What's your opinion on the amp? It was supposed to be great when it came out, Stereophile says that the NAD 3020 was one of the greatest budget amps of all time and this is just the 3020 with the 4020 tuner. I'm just worried that at only 20W/PC they might not be at powerful as something else I could buy for around the same price. I don't plan on playing music loud all the time, but I'd like to be able to crank it up every once in a while.
EDIT: Also, at this price range I could throw in a budget sub and add to the bass without going over-budget. Any suggestions? I found a PDR 10 on craigslist for $80, will this work for me?
Do you really mean the
7020? Or do you mean the
7020e or
7020i?
In any case, NAD is a well-respected company, and they are known for being able to exceed their continuous power rating for musical peaks. However, it is better if an amplifier is capable of plenty of continuous power than just for peaks, as the value of "peak" power depends on how long of a peak you require and how long the amplifier is capable of providing that peak power. If the amplifier can do some level of power continuously, it can handle any peak at or below that level of power for as long as the peak lasts.
Personally, I would not pay $200 for that receiver (no matter which one it is), but it is likely that it is adequate.
As for the subwoofer, I would wait until I had enough to buy a really good one, but your tastes may be different from mine, and you may very well enjoy some added bass to the speakers. Also, a really good one will cost about what your entire budget is (that is, for a new one), so if you think you will never be willing to pay that, you might decide to get a lesser one instead. I do, however, recommend that you see how you like the speakers alone for a while before bothering with a subwoofer, unless you are getting some sort of package deal at a reduced price.
Novice question here, but how do I find out how efficient the speakers are? I know a little bit about impedance matching, but I wouldn't say I have a firm grasp on it. They have a nominal impedance of 6Ohms, but to be completely honest I have no idea how that effects the speaker practically. I also noticed that they are recommended to have 10-100W of power, but how can they be compatible such a wide range? If you'd like to send me some good educational materials or explain this to me, I'd really appreciate it.
For the long answer to that and a few other questions, read this:
http://en.wikipedia.org/wiki/Loudspeaker
Although it is not accurate to do so (see link above), most people use the words "efficiency" and "sensitivity" interchangeably, and the rating you would look for is the sensitivity. A pretty average speaker will be rated near 90dB @ 1 watt @ 1 meter, and a very sensitive speaker will be 6 or more dB above that, with some being significantly over 100dB @ 1 watt @ 1 meter (
here is a famous example). Low sensitivity speakers will be about 5 or more dB below 90dB (please note, "high" and "low" do not have precisely agreed upon definitions in this context; this is vague and approximate).
Now, a few dB difference in sensitivity can make a very significant difference in the power required, as it takes a doubling of power to increase the volume by 3dB (this ratio applies to all speakers of any sensitivity whatsoever, until one is reaching the maximum limits of the speaker). Thus, a speaker with a sensitivity of 90dB @ 1 watt @ 1 meter requires 2 watts to produce 93dB @ 1 meter, 4 watts to produce 96dB @ 1 meter, 8 watts to produce 99dB @ 1 meter, etc. Now, 90dB is fairly loud, but usually people sit further away than 1 meter, and it is not terribly uncommon to listen to music with peaks that go louder (or, if you are trying to cause deafness in yourself by recreating the loudest rock concert ever, you will go significantly above 100dB).
For examples of how loud something is at various decibel (dB) levels, see:
http://en.wikipedia.org/wiki/Sound_pressure#Examples_of_sound_pressure_and_sound_pressure_levels
The
Snell speakers you are considering are rated at 90dB @ 1 watt @ 1 meter, so for normal use by sane people, 20 watts will be adequate, but if your room is particularly large or you want it very loud, it may not be. The way to find out is to try it, but you had better get the woofers refoamed first.
As for the range listed for power appropriate for a speaker, the reason there can be such a range is that not everyone requires the maximum volume of which a speaker is capable, and normal use often involves using very little power. With most speakers in normal situations, listening to background music is going to be using less than 1 watt, though obviously this somewhat depends on what counts as "background" music. Also, how loud it will be in a specific room depends upon the acoustics of that specific room, so even two people who want the same exact volume from the same speakers may require different levels of power due to differences in their rooms.
In general, if you are going to listen at background music levels, the minimum the manufacturer suggests is probably adequate, but if you listen at really loud volumes, you will probably want something at or near the maximum power suggested. But there are no hard and fast rules on this, as a suggestion by a manufacturer is whatever they personally think; there is no objective standard for this.
The impedance of a speaker is important for amplifier matching, but it has no direct relevance to how good the speaker sounds. There are some great speakers that are an easy impedance to drive, and some great ones that are quite difficult for amplifiers (
here is a famous example). The impedance of a speaker varies by frequency; the "nominal" impedance is supposed to be what you can pretend it is at all frequencies for the purpose of amplifier matching. If the speaker manufacturer is honest and competent, you can pretend that the speaker is the rated nominal impedance, but some give a higher impedance than is appropriate for this, because they want to sell their speakers and do not want to miss out on a sale to someone just because they lack the proper amplification for it. The best way is to look at an impedance curve of a speaker to determine this, though if you know the minimum impedance of the speaker and if your amplifier is capable of continuous output into that impedance, you should be fine. If the impedance dip is very high at 20kHz (as with some electrostatic speakers, such as some Martin Logans), it will not matter so much as if it were in the midrange or bass, where more power is required and where more musical content exists. One can safely drive such a speaker with an amplifier that is not rated for continuous output into that impedance, provided that there are no such dips in the impedance curve lower down, though you will not want to use just any amplifier with such a speaker either. So it is not quite as simple as just looking for the minimum impedance.
