amps is the ohm rating of the speaker. now the catch to the ohm rating is that it changes depending on the frequency it is playing, the rating on the speaker is the ohm rating when the speaker is at rest.
the amplifier will basically give you different amounts of power output depending on what ohm rating the speaker has. the lower the ohm rating the more power the amp can send. say you start with an 8 ohm speaker and the amp gives you 10 watts of power, usually everytime you halve the ohms of the speaker the amp will double the power so a 4 ohm speaker on the same amp will receive 20 watts, and so on all the way up to the amp's lowest stable ohm load rating. its more complicated than that but this is how it works in general.
so, back to my point... if you have a 100w speaker that is rated at 4 ohms, then you would look for an amp that is rated to output around 100w at 4 ohms. but, the reason why it doesn't matter to match the power ratings exactly is because while the speaker plays you will not be getting 100 watts of power at all times, it will go up and it will go down as the the music changes. if that speaker can truly handle 100 watts continuously then using an amp that outputs a little more wont hurt it as long as the distortion is kept in check while you are listening to music.
hope that helped
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