Gentlemen,
I used
I only used better operational amplifiers - LME49720.
PCB was made by one of many companies in my area, assembly of elements is my job.
After listening to the system and measuring with a calibrated microphone, I added a subsonic filter with a 25-40 Hz range boost - I attach the diagram, I will gladly help in choosing the value of the elements.
I have 4 PCBs left, 2 have holes drilled. We have a common passion, which is why I will gladly send free them to colleagues. If it is not enough, I will order more.
I used Hypex NC500 amplifiers with Hypex SMPS 1200/700 power supplies. I removed high-current connectors from the boards, shortened the wires to a minimum and soldered in the PCB.
Earlier I wrote about my experiences with DSP, you guess from which manufacturer. But the rest is great.
Regards
Wiesiek
Quality of electronics work I can only wish I had the patience, skill, and dexterity for - very nice 
Sorry to be contradictory but DSP-based loudspeaker management allows for things like very steep filter roll off and absolute stability with temperature. Analog crossovers cannot match this kind of performance. Try building an analog low pass filter with 48dB/octave slopes. Not practical.
Thank you. Electronics has been my passion since childhood, it has also been a profession for 40 years. I am currently dealing with wireless microphones, which is why I have a RF generator and spectrum analyzer - I attach a photo.
I have already noticed that you also assemble electronic circuits yourself. If you would like to build an active loudspeaker, I will gladly send you a PCB to mount the active crossover. I recommend Hypex amplifiers, I have a single NC 500 with a separate power supply, they have recently been producing double ones with a power supply on one board. I don’t benefit from it, but I think they are very good and easy to apply.
Regards
Wiesiek
MMMmmm toys
Yeah Everyday Electronics was my go to magazine aged 11 or 12, and before that a Phillips X40 electronics kit for Christmas kinda started it off, prior to that it was batteries and bulbs from the hardware shop so I could read at night after my light was suppposed to be off! (nothing so easy as using a torch).
I lack test equipment*, which is a shame it would probably encourage me to dive back in a bit deeper, that and some better glasses!
- beyond multimeter and, a recent acquisition, an LCR meter, for 30 odd quid (I am sure the accuracy is iffy, but it worked a treat for some passive crossover playing I was doing, what times we live in!).
The last time I was working with RF (20 odd years ago) I seem to remember spending a lot of my time making test equipment and sig generators into bespoke noise generators/synthesisers. This was not an approved usage, but man I did make some spacey sounds 
Your offer is very kind (note - I am in the UK) but wait awhile in case someone more likely to use them in the short term shouts up, it would be at least a year until I am in a position to make the spend on components / amp modules etc. all dependent on pension funds and all that yada yada
But why 48 dB / oct? Who uses such a high slope? In this forum we deal with high-quality equipment, which should only use good speakers, and they will sound very well with simple filters. I think that excess filters damage good sound.
I suffered from mild but persistent withdrawal symptoms after junking my trusty dual trace scope when we downsized radically 13 years ago. I recently cured this dull ache by buying one of the tiny Chinese dso150 based training scopes for about £25 from Amazon. Adequate for audio and has already shown me a problem with my amp which I had been happily oblivious to previously. It is a relatively small investment for being able to feel yourself a whole man again
Ooh that sounds about right, certainly in keeping my 30 quid LCR meter
I shall look later, thanks for the tip!
I’ve been contemplating pulling the “Trigger” (pun intended) on one of those scopes but haven’t seen to much info with regards to performance. But a Tektronix or TEK clone would be cool too !
The major problem I see with DSP is the extra AD/DA conversion.
I absolutely am in favor of the concept of Wiesiek: Good closed, not ported, cabinet with as much Volume as possible (visually acceptable, this is subjective), thick walled and braced cabinet, good drivers. The less that needs to be tweaked with filters the better.
Hypex nCore is the best available for DIY today. They are utilized in top high end brand amplifiers too.
I Am not sure if I dare to go DIY, it is tempting though, but the price level and sound quality Abacus offers with exactly this concept. The only difference is, they have their own amplifier concept, which controls each driver in servo mode. They call it Dolifet-technology (Drain-Output Load-Independent Field Effect Transistor). I have heard these speakers, they disappear and simply play music.
However I see Kii and Dutch & Dutch do things with the DSP that make sense too and probably, I would have to hear it for my self, do things that are very useful:
Cardoit dispersion of sound and very close to the wall placement.
