As we shop for speakers, amplifiers, and other audio equipment, the term "headroom" often arises. But what does this mean and why is it important? Put simply headroom is the amount of music above and beyond the average listening level that your system can play before it begins to clip the music. In the old days, music was mastered to have a large dynamic range, 20dB or more. Unfortunately, these days, music is mastered to have a very limited dynamic range, perhaps only 6-9dB. What this means is that much of our music today will sound louder when played over the radio, which is why it is mastered this way, but the cost of decreasing dynamic range for this purpose causes the music to be clipped off, or compressed.
I've attached some .mp3 examples that take a well mastered recording of ABBA's Take a Chance on Me and compressed them with various levels of compression. The original recording was mastered very, very well. None of the peaks were clipped and so the total dynamic range is about 24-27dB, which is HUGE, at least by our standards today. If this recording were mastered today, it would only have 6-9dB of dynamic range and wouldn't sound nearly as good.
The files can be interepreted this way:
1. 0db compress -> ~27dB dynamic range, no clipping
2. 6db compress -> ~21dB dynamic range, only tips of transients clipped
3. 12db compress -> ~15dB dynamic range, some clipping of music,
4. 15db compress -> ~12dB dynamic range, this is about how this would be mastered today (and that's being generous). after listening to the other clips, you can tell how bad it sounds.
5. 18db compress -> ~9dB dynamic range, sounds awful, severe clipping
6. 24db compress -> ~3dB dynamic range, massive clipping for demonstration*
* included just so you can hear how significant clipping distortion sounds
So how does this matter in choosing audio equipment? Well, to listen to ABBA at original 27dB of dynamic range, you need to have *a lot* of headroom in your system. If you like to listen to your music at around 80db, which is moderately loud, then you need to have about 90db coming out of your speakers, roughly speaking. Most "hi fi" type speakers will produce around 90db with one watt.
Now for the difficult part. In order to increase dB by 10, power must increase by TEN times. So, 27dB of headroom, translates to almost 1,000 times power. Of course, most people don't have 1,000 watts of power nor speakers that could handle that without introducing all kinds of other distortions. The advice therefore is buy as efficient of speakers as possible and as much amplifier as you can possibly afford. This will help minimize the clipping that your system is doing when playing well mastered recordings.
take_a_chance_18db_24db_compress.zip 459.0068359375k . file
take_a_chance_12db_15db_compress.zip 458.9677734375k . file
take_a_chance_0db_6db_compress.zip 459.060546875k . file