Holographic imaging

This thread is a gas

I get the feeling that a lot of these holography systems that have appeared over the years are aimed at those who have a lack of resolution in their systems- and can stand listening to an effect, rather than the music.

FWIW: It is easy to add holographic effects or wide soundstage by using a flanger or adjusting phase between two channels - guitar folks know this all to well - there are literally hundreds of sound effects. Another effect is reverb circuitry like Harmonix

There is a science behind these effects too but it is too much to go into here. I share Ralph's opinion though - I prefer not to add extra effects to the CD's I play - even if some of it on some tracks can be pleasing addition/change.

It is the CHANGE in volume that affects the pitch

Since you make no mention of frequency (group delay). I take this to mean that you suspect that the absolute signal level changes the propagation delay in the circuit. This is a non-linearity that should cause IMD distortion and it should be measureable. (Signal level or amplitude is modulating the frequency of output - creating new frequencies. For example a cymbal high frequency sound riding on top of a large oscillating bass guitar note - as the bass guitar signal goes up it changes the of pitch of the cymbal HF sound - giving side bands)

FWIW - this is already a huge problem in speakers and especially those with overhung voice coils that are not particularly linear throughout their driver excursion.

You don’t have to manually change the volume (yourself) – your amplifier is changing the gain on the fly

I understood that from your previous post. My question is why we do not see this in THD and IMD figures or an analyzer which looks at the distribution of harmonics - it appears to be a non-linearity much like any other. (I would still expect speakers to be far worse than an amp on this issue)

Lets assume that a 200 Hz bass note is modulating the 1000 Hz note.

This will cause a 1khz tone to shift up to 1005 hz At this level it is a mere twinkle in the eye of “harmonic distortion” but is distortion nonetheless.

Not the way I understand Fourier analysis. You would not get a 1005 Hz note (this note only exists in theory or in the infinitessimally short space of time or "twinkle of an eye" and you woudl not be able to hear it as it would have no power spectrum as it does not exist over time).

I think you would end up with a 1 Khz signal with side bands at 1200 Khz and 800 hz and 1400 Khz and 600 hz etc. etc. as the non-linearity would cause IMD that had a power spectrum that relates to the mixing of the 200 Hz bass note with 1 Khz tone under a non linear amplifying condition.

The way I understand fourier analysis - shifts in time are similar to other non linearities and can be treated that way - in the same way jitter shows up as side band distortion on audio signals when jitter has a distinct periodicity to the signal (i.e not just uncorrelated random jitter that will simply raise the noise floor).

I was referring to an instantaneous shift in velocity of 1:1.005

Well you'll have to be more precise then if you want to help me understand. What you have described is just too vague for me to follow which is why I gave a specifc example with specific frequencies with a hypothetical result.

FWIW- We don't hear "instantaneous shifts in velocity" - we hear sound vibrations or oscillations which is why I tried to boil things down to frequencies and power that would result from IMD distortion from two frequencies passing through a non-linear amplifier. (non-linear meaning that the signal gets amplified differently depending on its level)

BTW an "instantaneous shift in velocity" would cause a sharp discontinuity in what is normally a smooth waveform - it would necessarily contain lots of high frequencies and not 1005 Hz. This is a fundamental fact from mathematics.

IMO we are dealing with a case of the Emperor's New Clothes. IOW I'm with Tvad on this one.

I second Tvad and Ralph but folks remember I am dumb engineer so I don't believe a tenth of the scientific claims in any subject in the audio domain - unless it fits my college brainwashing, which means it is well known and documented in AES journals (who still make mistakes but far less often or with such hyperbole as found on internet threads or in audio rags).

What surprises me though - is how highly selective we are being - why are we attacking Roger Paul's gear in particular? - I mean there is a lot more out there that is WAY WAY WAY WAY more dubious - magic pebbles, Shakti holograms, $7000 cables, $1000 interconnects - nobody jumps to shout the "Emperor has no clothes" with any of that gear - even if it is patently obvious to anyone with a science background. Why is this?

I suggest a truce here. FWIW - If the H-Cat sounds great (like the Harmonix Holy Grail box I gave a link to earlier in this thread) then for those who like what it does then good luck to 'em - whatever it does is a good thing to those who like it! We don't need to know why - just as nobody can explain why Anjou Pear is so utterly amazing and why dozens of people jump to defend the incredible benefit to be had with esoteric cables when this subject is raised (perhaps they all work for Noel Lee!).

