AcousticTheory

Home theater receivers and pre-pros are actually incredibly expensive to develop, and complex. Emotiva has been more transparent about this than most companies; rapidly changing standards for things such as HDMI, HDCP, HDR, etc. have resulted in multiple revisions to internal modules; Emotiva's modular design has enabled them to keep up with this but it is still a treadmill that most pragmatic manufacturers of hi-fi gear would prefer not to even set foot upon, for that reason alone.

My audio system has included, at various times, Mark Levinson, Hafler, Musical Fidelity, Emotiva, Aragon, Hypex, Goldmund/Job, and Marantz gear, connected to Thiel, M&K, Vandersteen, Morrison, and my own speakers, but my focus has always been on value; the most I have spent on any single audio system upgrade was for the Hypex NCore monoblocks earlier this year, prior to that it had been the Thiel CS1.7 speakers, which came my way for a very good deal on a B-stock pair with the original Thiel tweeters, not the later SEAS tweeters. I highly suggest used gear for those who want a taste of high end magic for a lot less money than new equipment. I have had more used gear than new gear. My main interest in the hobby is through speaker design, not electronics or just spending a lot of money, so I am fine for my front end to be more modest in order to serve audio to speakers of my own design and construction.

Will the dCS vs SMSL comparison test ever occur? Will anything be learned? I agree it would be a good idea to keep the subjective and objective sides of the evaluation in their own separate lanes - one person working on a sighted subjective comparison, another person maybe working on blind-ABX testing, and one person conducting the lab bench measurements. We could learn a lot about how perceived quality and value of audio gear is related to each domain. I also think it's plausible that ideal performance in certain measured domains might eventually negatively correlate to desirable properties of the sound, such as 'warmth and richness' originating from a frequency response charateristic or a distortion profile, but at least through that activity we would be able to say something about what type of listener or buyer a certain product is 'for'.

On the subject of the SMSL RAW-MDA1, I received mine yesterday, but I was delayed in setting it up until very late at night so my listening was limited. I used it with a pair of IcePower 300AS1 monoblock modules in Ghent cases, and fed it from a WiiM Mini. Initial impressions are that the RAW-MDA1 (with those amps) is very, very good. I have modestly priced 3-way speakers that I built in 2015 that use planar tweeters, and I had been driving them with an Emotiva TA100 and then a NuForce DDA-120, but with the RAW-MDA1 as DAC/volume control, new life was injected into my downstairs system; I now prefer it to my upstairs system which has Hypex and Thiel. The RAW-MDA1 was not edgy, etched, or overly 'crisp'; it was just transparent to the music, with three-dimensionality and scale. I am looking forward to more listening this evening. Not strictly on topic, but my comments do address the mention of the RAW-MDA1 in the last post - and it is not a component to be sneezed at. I wonder what other products SMSL will release in their RAW series. Whether or not the RAW-MDA1 can unseat dCS is of great interest to me, but at its price it really doesn't need to, in order to be an excellent buy.

Please remember to look after your ears. Talk to your doctor about an ear cleaning, which can take care of the outside. Changes in weather can change how your ears drain moisture and relieve back-pressure from the middle part behind the eardrum; if you have nasal congestion then you may experience 'congested' sound as well. Very gently 'popping' your ears as you might do on an airplane can make sure the pressure is equalized in front of and behind the eardrum (don't overdo it); this makes a big difference for me. Secondly, make sure the speaker set up is just right - you can adjust the amount of toe-in to change the high frequency balance of the speaker fairly significantly, and the speakers being too close to walls can close their sound in due to early reflections.

They've realized this is a risk, so they pre-empted it (though in true AP fashion it's still expensive): https://www.ap.com/analyzers-accessories/apx500-flex The RME interface that used to be in the product photo has now been cropped out.

Why involve human subjects and an fMRI facility then? Seems like they would just be wasting the subjects' time if they were just comparing models to one another to look at the variance between them. The point is that the model based on perceptual descriptors of timbre more closely matched brain activity in certain areas of the brains of human subjects, listening to actual sounds played for them. The relevance to this forum's category of discussion is that conventional measurements can show you data about a signal passing through a device, but they cannot 'hear' the sound for you, and this is the first paper confirming the timbre model of Elliott (correlating acoustical dimensions of instrument timbre to subjective descriptions of timbre) more closely mimics how human beings process timbre in parts of the brain according to neuron activation than one that is simply based on spectrum distortions or temporal distortions (STM) which may be easier to treat or correct in isolation. The Elliott model demands a more complex synthesis of the analysis of those distortions to figure out how a person will perceive those distortions. The problem, in the minds of audio omniskeptics, is that this is a step away from eliminating the pesky listener entirely, because it suggests an analysis that is perceptually derived has significant value, instead of eliminating the listener's perception from the analysis. The response is to dig in and insist that this thing is not a thing.

