When the sound of the music at a milonga is truly great, you don’t notice the music, but you dance in a deeper connection with your partner. What causes the music to sound so good in one dance hall and so clangorous in the others?
Dance music is easier to hear and easier to dance to when it is “crisp” rather than “muddy”. Let me define “crisp” as the best and clearest sound quality to which you have access, and “muddy” as somewhere on the spectrum between “crisp” and noise. We spend money on an Apple computer instead of buying a Toshiba, or we buy an external DAC, for the crisp sound quality. When the music is muddy, the rhythm is less clear, more effort is needed to dance on the rhythm, partners may hear the rhythm differently and dance out of sync, and often the music is played uncomfortably loud to help the dancers hear the rhythm. As focus is distracted to hearing the rhythm of the music, the connection between dancers is impacted, which is crucial in tango, where the connection is the object of the dance.
At Salon Canning, at Milonga Cachirulo, with an expert DJ, where connection is paramount, since they dance mainly milonguero style, the sound quality was the best I have heard in any dance hall. It was crisp. It was easily heard without being overly loud. It was comfortable to be in the room with that sound. One felt welcome and coddled.
What causes the sound to be muddy? The quality of the source, the amplification, the cables, the room acoustics and the speaker placement all have an impact, but the biggest, and hardest to solve, is the speakers themselves. So let’s deal with speakers.
- Every speaker is non-linear in its response; at louder sound or higher frequency the speaker cone support will increasingly restrict the movement of the speaker cone, such that the electrical impulse will create less sound than at the center of the cone’s travel. As the speaker cone nears its travel limits, the inaccuracy of its response sounds like distortion.
- A speaker box contains 2 or 3 speakers, and a crossover, which uses an RLC network to separate higher frequencies from the lower frequencies. The higher frequencies are routed to the smaller of the speakers (tweeter or mid-range). The RLC crossover introduces a time delay, however, and the woofer makes its sound before the tweeter does; the speakers are then out of sync.
- The sound bounces off the walls, ceiling, furniture and floor, and this echo arrives at your ear slightly later than the original sound. In the worst cases, you can hear an echo; even when you can’t hear an echo, it reduces the crispness of the sound, which then sounds muddy.
- Multiple speakers generating the same sound emit waves which interfere with each other at some location in the room, and amplify or cancel each other; this effect varies with frequency.
The solution to the non-linearity of a speaker is to play a sound, at a certain frequency and volume, through the speaker, and take note of how loud it is. If sounds of many frequencies and volumes are played over a speaker, and the results recorded, one could make a “profile” of this speaker. When playing music, this profile could be used to adjust the volume to compensate for the speaker’s varying response, note by note. And since one note of music is made up of many frequencies, this profile can be recorded and applied to each frequency, accordingly, within each note. The creation of the “profile” is the key, and applying it to each sound as it is played corrects for the speaker’s deficiencies, such that a $100 speaker can be made to sound like a $1000 speaker.
To carry the process further, each speaker in the system can be played, and the delays at the different frequencies noted, to create a profile which compensates for the crossovers. With overtones distinctly rendered, you can distinguish between the sound of a given note as played on a piano or violin or guitar, which might all sound similar if the sound is muddy.
If you play a short sound, and then listen, you can hear the echo. The echo will vary greatly according to the room acoustics, furniture, people, and speaker locations, so you can create an echo profile for a certain space, under certain conditions. If you then play a sound, and use an echo profile to play the same sound – inverted – after a short delay, the second sound will cancel the echo from the first.
Wave interference can also be profiled, and the profile applied to the music being played, such that each frequency component of each note is volume-adjusted to compensate for points of cancellation or amplification.
This theory was researched thoroughly 40 years ago, and software was developed to apply it. It was explained to me by one of the originators – the manufacturer of the super-fast computers needed to apply these profiles in real time. It was incorporated into upscale home stereo systems which sold for upwards of $30,000 at the time. Later, it was licensed by Pioneer and incorporated into their Elite receivers – and called MCACC (Multi-Channel Acoustic Calibration System). My home stereo is a Pioneer Elite, and it is the best quality sound I have ever heard in a home stereo system (and I have been an audiophile for 60 years). I have tested this theory . . .