Why are speakers measured at 1 meter?

[localhost128]

This is simply wrong Im afraid .

then it should be easy to prove the claim.

kindly detail how at 1 meter in a normal residential room that the indirect sound-field is equal in magnitude (Dc) to the direct signal (Ld), and thus-then moving further away from the source the indirect sound-field becomes many times greater than the direct signal.

and it is not wrong that small acoustical spaces such as home residential rooms lack the volume, mean free path, etc to support a statistically random-incidence reverberant sound-field. this is the foundation of much of the work by Dr Manfred Schroeder and is literally why the subject of acoustics is separated into Large and Small Room subcategories. this is also why indirect signals (indirect sparse, focused specular reflections) are surgically identified in Small Rooms and addressed vs statistical application of absorption to bring down homogeneous reverberation time in Large Rooms. the physical characteristics of the indirect sound-field differ wildly. it is also why RT60 is not relevant/applicable in home residential-sized rooms because the pre-requisites for it to be considered valid cannot be met.

 

[Jukka]

How can a simple question generate so much bull?

As few others pointed out, it's a spec to make numbers comparable.

If you had 5 different speaker sensitivity numbers, at 0.3, 0.7, 1.1, 2.3 and 4.7 meters, you wouldn't be able to tell which one is the loudest.

 

[anmpr1]

How can a simple question generate so much bull? As few others pointed out, it's a spec to make numbers comparable. If you had 5 different speaker sensitivity numbers, at 0.3, 0.7, 1.1, 2.3 and 4.7 meters, you wouldn't be able to tell which one is the loudest.

For a consumer, a published sensitivity measurement is a pretty meaningless specification. I guess if one's idea of amplification is a two watt SET it would be helpful to know more about it.

For manufacturers it is a spec that allows them to claim just about anything, because usually the details of how they measure at one meter are not specified.

 

[Head_Unit]

How can a simple question generate so much bull?

Because it's not so simple actually if you really want to find the origin of that measurement. I wonder how far back 1m was prevalent-wish my old boss Jim Novak was around to ask, he was literally there at the dawn of modern speaker design, and in those days damn the international standards and full speed ahead, "we don' need no steenkin' metric system!!!" Paul Klipsch measured at some other distance because 1m did not make sense for his horns. I also remember a lot of "1V @ 0.5m" specs in the 80s-equivalant in a way to 2.83V@1m but due to driver position probably won't measure the same. Sensitivity is one of the most baloney specs since each maker measures on different physical setups with different equipment and different settings (like smoothing)...and then the marketing department adds a pair and/or "room gain" to inflate the numbers versus competitors...

 

[Tangband]

then it should be easy to prove the claim.

kindly detail how at 1 meter in a normal residential room that the indirect sound-field is equal in magnitude (Dc) to the direct signal (Ld), and thus-then moving further away from the source the indirect sound-field becomes many times greater than the direct signal.

and it is not wrong that small acoustical spaces such as home residential rooms lack the volume, mean free path, etc to support a statistically random-incidence reverberant sound-field. this is the foundation of much of the work by Dr Manfred Schroeder and is literally why the subject of acoustics is separated into Large and Small Room subcategories. this is also why indirect signals (indirect sparse, focused specular reflections) are surgically identified in Small Rooms and addressed vs statistical application of absorption to bring down homogeneous reverberation time in Large Rooms. the physical characteristics of the indirect sound-field differ wildly. it is also why RT60 is not relevant/applicable in home residential-sized rooms because the pre-requisites for it to be considered valid cannot be met.

The best way to find out how the microphone works differently to your ears, is to make your own recordings.

Please read more about ”critical distance” and ” the precedence effect” . Those effects are very real but you never read about them in hifi-magazines .
https://www.vocal.com/dereverberation/critical-distance/

 

[Blumlein 88]

What about critical distance? In most rooms at some point being twice as far from the speaker no longer results in -6 db sound level. Reflections in the room come into play that create the diffuse sound field.

http://www.moultonlabs.com/more/acoustical_measurements_for_the_rest_of_us/P1/

http://www.bnoack.com/index.html?http&&&www.bnoack.com/acoustic/criticaldistance.html

 

[Mesh]

Because it's not so simple actually if you really want to find the origin of that measurement. I wonder how far back 1m was prevalent-wish my old boss Jim Novak was around to ask, he was literally there at the dawn of modern speaker design, and in those days damn the international standards and full speed ahead, "we don' need no steenkin' metric system!!!" Paul Klipsch measured at some other distance because 1m did not make sense for his horns. I also remember a lot of "1V @ 0.5m" specs in the 80s-equivalant in a way to 2.83V@1m but due to driver position probably won't measure the same. Sensitivity is one of the most baloney specs since each maker measures on different physical setups with different equipment and different settings (like smoothing)...and then the marketing department adds a pair and/or "room gain" to inflate the numbers versus competitors...

