OK! Sounds like a Plan!
In spite of all current events, I'm open for Business! At present, I'm on assignment in the Caribbean. Maybe our Time Zones are wildly different, but Trust that I want to lend you a hand, and will do my best!!
The Objective is for you to find an even greater appreciation of your RME! DUDE! This thing is High Class!!
Let me first say that I guess you are a generous person and I would like to know you in person. By the way, if I read 962 as your birth year correctly, I was born in 1960, so we could be close in age.... On another item, well, the Caribbean is not the worst place to be quarantined in these days, isn't it?
About my system room eq. let me explain some basic facts before tuning up further together the set-up. I am a physicist, so I know in great detail everything about waves in general, closed-boundary acoustics, standing waves, reflection, diffraction, interference and whatever else is scientifically known about sound transmission between sources and detectors, be them ears or microphones, in any given propagation space.
Speakers are the B&W 800D2, remarkably flat in frequency response but a difficult load to drive. That's why as a power amp I chose a Classé CA-2300, with its 0.015Ω source impedance (!), measured at 2x300W on 8Ω, 2x600Ω on 4Ω and 2x1200Ω on 2Ω (!).
The room itself is a difficult environment, because it is very tall and as such there is still a relevant naked surface area, even if I have large absorbing and/or diffractive pieces of furniture, a fireplace, a slightly tilted wall, a recessed window and a vaulted ceiling, all contributing to deviations from the "nude rectangular box" nightmare. Approximate dimensions are 6.6 meters length, 4.5 meters width and 5.5 (at the top) meters height, 1m solid brick walls, built in 1765.
Of course, for the best possible acoustics I should first put in place a thick absorbing false ceiling, but I don't want to hide the precious 18th century fresco on the ceiling which I recently have had carefully restored in the house.
In order to get the best possible sound out of this room and that equipment, I first played a lot with careful placement of the speakers and the listening position. I spent a long time moving the speakers and the sofa around, sometimes by large amounts, sometimes by very few centimetres, each time measuring the frequency response with an MiniDsp umik-1 microphone and using the REW software, but mostly listening for days and days to all the music I like most and know better.
Once the geometrical problem was stabilised, I started playing with equalisers. I tried digital ones, included the RME ADI-2 DAC 5-band, analog parametric ones and analog graphic ones. I ended up choosing an analog graphic equaliser placed in the tape monitor loop of my preamplifier, because 1) it allows me to room correct any source, both vinyl and the digital ones 2) when listening to vinyl I have a full analog chain, equalisation included, without any AD/DA conversion 3) it allows me to switch immediatly between equalised/not equalised with a touch on my preamp remote 4) because I am an old fart and that's the old way, well known to me, to accomplish the task.
As far as the quantity of the boost is concerned, it is not huge at all. My graphic eq which you see in the pictures is operated at +/-6 dB full scale. In its current set-up, 52 out of 60 sliders apply a correction of less than 3dB. The one and only big correction is a notch filter (very narrow, included in my equaliser) at 32Hz to dampen the vertical fundamental frequency of the room.
You can see the end result in the following picture:
The purple line is the system frequency response without equalisation and the green line includes equalisation. Both channels summed and smoothed at 1/3 octave. There are still small bumps at 50Hz, 300Hz, 1.25kHz and 8-10kHz. I could kill them with the sliders, but I tried to do so one by one and still my ears tell me it's preferable to keep those small irregularities instead of flattening them.
What I got is a frequency response close to a smooth curve within 1 or 2 dB from 25 to 12.5k Hz, and not "any" smooth curve but what my ears feel to be the most neutral one in my room, by applying +/- 3dB correction MAX on 87% of the sliders, +/- 1.5 dB correction MAX on 50% of the sliders.
Of course I am always ready and willing to experiment and learn whatever possible improvement any idea or piece of gear can bring to my listening pleasure, so if you have something to suggest me you are more than welcome.
And I agree with you, The RME ADI-2 DAC is high class indeed! A great all-around tool to enhance music enjoyment and tuning. I have often played with the in-built equaliser to understand how far or how close I was to my target because the continuous frequency and Q-value regulations offer real-time checks on f.r. adjustment impossible with the graphic tool. The RME is both a pleasure to listen to and a scientific tool. Really outstanding!
All my best,