I have NCx500 monoblocks with SMPS1200A700 power supplies, built by Deer Creek Audio. I like them pretty well, though I needed a bit of adjustment time from my prior solid state amp which was an Aragon A2004. The more I listen to the NCx500 the more I appreciate their clarity, unlimited dynamics, and speed, though their bass tends toward the overdamped side, which has been my experience with all NCore amps. I can recommend the NCx500 for you if you have speakers that need to be controlled. If you buy an amp based on NCxxxMP modules, make sure you invoke your warranty if the modules have any sort of weirdness. I've had a NC252MP that made a high pitched whine just above the noise floor that was audible within 12" of the speaker, and the NC122MP I bought to replace it has an epic turn-off pop that makes me fear for my tweeters. Hypex's competition doesn't have these issues with their mains-powered amp modules, and the IcePower 300AS1 has 3dB lower SINAD than the NC252MP, so Hypex needs to get it together in that product area. I have also heard of NC502MP modules having weird interactions with long speaker cable runs. If you buy one of the MP modules, pay very close attention and if there's any strange behavior from them that you don't particularly like, it's time to send it back.

see my response.

From the abstract: "In cortical regions at the medial border of Heschl’s gyrus, bilaterally, and regions at its posterior adjacency in the right hemisphere, the timbre model outperforms even the complex joint spectrotemporal modulation model. These findings suggest that the responses of cortical neuronal populations in auditory cortex may reflect the encoding of perceptual timbre dimensions." (Allen) I take it somewhat for granted that these experiments were devised by someone smarter than I am, and peer-reviewed by other people smarter than I am. If the conclusions in this article could be dismissed offhand based on a 'gotcha' hidden in the article somewhere, the paper would be taken apart by its reviewers and the broader community of academics, and it would be better not to publish it at all. The methodology of this paper compared the outputs from computer brain models to the observed stimulation in human subjects as monitored using functional MRI. When performance of the paper's modeling was restricted to the above named areas of the auditory cortex, perceptual timbre models outperformed the STM model in predicting the real-world fMRI results; you cherry-picked your quote to contain the words "no significant difference" so I'll cherry-pick another: However, we observed that the timbre model outperformed the joint STM model in a subset of the auditory cortical locations. Specifically, the timbre model performed significantly better in regions medial and posterior to HG, particularly in the right hemisphere. This suggests that while the timbre model only contains five features, it may be capturing some semantic or perceptual tuning properties of the auditory cortex that extend beyond those captured by the spectrotemporal model. (Allen) The superiority of the Timbre model, based on the 5D timbre model of Elliott, in predicting activity in some regions of the auditory cortex (of human fMRI subjects) confirms that the 5D model is able to account for some part of brain activity that the STM model cannot, and this is the key finding of the paper. Most of my other analysis comes from Elliott's work and not the subject Allen paper, in describing what may be important to audio designers for accurately capturing timbre, following from Elliott's model of timbre perception.

The activation of the neurons doesn't need to be directly measured in every case (that work was done by Allen, et. al. in the Neuroimage paper), but the different activation of neuron groups by sounds transformed according to spectral/temporal and subjective timbre models proves that timbre, as perceived by a subject, is based on more complex interactions between parts of the spectrum with respect to time than simply a spectral imbalance or a temporal distortion in isolation. If every part of the solution is right then the entire solution will be right, and the same holds true for reconstructing an audio signal, but if not every part of the solution is right, the 5-dimensional perceptual model of timbre developed by Elliott (2013) gives us a better idea where to look for why a perceptual change arose. The utility of any set of measurements of audio gear is dependent on accurately correlating those measurements to perception; this is why we don't stop studying perception even if the electrical measurements of an audio component's linearity are showing differences between one component and another. What it means to the listener is relevant. The solution is not to ignore the listener.