I just have not heard those speakers yet, perhaps I would try and arrange to get a Abacus and D&D test package at home and give them both a try.
But the Abacus have 6 models that offer the above mentioned attractive technology with AMT tweeter for far below the price of the Dutch & Dutch. And that money I trust is very well invested in the pre-amp and sources, as I also have to agree with Linn, a amplifier cannot add sound quality, it can only limit the loss. I.e. source first. For me that hopefully starts with the new Thorens TD 1601 a true worthwhile follow up of the old TD 160, for which one still pays way over thousand EUROS for a good maintained or revamped 2nd hand model.
Which brings me also right to the point why I hesitate AD/DA conversion in the speaker, somehow staying analog makes more sense to me, even with a digital front end that has already a good DAC.
You wouldn’t be getting that. They have small, fairly low resolution screens. The ADC is 12bit, and they are digital storage scopes. Good for up to 200kHz and handle up to 100v peak to peak so they are adequate for audio equipment. Adjustment of timebase, range, trigger level and offset is fiddlier than on a real scope, where you have knobs and buttons for everything. They need an external 9v supply but if you use a PP3 battery for this then you get a portability which a real scope lacks. For the casual user they offer great bang per buck, and I am very pleased with mine.
I’m on it - sounds good enough for my hobby fiddlings
You are correct Chris. About 20 years ago, my Boss mentioned to me that there are two types of Electronics Lab/Production Tech’s. Knob Twiddler’s (Scope’s, Spec An’s, VNA’s…etc.) and Button Pushers/Mouse Clicker’s (those fluent in LabView, PCB Layout - I am Jealous to this day of them). There is a place for both kinds and many are fluent in both. I never liked programming code to this day, but give me some data sheets, bench equipment, protoboard/smt board, a soldering iron, and I’m Dangerous once again 
I think I’ll save up for a decent DSO but order one of these “little guys” for fun. After all, I’m not looking at 10 Gb/s PCB traces or even 622MHz VCXO’s anyways like I used to
Thanks
Yeah real hardware with real buttons and knobs and lots of lovely inputs and outputs to patch together giving real-time graphs - can’t beat it
I have very much respect for all of your DIY activities. They tempt me, even if the result would cost as much as buying a finished product. Certainly your posts bring a good level of expertise to the forum.
On the other hand, I’ve got so many other projects at home, such that I decided to save up some money to buy good but reasonably priced audio equipment. The PS Audio Sprout, SGCD, S300 and M700 are such components at least to my budget.
But then I started diving deeper in the subject of what speakers would match best. I learned that for my situation active speakers are best suited. I love low frequencies for the music we hear in the living room. I need systems that play detailed and dynamic even at low volumes. Active speakers can offer that at price levels which are more attractive than many options of separates. I feel not much for adding a chunky subwoofer to our living room.
Keep up the good spirits in these challenging times.
Not knocking it - I have 2 main systems*, an active speaker/amp chain and a passive one , and gain great pleasure from both, both with listening, and adjusting
They each have their strengths (and weaknesses) not only budget-induced, tremendous fun!
- that share the same sources
Before buying the M700’s last year, I was contemplating buying the ICEpower 1000ASP boards (x 5), getting those cheap Chinese Tube Preamp PCB’s (replace all the fake passives as I always do), and build a beefy clean Toroidal power supply. The cost of all this as you mentioned Rudolf, outweighed buying the real deal from HiDef Lifestyles (PS Audio Dealer that came up with the Stellar Stack). I might build a two channel like that one day just for fun, but it won’t sound anything like an M1200 but would be an interesting A/B against my M700’s.
Steep filter slopes are essential if you want a given driver to produce the maximum range of frequencies but no more. In my specific case my hybrid electrostatic speakers‘ panels extend down to 170Hz thanks to very steep filter roll off. Otherwise the woofers would have to produce another octave higher and are not suited to that. Not trying to tell you what’s best as that depends on many factors. But dismissing DSP due to the extra A/D and D/A conversion misses the inherent advantages of manipulating signals in the digital domain.
I do not disagree with that completely, but the active speakers I listened to till date were all analog filtered and sounded good. I have not had a chance to listen to the Kii’s and Dutch & Dutch yet. But the concept of Abacus is very tempting, I heard them and they have a EUR 6400 to 2100 advantage above the Dutch & Dutch which is the less expensive between the Kii and the D&D. Spending that much money I would want to hear the D&D as well before pulling the trigger.