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Loudspeaker Sensitivity
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<blockquote data-quote="Ivan Beaver" data-source="post: 82548" data-attributes="member: 30"><p>Re: Loudspeaker Sensitivity</p><p></p><p>It really depends on what you are trying to show-HOWEVER there are also some "catches".</p><p></p><p>Let's say you measure the freq response a loudspeaker-basically a full range one. And your measurement is calibrated.</p><p></p><p>One of the things to consider is that the low freq cutoff (typically -3dB) HAS to be tied to the sensitivity-or it means almost nothing.</p><p></p><p>Some manufacturers like to state these differently-but that is VERY deceiving as to the actual performance.</p><p></p><p>Let's say that the "average" is 100dB. ie a line drawn through the middle of the response curve. But there is a peak at 1Khz that is 105dB. Some would say the sensitivity is 105dB. BUT if you do that-the point of -3dB would HAVE to be 102dB-which is higher than the average-so there is no "-3dB"</p><p></p><p>So to find the real -3dB you look for the points on the response graph that are 97dB on each end of the response. (100-3=97dB)</p><p></p><p>That would be your low freq number that "should" be published. Now one decision to make is-if you want the sensitivity to be "higher"-then you HAVE to accept a higher low cutoff and lower high cutoff.</p><p></p><p>But if you want to extend the freq response-then you have to state a lower sensitivity-AND maximum ouput (assuming you want the upper and lower freq to be part of the sound output).</p><p></p><p>One of the "games" that some manufacturers like to play is as follows. Let's keep the same 100dB "middle" of the response. Now state the freq response as +/- 3dB. Now that gives a 6dB window. So if you subtract 6dB from 100dB-then that gives a "flat response that goes down to 94dB (100-6=94dB)</p><p></p><p>NOW let's give a -3dB number-which would be at 92dB-which is actually NINE dB below the stated sensitivity!!!!!!!!!!!!!!!!</p><p></p><p>So that freq is MUCH lower in level than you would expect-based on the "simple numbers".</p><p></p><p>If you don't believe me-just go to some websites and look at the stated -3dB and look at their measured responses and see for your self.</p><p></p><p>Not everybody does this-but a good number do-you might be surprised of some of the "big names" that do this. I know of some sites that the stated -3dBis actually 15-20dB down from sensitivity. WOW I would love to see that math.</p><p></p><p>I assume the manufacturer is hoping that people will not look at the graph and just take the stated numbers as fact. NOT.</p><p></p><p>By looking at the measured data-you can come up with own numbers as to what you feel they should be. But that only applies if the response graph is supplied with a dB scale.</p><p></p><p>If only a 0 (zero) dB is the reference is supplied-then you have no idea what the "reference" is. Is it the stated sensitivity? How do you know? Did you just "assume" that? What if the sensitivity number is actually referenced to a peak on the response?</p><p></p><p>Sometimes you have to dig a bit deeper for the REAL answer.</p></blockquote><p></p>
[QUOTE="Ivan Beaver, post: 82548, member: 30"] Re: Loudspeaker Sensitivity It really depends on what you are trying to show-HOWEVER there are also some "catches". Let's say you measure the freq response a loudspeaker-basically a full range one. And your measurement is calibrated. One of the things to consider is that the low freq cutoff (typically -3dB) HAS to be tied to the sensitivity-or it means almost nothing. Some manufacturers like to state these differently-but that is VERY deceiving as to the actual performance. Let's say that the "average" is 100dB. ie a line drawn through the middle of the response curve. But there is a peak at 1Khz that is 105dB. Some would say the sensitivity is 105dB. BUT if you do that-the point of -3dB would HAVE to be 102dB-which is higher than the average-so there is no "-3dB" So to find the real -3dB you look for the points on the response graph that are 97dB on each end of the response. (100-3=97dB) That would be your low freq number that "should" be published. Now one decision to make is-if you want the sensitivity to be "higher"-then you HAVE to accept a higher low cutoff and lower high cutoff. But if you want to extend the freq response-then you have to state a lower sensitivity-AND maximum ouput (assuming you want the upper and lower freq to be part of the sound output). One of the "games" that some manufacturers like to play is as follows. Let's keep the same 100dB "middle" of the response. Now state the freq response as +/- 3dB. Now that gives a 6dB window. So if you subtract 6dB from 100dB-then that gives a "flat response that goes down to 94dB (100-6=94dB) NOW let's give a -3dB number-which would be at 92dB-which is actually NINE dB below the stated sensitivity!!!!!!!!!!!!!!!! So that freq is MUCH lower in level than you would expect-based on the "simple numbers". If you don't believe me-just go to some websites and look at the stated -3dB and look at their measured responses and see for your self. Not everybody does this-but a good number do-you might be surprised of some of the "big names" that do this. I know of some sites that the stated -3dBis actually 15-20dB down from sensitivity. WOW I would love to see that math. I assume the manufacturer is hoping that people will not look at the graph and just take the stated numbers as fact. NOT. By looking at the measured data-you can come up with own numbers as to what you feel they should be. But that only applies if the response graph is supplied with a dB scale. If only a 0 (zero) dB is the reference is supplied-then you have no idea what the "reference" is. Is it the stated sensitivity? How do you know? Did you just "assume" that? What if the sensitivity number is actually referenced to a peak on the response? Sometimes you have to dig a bit deeper for the REAL answer. [/QUOTE]
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