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<blockquote data-quote="Ivan Beaver" data-source="post: 82704" data-attributes="member: 30">Re: Loudspeaker SensitivityThe reference is 1M-but if you actually measure at that distance-there are all kinds errors that can come into the measurement.&nbsp; And usually in a &quot;good way&quot; for the spec and a &quot;bad way&quot;&nbsp; for the designer trying to use that spec in a prediction.When you measure to close-the low freq is going to measure higher in level and lower in extension than it would if you measure further away.This is due to physical size of the cabinet acting as a boundary-kind of like the proximity effect of a mic.&nbsp; Use it close to your mouth and the bass is louder.So the manufacturer will like the results-but if you are trying to use the spec for some useful information-such as predicting what the SPL at a particular freq will be at a particular distance.Then there is also the discussion of &quot;what is 1M&quot;?&nbsp; Sure we know the distance-but measured from where?I have heard (but cannot prove) that at least one manufacturer used to measure from the throat of the HF driver.This can be a real problem-like with our J4.&nbsp; The HF drivers are so far back in the horn-that they are about a meter before they get to the front of the cabinet.So at 1M-the drivers are actually 2M away-or 6 dB is already lost due to distance.If you measure at a further distance and then &quot;back calculate&quot;, you can minimize the effect of the depth of the cabinet.So where you measure-and how you measure can really affect the result-and what the manufacturer &quot;wants&quot; out of the spec.&nbsp; Data that designers can use or &quot;better specs&quot;.The only way to be sure is to measure the cabinets in question yourself-under the SAME conditions.-but even then that can cause some errors.It is one thing to measure-and quite another to do it right and get real usable accurate results.</blockquote>

[QUOTE="Ivan Beaver, post: 82704, member: 30"] Re: Loudspeaker Sensitivity The reference is 1M-but if you actually measure at that distance-there are all kinds errors that can come into the measurement. And usually in a "good way" for the spec and a "bad way" for the designer trying to use that spec in a prediction. When you measure to close-the low freq is going to measure higher in level and lower in extension than it would if you measure further away. This is due to physical size of the cabinet acting as a boundary-kind of like the proximity effect of a mic. Use it close to your mouth and the bass is louder. So the manufacturer will like the results-but if you are trying to use the spec for some useful information-such as predicting what the SPL at a particular freq will be at a particular distance. Then there is also the discussion of "what is 1M"? Sure we know the distance-but measured from where? I have heard (but cannot prove) that at least one manufacturer used to measure from the throat of the HF driver. This can be a real problem-like with our J4. The HF drivers are so far back in the horn-that they are about a meter before they get to the front of the cabinet. So at 1M-the drivers are actually 2M away-or 6 dB is already lost due to distance. If you measure at a further distance and then "back calculate", you can minimize the effect of the depth of the cabinet. So where you measure-and how you measure can really affect the result-and what the manufacturer "wants" out of the spec. Data that designers can use or "better specs". The only way to be sure is to measure the cabinets in question yourself-under the SAME conditions.-but even then that can cause some errors. It is one thing to measure-and quite another to do it right and get real usable accurate results. [/QUOTE]

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