Jul 3 Podcast #694: High Resolution Audio vs CD
Audio 
Over the past few months you have heard us mention high resolution audio on the show. There are audiophiles out there that swear that if you want the best quality audio then you must listen to high resolution audio. Others out there will tell you that CD quality is just as good. Then there are some that say mp3 or AAC files will suffice for the kind of listening most of us do.
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High Resolution Audio vs CD
Over the past few months you have heard us mention high resolution audio on the show. There are audiophiles out there that swear that if you want the best quality audio then you must listen to high resolution audio. Others out there will tell you that CD quality is just as good. Then there are some that say mp3 or AAC files will suffice for the kind of listening most of us do.
On today’s show we will take both an objective and subjective look at the subject. But this will be a different type of show this week. We’ll discuss the subject on the podcast but there is a companion video that will greatly help in the understanding of the topics discussed. Its available on our Youtube channel (HT Guys) or you can find it embedded on the website for today’s post.
Before we get into the discussion let’s define a few terms for the purposes of our discussion:
Hi-Res Audio - (From Wikipedia) There is no standard definition for what constitutes high-resolution audio, but it is generally used to describe audio signals with bandwidth and/or dynamic range greater than that of Compact Disc Digital Audio (CD-DA). This includes pulse-code modulation (PCM) encoded audio with sampling rates greater than 44100 Hz and with bit-depths greater than 16, or their equivalents using other encoding techniques such as pulse-density modulation (PDM).
High-resolution audio file formats include FLAC, ALAC, WAV, AIFF and DSD, the format used by Super Audio Compact Discs (SACD). It should be noted, however, that audio encoded into one of these file formats is not necessarily high-resolution audio. For example, a WAV file could contain audio sampled at 11,025 Hz and quantized at eight bits, which is lower quality than CD-DA.
CD Audio - (From Wikipedia) Digital audio encoding: 2-channel signed 16-bit Linear PCM sampled at 44,100 Hz.
Objective Comparison
For the objective comparison we start out with a Hi-Res audio file (24 bit 96KHz Sample Rate) and then we encode a CD version (16 bit 44.1KHz Sample Rate) from that. We also created 256Kbps AAC file from the CD version for the subjective test. We imported the 24 bit version into Audacity then we did the same but inverted the track. If the files are identical they should cancel out and the only thing you would hear is silence. That is exactly what happened.
The next step was to import the both the 16 and 24 bit files and then invert the 24 bit track. We expected to see a difference but not by much. What we saw was a resultant audio track with audio from 14KHz to 20KHz. The audio was not loud enough to hear. Our conclusion is that the two tracks are virtually identical.
Subjective Comparison
For this portion of the test we used an application called ABX. ABX is a cross platform (Java Required) blind audio test application that makes this type of testing fool proof. Our setup was a Macbook Pro, Audio Engine D1 24bit DAC (Buy Now $169), and Bowers and Wilkins P5 Headphones (Buy Now $250). While not audiophile territory, it's a far cry from earbuds connected to your phone.
We had friends and colleagues listen to the Hi-Res vs the AAC file and we found that Ara and two self proclaimed audiophiles were able to hear a difference between these files about 70% of the time. The remainder of the participants could not hear a difference . No one could hear a difference between the 24 and 16 bit audio tracks.
Some Thoughts
Is this a conclusive test? Not really. We will never say that no one can hear a difference between hi-res audio, CD, and AAC/mp3. So much has to do with the quality of the recordings, the hearing of the listener, and the equipment being used.
On the video we import some music that has been mastered since the loud wars started (late 90s) and it's pretty obvious that there is not much dynamic range. Do you really need 24 bits when everything is maxed out? If you are used to listening to music that is loud with little or no dynamic range then you listen to something that is pure and full of dynamic range you are amazed. Truth be told you would be impressed even if you weren’t listening to a hi-res recording. When there are just a few instruments and a vocal you can hear everything including little nuances in the recording. That’s why almost every demo I have heard used artists like Norah Jones or Chris Botti. Its because their music has a lot of dynamic range and the detail in the recording usually blows you away. You can also get that detail with CD quality while saving some money and being just as blown away.
