The plot thickens...
I removed my side wall absorbers today that have been in situ since 2013, and I also removed the two absorbers that I put on the back wall behind my listening position a few weeks ago. My corner treatments remain installed.
Removing the side and back wall treatments has had a huge effect, both on the measurements and my impression of the sound.
As you'd expect, reverberation times have increased (evident on the RT60 and waterfall), as has the number of reflections above -20dB arriving at the listening position within 20ms (evident on the ETC). However, the frequency response has improved in some areas, or at least that's what my ears are telling me.
How does it sound? Surprisingly nice!
The presentation feels more enveloping, and the tonal balance from the upper-bass through mids and treble sounds more 'liquid' and 'dreamy'. The increased reverberation gives the treble shimmery ambience, which I rather like! However, the low end sounds a bit less controlled now. Another down side is presentation in general gets a bit confused during busy passages if there's lots of loud stuff going on.
I don't know where this leaves me with regards to my room treatment strategy.... In an ideal world I'd like to reduce my reverberation times a lot in the low end, a little in the mids, but not at all in the highs, and do so using treatments that aren't going to bugger up the frequency response. Seen any flying pigs recently?...
I've uploaded the REW mdat files to my
Gearspace thread if you want to look at the ETCs and RT60s.