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Topic: Listening audio content above 20kHz (Read 18544 times) previous topic - next topic
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Listening audio content above 20kHz

Reply #25 –
My pretty cheap CD Discman I bought in the 1980's ($199 USD, if I recall) had a superior frequency response to any LP record, made with any cutting lathe/amp and cutter head, played back on any turntable using any cartridge/stylus, through any phono preamp, ever made, at any price. Oh, and get this, I'm talking about over the frequency range that humans actually do hear, so unlike this discussion of "Is what's up around >25 kHz on LPs really music or just noise and artifacts?" my Discman's superior, flatter, more neutral FR is actually discernible to humans, not just theoretical bats/dolphins listening to pure 30 kHz test tones in isolation.

Listening audio content above 20kHz

Reply #26 –
Quote from: mzil on
My pretty cheap CD Discman I bought in the 1980's ($199 USD, if I recall) had a superior frequency response to any LP record, made with any cutting lathe/amp and cutter head, played back on any turntable using any cartridge/stylus, through any phono preamp, ever made, at any price. Oh, and get this, I'm talking about over the frequency range that humans actually do hear, so unlike this discussion of "Is what's up around >25 kHz on LPs really music or just noise and artifacts?" my Discman's superior, flatter, more neutral FR is actually discernible to humans, not just theoretical bats/dolphins listening to pure 30 kHz test tones in isolation.


These measurement certificates came with the two 205CMK3's I have

[attachment=7965:U205CMK3.png]

Both has quite flat frequency response, don't they? I used the U205CMK3 for these example recordings related to this thread.

Listening audio content above 20kHz

Reply #27 –
@mzil:  I believe you are replying to the wrong topic.

This isn't about what is more accurate, or what is, or isn't inside the human hearing limits.  It is about the capabilities of the media, and concretely, in regards to frequency content above 20Khz.

Precisely, one of the objectives is to put light on one of your replies.
You expressed that whatever content there is, it is just distortion picked up from the stylus from lower frequencies. This thread gives two methods (one visual analysis of FFT, and the other, frequency shift down to hearable frequencies) to hear and understand what's recorded in those frequencies.
Are you able to discuss about this, or do we have to believe you?

Also, you went on with telling that the capture equipment used could simply not have recorded the content.
If a mic extends up to 30Khz, then, why are you even adding this to the discussion, if 30 is ABOVE 20? Also, that a mic extends up to 30Khz should, in theory, say that it is able to capture up to that frequency with less than 3dB of attenuation.  Well, the peak of the content that remains in this recording after filtering is around 24dB down. (without filtering it is just above -1dBFS)

We know several things:
Depending on how it has been produced, the recording might not even have real content above ~20Khz because of digital or analog filtering  (as shown in one of the topics that this thread references to, in the first post, concretely http://www.hydrogenaud.io/forums/index.php?showtopic=106196 ). It is not discarded that those screens could also be caused by using a wrong configuration (recording in directsound and having windows configured to record at 48Khz, as one example).
Depending on what is used, content is present, and this content can be analyzed and determine if it is of any use.  This isn't just about vinyl. It is also about high frequency formats.

Listening audio content above 20kHz

Reply #28 –
I took off the HF content file attached in 1st post to get some space for this 2nd example recording.

24-bit/192kHz sample (28s): [attachment=7966:test_hf_JA_28s.flac]

Spectorgram plot:

[attachment=7967:JA_hf_28s.PNG]

Earlier [JAZ]'s post describes a method for to test the hf content of linked audio file.

Listening audio content above 20kHz

Reply #29 –
Quote from: Juha on
These measurement certificates came with the two 205CMK3's I have

That's why I specifically inquired about earlier (in the other thread) third party measurements. I personally ignore manufacturers' claims, especially with things like the frequency response of analog devices such as loudspeakers, headphones, mics, and phono cartridges. They have a stake in the game and many thing are called into question. As just one example, the exact test conditions used will often yield markedly different results, especially with a low level signal like a phono cartridge, where the specific phono preamps' actual load (not the published spec) and one's connection wire (if we're talking about a turntable where it isn't fixed but rather is replaceable) can dramatically alter the results. For example, a longer run's changes to the R, L, and C can alter the response.*

* which is why one should generally never extend a turntable's cable, but instead place your phono preamp close to the TT and extend its more robust ~2 V signal to the other gear's AUX input.

Listening audio content above 20kHz

Reply #30 –
Quote from: [JAZ] on

@mzil:  I believe you are replying to the wrong topic.

Assuming you are referring to my post #26, it wasn't a reply, it was merely an observation. I stand by it.


Listening audio content above 20kHz

Reply #31 –
Quote from: [JAZ] on

Depending on what is used, content is present, and this content can be analyzed and determine if it is of any use.

Of use to bats and dolphins, you mean? To humans, it is of no use. Ever.[Not that the content you speak of is actually a faithful reconstruction of the true original music, and not simply harmonically related junk which seems to be "tonally related" because that's exactly what harmonic distortions are.]
 

Listening audio content above 20kHz

Reply #32 –
As for this ultra HF content being "present", we don't even know that! This spurious junk could be very well be harmonic distortions of the cartridge's output and not actually be embedded as undulations in the vinyl groove wall at all. [Carl Haber's newer IRENE system, whatever it will be called, which can optically scan not just horizontal but also vertical groove modulations, will help determine this.]

If you think about it, even if we pretend for the moment that cutting lathes/amps/cutter heads were "perfect" and free of harmonic distortions [they aren't] and that our turntable/cartridges/styli/and phono preamps were perfect and free of harmonic distortions [they aren't], the vinyl material itself [or rather the mother it is stamped from, actually] is still prone to distortions. Think of for example LP pre-echo: it isn't the cutter head's fault, and it isn't your pickup's fault, it is the fault of the elastic material the cutter head gouges out, just like the multiple ripples one sees in a pond after tossing in a rock. Rocks don't have harmonic distortion; the pond water does.

Listening audio content above 20kHz

Reply #33 –
Very interesting thread. Has everyone forgot the CD4 discs from the 70's. Weren't they good for 48Khz If I remember.

Doug Self in his Small Signal Audio book (page 168) explains about the 50kHz roll off in Neuman SAL 74B cutters and, according to him, there is a 2 pole roll off at 3.19uS giving 12dB/Octave Roll off. The loss at 20kHz is less than 0.1dB.

I worked for Westrex until its demise in 1984 and our cutters also had a 49.9Khz roll off.

Steve.

Listening audio content above 20kHz

Reply #34 –
Quote from: Steve Grant on
Very interesting thread. Has everyone forgot the CD4 discs from the 70's. Weren't they good for 48Khz If I remember. ...


"Yes, but..."

- They had to be cut at half speed.
- Maximum velocities for the >20KHz carriers had to be strictly limited. 
- Baseband (L and R front) channels had to be low passed at about 15 KHz.

Regards,
   Don Hills
"People hear what they see." - Doris Day