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Old 8th April 2012, 02:28 PM   #241
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Quote:
Originally Posted by abraxalito View Post
So then - what's your working hypothesis to explain why there are soooo many glowing reports on its sound. That all listeners are lying and secretly on Metrum's payroll? Or all are totally deluded or have cloth ears?
Let's take as a fact that the Metrum sounds good; there is ample evidence on that, and as I own one I can only confirm.
Then it might make sense to investigate why it sounds good, and what measurements are relevant.
Members like SoNic prefer to trust on traditional mearurements, and prove not to be open to any other insight; they are "sure" that -60 dB THD "can't sound good", and -2dB at 20 kHz "must be audible and detoriate the sound...". IMO these guys are pulling a dead horse, and it does not contribute at all.
It was already mentioned in a previous post that time domain factors might be more important than absolute flatness up to 20 kHz, and audibility of THD is another debatable factor.
Perception of sound and results of measurements do not correlate; this fact has been the subject of discussions on audio gear a million times, and the discussion here (with respect to dacs) is no exception.

Last edited by pieter t; 8th April 2012 at 02:53 PM.
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Old 8th April 2012, 03:40 PM   #242
jitter is offline jitter  Netherlands
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As another owner of the Octave, I can only concur with pieter t's remarks.

I think we must seriously reconsider the correlation of measurements with actual perceived sound quality. First I heard the Octave, then I measured it. These measurements turned out far worse than I could ever have predicted on the basis of what the Octave sounds like.
To me there is no doubt that a scientific experiment will show that correlation may only be a fraction of what it is thought to be.

Several things that come to mind:
1) In the good old days of casette, tape hiss could only be heard during quiet passages and distortion wasn't very low either. Why obsess with them now they're much lower?
2) Flat frequency response the thing to go for? What does it matter if at 20 kHz the signal has rolled off 2 dB when you might not even hear above 16 kHz without seriously turning up the volume?
3) Flat frequency response of speakers in a real life living room? Not going to happen.
4) Even in a quiet living room ambient noise might drown that of the equipment.

With respect to filtering in digital audio: I got the PDR-555RW working and could measure some of the frequency responses. Legato Link conversion indeed doesn't suppress all of the first image! In other words: a big mainstream company already doubted the need for brick wall filtering 15 years ago.

Images from left to right:
PDR-555RW: 44.1 kHz; 20 kHz sinewave;
PDR-555RW: 44.1 kHz; 20 kHz sinewave spectrum;
PDR-555RW: 44.1 kHz; 19 kHz + 20 kHz sinewave; 1:1; audioband;
PDR-555RW: 44.1 kHz; white noise spectrum, marker at fs/2.
Attached Images
File Type: gif 555_20k_dso_44k.gif (8.2 KB, 176 views)
File Type: gif 555_20k_fft_44k.gif (7.0 KB, 169 views)
File Type: gif 555_ms19k20k_fft_44k.gif (7.7 KB, 170 views)
File Type: gif 555_wn_fft_44k.gif (5.6 KB, 167 views)

Last edited by jitter; 8th April 2012 at 04:02 PM.
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Old 8th April 2012, 04:35 PM   #243
qusp is offline qusp  Australia
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Thanks for the measurements, wow that sinewave, are you sure you measured it right? thats terrible.. I read that there was an imposed 4khz FM modulation, I guess thats it? I wont go on, they speak for themselves, but please, others i'm not talking to, dont take a snippet from this first post, quote it and argue; i'll simply ignore it (not at you jitter, most of this post is more general, but some directly replies to you)

I dont deny, nor did I even claim that time domain isnt important, ive spent the last 6 months working to tune the i2s and clock handling in my dac. this is just one of the parts of my post, lept on, misrepresented and reacted to, please read carefully.

I only mentioned that it was often lesser known or sometimes esoteric types of often phase related distortion that are often used as buzzwords to promote dacs that otherwise measure poorly. Phase noise/phase distortion/jitter can all be measured quite successfully too these days (not easily, but successfully), but i wont harp on.

