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Absolute Measurements
PostPosted: Mon Nov 14, 2005 2:14 pm Reply with quote
Tobi @ Fohhn Audio AG
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Joined: 25 Oct 2005
Posts: 13




Hi,
how can I measure the absolute SPL of different loudspeakers with EASERA, e.g. 1W at one meter on a 4Ohm Speaker ??

Tobi
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PostPosted: Tue Nov 15, 2005 2:47 pm Reply with quote
Stefan
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Joined: 19 Apr 2005
Posts: 167
Location: Berlin, Germany




Hi Tobi,

if you have calibrated the input properly you can use the Live RTA to see the true input levels.

On the other hand, if everything (in & out) is properly calibrated, EASERA will also show the transfer functions in View&Calc with the right level. Note that this data is normalized to 1V peak. That means to keep measurements comparable, both input and output gains (and clip voltages) are compensated for. So, if you apply a sine signal with 1V Peak you see the same levels at the input as in the transfer function display of EASERA.

We currently work on a more thorough documentation of this topic along with a program update in order to make this clearer.

Stefan
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PostPosted: Sun Feb 12, 2006 5:57 am Reply with quote
Ron Sauro
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Joined: 29 Oct 2005
Posts: 27
Location: Elma, Wa




Hi Tobi...


If you use sweep or log sweep...you should look at the digital output gain level and then place the inverse into the input gain area in the lower left window.... EG..... if the DOG is -15db then the input gain should be +15db
Ron Sauro
NWAA Labs
www.nwaalabs.com
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PostPosted: Sun Feb 12, 2006 9:32 am Reply with quote
Stefan
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Joined: 19 Apr 2005
Posts: 167
Location: Berlin, Germany




Hi,

Ron is right, at present EASERA considers the digital output gain (DOG) as part of the known measurement chain and therefore compensates for it in post-processing. For measuring real sensitivity levels, the easiest way to go is indeed to adjust the DOG to your needs and then to "counter-compensate" it using the field for external gain.

We will have a switch for this functionality in one of the next updates.

Stefan
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