Default standard for speaker "sensitivity" measurement listings? Anechoic? In-room? Other?

I would say only 1% of speaker makers have access to an anechoic chamber. And extremely few of those have access to a chamber large enough to work below 100Hz. Even the few that do have chambers use them mostly for research and product development testing.

Most numbers from experienced manufacturers are calculated in half space, speaker on its back pointed up at the sky, no boundaries close by. That’s not easy to do either, as some just use a parking lot or roof top. Avoiding boundaries nearby is critical to avoid any gain being added by reflections of sound off boundaries.

This is the reason many manufacturers don’t bother, its not a level paying field as many products have deceptive measurements. Some more consumer oriented just put a spec down that sells speakers.

Brad

Jim Salk might have built his own "anechoic room".  Some passionate engineers do exactly that, build one in their office or their warehouse or factory.  They are not necessarily true anechoic, as that is very expensive, but it can give you an idea.  This can yield good info but with limitations.  One of the most critical things in a true anechoic environment is noise floor.  If there is any noise leaking in, say HVAC, a truck driving by, wind around the building, it will screw up your measurements.  So if you built a chamber in your office, you'd turn everything off when you measure.  The fact that he states measurements only down to 200Hz is admirable though, as 200Hz would represent 5 or 6 feet dimension- whihc sounds like it clould have been a custom built chamber.  The other possible reason for the 200Hz is the measurement microphone being used to measure, which may not have had reliable flat response below 200.   

Here again,  MUCH we dont know about how it was measured, which makes the measurement relaible only in comparing his speakers to each other.  His measurements are not useful in comparing them to other brands, which would have been measured differently unless it was done in HIS chamber using HIS system.

This is the problem with specs: many many ways to affect results that make them  not comparable to anyone elses measurements.   Its like saying your table is  "brown", its not an absolute and is not translatable - there are 1,000's of different browns.  

Brad

HIlde45, yes you get it. the challenge is many want to assign "brown" a specific value. Will we all know for certain what color your table is if you call it a "brown"? Saying a speaker is 92dB efficient means zero. Saying its 91dB SPL 1w/1m at 1K is a proper spec. If someone else says on an spec sheet "91dB SPL" , that is not the same.

Ive seen companies post specs of a speaker as "20 to 20K". No plus or minus variance (so we dont know how much it varies in between 20 and 20K), no distance or power spec. Inverse square law says if you stuck a microphone at 1 meter or at half that distance, those specs would be 3dB apart. So a 92dB (no power or distance) spec could really be 89dB 1 w/1m @ 1K- or worse. For someone searchng for a highly efficient speaker to mate up with his low pwer tube amp, this ommission of info could be costly as it would mean the speaker actually needs twice the power you thought it did.

Another example is your speaker spec sheet says "20-20K". Is this comparable to a spec sheet that says 100-15K +/- 2dB? Which one is better?

Its impossibel to say from this little information but I’m gonna bet the 100-15K +/- 2dB spec is a better speaker because the "20 to 20K" is deliberately deceptive. It could be + or - 20dB, which would be a crap loudspeaker. You have no idea if the spec doesnt tell you how much the Frequency Response varies between the two points. . 20-20K +/- 10dB means the Frequency Response varies as much as 20dB up and down, which is huge! A variation of +/- 2dB is the normal variation we like to see, so the real spec of this 20-20K speaker could be 200-8K +/-2dB @1K ! If it was really 20-20K +/- 2dB, you can bet they would print that +/- 2dB because they would sell more! Everyone in the engineering and manufacturing business knows what a proper spec looks like so this isnt some innocent ommission. This 20-20K is something I often see with "no name" speakers, or bluetooth speakers, or something that is of low quality. So for some companies, sales today is the single most important thing; for others its the integrity of the brand and building up a reputation for quality.

Brad