D1080 MkII 08 actives - mod summary and listening - diyAudio
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D1080 MkII 08 actives - mod summary and listening

Posted 1st January 2011 at 11:41 AM by abraxalito
Updated 2nd March 2011 at 11:12 AM by abraxalito

Before describing the changes brought about by the mods I've described, here's a summary of what they've been:
  • Crossover tweaked to flatten the lower end bass hump and knit the handover to the tweeter more tightly
  • Power amp sensitivity reduced to allow the volume control operate closer to maximum with my Asus soundcard or a standard CD player output.
  • Rectifier snubbers and additional filtering to the regulators fitted to reduce RF ingress on the power supplies.
  • Power amp supply decoupling improved at both LF and HF.
  • Signal grounds are now separate from power grounds and a star point established on the amp PCB. A ground loop between the two PCBs has been eliminated. The input signal ground is no longer connected to the tone control PCB ground - instead given its own dedicated wire to the star. Decoupling to ground on the tone control PCB has been removed.

Listening impressions

OK, so on to the part that you've been waiting for - how do they sound with all these tweaks in place?

I bought a second pair of speakers and left them as-is to make the comparisons. The source is my modified Taobao DAC with CS8421 ASRC fitted, fed from an ultra-cheap DVD player.

First up, Ravel's Sonata for Violin & Piano, Lina Matsuda playing the violin. A CD I've only recently acquired, the recording was made Jan 2010. I listened to the 2nd movement twice on each pair of speakers. The modified ones revealed the ambience of the recording space admirably - the piano set back behind the violin, the violin slightly to the left. Focus remained tight over the full pitch range of the piano and I got the impression that the two instruments interacted musically. The music has plenty of percussive elements and these were conveyed with considerable bite - at one point I began to imagine the smell of rosin on the violin's strings as it was plucked almost as it were a guitar.

Contrast this with the unmodded speakers - the major difference being the unconvincing nature of the ambient space, this would come and go - some piano notes would be heard in the space, others were smeared out. There was almost no sense that the violin and piano occupied the same auditorium, a complete lack of air around each instrument. The percussive playing didn't sound so percussive, as if the notes' leading edges were dulled.

Second up, one of my reference tracks for evaluation - Rebecca Pidgeon's 'Spanish Harlem'. Here Rebecca's voice has notable sibilance on the unmodded units - she sounds like she sings 'SpaniSH harlem'. The plucked double bass line is overblown given the high Q of the low-end highpass. On the modded ones, her voice sibilance is almost eliminated, the bass is restrained and what becomes apparent in her voice are her breathing and swallowing between lines. It was almost as if I could feel the warmth of her breath as she sung - but only on the modded ones. In verse 3 she stops singing and there's an instrumental - here the shaker to the right and rear sounds splashy, sometimes close and always indistinct on the stock speakers, but rock solidly placed with a rear wall reflection apparent with the modded ones.

On this same disk, the Chesky Ultimate Demonstration disk, there's a recording of Vivaldi's Flute Concerto on period instruments. I listened first on the unmodded ones - the solo flute is smeared on transients. This gives the impression of being able to localise it only on sustained notes, as soon as a new note is played its position dashes off to one or other of the speakers. The strings sound close up to the speakers, almost piled up inside them. Switching back to the modded ones, within a second my brain has worked out the acoustic and the strings are pushed back into their alloted seats and the flute stays in focus the whole time. This is so much more relaxing to listen to!

Lastly, the torture track for ambience retrieval, the Britten Festival Te Deum which was recorded on a boom mike 35ft long. This one I've heard on a few systems and its a toughie to make sense of as there's so much ambience. The modded speakers did a brilliant job here - on switching to them from the unmodded, the goosebumps went down my back as I was transported into a credible cathedral acoustic. When I lived in Cambridge UK I'd go to evensong at King's College Chapel just to soak up the acoustic - this recording gives almost an enveloping effect even on two channels with the tweaked boxes. The voices sound distinct and interact convincingly with the reverberant sound. On the straight speakers, the voices were closer but less individually distinct - I'm guessing my brain was struggling to interpret the ambience cues which made listening rather uninvolving. Just as with the flute recording, on vocal consonants, the imaging smears so the location of the singer is lost for an instant which gets fatiguing. On the other hand, with the tweaked pair I was totally drawn in. Most impressive.

What I'd like to understand is the way that the ambience cues are messed up when the grounding isn't done properly, but I don't have any leads to try to understand that just yet. It seems that sibilance and ambience are two sides of the same coin - in that whenever sibilance is present, ambience is messed up too. Fixing sibilance corrects ambience as a side-effect. Or perhaps its the other way around? Any comments or suggestions for how to go about searching are welcome.
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