Flat Anechoic Measured Frequency Response Speakers

Looking at the measurements for several speakers I know well, it surprises me how similar many of them are. For example, Dynaudio C1 and Thiel 2.4 look quite similar (and both very flat) to my uneducated eye, although they don't sound the same. Interesting to look at something like the Reference 3a MM decapo, which seems to measure pretty horribly. Or the Silverline Sonatina, which has a big midrange dip. Even the Watt/Puppy is a bit ragged. How important is this, I wonder.

Would love to see measurements for some models of Harbeth.

The ATC has a very flat response. Do you find that flat responses sometimes limit the 3rd dimension to the soundstage? In other words, do you find it is more like a two dimensional picture than a three dimensional picture depth-wise?

No not at all. A flat "power response" without the usual treble and bass boost can sound extremely natural and is hard to distinguish from live or real instruments. The vast majority of speakers have a strong off axis response in the bass and treble with a dip in the midrange. Sometimes called the "BBC dip", this has become so popular in consumer speakers since the 80's that a flat power response is rare and is usually interpreted as "forward" or "harsh".

There is a strong correlation to soundstage (although most depends on the recording)...there is a tendency for instruments to sound closer as if they are in the room with you - so you could argue that there is less depth with this pattern - conversely you could argue that other speakers will never reach as forward into the room or close to the listener forever relagated to sounding as if you are at the first balcony....so I think the soundstage moves forwards somewhat but is no less or more compressed than speakers with a BBC dip.

According to Dr. Toole's group that has been researching subjective listening for the past 2 decades, it seems to be very important. Not necessarily flat, but smooth.

The not necessarily flat point is important. Supposedly people like a deviation from flatness in the mid-bass and on top, according to Paul Barton (who also worked with Toole).

The thing that doesn't impress me with their methods is that they cherry pick their testers and instruct them in what qualities they should listen for in the speakers before using them in the tests. They only keep the people who demonstrate an ability to pick out the qualities they are instructed to pick out for the tests.