Jitter, I had prepared a response to you that basically said that i thought on the whole we were on the same page, my main objection is using terms that promote an extreme difference where it is more subtle than that, but without proof of such differences and calling others who dont hear such big differences deaf; going by your wording in response it seems you feel mostly the same. I made no claim there were no differences either and I was NOT talking down when I mentioned liking harmonic distortions that are perhaps missing where they should be there, but that still being a form of distortion

We dont know it all, not yet, but extreme phrases like I objected to will be correlated in the bank of measurements. other longer term harmonic or experiential differences may not be so easy to detect, or define

The proof is in the pudding and I by no means belittle anyones enjoyment, but i pertained and still do, that many of these enjoyable factors can be put down forms of distortion or harmonics. man I LOVE distortion and harmonics!! I found my teens and 20's in the late 80's-late 90's and my whole world was distorted lol. So I like it, just not in my dac as I like many and varied forms of music, different priorities I guess.

Quote:
Several things that come to mind:
1) In the good old days of casette, tape hiss could only be heard during quiet passages and distortion wasn't very low either. Why obsess with them now they're much lower?
yes i look back on those days fondly, but not on the hiss, it, like record pops and crackles hold a certain amount of nostalgia, but i'm glad they are gone; without the dynamic range issues of the noise reduction techniques of the day

Quote:
2) Flat frequency response the thing to go for? What does it matter if at 20 kHz the signal has rolled off 2 dB when you might not even hear above 16 kHz without seriously turning up the volume?
yeah but I do, not as well as I used to but I do and i still pertain its part of the room and spacial information that is not directly heard, but has an effect

Quote:
3) Flat frequency response of speakers in a real life living room? Not going to happen.
I do a lot of listening on high end headphones, one particular pair are TT-MM-WW 3 way custom fit in ears with extremely low distortion and high efficiency, the room is my ear canal and its a known quantity that the crossover is tuned for digitally using the casting taken of my ear canal and conch that they make the monitors from.

My in progress new speakers are digitally crossed with room correction/convolving and i freely admit this is a fairly extreme form of distortion (in frequency and time domains), but damn does it sound good! I feel no less of a music lover for enjoying this effect, I dont know why others can get so offended when its suggested as a factor


Quote:
4) Even in a quiet living room ambient noise might drown that of the equipment.
see above

Last edited by qusp; 8th April 2012 at 04:55 PM.
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Old 8th April 2012, 04:45 PM   #244
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I use headphones a lot exactly because of room response and noise. Use speakers only for surround.
To say that "cassete tape never bothered us" is just laughable to me. I was fanatic about the sound even then, my LP's where perfectly clean while listening, I was using reel-to-reel recorders to transfer LP and avoid wear, looking for the best magnetic tapes that I could get, I did my own preamp stages for RIAA and modded the ones in the reel-to-reel, bought better cartidges and heads, ballanced the arm... When katter I got a cassete player, it had dbx and I used minimum CrO2 tapes with dynamic bias.
I could hear the hiss and distortions then and I hated them. My analog devices where all better than -60dB, I don't see why I would take less today.
I guess I have to agree that some don't care about the real details in music and like better to hear the artificial colorations and products of the unfiltered NOS.
Time to leave this thread.

Last edited by SoNic_real_one; 8th April 2012 at 04:50 PM.
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Old 8th April 2012, 05:10 PM   #245
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Hi,

Quote:
Originally Posted by SoNic_real_one View Post
I really think that -60dB cannot realistically sound good...
I really think you must stop to listen to music then.

Because -60dB OR WORSE H2 is very common for many "high fidelity" speakers at 1 Watt input and HD rises with level, H3 to a cubic function. Hence if -60dB cannot realistically sound good - then good sound is essentially impossible, using current speakers.

One of my personal favourite speakers (Tannoy corner horns loaded with alnico magnet 15" Monitor Red's) are actually very low HD speakers, but even they exceed 0.3% HD at 101dB/1m, though it is mostly H2...

Ciao T
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Old 8th April 2012, 05:18 PM   #246
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Hi,

Quote:
Originally Posted by SoNic_real_one View Post
My analog devices where all better than -60dB
Did that include your speakers at 102dB/1m or rated input power (whichever comes first)?

BTW, the same applies to headphones, though some of the best are moderately low distortion, but < -60dB HD at 102dB 20Hz-20Khz still seems a tall order..

