Posts Tagged ‘audio compression’

How bad is MP3? (Part 2)

Wednesday, September 29th, 2010
lego mp3 player

Image courtest of stuffwelike.com

Last week I wrote up a post about my opinions on the MP3 format which included a few listening reviews of various MP3s in my collection. I admitted the weakness of this experiment, in that I wasn’t comparing these recordings to any other format, so I concluded that I needed to do a review the same recording in both MP3, CD and vinyl forms.

I chose to review Van Cliburn and the Chicago Symphony Orchestra’s 1961 performance of Beethoven’s Piano Concerto No. 5 in E-Flat, Op. 73 “Emperor”. Specifically, the third and final movement. I own this recording both on vinyl as part of the Great Men of Music boxset I reviewed a while back and as an RCA Living Stereo SACD . I ripped an MP3 copy at 160 kbit/s using iTunes, which was sourced from the CD layer of the SACD disc. Before each test, I calibrated the sound level for each source to -25 dB using the trial version of Electroacoustics Toolbox 2.0 , a versatile sound analysis program. To do this, I placed my laptop in my listening position and then played a 1 KHZ test tone from the Stereophile Test CD , test MP3 file in iTunes, and the Cardas Test record . The laptop microphone picks up the test tone and displays the current SPL (sound pressure level) ,and I would adjust the volume knob on my amp until it reached -25 dB. Performing this adjustment for each source reviewed ensured that the music was being pumped out the amplifier at a consistent level so that differences in the sound pressure wouldn’t color my judgment. So, here’s what I came up with:

CD- I made sure to play the CD layer of the disc for this test, as it wouldn’t be fair to compare the MP3 it was sourced from to a hi-rez version of the same recording. Bass frequencies are very present (if not fairly boomy) and Cliburn’s piano is fresh and lively but demonstrates some “smearing”. The strings are dense without sounding excessively stodgy and the soundstaging is good. Everything is in its proper place, and since I have actually attended a concert in that hall before, I could really reimagine it.

MP3 – A marked flatness is apparent right off the bat, the dynamics are severely reduced. Just as I had remarked about some tracks in the previous week’s part of this review, the music just can’t seem to escape or transcend the speakers. The orchestra is trapped in a wood and kevlar prison. In contrast to the CD recording, the piano seems a bit more defined and runs together less. But despite the improved clarity, the piano still suffers from a loss of energy. The soundstage has shifted to the left somewhat…somehow. Overall, the MP3 was not unlistenable but still not ideal.

LP- Well, to start off, hissing, rumble and clicks are apparent in quiet portions (no shit) but it’s not bad enough to be distracting. This recording shows excellent soundstaging and the bass is subdued when compared to the CD and MP3 edition. The piano isn’t as shiny as the other two tests, it lacks in high treble which can be a limitation of vinyl records. This was craploads better than the MP3 and rivaled the CD for clarity, warmth and overall enjoyability.

So to conclude, MP3s still kinda suck. But as I wrote last time, they have their definite advantages if you’re concerned about space and price. I understand that this wasn’t a double-blind ABX test , the gold standard for hi-fi experimentation, but the point of these reviews wasn’t to determine if one could tell a difference between the formats (which ABX does), but instead to assess the subjective qualities of each format. Sound is still always a matter of taste and preference, so you might not mind or even care about the sound of an MP3 if it seems okay to you. But for me, i’ll stick to MP3s cranked out of a portable device for when i’m on my way to work, and i’ll use CD and vinyl for when I really want to sit down and enjoy the music.

How bad is MP3? (Part 1)

Tuesday, September 21st, 2010
an mp3 player made out of a grenade casing

Image source: geekologie.com

In my very first blog post I briefly bashed MP3 as an inferior format for tone deaf plebes. I soon realized that was an extremely hypocritical thing to do, as the majority of my music collection resides on my laptop and iPod in either AAC or MP3. But whenever I listen to these formats, I’m usually doing something else at the same time: riding the bus or subway, walking to class, fidgeting in an uncomfortable airline seat, or hunched over my laptop surfing the internet. I reserve my “critical listening” sessions for vinyl, CD and SACD and so I had never sat down and really listened to MP3s. As far as I know, MP3 sounds pretty damn good when piped into a hi-fi setup but I was just going off the standard snobbery and assuming that it sucks.