Our recommendation is that you rip your CDs in two formats. Do a lossless version for listening at home in a dedicated environment. Then create a compressed version for your portable devices. If you try the test and can’t hear a difference then just go compressed. If you try the test and you can hear a difference, congratulations on having some fantastic hearing skill. This is a blessing and a curse.
Finally, don’t get so caught up in listening at the music to find flaws or a reason to not be happy. You can spend thousands of dollars to diminishing returns. Instead do some simple things like listen in an environment that is comfortable and noise free. Pour yourself a drink and let the sounds take you away to someplace that makes you happy and stress free.
The Video
Reader Comments (3)
I'm surprised that no one heard a difference between the 24-bit track and the CD rendering. A common argument against the digital audio CD format is that the necessarily aggressive low pass filter required because of the 44kHz sampling rate audibly corrupts the upper frequencies. It seems the architects of the format chose wisely.
It is true the main goal is to simply to enjoy the music and it doesn't have to be played on the highest quality system or in the highest quality format to be appreciated. We can enjoy it for the musicianship of the artist or the lyrical content, or just how it makes us feel. But with that said, if you listen to a well recorded piece of music on a high quality system it can offer a much more involving and emotional experience. Most people listen to music on what would be like trying to watch high definition material on there 480p tv. Your not going to see any difference as the program materials resolution far exceeds the TV's ability to reproduce it. Now when you evaluate video material you simply look at it and (hopefully on a good HD set that is properly calibrated) and you simply can see more detail, deeper blacks etc. Most people don't know what to listen for when comparing the quality of reproduced music. Higher resolution music allows you to hear more harmonic richness in instruments, more ambient decay, it simply sounds more real. Listen to cymbals, or string instruments lower resolution material even 44.1 kHz does a poor job of reproducing music in these areas, they sound splashy, harsh and shrill. Lets not forget that how it was recorded and mastered also plays a huge factor, the higher quality the recording the greater the difference you will hear. That also goes for the system the better the system the greater difference you will hear in the recordings, which can be a negative to as it will show you the flaws in recordings really quickly. A big reason many audiophiles often try and find the best recordings to get the full enjoyment from their music. Receivers are not going to give you high quality music reproduction. They are simply to limiting. Price points are a factor and simply having to get to many components in to one chassis and often many features, tone controls surround effects etc. Parts quality is compromised to meet these requirements. Integrated amplifiers are the first step to getting high quality sound. Most use better parts and don't put unnecessary features (like tone controls)that will compromise sound quality. It takes many years to understand the complexity's of designing a truly high quality music system, and they wont be purchased at your local box stores, they can only be purchased at your local independent high end audio video stores. Not only do they carry the best brands of speakers and equipment available most of the salesmen at these stores have many years experience designing high quality systems. Its both art and science, and everything in the chain has an effect on the overall sound as well as the setup. Speaker positioning for example is critical and has a HUGE effect on the sound. When you really get into high end audio everything matters, the quality of power, the rooms acoustics, and yes the cables you choose. Its a real shame more people have not experienced and discovered high end audio. Do yourself a favor and go and discover your local independent high end store and experience high quality music reproduction, you will be hard pressed to go back to what you thought was good sound. Kevin 40 years high end audio video specialist
Also on your evaluation of high resolution audio you can see and hear differences, but there is much more to it than that. Simply look at a lower resolution file to a higher resolution file side by side and you can clearly see there is more information which will translate to more detail and greater harmonic richness to the instruments. You can also see that high resolution music goes well beyond 20hz. This is not unnecessary information because you think it goes beyond the human hearing limit. All instruments reproduce sounds well beyond human hearing, which include instrument overtones. A instrument reproduces the fundamental note as well as the overtones of that note, not to mention the instruments own resonances. These all help us hear the difference between different instruments. These sounds can go well beyond the "so called hearing limit" of the human ear. But we don't just hear sounds we feel them through our body cavity's. If we cut off those sounds beyond our "so called hearing limit" they effect the sounds in which we do hear. We hear it as lack of naturalness and tone of the instrument. High sample rate music and high quality music systems can reproduce that as they don't have the brick-wall filters that most average consumer grade equipment cut off.