Ciao T
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Old 8th April 2012, 06:16 PM   #247
jitter is offline jitter  Netherlands
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Quote:
Originally Posted by qusp View Post
Thanks for the measurements, wow that sinewave, are you sure you measured it right? thats terrible.. I read that there was an imposed 4khz FM modulation, I guess thats it?
The way I measured wasn't really scientific, i.e. no precise calibration of any sort. So don't look at the dB values in the plots. I did measure all three devices the same way so that comparisons between these three can be made.
I'm pretty sure that I measured the sinewaves correctly, there isn't that much to go wrong. For reference to a traditional approach I included the Micromega DAC1, and the sinewaves look fine on that one all the way up to 20 kHz.
The Legato Link conversion in the PDR-555RW and the Octave show other frequency components. Obviously the '555-RW doesn't measure that extreme down the frequency range as the Octave; the distortion as a result of gentle filtering runs out below 10 kHz, in the Octave it is probably present in all frequencies.

Quote:
I only mentioned that it was often lesser known or sometimes esoteric types of often phase related distortion that are often used as buzzwords to promote dacs that otherwise measure poorly.
I would argue that the Octave belongs to that group. But what are these esoteric types of phase related distortion?

Quote:
Phase noise/phase distortion/jitter can all be measured quite successfully too these days (not easily, but successfully), but i wont harp on.
Yes, I know, one of the standard measurements of PCBs for the broadcasting industry is the eye pattern and even a little bit of jitter clearly shows.

Quote:
Jitter, I had prepared a response to you that basically said that i thought on the whole we were on the same page, my main objection is using terms that promote an extreme difference where it is more subtle than that, but without proof of such differences and calling others who dont hear such big differences deaf; going by your wording in response it seems you feel mostly the same.
I think we are, indeed. When I was younger I read a lot of HiFi magazines but eventually stopped reading them. Not only were most of them biased towards products of important advertisers, reviews were written as if there was a world of difference between device A and device B. When I was making enough money to buy good quality equipment, I found that those differences we exaggerated.
I'm not saying that differences cannot be perceived as big by some, but I'm not among them. Is it my hearing? Who knows? Maybe I'm not so easily fooled by what some salesperson tells me. I'm very aware of the power of suggestion, so that in most cases it doesn't work with me anymore.
For auditioning of the Octave I had brought with me my own CD player. During warming it up I talked to the vendor for a while. Without having seriously listened to my CD-player he already knew to tell me that it couldn't hold a candle to the Octave. Yeah, right... I'll decide for myself. And of course, the differences weren't nearly as big as they were made out to be.

Quote:
We dont know it all, not yet, but extreme phrases like I objected to will be correlated in the bank of measurements. other longer term harmonic or experiential differences may not be so easy to detect, or define
I think we should already know quite a bit, there must have gone a lot of research into the properties of the human auditory system during the development of lossy compression.
Long ago I read an article on human hearing and the brain. Turns out that some people can go deaf for certain unpleasant sounds without any physical damage to the auditory system. The sound is completely blocked by the brain. If such an extreme is possible, no doubt the brain has all sorts of subtle influences on how and what we hear.

Quote:
The proof is in the pudding and I by no means belittle anyones enjoyment, but i pertained and still do, that many of these enjoyable factors can be put down forms of distortion or harmonics. man I LOVE distortion and harmonics!!
It's what makes one instrument sound totally different from another despite playing the exact same note.

Quote:
yeah but I do, not as well as I used to but I do and i still pertain its part of the room and spacial information that is not directly heard, but has an effect
Perhaps the idea of Legato Link, allowing some of the image that is playing in the same rythm as the audio band is in that respect not even so bad. Enter NOS and take it to the extreme.

Quote:
I do a lot of listening on high end headphones, one particular pair are TT-MM-WW 3 way custom fit in ears with extremely low distortion and high efficiency, the room is my ear canal and its a known quantity that the crossover is tuned for digitally using the casting taken of my ear canal and conch that they make the monitors from.
For me it's merely a Sennheiser HD600 on a diy class A headphone amp.
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Old 8th April 2012, 11:18 PM   #248
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Do you listen the headphones at 102dB? Because I don't.
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Old 9th April 2012, 12:02 AM   #249
ChrisPa is offline ChrisPa  United Kingdom
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Quote:
Originally Posted by SoNic_real_one View Post
Do you listen the headphones at 102dB? Because I don't.
so what level do you listen at?

What's the distortion at that level?
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Old 9th April 2012, 01:21 AM   #250
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Exactly... nobody listen for long term at the nominal levels. Or whan it does it doesn't care about distortions.
At medium sound levels the distortions of good, open-back, headphones are smaller than the usual graphs for 90-100dB. And all those are harmonic distortions, not random aliases.
A few comparative measurements:
Click the image to open in full size.

Last edited by SoNic_real_one; 9th April 2012 at 01:37 AM.
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