Room Correction vs Parametric EQ
From DRC
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It's all about definitions
In fact they are both quite similar, it all comes down to definitions.
Parametric EQ
Parametric EQ refers to adding a notch filter or boost at a certain frequency to lower or raise that particular frequency. Usually such systems perform the same filtering to left and right channels, but of course that's just an implementation detail (otherwise the user would have twice as many controls to fiddle with!). Usually you have just a limited number of channels of EQ, say 6 or 10 channels.
Room Correction
Room Correction is really just a very large, automatic EQ system. Implementation is normally done by the user telling the system what they would like the freq response to look like, and then the system calculates a single very advanced filter which implements what would otherwise take a huge number of parametric EQ filters.
Room correction systems usually also calculate seperate filters for each speaker. In this way we can match each speaker to each other - something which is very important for good stereo imaging.
Can we do the same with Parametric EQ?
Although the same job could in theory be done by parametric EQ it would take a great deal of attention to specify so many different bands of EQ to reach the same level of accuracy as a single room correction filter. Also implementation is normally much easier for us poor users, instead of having to measure the freq response of the system and then design a bunch of filters to transform what we have got into what we want, instead we simply choose "what we would like" and the room correction system does the hard work.
If we also assume that we want good imaging then it's also important to correct each speaker individually and this not only doubles the number of parametric filters required to be generated, but also the poor user has to make sure the final filter makes the freq response the same for each speaker!
Furthermore the phase response of parametric EQ filters usually is directly tied to the selected amplitude response and can't be changed indipendently, so it's pretty difficult to control the time behaviour of the system. To get the same phase response control of a room correction system using parametric EQ a lot of different overlapped filters often need to be used, making the filter tuning procedure really long and quite cumbersome. Even if you have the patience to tune an huge number of filters up to the desired magnitude and phase response, often the results aren't as accurate as a good room correction system. Despite these limitations there have been situations where excellent results have been achieved using parametric EQ, both in the magnitude response and in the time response, expecially in the bass range.
Links
Also see the TacT website here for their view on the differences:
