Audio Adventures

from Sonic
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Tunees will discern from earlier tuning adventures that I prefer wood from Mr Green under my equipment, having moved away from the metal cones of the MTDs and the AAB1x1/Deep Bells, not to mention the many failed attempts with Space Cones which caused an upward shift in tone and thinness with settling.

Yet in a different system, the results using these devices worked “as advertised”.

Sonic has an audiophile friend who owns a system more advanced than mine. Serious amplification from Audio Research and a high-tech loudspeaker of a similar size and price range of the Harbeth 30.1s set up in a dedicated listening room that is mostly drywall with a carpeted concrete floor.

As we talked about my system’s successes and failures he asked Sonic “let me try those cones that didn’t work in your system”. So I handed over my bag of Space Cones and the AAB1x1/Deep Bells.

A few days later, he calls and says that with the Deep Bell AAB1x1 under his amps and the Space Cones about his system, the music now "sounds amazing…those things from Green have finally removed a treble roughness I been working to cure for a long time and just using those cones and it is gone….my system is exactly what I want it to be!”

So what did not work in my set up were the very things that perfected someone else’s system and created one more happy, though an indirect, customer of RoomTunes.

I guess this is a bit of a coda on my Space Cones episode.

Any comments on this, Michael?
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mg

There are so many variables in audio that I try to make products that fit each situation. It's for sure not a one size fits all hobby. When I design I create different environments with different recordings and different setups. I've been doing this type of listening since the 70's and have always found it interesting that there always seems to be a sound or a structure that is different based on a particular setting than the rest. Our homes and listening environments are units of physical and energy uniqueness. Before doing home audio I found the same thing to be true in recording studios. That's why I spent most of my time playing in the studios when they were not in sessions, with maybe one or two music buddies and me.

I've always been attracted to sound, feeling and Vibe. That may sound weird if you are trying to do this hobby by using "Fixed" values, but if you see audio as a variable on a constantly energized planet, with all things being unique, we start to see something that is quite different from squares trying to fit in square holes. What we start to see when we tune is a continuum of flow instead of seconds ticking like on a watch. Energy is not measurement it's motion. We can't take a measurement at your place and transfer it to your friends house. What we can do is play with the physics at both locations and see how we can get those physics to do what we want.

"Remember when you saw me adjust the sound of (my) system? You heard some changes right? How many spots did I add or move wood from – it was just one spot right? I know my system well and that is the place I know where the changes can be made.”

“While I don’t know Michael Green’s system, I won’t be surprised that for that set up, he was such a good listener and experienced Tuner that he had chosen ONE “pressure spot” to tune and get the tonal and soundstaging effects he demonstrated.”

“I am sure neither Green or your RoomTune friends go about adjusting every cone, wood block or Tuning object in sequence or randomly just to get an effect. Our lives are too short for stuff like this! Let me ask -- if you hear a dull recording and want to fix it, where do you go?”

Sonic: “I go for the JVC Nivico SEA-10 Equaliser.”

Mystic: “and anything else?”

Sonic: “if I want a tighter center image at expense of width, I might tighten up the bolts of the PZCs, and if I want a super-warm presentation it will be (Low Tone Redwood) blocks on the DAC and its power supply.”

Mystic: “See, that is the idea Exclamation I am sure Michael Green and your friends have found their selected (tuning) points on their equipment racks or somewhere and they only tweak these to make the changes they are looking for….”.

“Is not that complicated is it, Sonic?”

Michael, is this a correct observation?
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Our system environment is a playground of energies in a continuum of action. Every time we go looking for an adjuster we can find one that is so powerful it can change the sound of the entire space. They're everywhere and all around us. It's fun to get to a place with our system where we can touch that one domino and listen to the whole chain go into motion, one move affecting the next. That's the first part of the fun and then there's the event of settling, my personal favorite. Hearing and feeling that adjustment we made mature. That's a thrilling ride!

Greetings Zonees

Here is an article explaining what Upsampling is and how it differs from Oversampling (but remember this article promotes a product so keep that in mind):

To upsample or not to upsample; that is the question.

Source: http://bitperfectsound.blogspot.com/2013/11/upsample.html

Tuesday, 5 November 2013

Back in late March, I posted some introductory comments here regarding how DACs actually function.  Anyway, following my recent posts on Sample Rate I thought it might be apropos to revisit that subject.

Today’s DACs, with a few very rare (and expensive) exceptions, all use a process called Sigma Delta Modulation (SDM, sometimes also written DSM) to generate their output signal.  A nice way to look at SDM DACs is to visualize them as upsampling their output to a massively high frequency - sometimes 64, 128 or 256 times 44.1kHz, but often higher than that - and taking advantage of the ability to use a very benign analog filter at the output.  That is a gross over-simplification, but for the purposes of the point I am trying to make today, it is good enough.

Doing such high-order up-conversion utilizes a great deal of processing power, and providing that processing power adds cost.  Additionally, the manufacturers of the most commonly used DAC chipsets are very coy about their internal architectures, and don’t disclose the most significant details behind their approaches.  I would go so far as to say that some DAC manufacturers actually misunderstand how the DAC chipsets which they buy actually work, and publish misleading information (I have to assume this is not done intentionally) about how their product functions.  Much of this centres around cavalier usage of the terms ‘upsampling’ and ‘oversampling’.  Finally, some DAC manufacturers use DAC chipsets with prodigious on-chip DSP capability (such as the mighty ESS Sabre 9018), and then fail to make full use of it in their implementations.

Let’s study a hypothetical example.  We’ll take a 44.1kHz audio stream that our DAC chip needs to upsample by a factor of 64 to 2.88MHz, before passing it through its SDM.  The best way to do this would be using a no-holds-barred high-performance sample rate converter.  However, there are some quite simple alternatives, the simplest of which would be to just repeat each of the original 44.1kHz samples 64 times until the next sample comes along.  What this does is to encode the “stairstep” representation of digital audio we often have in mind, in fine detail.  This is acceptable, because, in truth, the 44.1kHz audio steam does not contain one jot of additional information.  Personally, I would refer to this as oversampling rather than upsampling, but you cannot rely on DAC manufacturers doing likewise.

If we are going to use this approach, though, it leads us down a certain path.  It results in the accurate recreation of the stairstep waveform at the output of the DAC.  Even though we have oversampled by a factor of 64 in our SDM process, the output of our DAC has been a faithful reproduction of a 44.1kHz sampled waveform.  This waveform, therefore needs to go through an analog brick-wall filter to strip out the aliases which are embedded within the stairstep.  This is exactly as we discussed in my last post on Sample Rates.

In principle, therefore, by upsampling (using proper Sample Rate Conversion) our 44.1kHz audio by a factor of 2 or 4 prior to sending it to the DAC, we can avail ourselves of the possibility that the DAC can instead implement a less aggressive, and better-sounding, brick-wall filter at its output.  That would be nice.  But that is not the way many (and maybe even most) DACs that use this approach are built.  Instead, they use the same analog brick-wall filter at high sample rates as they do at 44.1kHz (because switching analog filters in and out makes for complicated - read expensive - circuitry).  If your DAC does this you would not expect to hear anything at all in the way of sonic improvement by asking BitPerfect (or whatever other audio software you use) to upsample for you.

So let’s go back a couple of paragraphs, and instead of our DAC oversampling the incoming 44.1kHz waveform, suppose it actually upsamples it using a high quality SRC algorithm.  Bear in mind that all of the audio content up to 20kHz in a 44.1kHz audio stream is aliased within the frequency band from 24.1kHz to 44.1kHz.  If we are to upsample this, we should really strip the aliases out using a digital brick-wall filter.  Done this way, the result is a clean signal that we can pass into the SDM, and which is precisely regenerated, without the stairstep, at the DAC’s output.  So we no longer need that aggressive, sonically worrisome, analog brick-wall filter.

Let’s take another look at these last two scenarios.  One had an aggressive analog brick-wall filter at the output, but the other had essentially the same brick-wall filter implemented digitally at an intermediate processing stage.  If the two sound at all different, it can only be because the two filters sounded different.  Is this possible?  In fact, yes it is, and there are two reasons for that.  The first, as I mentioned in a previous post, is that an analog filter has sonic characteristics which derive from both its design, and from the sonic characteristics of the components with which it is constructed.  The digital equivalent - IF (a big IF) properly implemented - only has sonic consequences arising from its design.  There is a further point, which is that digital filters can be designed to have certain characteristics which their analog counterparts cannot, but that fact serves only as a distraction here.  The bottom line here is that, if properly designed, a diligent DAC designer ought to be able to achieve better sound with this ‘upsampling’ approach than with the previously discussed ‘oversampling’ approach (again, I must emphasize this is MY usage of those terminologies, and is not necessarily everybody else’s).

Using the ‘upsampling’ approach I have just described, it should once again make little difference whether you send your music to the DAC at its native sample rate, or if you upsample it first using BitPerfect (or whatever).  However, all this assumes that the upsampling algorithm used by the DAC is at least as good as the one used by BitPerfect.  There is no guarantee that this will be so, in which case you may find that you get improved results by using BitPerfect to upsample for you to the maximum supported by your DAC.  And you should use one of the SoX upsampling algorithms provided by BitPerfect, rather than CoreAudio.

The bottom line here is that you should expect your DAC to sound better (or at least as good) with your music sent to it at its native sample rate than with it upsampled by BitPerfect.  And if it doesn’t, the difference is probably down to BitPerfect’s upsampling algorithm sounding better than the one implemented in your DAC’s DSP firmware.

So, in summary, in light of all the above, our recommendation here at BitPerfect is that you do NOT use BitPerfect to upsample for you, unless you have conducted some extensive listening tests and determined that upsampling sounds better in your system.  These tests should include serious auditioning of BitPerfect’s three SoX algorithms.

Posted by Richard @ BitPerfect at 12:23 pm

A Discussion with The Audio Mystic on Playback Levels

The Audio Mystic:  I think you (Sonic) and a lot of audiophiles play music too softly.  I like my music loud, to get the feel of a live sound.

Sonic: How loud is enough for you?

Mystic: Ok, we know that if a recording is mixed at one level and you play if softer than that, the balance will change and you will not be hearing the mix as intended.  There is the SMPTE standard that studios do their monitoring and this involves a 83db C weighted average level.

Sonic: That’s very loud.

Mystic: I knew you will say that.

Sonic: Your room is smaller than mine, won’t the sound be very “in your face”?

Mystic: I damp my room heavily.  My approach is to super damp the room and then reduce the damping a bit to the point where the music sounds right.  Whatever it is, my room is far more damped than yours. Although you seem to be using more damping than you used to.

Sonic: I broadly follow Michael Green’s approach.  A damped room robs the life from the music.  I say keep the room balanced acoustically with RoomTunes and Pressure Zone Controllers and use as little curtains, carpets and stay away from the foam.

Mystic: I heartily disagree! I damp till I can get average levels of about 83 dbC at my listening chair from my JBLs. Then I know I am hearing Miles Davis the way it was intended. You like the classic Absolute Sound yes? You bought up [Name of Audiofan]’s collection.  If you read carefully, HP and J W Cooledge listened at levels far higher than you.  When Ken Kessler went to listen HP’s Infinity IRS system he was warned that he might come back with jellied internal organs.  How HP and his friends are getting real music – you are getting only half the music. So much for your lip-service to King Tone.    

[Remark from Sonic: neither of us have heard each other’s system, only seen the layouts and pictures. This discussion is not adversarial. Mystic and I were having strong coffee when this conversation occurred and the caffeine buzz contributes to the fun.]

Mystic: HP has been known to blow out tweeters of smaller speakers like the Advents during testing.  How loud do you think he must be playing for this to happen?  One reviewer Patrick Donleycott said he listens at 85 dB and over.

So what levels do you set to?

Sonic: I generally listen at 70 dB C average, if want LOUD then I crank the system to about 75 - 78 dB C.

Mystic: Ha ha….you call that Loud? Thanks because in your “live” room you cannot crank your system beyond 80 dB C before your room shrieks and honks and compresses. Go home and see if you can get 83 dB C average. You will never get 95 dB peaks like I can. You can’t do it, it will blast your ears. Enjoy your coffee.

Sonic’s view…..such are friends…..look at this May 2014 Sound on Sound article in particular the charts to calculate the optimum reference level for your room:  

https://www.soundonsound.com/techniques/establishing-project-studio-reference-monitoring-levels

The writer Hugh Robjohns makes this point:

“This 83dB SPL reference level (with 103dB peaks) is perfectly acceptable if you're listening in a big space, like a cinema or a film dubbing theatre, or even a very large and well treated commercial studio control room. Unfortunately, it will be completely overwhelming in a smaller space, because the listener is inevitably sitting much closer to both the speakers and the room boundaries. The very different nature of early reflections makes the level seem, psychoacoustically, much higher than it would be in a larger room.

Consequently, the optimum reference level for smaller rooms needs to be lower, on a scale which is dependent on the enclosed volume of the room in question. You can work out the volume of a room simply by multiplying together its length, width and height, of course, so a home studio which is four metres wide, six metres long and 2.5 metres high has a volume of 60m³. If you prefer to work in imperial measurements, the example above would be roughly 13 x 19.5 x 8 feet, and 2028 cubic feet in volume.

The recommended reference monitor SPLs for different room sizes are shown in the Room Size vs Reference Level Table.

For the example room cited above, this table suggests the ideal monitor calibration level is 76dB SPL.”

Sonic’s room is about 2,900 cubic feet and the recommended level from the chart is also 76 db C.

Interesting how my “Tune instinct” level for “loud” listening corresponds to this.

Am I losing the balance of the records in my music collection? Definitely not if I am listening to near the 76 dB C reference level.  Does it worry me that my room system cannot allow 85 db C average levels due to acoustic compression (I tried and it can’t)?  Yes it troubles me a little perhaps knowing that my system has a weakness but should it be a problem if I am getting all the music at a lower and hearing-friendly level?

From this I can understand that “The very different nature of early reflections makes the level seem, psychoacoustically, much higher than it would be in a larger room” makes a specific measured level for home listens less important as long as we can achieve high levels psychoacoustically – meaning, in a Tuned room you can play Deep Purple at what is subjectively 100 db when in the room, it might be 80 db.

Good enough for Sonic.  

Sonic

Sometimes taking a "changed" journey can be fun. You can end up in places where you discover parts to recordings that surprise, plus it's fun to explore. But, I always keep my eye (ear) on my basic starting points sonically. It's about having the confidence in knowing we can go anywhere we want through Tuning.

Many times in my listening I'll hear something and then I have to decide if I want to chase or not. Having only two listening areas now (one fixed and packed full to the ceiling), I tend not to do too much chasing, a small adjustment and that's it. But, I take mental note of any changes that happen at my place from things being moved in and out. The SAM wall saves my listening, thank God for that wall.

Your room and system is quite the feat in patience Sonic. I'm sure even in moments of you feeling that you are in the spin cycle, there are nuggets for folks to identify with, and no doubt relate to as they are on their journey. Plus seeing how quickly you catch yourself before going to far on that possible side track has shortened dramatically. Which is a prize all on it's own.