Freqency response

I am new to high end. If a speaker has a freqency response of 30Hz to 40Khz do the components up stream have to have equal frequency response or better in order to achieve the full pontential of the speakers . thanks for your help
Yes indeed. Often however, the speaker will have the most restricted frequency response so it is the deciding factor. Not always the case though.

Check to see how the frequency response is measured too. Some do half-power (-3dB) and some don't. Both need to match in measured position for a fair comparison to be made. In other words, watch out for marketing. Arthur
Good luck hearing anything in the neighbourhood of 40 KHz. It wont happen. Depending on age, you are lucky to hear anything above 12 KHz. A lot of audiophiles are in denial over this. I don't think they ever went to an audiologist for a test. One suggestion: try to learn about audio starting with the basic (aka "scientific")stuff. Once you achieve a measure of this, you can go into the audio deconstructionist philosophy adopted by almost all "subjective" audiophiles in TAS, etc and on sites such this one. Good luck.
First of all, any speaker spec sheet that claims a frequency range that wide is highly suspect. There are a lot of ways to cheat at specsmanship, and I suspect this particular manufacturer is well-practiced in them (assuming you're citing a real case here).

Now, it's certainly possible that a speaker might be able to deliver some energy at those frequency extremes, but that's not what matters. What matters (to the extent that this spec matters) is how flat that response is--whether it's louder at some frequencies than others (which it always is) and by how much. That's why an honest FR spec will look like this: 48-18kHz +/-3 dB. In other words, no frequency is reproduced at a level more than 3 dB higher or lower than some "average."

Now, there are still a lot of ways to fudge even a FR spec like that, so it's important to take ANY spec with a large grain of salt. But at least a manufacturer who quotes a dB range in his FR spec is making a nod toward honesty.

I'd also echo Arthur's point that speakers usually are the weak point here. You can spend less than $300 on a receiver and CD player at Best Buy and get flatter FR than almost any high-end speaker system on the planet. (In fact, a lot of so-called high-end speakers aren't all that flat, because the manufacturers are trying to make their products sound distinctive.)
Wow...Three responses that I totally agree with. I have nothing else to offer.
Pbb: I think your upper end of 12KHz is a bit low for the average male. I am 42 and have upper end acuity of 17KHz.
The problem with 'averages' in presbycusis is that the environment plays a very large role and that, of course, varies considerably.
Thank you all for your help, it really helped me ARF