Sensitivity is measured as how loudly the speaker will be, driven by 1 watt of power at a distance of 1 meter. A sensitivity of 98db suggests this speaker will play very loudly with very little power. This is very desirable when using small tube amplifiers in triode mode.

An anechoic chamber is a specially designed room that is very well damped and can measure speakers with virtually no room interaction. As indicated by the second measurement, in a typical room, the room can effectively increase various frequencies (and sensitivity) with reflectivity of the sound waves and pressures. Imagine removing the box where the speaker drivers rest as opposed to the increased energy provided by the enclosure. A room can have the same effect.

first up without some facts about the power required the numbers are meaningless.

Most usefully we need to know if this power applied to the spkrs for the test is the voltage that would give 1 watt into 8 ohms. 2.83 volts.

the we need to know how tightly /loosely this measure is averaged / adjusted, that part of the bandwidth given the most weight etc.

We don't just want sensitivity, we want an easy load too, if we are using fleapower amps.

If a spkr was that sensitive at ELF's, well below 30 hz, it would be a big mutha.

'kay?
so a sensitivity spec should read 91db/w/1 metres (8 ohm watts) or similar.

NEXT? Efficiency and sensitivity and impedance are intertwined.

Later?

Timbo in Oz

Ooh!

Can I add a question?

If a speaker has 91 dB/1 watt sensitivity, do we KNOW that it will give 94 dB at 2 watts, 97 dB at 4 watts, etc?

I know the "doubling of power = 3 dB increase loudness" rule, but is sensitivity always linear like that? (Well, logarhythmic, but you know what I mean... ...)

Could there be a speaker that's 98 dB/1 watt, but then only 99 dB at 2 watts, etc?

Hi buddha

Actually,manufacturers "measure" their speakers in the way you describe but only for their own reference.Of course , it doesn't involve doubling of power etc. The reason they give us measurments in 3db increments,is exactly because it involves doubling of power,ie convinience.

Yes. Absolutely. "Efficiency, sensitivity, and impedance are intertwined." I'm not certain there is any one test instrument, meter, or arithmetic formula that can measure the combination. It is the way the amp "sees" the speaker that reveals this fact to our ears, so perhaps an amplifier is the one "true" instrument capable of measuring a speaker, as perverse as this sounds. The combination is everything. I guess that's why I am so skeptical about the measuring mentality -- it gets so carried away, often, with data that don't get confirmed by listening. Now, throw in software variation, and you get an idea why system design is a black art. Some of the most magical combinations absolutely defy logic. William Blake said, "Bring out Number, Weight, and Measure in a year of Dearth." While recognizing the need for designers/manufacturers to record and analyze abstract data for the sake of product-to-product consistency, I'm with Blake when it comes to the final product. Cheers, Clifton.

OK, this may sound really dense, but...

Can two speakers with the same 1 watt sensitivity differ at other wattage measuring points?

Could one 91 dB speaker be less efficient at, say, 8 watts, than another 91 dB speaker?

Or is the relationship fixed?

If the input power to a speaker is doubled, but the acoustic output power does not double that is called distortion.

All speakers distort to different degree, all speakers have some upper limit beyond which they will not get louder (just self destruct). They also have a lower limit where the input signal is just too small to move the cone.

It is never specified , but I would guess that most reasonable speakers have a 70dB or so dynamic range. This means they are mostly linear from power levels of probably 50dB below the 1 watt rating and probably 20 dB above. That would be from about .009V to 28.3V (both RMS) Very good speakers probably have a greater dynamic range

Yo Buddha

No,it is not a fixed relationship,even on same load loudspeakers.Remember,load is not constant.To give you an example,take 2 8 ohm woofers,one drops to say 6.8 ohm at 100 hz and the other at 6.7 or whatever at the same frequency.