What can we learn from this paper? The portion of the brain that perceives timbre is not perceiving spectral content directly based on spectrum centroid, but is being activated by aspects of timbre and time content that correlate well to subjective descriptions of timbre. Yes, spectrograms of the signals are provided. The spectrogram of each signal shows frequency content over time. That's just what it does. (It does not, however, 'hear' the signal content for you, and the spectrogram may not be resolving enough to show artifacts you are able to hear.) What the article is describing is how those sounds activate groups of neurons according to perceptual descriptions of timbre rather than according to descriptions of timbre based on spectral weighting, lower or higher. In other words, the fMRI results are being used to 'see' timbre in the form of neuron response generated, and that neuron response is being generated more consistently according to perceptual descriptions of timbre than mere spectral weighting. "Grey (1977) used MDS to identify three dimensions that best represented the distribution of timbres. The first dimension was related to the spectral energy distribution of the sounds (ranging from a low to high spectral centroid, corresponding to timbral descriptors ranging from dull to bright), and the other two related to temporal patterns, such as whether the onset was rapid (like a struck piano note or a plucked guitar string) or slow (as is characteristic of many woodwind instruments) and the synchronicity of higher harmonic transients." (Allen, Neuroimage) "Elliott et al. (2013) extended Grey’s approach by using 42 natural orchestral instruments from five instrument families, all with the same F0 (311 Hz, the E♭ above middle C). After collecting similarity and semantic ratings, they performed multiple analyses, including MDS. They consistently found five dimensions to be both necessary and sufficient for describing the timbre space of these orchestral sounds." (Allen, Neuroimage) Elliott paper From the Elliott paper, five dimensions of timbre are identified: 1) Tendency of an instrument sound to be hard, sharp, explosive, and bright with high frequency balance 2) Tendency of an instrument sound to be ringing, dynamic, vibrato, or have a varying level 3) Tendency of an instrument sound to be noisy, small, and unpleasant 4) Tendency of an instrument sound to be compact, steady, and pure 5) A fifth dimension which had no correlation to a semantic descriptor but still appeared in identified similarity between sounds Each of these five dimensions describes a continuum between the semantic descriptor and its opposite, for each dimension: 1) hard, sharp, explosive, and bright with high frequency balance vs. dull, soft, calm, and having a low frequency balance 2) ringing, dynamic, vibrato, varying level vs. abrupt, static, constant (steady) 3) noisy, small, and unpleasant vs. tonal, big, pleasant 4) compact, steady, and pure vs. scattered, unsteady, and rich. 5) some undescribed quality vs. some other undescribed quality. The Elliott study associated the following acoustic correlates with each of the five dimensions: 1) Broad temporal modulation power, fast transients with equally fast harmonics 2) Small temporal modulations of broad spectral patterns, small decreases in the fluctuations of specific harmonics, slower than average modulation of partials. 3) "Perceptual ordering of this “noisy, small instrument, unpleasant” dimension does not depend on spectrotemporal modulations, or...it does so in a nonlinear way" (Elliott); though the associated descriptors describe audible strain or compression. 4) Distribution of spectral power between odd harmonics or even harmonics; small decrease in spectral power in the range of formants, where spectral modulation was slower; faster amplitude modulations typical 5) Slower amplitude modulations in certain areas of the spectrum; subtlety of this is likely the cause for not being associated with a descriptor. The subjective timbre model employed by the subject paper (Allen, Neuroimage) is based on the Elliott model, so understanding that model is crucial. The finding that the neuron response more closely aligned with these five dimensions than other models based on isolated spectral or temporal characteristics of sounds is essentially a strong proof that Elliott's model of timbre is the one most closely associated with real brain activity and thus real perception of timbre. The instruments used to produce the sounds introduce much more error to the fundamental pitch than audio circuits can, which is why those instruments are used to create the instrumental sounds on a recording instead of oscillators fed to choruses of audio circuits that were otherwise optimized for linearity. When we do feed oscillators to audio circuits to produce instrumental sounds, we mean for those audio circuits to introduce a huge amount of nonlinearity and spuriae. However, our sense of correctness of timbre of an instrument is going to be based on the perceptual model proposed by Elliott and confirmed by Allen, so the purpose of audio playback circuits and electromechanical means, acoustical spaces, etc., will be to reproduce those timbral dimensions unmolested. If those timbral dimensions are impacted by adding or changing audio components, we must look to the spectral or time basis of all of those identified components of timbre to identify what happened. Out of the Elliott 5-dimensional timbral model, we can see that the following areas of a reproduction system's performance are especially important for accuracy: Spectral modulation power over the entire spectral frequency range or narrower spectral bands, temporal accuracy of the modulation of spectral power, low intermodulation distortion between spectral bands, low dynamic compression, minimized impact of large signals and their harmonic structure upon quieter signals and their harmonic structure. In particular, low intermodulation distortion and low dynamic compression stick out as being essential to timbral accuracy in a system where frequency response linearity and high signal-to-noise ratio are already assured. Additionally, control of reactive loads is something that should not be neglected because of the need to control not only dynamic attack (through high spectral modulation on the leading edges of sounds) but also the decay of sounds. Modern highly linear amplifiers, DACs, preamps, etc. are able to do all of these things well, essentially perfectly, but modern speakers and even headphones stick out as the remaining source of most audio system nonlinearity. Harmonic distortion of audio components, if large, may also have a significant impact on timbre, but it is not necessary to have those distortions present at all in the signal chain if not desired. Here is how the finding might be applied: A brightening or a darkening of perceived timbre associated with a component's addition or removal may not properly be restored to a realistic condition exclusively by modifying the component's frequency response to move the centroid of its response curve. Because no conventional measurements of audio components directly predict the neuron activation by those timbral dimensions, only the linearity of audio components passing a signal from input node to output node, we have to synthesize from available measurement data some kind of expectation about what improvement we would need to see within the conventional measurements to correct the timbral issue, even if the frequency response looks flat. It is essential to point out that perception of timbre by the listener is not considered within that group of conventional measurements, so the realistic perception of audio (timbre or otherwise) is also not considered, only the electrical linearity of the device passing the signal.

