Friday, 1 November 2013

Digital Audio SD to HD

Digital Audio SD to HD
An honest look into what problems I’m facing
By Martin Pearman

Ok guys, as you know I recently purchased a pair of Bowers & Wilkins In Ear Monitors (IEM) and I found the reviews online to all point to one troubling conclusion. Even though they were great they tended to be bass crazy, here are what some reviews said:

“And bass. Wheelbarrows of bass. At times it’s great, providing depth and detail you won’t find in any rival; but with some tracks it’s simply too much, drowning the rest of the track and making us feel like we’re sat in a boy-racer’s souped-up XR3i.” - What Hifi Magazine

“Moving back to comments on the bass some might be initially confused by the rather bold bass presence. In some cases it feels as if the bass frequencies need to be tamed in so that the overall composition has a more polished and articulated focus.” - The Pro Audio Web Blog

In my own review I found this to be partly true, the C5’s do have an abundance of bass and sometimes this is detriment to the overall listening experience. But I only had this experience with the iPhone, when playing the same music through and Arcam amp with an Arcam CD as the source the C5’s performed beyond what they are capable of with the iPhone, putting the weak link as the source not the IEM’s.

This got me wondering what could be the cause of this issue, it clearly isn't the IEM’s so is it the iPhone? or maybe the audio source itself?

So I’ve decided to try and find out what it could be and what I could do to get the best from these headphones while out and about and I’ve found some interesting things, and it paints an interesting picture of the whole digital audio marketplace and also the manufactures of our audio equipment.

Now I'm presuming that B&W tested their headphones with a variety of components to make sure sound was acceptable across a wide range of products on the market. I also presume they tested iPhone, iPod and iPads as this would be the main target for such a premium priced pair of IEM’s like the C5’s. Based on my basic tests (I’m not an audio engineer but I have sensitive ears) I find it hard to believe that B&W would push out something with such poor bass control and dynamic timing.

So I decided to try one CD knowing it was recorded with care and also knowing it has very high levels of low frequencies, it also mixes Classical and electronic elements so has a wide range of sounds. This CD was Tron Legacy soundtrack by Daft Punk. I decided to use my Macbook Pro running OSX 10.9 and it uses Intel HD Audio.

First up was the MP3 320kbps. It sounds ridiculously booming so much so the small sounds of sheet music being turned and breaths from the orchestra were lost and the midrange got so muddy it was a dog to listen to.

Next was the CD directly played via VLC, as predicted it was a sheer delight to play and all the small and delicate sounds were there, bass was controlled and the mids and highs were never swamped by anything else. The headphones also showed a nice sense of space and pacing that was lost in the MP3 version. The problems arose then as in parts it was too bright and bass was lost entirely, I put this down to VLC and tried Quicktime, low and behold the audio settled down and became solid again, one thing I did notice was the noise reduction used and this seemed odd. I then tried Track 5 and I can clearly hear noise reduction kicking in, this was audible in three stages 1. zero noise before play was pressed, 2. play was pressed and noise levels were high, 3. music started and noise was then cut down, but this was causing some audio loss. At the end of the track you can hear the audio noise being cut again down to a whisper then a ‘click’ and total silence.

This suggests that the Intel HD audio is playing around with sound levels but to what benefit or cost to the audio reproduction. Clearly this is not good and very distracting. So playing CD through a Mac is not going to work.

Ok so on to an AIFF rip of the CD. I did this using XLD to ensure the best quality I could get and as its an uncompressed file the size compared is relative.

The MP3’s took up 141.1MB of space while the uncompressed AIFF’s took up 622.9MB.
So why the AIFF over say FLAC? Well for me as much as I love my music I don’t want to have to use different players and streaming software to play the damn stuff. I want to be able to use my Apple TV and stream my music if needed for example AIFF -> iTunes -> Stream -> Apple TV -> HDMI -> Sony TV -> Analogue Out -> HiFi -> Speakers -> Ears. This is a long way for data to travel and its going to get messy on its trip but most of the time I don’t care and its not critical I have the best audio.  But when I do decide to listen I prefer the CD or Vinyl but this isn't always practical so a digital file as close to will do. AIFF is supported more on the Mac through iTunes and will be playable on my many devices and FLAC won’t, not because its a poor codec but because Apple wont bloody support it.

I can say now that out of the tests I’ve done so far the AIFF sounds great and is a fantastic compromise when using my Mac to play sound, its clear and doesn't seem like it employs much if any noise reduction when playing back files. Bass is under control and doesn't overwhelm the rest of the frequencies and mids are clear and seem well balanced, the highs do seem a tad bright so maybe iTunes is boosting this as its used to playing MP3’s that might be missing this data and is resulting in this slightly over bright reproduction.

The MP3’s being played in iTunes do sound poor and clearly are missing something, so is it worth the space and time to rip to a lossless file like AIFF? If your a critical person and want to get the best from your CD’s then yes, if you’re tight for space and use mediocre audio equipment then no. iTunes or Intel HD audio is boosting the MP3 conversion so should help it sound like its better than it is. To some people ears this will be fine and you can go on knowing that it sounds ok, but if you’ve just ripped your CD collection and sold the CD’s and you’ve not done it as an AIFF or FLAC then oops!

So what does this mean for the headphones and the reviews done by these respected publications? Well I can’t say for certain but its evident that they haven’t tested them in every way possible and maybe they didn't need to as most people who use these IEM’s maybe playing low quality MP3s and their review fits what people will hear, this then makes the publication seem accurate and people will listen to them again in the future ensuring sales of said publications. At the same time though they are masking a problem for HD audio lovers that companies like B&W are clearly providing excellent products but their potential is being stopped by what can only be described as inferior audio source such as an Apple or Intel product designed for the masses.

Now I cant say at this time if outputting a digital source and doing the conversion on an external DAC will help, I presume it does as a lot of people who audition HD audio use them. I’ll let you know about this once I get a DAC that can do this for me.

My statements are all subjective to my own ears and I’m sure that others will have a different opinion. I may also be advised I’m going about my HD audio quest in the wrong way. Unlike video however sound is a much tricker concept to sell and perceive and music makers, audio hardware makers and software developers have a long and difficult road to go down if they want to have the public listening to HD audio.