So, I decided to plug my laptop into my amplifier and give some tracks a good analysis. I had done this before in my previous apartment, but again I never had a chance to critically regard it since it was usually done during parties. To do this, I bought a cheap 3.5mm to L+R RCA adapter much like this one which Amazon is selling for an unbelievable penny, not including shipping. The red and white plugs go into the amp and the other end goes into the laptop or other MP3 device. Some newer amps have a port in the front that you can plug a player straight into using a cable like this.

It’s important to first briefly summarize bitrate: basically, higher bitrates translate to better sound quality. The most common bitrate seems to be 128 kbit/s ; this is what you’ll likely find on filesharing networks unless otherwise specified. By default, iTunes rips CDs to 256 kbit/s AAC format, and the same goes for stuff downloaded from the iTunes Store.

Now that i’m plugged in, I try a few selections:

The Chameleons – What Does Anything Mean? Basically (224 kbit/s MP3) : This layered, atmospheric post-punk/goth really suffers from the MP3 encoding. It sounds as though the music is struggling to escape the speakers, and this tires out my ears because I have to force myself to focus and interpolate what i’m supposed to be hearing. Turning up the bass knob on my amp filled out the bottom end a bit, but I really don’t like to play with the tone controls if I can help it.

Catherine Wheel – Chrome (160 kbit/s MP3) : A slight improvement, but the music still lacks any sort of punch or edge. This might be blamed on the album’s production; shoegaze bands liked to go for the muddy, distant sound.

J.S. Bach – Brandenburg Concertos, Benjamin Britten: English Chamber Orchestra (256 kbit/s AAC) : This is one of the better selections so far. The music actually has life and presence, although the violins lack attack/decay. Could this improvement be a property of the AAC encoding?

Dave Brubeck Quartet – Jazz Goes to College (141 kbit/s MP3) : First off, this is a live concert recording, so the overall acoustics will differ from something taped in studio. Nevertheless, this actually sounds fairly musical and I would say is the best set of MP3s i’ve sampled so far. The sax and piano are smooth and feel as though they are in a concert hall like they should. However, like all the tracks i’ve tested, the bass is disappointing and there is still that lack of thrust and definition that I like to hear (Additionally, a minor gripe: the applause and whistles of the audience don’t feel “live” either).

Now there are some flaws in this experiment that I’ll readily admit:

1. This is an entirely subjective test. I didn’t take any actual measurements of the sound output (such as level or frequencies), although I kept the volume the same.

2. The output level of my MacBook is probably less powerful than other sources, thus giving the amplifier less to work with. An MP3 player might give different results.

3. I didn’t do any sort of A/B comparison between the same recording on a different source like CD or vinyl. This is why in Part 2 of this article I intend to listen to Van Cliburn performing Beethovens Emperor Concerto , a recording that I have on both vinyl and CD, so I can compare the two to an MP3 rip I made.

In the meantime, I can say this about MP3s : They clearly have a lot of advantages, in that they’re , uh, “free” and they take up very little space on your hard drive. And despite that they aren’t a hi-fi medium, i’m willing to bet that most of my readers have a substantial amount of their music in this format. To take advantage of this, and to get the best sound possible, hook your MP3 player into an amplifier + speaker combo. By simple virtue of playing through actual speakers and not earbuds or a cheap docking station, you will reveal details that you wouldn’t have noticed before. For example, Kitchens of Distinction’s Love is Hell was an album that I had only listened to on my iPod, so when tried it through my system it revealed details like fuller chorus guitar effects.

If you want to get your feet wet with hi-fi, get yourself a setup like the one I recommend and plug in your computer or MP3 player. You’ll get a taste of good sound while keeping your current collection, and I have no doubt that it will inspire you to do more with your system.

For further reading, Stereophile has a good article about the difference between various audio compression formats.

Check out Part 2 of this article for more analysis