Dynaudio (Evoke) + ExpertPro 220

[Jean-Marie]

@jvoki , @Delija ,

Thanks for those posts and measurements, much appreciated, but I find myself left with a problem. I got the sort of information I was looking for but I didn't get the answers I was looking for, instead I was left with more questions.

OK, we're looking at data from 2 different rooms with 2 different pairs of speakers. That means I really can't compare one set of measurements with the other but one set shows  a significant difference with SAM off vs on at 0% and the other includes a report that there is no difference between SAM off and SAM at 0%. I think we can reasonably expect that if there is a difference, it should show in both cases and if there isn't a difference, that should show in both cases. Something is going on.

I have to say that, based on the comment from Floyd Toole which I mentioned, and what I hear when I compare SAM off and SAM on at 0% in my system, I expected to see a difference which leaves me with 3 possibilities I can think of to explain the different results:

1- the speakers because they are going to have different frequency and phase responses in the low bass;

2- the difference in software and mics used is a factor;

3- XTZ Room Analyzer and REW are doing something different in their measurement process.

There is also another possibility which is that neither set of measurements relates to the most indicative parameter and that parameter is probably phase response.

My interest here is that I'd really like to get some kind of useful sense of what the difference between SAM off and SAM on at 0% is because I do hear a difference, and also some understanding of what the % setting adjusts—does it affect the range over which phase correction occurs, does it introduce some level of bass boost over a freqiemcy range with a change in either or both depending on the level of the setting, or is it a combination of bot of those things or even possibly something else. Devialet are fairly uninformative on what actually is going on, as usual.

It would be interesting to see this discussion taken further but I think if that's going to happen we should really move it to another thread because it is off topic for this thread but I think it may be simpler just to leave things where they stand at present. I have a suspicion that it would be a lot easier to get measurements which give us a better idea of what is going on if Devialet were more informative about what actually is going on so that we knew the appropriate measurements to make but then, if Devialet were more informative, there wouldn't be a need for this sort of discussion.

Once again, thanks for your measurements and information which has been really interesting, even if I am left with a few more questions than I started with.

And apologies to @zoran_pavlovic for raising an issue which has taken his thread so far off topic.

I would definitely expect the difference between SAM off and SAM at 0% to be very speaker specific.
As a thought experiment let's assume the following:

1. Floyd Toole's statement that phase correction in the bass can result in up to half an octave of bass extension
   
2. a pair of Speakers A where the geometry and the filter performs phase correction
   
3. a pair of speakers B where phase has not been considered as a pertinent dimension. 
   

It seems quite logical to me that there would be no difference between SAM off and SAM at 0% for speakers A (because SAM would not add any additional phase correction while speakers B would exhibit the expected difference.

My two cents,

Jean-Marie