Originally Posted by wingnut4772
Have read that Audyssey can boost nulls - a lot- a no no from what I am told. Will Audyssey boost enough to actually ruin a sub driver?
The phenomenon you describe is not Audyssey boosting nulls in the low frequencies. It is caused by the "volume normalization process" that Audyssey invokes. It is described here: http://www.avsforum.com/avs-vb/showt...2#post16972252
and explained here: http://www.avsforum.com/avs-vb/showt...2#post16982682
Quoting from those two posts:
Here is a graph that depicts what is going on:
Red = Line level calibrated with Audyssey off to create a reference line for the following trace
Green = Line level with Audyssey on
Aqua = in room noise floor measurement
Blue = In room measurement with Audyssey off
Purple = In room measurement with Audyssey on
- The green line, which represents the Audyssey filters, should be close to the inverse of the blue line, except here the green line represents the composite filters for all measurements fuzzy logic adjusted, whereas the blue line is the response at a single location.
- The fact that the green line doesn't go horizontal until around 10 Hz suggests that Audyssey calculated the lower -3 dB roll-off in that very low range.
- The fact that the green line crosses the reference red line at 60 Hz is result of normalization. Normalization adjusts the filter level up or down to set the area between the green and red lines above 60 Hz to the upper limit, equal to the area between the green and red lines below 60 Hz to the lower limit.
- Prior to normalization the left-most portion of the green line sat on top of the red reference line.
- Since the entire frequency spectrum per channel is not considered when normalizing the levels, the before and after Audyssey average SPL levels will not measure precisely equal, but nevertheless they will sound about the same level.