Speaker sensitivity, impedance, and calculating amp power

Al, Erik, Miller C, Tomic601 and others, thank you for the discussion/knowledge above.  Tried both calculators, they are within a db or so.  The above shared knowledge is priceless, much better than a school.  Thank you folks for helping me in understanding a very complex aural subject.  Enjoy the music.

How can an amp have different current output with them same "wattage" as a different brand?  I would think current output capabilities would go a long way into driving a given speaker.   Also it seems hard to get impedance vs frequency curves for a speaker system.  Or do I just not know where to look.  It also seems that in an effort to boast low frequency response in a single cabinet, we lose efficiency.  Am I wrong with any of this?  Just curious.

Glad you didn't delete the thread. I wanted to know this too

@daledeee1 This conversation with Jim Salk has a graph, perhaps of the kind you're asking about? Of course, you're asking about getting graphs for *any* speaker we want to buy. Salk's graph is not in this excerpt but you can find it here:

https://www.innerfidelity.com/content/beauty-sight-and-sound-salk-wow1-mini-monitor-page-2

This part of the Inner Fidelity conversation bears a bit on this topic:
"Q: Tying in with the above - desktop users don't typically have space for a massive amp. They tend to use compact units with relatively low power ratings, with Class D implementations being more and more common. Any comment on amplifier matching with these speakers?

A: Today, the trend in speaker design is to develop smaller and smaller speakers that play deeper and deeper. The problem is, the laws of physics dictate that the resulting speakers will be somewhat insensitive and will require more power to drive. But since that is what speaker manufacturers want to produce, most of the R&D for cutting-edge drivers these days is focused on insensitive drivers that play deeper in smaller cabinets. So if you want to use the cutting edge drivers (which we do), the models you develop will tend to be lower sensitivity. They will require more power to drive, but will be more accurate and exhibit higher sound quality.

At the same time, amps are becoming more powerful to address this need. This is especially true of Class D amplifiers. These provide a lot of power at a very reasonable price and are very efficient as well. While some people feel that Class D amps are not quite ready for prime time and can be a bit analytical, they are certainly accurate and provide a lot of performance for the money. Plus, they run cool which is another advantage.

As for the small class D amps, these are quite attractive cost-wise, but don't work all that well with low sensitivity speakers. Years ago, some friends did some interesting experiments at the Rocky Mountain Audiofest. They set up both average power meters (RMS) and peak-reading meters and monitored the power levels while playing music. While the RMS meter registered 5 - 8 watts, the peak-reading meters hit peaks of 200 - 250 watts during instantaneous transients (drum hits and the like). So while, on average, 5 - 8 watts is sufficient, if you want the cleanest possible performance, the more watts you have, the better. So while these small "T-amps" are quite inexpensive, many of the lower power amps won't have the muscle required to control the woofer in the bass region. So I'd pass on trying to marry them up." (Jim Salk)

There are two kinds of audiophiles when it comes to amps and this subject; the good enough type, and the overkill type. The good enough type look at the rating and usually stay within that range, i.e. 50-100wpc as good enough. The overkill type, such as myself will use amps that are seemingly far more powerful than necessary.

I have seen no preference emerge as to any given simple formula that will assure satisfaction. I disagree that you must stay with very efficient speakers; the sonic characteristics vary so widely in terms of frequency extension, tonality, etc. That simple formulas are not helpful either in regard to speakers or amps.

Actual comparisons reveal one’s priorities quickly. :)