speaker sensitivity dividing lines

Yes these specs can be useful when pairing componets...but the bottom line...speaker sensitivity has little bearing on how a speaker SOUNDS....it does have some relation on how a speaker will BEHAVE with sufficient or insufficient power and at certain volume levels...if you like a speaker(which is a selection process in itself)...then finding suitable power is not really a mystery....i know there are those that believe this is a hi-end art...and all things being equal..the amp has the least influence in a system vs. source and speakers....like cables....there are many who get and ego trip "hung up" on speaker specs...

Phasecorrect: Have you ever actually watched / measured how an amplifier loads into a speaker and how the speaker can modulate the amplifier ? In some cases, you can literally watch the input waveform from the preamp or source change as the amp has to deal with the reflected EMF of a speaker. This can vary as signal amplitude changes i.e. the harder that you drive the speaker, the more reflected EMF that you have to deal with. Obviously, some amps will deal with the reflected signal a LOT better / differently than other amps. This is not to mention the amount of crosstalk that is generated between channels in such a situation. If you or anyone else think i'm nuts, try talking to ANY electrical engineer worth a salt and see what they have to say. As to whether or not this is audible, you betcha. The fact that many people may not have ever really noticed this probably has more to do with the fact that most speakers present relatively "benign" or "easy" loads and the amplifiers aren't being worked to death in such situations. That does not mean that such occurances don't take place on a regular basis though for some of us with reactive speakers.

As far as my thoughts regarding sensitivity of a speaker go, i never implied that one should delete "low" efficiency speakers from their list or only consider speakers of "reasonable" sensitivity. My thoughts in trying to work with this is that many newcomers don't understand that there is such a thing as "matching" when it comes to building a quality component system. All things being equal, starting off with a more efficient speaker will typically make amplifier selection a little easier and open up more available options. If they knew that a speaker was considered "less sensitive" as compared to others, they might be able to make a more informed decision as to the suitability of said speakers and amplification choices. I was NOT saying that this is the most important spec, only that it is one of several factors to look at.

For the record, i have speakers that are 2-3 ohms that are appr 82 dB's output. I also have 3-4 ohm speakers that are about 85 - 86 dB's output. If i had only used speakers that were 8 ohms nominal and 90+ dB output, i would be in a world of surprise in terms of wondering why my amp sounded "bad" ( clipping with lack of control ) and the speakers wouldn't play very loud. If i had some type of a chart to compare sensitivity / output levels of various speakers, i would know that if i went noticeably down on efficiency, i would have to go up on power output to achieve the same spl's and level of control. However, if i stayed within a dB or two from old to new speakers, i might not notice a big difference. Granted, there are other variables here that could come into play, but i'm talking "simple" stuff here for those that aren't that "audio educated", not trying to teach the world physics in one thread or post.

Try to keep things in perspective. If we could cram all we needed to know about each subject into one thread, there would be no need for these or any other forums. I'm still learning and i hope others are too. Sean
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Using a spectrally-weighted specification for sensitivity sounds divine, but probably isn't necessary. I don't think any manufacturer would leave a midrange bump at 1kHz just to get a higher sens spec! At least I hope not.
The problem lies in the bandwith, of course. Since we perceive average loudness in the midrange mostly, then maybe an "average sensitivity" from 100Hz to 10kHz would be sufficient, and not have errors related to bass response averaging, nor tweeter roll-off.
Make sense? And is the spec to be on-axis, or a power-response? Shouldn't make too much difference. But what do you do with bi and di-polar radiation?
In general it is nice to see a trend toward less-thirsty cross-overs and slightly bigger boxes that use volume and bottom -end driver piston area to boost efficiency a bit.
Nothing like being irked by an 84dB baby monitor that sucks an amp down and still gets congested as hell....

Sean...you obviously know more about this than I do...over the years I have had 4,6, and 8ohm monitor speakers with varying sensitivity....all being powered by a 40 or 60w intergrated amp that can handle these more "difficult" loads...and even at moderate to loud volumes...never felt my system was underpowered...however my listening room is fairly small...which comes into play as well...at any rate...I have never felt compelled to really add any additional power...as we all know...even doubling your power has very little advantages...often under 3db...and low to moderate listening levels actually require very little power...often 10w or lower....these examples might be "oversimplified" ones...but they used to illustrate a point (I hope!)...cheers

Sean makes an extremely important point - EMF is a crucial factor in amplifier-speaker interaction and it is often ignored.

When it comes down to it sensitivity is really not a very useful specification at all. Impedance, capacitance, and back EMF tell you much more. Impedance and capacitance are easily measured and graphed. Back EMF is not as straightforward but it's pretty easy to tell if a speaker is pumping it out in large amounts or not from listening tests. Because Back EMF feeds on itself, and the louder you play, the more you are generating, it's a really important factor in loudspeaker-amplifier matching.

For more info see an article we wrote:

http://www.symphonysound.com/articles/tubefriendly.html