Hello mitch2,
I remember we've discussed your experiences before with very good quality class D amps, I think you had the Acoustic Image Atsahs using Hypex NCore 1200 power modules if I recall correctly. I think you liked the idea of their small size, light weight, low heat and being so efficient you could leave them on 24/7. You thought they sounded very good but thought your class A Clayton M-300 mono-blocks sounded better.
It's interesting that you mentioned that you thought the bass on your Mola Mola Kalugas (not Acoustic Imagery Atsahs?) was unnaturally overdamped and not what you hear on live music. You consider the bass from the class A Claytons more natural and better refined since they didn't have this truncated quality. I think I understand your meaning of truncated bass, which is bass that lacks the natural decay of deep bass tones when heard live. Please let me know if I'm correct.
I've also been trying to determine why you perceive this truncated bass quality on your class D amps but I don't on my D-Sonic M3-600-M mono-blocks. I know my amps are very good but, having only read reviews on the performance of the Atsahs and Kalugas, I believe it's safe to rule out the very slim to no possibility that my amps outperform either of those.
I understand that the generally very high damping factors of class D amps could be the cause of your perceived bass truncation. However, I've thought of a few alternative possibilities that may also explain our class D bass perception discrepancy that I'd like your thoughts on:
1. The music we play. I mainly listen to electronic and acoustic rock, blues and jazz and very little classical music. I perceive the detailed decay on bass notes on all of my music that's important for giving a sense of the venue but understand that it's often even more important and appreciated that it's natural to listeners of classical music. I don't know the typical types of music you listen to.
2. The speakers we use. I use large 6'x 2' 3-way Magnepan 2.7QR dipole planar-magnetic panel speakers that each have a 625 square inch bass section that produces very accurate, detailed and 'fast' bass response. The combination of my class D amps having damping factors >1,000, and outputting 1,200 watts each into the 4 ohm Magnepans, resulted in the best bass performance I'd ever heard from these speakers.
The bass was incredibly accurate, detailed and fast but the 2.7's have a rated bass extension of only 34 Hz +/- 3 dBs and I was also a bit disappointed with their deep bass impact. In an effort to improve my system's bass extension, dynamics and impact I added an Audio Kinesis Swarm bass system. Here's a link to an Absolute Sound review that describes its effects on my system and 23' x16' room very well:
https://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/ I added the Swarm fairly soon after adding the class D D-Sonic amps to my system so it somewhat complicates my evaluation of how much the class D amps and the Swarm contributed to my vastly improved overall bass response. The Swarm consists of four relatively small (1' x 1' x 24" ported cabinets, each weighing 44lbs with a 10" aluminum long-through 4 ohm driver) all positioned in a distributed bass array configuration in the room and all powered by a 1K watt class AB amp that also controls the volume, crossover frequency and phase on all four subs operating in mono.
I run the 2.7s full-range and the four Swarm subs are all run in mono, in-phase,at about 45% volume and at a crossover frequency typically set between 40 and 50 Hz. This means the majority of the bass in my system and room from 20-50 Hz is actually produced by a traditional linear class AB amp and traditional cone drivers with only a minor bass contribution, perhaps only on the leading edge of bass tones, between 34-50 Hz being powered by class D amps powering very accurate, detailed and fast planar-dynamic dipole panels.
I definitely know that the net effect of this combination is what I consider near state of the art bass response performance throughout my entire room; accurate, detailed, powerful, with a sense of ease and unlimited bass capacity,smooth and natural bass with extension down to 20 Hz, powerful dynamics and bass that is felt as well as heard.
My current conclusion is that the reason your perception that the class D amps you auditioned in your system truncated the bass and I did not perceive the same bass truncation is likely due to one or more of the following causes:
1. I spent a limited amount of time listening to purely class D bass reproduced solely on my main speakers since I fairly quickly added the four sub Swarm bass system which is actually class AB bass reproduced mainly on conventional cone subs that do not tend to truncate the bass. This is closely related to "#2 The speakers we use" I described earlier above.
I don't know what type of speakers you use in your system or whether you utilize subs but I now believe it's very possible that class D does truncate the bass somewhat. It's just more noticeable on certain types of music and disguised to a degree when non-class D powered subs are utilized. In any case, some interesting questions will still remain such as what would the results be if the Swarm used a class D amp? and what results are achieved when utilizing self-powered subs utilizing class D amps?
So, that's my current viewpoint and I'm interested in your and others thoughts on this matter.
I'm definitely not going to question your decision that you prefer the sound of the excellent Clayton M-300 amps in your system more than the class D Kalugas or Atsahs, even though I know they're both excellent amps, too.
Now you're having new amps built with custom Plitron toroidal transformers? Can you give more specifics on the new amps being built and your speakers?
Thanks,
Tim