While @Jukka answered in a straight manner, he does capture what the core intent is.

It is sadly true as you say also, that just because a measurement is presented, it cannot be taken as 'truth'. Some manufacturers are extremely transparent and already have an established reputation for showing trustworthy measurements (of all kinds). Others are less so, and therefore muddle the value of the SPL measurement.

This further shows why having independent measurements of many brands is valuable even if the end result is sometimes a bit of a 'yeah, they actually measure as well as they claim to do' such as in the case of some of the Genelec and Neumann tests that @amirm has done. While I love to see any additional comments and comparisons he does, the fact that it uncovers which companies are more reliable in terms of their own measurements is probably the biggest contribution (in my humble opinion).

The previous answers with more elaboration on speakers actually being measured at other distances, and then being calculated as to their 1m performance also answer how things are done in practice. The end result of that is still to produce a comparable number regardless of manufacturer or speaker design, without taking any room aspects into consideration (as that is simply useless to do as there is no way to predict all rooms accurately). Having said this, I honestly very seldom care much about the SPL unless it is crazy low or crazy high, as how much distortion I can take and the speakers produce at whatever volume I like to listen at is probably more of a deciding factor than a few db in any direction.

 

[localhost128]

The best way to find out how the microphone works differently to your ears, is to make your own recordings.

Please read more about ”critical distance” and ” the precedence effect” . Those effects are very real but you never read about them in hifi-magazines .
https://www.vocal.com/dereverberation/critical-distance/View attachment 102372

kindly explain how the terms used in my past reply impart the need that i require to be explained at a basic level as to what critical-distance means and entails.

and precedence effect is irrelevant as to critical-distance in the context of your prior statement. the field of acoustics is not concerned with what is discussed or what is omitted in "hifi-magazines". these are very-well understood concepts.

fact is you made a claim that at 1m in typical/normal room the reverberant sound-field becomes equal in gain to that of the direct signal. ie, the delineation of critical-distance (Dc) and where-by-beyond the reverberant sound-field becomes higher in magnitude (dominant) than the direct signal and thus one is "in the reverberation". where is any simple objective measurement to support this claim? i would be highly interested to see this seeing as how it would turn the acoustics world upside down in terms of physical indirect sound-field characteristics of small rooms.

fact is critical-distance and reverberant sound-field are properties of Large Acoustical Spaces as home/residential rooms lack the volume for such to be supported.

providing a basic illustration that defines what critical-distance means does not satisfy your claim that such takes place in a normal room at a measly 1meter from the loudspeaker/source. disregarding measurements, is this your subjective experience that at 3ft from a home loudspeaker that the indirect sound-field is equally perceived to that of the direct? and thus at 6, 9, 12ft away from source the indirect field completely dominates that of the direct?

what objective or measured data have you used to derive your original statement that Dc exists at 1m in normal room?

 

[Blumlein 88]

I've measured or attempted to critical distance in some larger living rooms. In my own room, it is about 2.5 meters. The definition I'm using is where you double distance from the speaker and level drops 3 db instead of 6 db. Doubling again it drops even less than 3 db, and then doubling again in my room is not possible.

So critical distance would seem to be 2.5 meters and I listen at 3 meters. You don't have enough space to reach a truly reverberent condition.

 

[amirm]

fact is critical-distance and reverberant sound-field are properties of Large Acoustical Spaces as home/residential rooms lack the volume for such to be supported.

Only if you want it to extend down to 20 Hz. Otherwise statistical properties set in in just about every room at a few hundred hertz above transition frequencies.

 

[localhost128]

Only if you want it to extend down to 20 Hz. Otherwise statistical properties set in in just about every room at a few hundred hertz above transition frequencies.

is this something you-yourself have personally measured across a myriad of ("statistical", no pun) home, residential-type rooms and subsequently presented for peer review?

or how exactly are you able to qualify this statement seeing as how it is contradictory against the work of Dr. Manfred Schroeder? are you presenting evidence to invalidate his prior "Large Room" equation? my university would be interested in that, certainly.

what particular measurement was used to determine whether the indirect sound-field was sufficiently "random-incidence" and thus which particular rooms "a few hundred hertz above transition frequencies" statistical properties would then be applicable?

if typical transition freq is 250hz (dependent upon smallest boundary size wrt wavelength), you are implying that at 450hz and higher that the indirect sound field in "just about every room" will be equal to the direct signal at a mere 1meter (as the user stated above) - and beyond at 6, 9, 12ft+ etc the indirect reverberant sound-field dominates???

what data can be provided to substantiate this wild claim?

