Successful protoype for my Casio AP-460 / PT6 project

Hi all,
as mentioned in my previous posts I am trying to pimp my Casio AP460 piano with PT6.1 and a new sound system. After many hours of frustration I now have found a prototype setup that works well. I would like to share my results and would appreciate your feedback.
Apologies that this is a longish post, but I want it to make sense to you.....

Background first: why am I doing this? I'm not a very competent pianist, trying to get back into playing after a break of 30 years. I want a digital piano because to my ears acoustic pianos only sound better when they are perfectly in tune, which in real life they rarely are. I live in my own house, so I am not interested in playing silently with headphones. I am not trying to get the most realistic copy of an acoustic piano, I want a digital piano with decent keyboard that sounds good in its own right so that I have fun playing it. I guess my benchmark is not a live piano concert, but a good recording played on a good stereo.

How did I get to the point I am discussing here? I tried more or less all digital pianos between €1000 and 5000, including most top models (Roland LX17, Casio GP500, Kawai CS11, top Clavinovas, Yamaha NU1X). The NU1X is the only one that stood out for me, as the keyboard feel is in a league of its own. For all the others, I did not see an improvement in keyboard and sampled sounds worth €4000 between the Casio AP-460, which in the end I purchased for €800. I am sure that skilled pianists will notice many more differences between keyboards types, but after hours of testing I really could not detect a big increment that mattered to me. It also should be noted that Casio has few types of keyboards in its range, so that the low end models have the same mechanics as much more expensive models.

While testing pianos, I noticed that I generally liked the fully synthetic sound of the Rolands better than all the sampled pianos. This led me to find Pianoteq, which is yet another league of sound quality.
I should point out that I could have afforded a higher spec Piano, but that I just did not like any of them significantly better than the Casio (I thought about buying the NU1X, but before spending €5k on a whim I wanted to set myself the task of actually learning to play again ;-)

However, I like building things and having a project, and the PT6 sound is better than the NU1X.
So, the task is to use the Casio box as a MIDI controller and container for a PT6.1 based sound system.

I took some advice here in the forum, the bottom line being that I should get myself a set of decent monitor speakers. I tried that, but did not like it very much. A real piano does not blast the sound into your face from ear level at a 45 degree angle. This might work for listening to recorded piano music on a stereo, but was not an option for playing live.

I tried several permutations, all of them disappointing. The most elaborate disaster was sending multichannel PT6 output via HDMI into my 7.1 receiver: a wall-of-sound that Phil Spector would have been proud of, and horrible latency. Don't try this at home ;-)
Also not worth trying is the use of hifi speakers with 16-20 cm bass/midrange chassis, or 2.1 satellite/subwoofer systems: the bass sounds are very much overwhelming the upper two thirds of the keyboard. To my surprise, I found out that sound can be just too much, too fat. Just like food....

What made me persist was that the sound of PT6 was great when recorded or when playing with headphones. And finally, I think I found a good and simple setup yesterday:

PT6.1 is running on a 2012 MacBook Pro, hooked up to a Roland Mobile UA-M10 USB Interface. The interface offers 4-channel output, which are recognized without any problems by PT (if you try this and only get 2x stereo: 4-channel output has to be activated in the Roland driver. It does not work when the Interface is just used plug-and-play). I did already post that whatever latency this interface might have, I can't hear it at 256 samples, and am not sure if I can hear it at 512 samples.
The analog output is connected by 2x mini-jacks to two simple Class D amps. So far, one is just a bare no-name amp board (€20, HS Sounds, eBay item 222619289731), the other taken form an Edifier C3, a mid-range 2.1 desktop sound system (€200 new a few years back, now bought used for €50).

After all my false starts, the setup of the speakers turned out to be rather straightforward: a pair of JBL Control One passive monitors placed left and right under the piano, on top of the box holding the pedals. The second pair of speakers are the satellites of the Edifier 2.1 system, small two-way speakers with 8cm mid-range chassis and small tweeter. These speaker boxes are places IN the body of the Casio piano, facing upward. The Casio has a lid that can be opened as in some upright pianos, so that the sound is reflected similarly to an acoustic upright. As all the Casio's electronics are in a box hung under the cabinet, the cabinet is largely empty. Great for my project!

A crucial step is the choice of PT preset: I like the Grotrian best, and modified the "under lid" preset by placing two mics under the soundboard of the virtual piano, and two mics sampling from under the open lid. Obviously, the lower mics have their output sent to the JBL monitors under the Casio, while to upper mics drive the speakers I dropped in under the lid.

With volumes set to about 70% lower / 30% upper speakers it sounds grrrreat to my ears. The sound is well balanced and detailed, the bass is just right and not overwhelming. Using only the JBL monitors close to the floor is already pretty good, but adding the small speakers placed in the box makes audible all the fantastic detail PT6 puts out at higher frequency. For example, when holding a note, I can hear the floating harmonics that are lacking in all the sampled pianos. In contrast to the "monitor on ear level" setup, the sound now reaches my ears in a way similar to an acoustic piano, giving it a sufficiently natural feel when playing.

This is only a simple prototype cobbled together one morning, but to my ears it already does 80% of what I hoped to achieve. I will use this as a basis for building a system where everything is permanently fitted into the Casio body. I will get a second amp board, and maybe try other amp boards (e.g. Tripath). I plan to use a second set of JBL Control One as donors for speaker chassis to be fitted into the box as the upper speakers (the Edifier satellites are ok, but nothing more). Further down the line, I consider using broadband chassis of higher quality (e.g. TangBand W5 2106 etc).
What would top it off would be a touch screen computer on top of the box, to read scores and to play with PT sounds.

Finally, how much did I spend on the experiment so far?
Used Roland UA-M10: €100 on eBay
Pair of JBL Control One passive monitors: €90
Used Edifier C3 2.1 amp and speakers: €50
HS Sound Class D amp: €20
MacBook had already been around, and after using PT in demo mode for long enough I will now have to buy the standard version to have control over the mics.
Even if I had purchased dedicated computer for the project, it would have been less expensive than a mid-level piano, but sounds a lot better.

So, I hope this might be useful to others using PT for live playing in their homes. I would very much appreciate your feedback and suggestions.
Best wishes,
Andreas