In short, nothing. Because no conventional measurements of audio components directly predict the neuron activation by those timbral dimensions, only the linearity of audio components passing a signal from input node to output node. Perception of timbre by the listener is not considered within that group of conventional measurements, so the realistic perception of audio (timbre or otherwise) is also not considered, only the electrical linearity of the device passing the signal. Here is how it *might* be applied: A brightening or a darkening of perceived timbre associated with a component may not properly be restored to a realistic condition exclusively by modifying the component's frequency response to move the centroid of its response curve. (Now I will point out that further discussion of this specific paper is going to put this thread off topic, so instead I'm going to link to the thread where this paper was mentioned, so discussion can continue there, or else these posts might get moved and break the continuity of the discussion. Linked)

The spectrogram of each signal shows frequency content over time. That's just what it does. (It does not, however, 'hear' the signal content for you, and the spectrogram may not be resolving enough to show artifacts you are able to hear.) What the article is describing is how those sounds activate groups of neurons according to perceptual descriptions of timbre rather than according to descriptions of timbre based on spectral weighting, lower or higher. In other words, the fMRI results are being used to 'see' timbre in the form of neuron response generated, and that neuron response is being generated more consistently according to perceptual descriptions of timbre than mere spectral weighting. From the abstract: "Results show that this timbre model can outperform other models based on spectral characteristics".

"If you can produce objective evidence that better sound quality is not correlated with known measurements, then yes, it would be a topic for a good research paper to try to explain the finding." An example of this would be the fMRI-based study (published in Neuroimage) mentioned in another thread that found five subjectively-derived aspects of timbre that more accurately predicted timbral descriptions of sounds than a model based on spectral content alone. So such a thing is not, as one might incorrectly infer from your opening statement, unknown, nor is auditory perception an entirely settled science at this point, since these new findings do appear. (Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5747995/ ) And why should such a new study take place at all? Because there is a hypothesis formed by someone that a more complex analysis of auditory stimuli may account for auditory phenomena, resulting from dissatisfaction with the results (a subjective evaluation) of outcomes applying the former model, indicating a need to evolve the paradigm. The discussion of timbre in that article is significant because timbral descriptions are very commonly applied to audio equipment ("bright, harsh, neutral, dark, warm"). So the researchers tested additional dimensions to the perception phenomenon, and the findings can inform downstream reevaluation of the measurement regime meant to correlate with timbre, since it previously focused mainly upon spectral content. The importance of one's dissatisfaction with the results of applying generally accepted measurement criteria is that it motivates additional study, or else on an individual level, casts enough doubt on the current way of applying those criteria that they are able to break out of the mental model enforced by those criteria and accept their own perceived evaluation of sound quality instead of doubting themselves as they are so often encouraged to do.