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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Define accuracy posted by Presto on November 10, 2012 at 20:23:00:
Accuracy is basically "what goes in, is what comes out". If the signal is changed somewhere along the way by the electronics it is deemed for this discusssion as less accurate.To determine accuracy in a loudspeaker from a measurement point of view, it must be measured under a prescribed "control" condition. This is why anechoic measurement is essential and an accepted pratice when measuring the performance of a loudspeaker. A condition where room effects do not exist is the only way to measure the performance of a tranducer like a loudspeaker. Measuring a loudspeaker in a "normal" room is pointless. It is like pouring 100% pure water in a glass that has some salt in it. Then tasting the water. The water will taste salty. How can you draw conclusions about how pure the water is (or was) in this case? You can't, there is no control. The point of measurement is to see whether a given device is perfoming in way that is consistant with its design or determine its actual accuracy. If other variables not created by the device are perceived in the measurement the data is meaningless. You cannot quantify whether the data is the device or whether the data is "the room" and its interaction (or the salted glass in the water example). You need a standardized control.
Of course, you can design a loudspeaker for a given room (your listening room for instance), but how does one tell how this speaker will perfom in other locations. You can't, you have no control, no true method of comparsion or accurate measurement of the loudspeakers perfomance other than in the room the loudspeaker was designed for. It's proprietary. It may work well in that room, but horribly in another. Is that the loudspeaker being bad? No ... in actuality the performance in this example is the effects of the room and the design criteria. What the loudspeaker is doing is not accurate unto itself, it is only accurate when used in the room it was designed for. Measuring it would be pointless, except in that room.
So when building a loudspeaker for sale its measured accuracy can only be determined when measured in a standardized controlled environment like an anechoic chamber. And how well the signal put into it is reproduced when measured in this control determines its accuracy. How good it sounds in a room is then purely a factor of the room itself. You can always clean the salt out of the glass before you taste it, but if the water isn't pure to begin with ... do you follow?
This is also the problem with subjective listening for review purposes. While something may work well in a given situation (with its multitudes of affecting variables) its give you no real valuable information for your multitudes of variables. There is no control. Its relativistic. Is the subjective perception and artifact of the device in tests, or are they interactions of the variables alone. The device may be 100% accurate, but the test variables do not allow you to perceive this.
Controlled measurement removes the variables. Let's use this example. Let's say you some miracle device that tranfers a signal perfectly. This hypothetical device is 100% accurate. You measure this in a controlled situation. So you know the device itself is perfect. So now you place this device in an uncontrolled situation. The device has not changed. It is still 100%. It's the situation that is different. So you now know the variables is the situation and not the device.
The same can said for loudspeakers. If you measure the performance of a loudspeaker in an anechoic environment, where the variables are non-existant you know the actual performance of the loudspeaker itself. You know its characteristics, good and bad, accurate or inaccurate. Place it in a real room and it doesn't change in any way. What it does is still the same. It's the interactions within the room that has changed, so you know any difference is the room and not the loudspeaker. No loudspeaker will change the rooms charateristics and visa-versa. They both stay the same. Only if you physically modify the room or the loudspeaker do they change. A loudspeaker cannot remove a wall reflection for instance (it may be able to avoid it, but the reflecting surface is still there in the room). But if you know the actual performance of speaker, you can then determine what influence the other variables are having on the performance overall. So you simply wash the glass, you already know the water was 100% pure before you put it in the glass. But you have to know the water is pure first, or at least how pure and in what way. This way you can say with certainly where the salty taste is coming from and make changes to make the water pure again.
Edits: 11/24/12 11/24/12 11/24/12 11/24/12 11/24/12
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Follow Ups
- RE: Define accuracy - jrlaudio 13:11:29 11/24/12 (1)
- RE: Define accuracy - Presto 19:29:36 12/03/12 (0)
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