 

[dasdoing]

here is a calculator for critical distances http://www.ohl.to/calculators/targetcurve.php

 

[dasdoing]

at about blow 1000Hz the room turns into our loudspeaker in our (acousticly) small rooms: https://www.audiosciencereview.com/...tudio-monitor-review.14719/page-4#post-459114

 

[localhost128]

here is a calculator for critical distances http://www.ohl.to/calculators/targetcurve.php

we need measurements, ie, objective-data that show that at a mere 1m from the loudspeaker in a "normal room" that the delineation of critical-distance (Dc) exists. and thus where beyond this (ie, 2,3-4 meter from loudspeaker) the indirect sound-field completely dominates over the direct.

the user above made such claim with no data thus far to substantiate. a calculator is not measured data.

small rooms (ie, home-residential rooms) do not exhibit the development of an exponentially-rising, exponentially-decaying diffuse/reverberant sound-field above the ambient noise floor at appreciable frequencies relevant to stereo reproduction. they are dominated by modal resonances and broadband sparse (focused) indirect specular reflections - all of which have direction (vector) components and thus are not random-incidence (ie, in direct contradiction to the acoustical definition of reverberation).

your calculator also requires input of Reverberation Time (RT60) which also does not exist in Small Rooms.

this calculator is a textbook example of garbage in = garbage out. the calculator (or RT60 button within your measurement suite) may spit out values based on your input, but if the pre-requisites are not met the output cannot be considered valid.

what data is there to substantiate the claim that at 1m in my normal living room suddenly the indirect sound-field is equal to that of the direct?

also if the claim "Otherwise statistical properties set in in just about every room at a few hundred hertz above transition frequencies. " were true, we would treat the home normal room 450hz and above by statistically (randomly) applying absorption within the room to bring down the homogeneous reverberation time (as is done in Large Acoustical spaces such as auditoriums and concert halls/churches) - and not do surgical application of absorption (or other treatment) to address a specific focused specular indirect reflection (which is how the actual indirect sound-field exists and impedes the listening position). this simply isn't true. acoustical issues at 450hz and above are not addressed statistically as there is no statistical property of the indirect sound-field.

 

[Rock Rabbit]

Any loudspeaker SPL online calculator don't say it explicitly but there is an implicit ANECHOIC assumption. They use the inverse square law for distance attenuation....so please, forget about reflections! diffuse field or whatever!
Happy new year!
P.S.: the calculated frequency response is anechoic too, ...or with gated response in a room. Designers don't bother with "your" particular room

 

[dasdoing]

we need measurements[.......]that show[........]the indirect sound-field completely dominates over the direct.

have you clicked the link I posted below that post you are responding?
we hear the room below 800-1000Hz-ish.
you can do a simple test with a tone generator. run a sine wave at let's say 100Hz and move in you room. how come there will be HUGE variations in SPL? because you are not hearing direct sound. you can actualy find frequencies where the SPL directly in front of the sepaker will be quite low, and huge elsewhere in the room. play around with a tone generator since it will show you so much about your room in general

 

[dasdoing]

that's why in professional audio the room is the first thing you will invest in, only then comes the sound-system.

 

[ernestcarl]

that's why in professional audio the room is the first thing you will invest in, only then comes the sound-system.

A lot of people are just renting in N. America. And even if they do own the house(s), many are probably planning to move eventually. Few people want to invest from the ground up some construction-level room acoustics planning with a real acoustician.

 

[ernestcarl]

Any loudspeaker SPL online calculator don't say it explicitly but there is an implicit ANECHOIC assumption. They use the inverse square law for distance attenuation....so please, forget about reflections! diffuse field or whatever!
Happy new year!
P.S.: the calculated frequency response is anechoic too, ...or with gated response in a room. Designers don't bother with "your" particular room

With the usual narrow band pink noise used in calibration, I lose 5dB instead of 6dB at my own MLP (2m).

 

[dasdoing]

A lot of people are just renting in N. America. And even if they do own the house(s), many are probably planning to move eventually. Few people want to invest from the ground up some construction-level room acoustics planning with a real acoustician.

with the efford people here are putting into understanding the sound producing process, they can equaly start learning the room acoustics part. I never contracted an accoustian. and I came up with a solution that only requires e few holes in the walls/ceiling and used pet-wool that wont rot over time and can be reused in a new room when I move.
I think the wife-factor is the biggest problem here... a man-cave is mandatory hehe