That's not an attack. That's due diligence.

Good point but why are some things allowed to go without any demand for due diligence - most cables "technology" for that matter - that was kind of what I meant to imply but you are right to correct me.

I've read many posts where requests have been made to explain cable "technology", so I don't agree that it's been given a pass

Yes but there is always an army of followers out there ready to jump to the defense of even the most dubious scientific claims for amazing differences between cables - (where no electrical science has gone before - cryogenic treatments - you name it - the wackier the cable theory the better it would seem!)

So why not Herr Doppler effects?

It is a fact that some people hear pitch better than others, but from what you are saying, none of this has any bearing on your 'phenomena'.

Yes but it is also a fact that we ALL hear pitch or frequencies more accurately than just about anything else (in the midrange of course)

We are sensitive to amplitude with a threshold of about 10%.

We are sensitive to pitch (frequency) at a threshold of about 0.2%.

Fortunately most equipment (other than a TT or analog tape) is always way way more accurate than 0.2% in frequency.

It has occured to me, however, that doppler effects coud be a real problem for those who like to listen to music on a high speed unicycle, which probably explains why NO clowns can be audiophiles even if audiophiles can sometimes be clowns...like me ;-)

is there any reason why the two may be mutually exclusive - that is, does the most accurate equipment in terms of one mean a lessening of the other?

My experience is they are hard to find. Most horns give you dynamics of live music but lose that natural sound due to narrow dispersion. Most well designed dynamic loudspeakers have the wide dispersion to sound natural and image precisely but lack the dynamics of live music.

Of course there are a few horns and a few dynamic speakers that do an admirable job at both and sound extremely convincing as if you are there - but it is only a very few, IMHO.

**above** the ensemble, which produces an odd perspective, unless you happen to know that that is where the mics are placed.

Wood floors and microphone height above floor are key in recording. The floor will produce comb filtering as the sound is reflective from it and cancels with teh primary sound - it creates a pleasing spacious sound. Depending on the instruments there are a variety of rule of thumb positions for mics - choral works are often recorded with overhead mics.

BTW - this happens with your speakers in your room too particularly in the low midbass where soudns radiate in all directions => you get quarter wave cancellations off the wall behind the speakers.

They key to this effect is a large flat reflective surface which is positioned symmetrically with repect to the microphone or listener. Some sudios have special plates just for this purpose although often recordings are now made in a an acoustically dead booth and th esoudn of a platye is added by using a reverb (the advantage is you can dial in any reverb you want)

For example side walls do not produce this effect in a listening room - only the rear wall behind the speaker and listener which is symmetric with the bass and midbass frequencies. It is the same for a microphone - if you want to maximize the effect then the mic needs to above the source of sound so that the sound is in between the microphone and the reflective floor.

I recommend Bob Katz book (Mastering) for people who want to read up on this. I am sure Ralph knows more than I do about all this - but I thought many readers may be unaware of this - although as an audiophile I think it is only natural that one should want to understand this stuff (nearly half of what we ever hear is reflected sound)

I mostly drive Senoritas (oops this ain't the four word thread - sorry, my bad)

You think great DACs are realtively immune to the transport use? I always naively[?] felt thgat a good DAC should be able to deal with whatever jitter the source might present; maybe we are there

Interesting question - I wonder what experts think?

I suspect some DAC's are becoming relatively immune to digital source and jitter. Clocks and algorithms continue to improve so inherent jitter reduction is improving also (we went from PLL to double PLL's to buffering and asynchonous sampling). However not all forms of jitter are the same so the quality of the rejection may vary depending on what the source is creating. Some will reject a greater variety and a greater level of jitter than others so in essence they might sound the same with most transports. Of course some combinations, even older ones, may just happen to work really well, as the transport jitter is just the type that the PLL loop can deal with.

An old AES paper showed that certain forms of 20 nanosec jitter were inaudible - this is a huge amount by modern standards - so if people hear jitter artifacts then it may not even be an issue of "how much jitter" at all but a more sinister issue of "what type of jitter". If you consider source music and jitter may be related to eachother (IMD) then there are probably an infinite number of combinations. Added variables are that one may not be able to hear it, or your speakers may hide/mask it, or the track may be hypercompressed (other distortion dominates), or the track was recorded with a jittery A to D in the first place (so nothing can fix it)

I suspect we are way closer to jitter immmunity to the point of inaudibility than we were in the 80's and even the 90's. I wonder what others think - Are we really there?