ack's system - end of round 1

Kingsrule

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What comprises Spectral's reference system, the one they use to voice their electronics?
Speakers in particular.
As far as I can recall, its a mystery.......
 

ack

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Good question. I don’t really know, but I do know they are coming out with their own speaker soon, and I may have heard that they use a basis turntable. I have to assume Avalon is one of the other speaker lines they use and I heard rumors about magico as well. Beyond that, I have never been able to get any real meaningful straight answer from the dealers. Sorry.
 
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Mdp632

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Here is a picture of the Spectral's factory listening room. I'm not sure on age of the photo but, you can see they are using Sasha Series 2 speakers.


Screen Shot 2019-01-26 at 9.27.18 AM.png
 
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PeterA

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Here is a picture of the Spectral's factory listening room. I'm not sure on age of the photo but, you can see they are using Sasha Series 2 speakers.


View attachment 47956

Nice photo and thanks for posting it. Very interesting that all gear is on rollers, including the speakers. I wonder how much acoustic treatment is in that room and if those are MIT cables.
 

Mdp632

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Nice photo and thanks for posting it. Very interesting that all gear is on rollers, including the speakers. I wonder how much acoustic treatment is in that room and if those are MIT cables.

Thanks. Most likely, the amps are on rollers because they are easy to swap out and test. Same with the speakers.
 

PeterA

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Thanks. Most likely, the amps are on rollers because they are easy to swap out and test. Same with the speakers.

Yes, convenience is one thing, but I suspect the bass quality that they hear would differ if the rollers under the speakers were replaced by spikes or footers. I suspect that this is a testing lab to detect very subtle differences in sound caused by slight changes they make to the electronics before releasing the next, improved versions. I assume they listen critically as well as use test and measurement equipment.
 
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Jazzman53

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Nice rig you have there, Ack

ESLs have an addictive sound that I think most people who've owned them would find it hard to give up for something else (I have some very nice ones, myself). I've always been a jazz fan but of late I've had the urge to explore the classical genre -- I just don't know enough to buy it intelligently. So; I thank you for posting your reference classical music list; which I intend to start auditioning right away!

Regards,
Charlie
 

ack

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Thanks and welcome to the forum Charlie - I saw your system the other day and been meaning to ask you about your custom-built electrostatics, and will asap. Meantime, you've come to the right forum for audio and music! You will find exceptional threads about classical music specifically, and my list on page 1 is just a start - I have not updated it in years because we don't have the ability to edit posts older than a day, so there is a LOT more to be said about reference recordings.

I've also been meaning to post about a couple of visits in recent months by non audiophiles, relating to all the shielding I have done in the system, in particular all around the sensitive phono. The first of the guests, a computer engineer, looks at the shields and loudly proclaims "WHY? Why would do that!" - he was particularly "offended" by the exposed-tonearm-cable shield. The second one, a neuro surgeon, looks at it and points out the copper and mu-metal shielding all around and says "Yeah, we see all of that in the MRI rooms".

So if you were to explore some major tweaks, this would be a good place to start. We've had a couple of successful adopters here.
 

ack

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Charlie, I just read your blog on your own custom electrostatic speakers, and couldn't be more ecstatic and happy for you! WOW! And what a coincidence for me to be playing with treble adjustments in my own panels lately.

People should spend some serious time reading his blog referenced in this thread https://www.whatsbestforum.com/threads/diy-esls.28023/

Congratulations!
 

ack

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A tale of two resistors

In the last two months, I had shifted my focus to treble response in my system, since there was something that still bothered me, with trimbre being audibly off in some cases. At the same time, the very powerful and utterly complex Mahler 2nd's Finale (BSO/Ozawa on Philips CD) was still uncomfortably distorted, despite the fact it was orders of magnitude better through the older 400RS.

The thinking was that the very low speaker impedance in the treble region was stressing the 500AR amplifiers, which despite being so much better than any other in here, I felt they were still struggling a bit. So I started experimenting with in-series resistance to the panels in hopes that it would dampen treble response, and provide a smoother overall impedance.

Then, I read jazzman53's blog on his own electrostatic panels, and to quote the aforementioned link in the previous post:

The transformer's winding capacitance adds to the load capacitance and its leakage inductance combines with the load capacitance to generate an ultrasonic resonance peak in the frequency response and rapid rolloff above it. Coincident with this response peak is an impedance minimum which can be a difficult load for the amplifier. When series resistance is added on the primary side it dampens this resonance peak. However, as previously noted, too much resistance over-damps the resonance, rolling off the audible highs.

The general guidance is to omit the section one resistors on the secondary side, add a 1? series resistor on the primary side and give it a whirl.

His blog could not have come at a better time (thank you!), putting a stamp for me on what I had suspected.

