An audio system can be compared to links in a chain where the chain is only as strong as its weakest link. Loudspeakers or headphones can be characterized as one of the most important links in the system. Both transducer types have their adherents with each type having benefits over the other.
Apart from the easily defined differences, are there discernable sonic differences between the two? While it’s possible to obtain excellent results from both, there are some points worth noting.
Despite recently released surround audio formats, musical reproduction remains a stereo dominated medium. Generally speaking, in the recording studio, music is mixed and played back in stereo through high quality loudspeakers. In this way a percentage of sound emanating from the right speaker in the recording studio will be heard in the mixing engineers left ear and visa versa. The engineer’s final mix will automatically take this aspect into account. The ear and brain interact to detect and process and pinpoint directional sound. The pinnae (outer part of the ear) also play a crucial role in this process. When listening to music in stereo through loudspeakers you are hearing music through the same playback method as the studio mixing engineer uses.
When listening to stereo music through a pair of closed headphones the left ear cannot hear what the right ear hears and visa versa. Open backed headphones do however go some way to addressing this issue.
The concept of imaging & soundstage are usually engineered phenomena mixed in the recording studio in order to better recreate the placement of the instruments and their relative position to the listener as they would appear on stage. When listening to music through loudspeakers it will be more likely that what the listener hears is representative of what the mix engineer created. The concept of soundstage is more difficult to recreate effectively with headphones as the sound appears centrally in your head as the pinnae play no effective role.
Loudspeaker based audio systems are susceptible to room effects. The listening room can greatly influence the end result. Speaker placement and acoustic treatments may be significantly influenced by aesthetics. The effect is often cumulative and can have a significant effect on the quality of the sound reproduced. This effect on headphone users is negligible as the variances in ear canal volume are miniscule by comparison.
Serious listeners go to great lengths to optimise their audio system. One problem with conventional loudspeakers is that the music is often listened to in competition with background noise. (Children, road noise, neighbors etc) The listener may also be seen as a significant nuisance to others who consider your music a real irritant! In this way loudspeaker systems can be significantly handicapped by the ambient environment and are therefore negatively influenced by background noise. You could choose to drown the background noise out by increasing the volume, but falls outside the scope of the discussion. Conventional headphones are very effective at attenuating background noise and offer distinct advantages when listening to music in higher ambient noise environments. Open backed headphones attempt to recreate a similar environment to conventional loudspeakers and in this way are held in high regard by audiophiles but offer only slight advantage to the user in the event of background noise problems.
Both loudspeakers and headphones can be designed to produce low frequencies. As experienced with live music, only loudspeakers can create a low frequency pressure wave effect that is absorbed by your entire body. Headphones, No matter how good are not capable of recreating this “full body” effect.
Not even the very best equipment can fully recreate the atmosphere and dynamics of attending a live music concert. Both transducers have their merits and adherents. Importantly don’t get too bogged down in the technicalities of the medium... relax and enjoy the music.