The sound:

This quest has been more fascinating than I had expected; while two weeks ago I thought I had settled on 1.8 ohms, I discovered more improvements at 2.2, while anything higher (like 2.35) dampened treble too much and timbral accuracy suffered the other way. Then I tried 2.13 ohms (4.7 || 3.9), and was thrilled to discover that not only did timbre improve further, but resolution went higher. The latter was just shocking and unexpected. I started noticing things I never did before, like the tubular bells in the pandemonium that is the very end of the Mahler 2nd, and it goes on and on. There is no doubt that everything is clearer than ever before, with sweeter string tone from digital to top it off. The presentation is also less in-your-face. The result counts a lot, but the discovery is just as important to me. And yes, I had to turn the sub down a bit as well.

If anything, this endeavor has demonstrated to me how excruciatingly difficult is to properly voice a speaker, or anything for that matter, and I have so much more respect for those manufacturers that do it and do it well.

Here are those two CAST-Graphite Duelund resistors being tested externally:

1559050987537.png

And the quest continues...
 
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Folsom

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In series resistance reduces amplifier damping by raising Q. So this works on a fullrange crossoverless speaker, but not on a 2-4 way speaker with passive crossovers.

Don’t some people use autoformers on those speakers?
 

ack

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Thanks; never seen an autotransformer in a Logan, certainly not here. Not sure about the CLX or Monolith.
 

microstrip

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We can't forget that adding resistors in series with the ML panel section will also significantly modify the frequency response, reducing its output at very high frequencies. Probably in your case it was an welcome effect.
 

ack

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Thanks micro - this is what I also said, and the stated goal.
 
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ack

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Hi George,

Post #1 in this thread is it. I highly recommend playing with a series resistor to your panels as well; but it is painful trying to find that narrow range of values that improve and do not harm.
 
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ack

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More fun with digital

Here a few more modifications to the Alpha DAC:

1) Digital volume setting now at 47.0, down significantly from the previous settings I was using before (~53.0). It took months to realize, but the output section can be overdriven at higher settings, with a slightly euphonic and less-resolving character as the program got more complex. This volume setting ended up maintaining the DAC's high resolution and clean sound with all tough material I have tried, and tamed treble energy a little bit.

2) The output section's corner frequency has been lowered to ~68.5kHz (from ~193kHz), using Vishay 1837s in a 31nF configuration in the output RC filter [first picture], for more natural treble, much closer to my analog rig's.

3) At the urging of a fellow WBF member - who contacted me actually about my XP-25 phono mods and suggested that I try out different diodes in the power supply - I decided to replace the Alpha's diodes with them first. They are the Vishay HEXFRED VS-HFA15TB60-M3, 600V/15A continuous, "state of the art ultrafast recovery diode" [second picture, wrapped in heat shrink for protection] - https://www.mouser.com/datasheet/2/427/vs-hfa15tb60-m3-1351136.pdf - cost about $1.06 each, and that's considered expensive. By contrast, the stock ones appear to go for roughly $0.16 retail.

Well, the results here were just shocking, so I already blindly put them into the phono as well, though I still do not have my A90 back from repair to listen to. The other WBF fellow says he's replaced his Pass XS Pre and Phono's diodes with these as well.

The increase in speed (attack and settling) was quite obvious - from piano to snare drums - as was the additional smoothness in the midrange and treble, with a tighter and more well-defined bass, and indeed, more resolution than ever before at the highest of program levels, finer micro dynamics, and greater body, and of course, even better timbre and articulation. The Berkeley Ref3 doesn't sound like this at all, and neither do the Vivaldi 2.0 and others I've had in here at various times. The one exception again being the Spectral SDR-4000SV player, which continues to be my digital reference in terms of crispness, vividness and clean sound - it really is that good, and I continue to prefer it over the $100K+ Vivaldi 2.0 stack and everything else I've heard. The other DACs and players seem to want to make digital sound beautiful, rather than accurate in the best analog sense. Different strokes for different folks.

Al M - who visited - and I were talking about the cost of digital products, and how dangerous it is to spend a lot of money on it, when: a) there are true diamonds in the rough that can be modified with spectacular results; and b) the pace of improvement in the digital world is so fast.

We played a Shostakovich symphony, piano solo, piano/string sonatas, vocal, jazz, winds, etc - and the DAC's sound simply shocked me. Well, we do know that the quality of the power supply is paramount, so why can't more manufacturers spend a dollar per diode?!?!?

So there we have it: the sound of an ultra-fast, beautifully engineered diode - fascinating!

IMG_3653.jpg

IMG_3783.jpg



IMG_3781.jpg
 
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ack

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So that they don't accidentally touch; pin1/cathode and the body are the same
 

MadFloyd

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Hi Tasos, seems like you made significant improvements yet again - congrats.

May I ask you what a 'corner frequency' is?
 

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