Do cables really matter? (Part 1)

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It is very common for people to pay little attention to cable quality when building electronic systems. Cables play a huge role in your system potentials, as they are the medium for transmitting data or power. If the cables are inefficient as a transmitting medium, the performance of the system will suffer as there is a high level of signal losses.

Before we continue with this topic, we must first recognise the difference between a wire and a cable. In simplified terms, a wire is a conductor (e.g. copper) whereas a cable is made up of multiple conductors. For instance, a speakon connector cable will usually have a pair of conductors in order to transmit amplified signals to the respective speaker cabinet.

A 4 pole speaker cable

As a result, good quality cables are definitely important when it comes to building a system. In this post, I would like to address a few considerations for any practitioners building an audio system. All audio cables are screened (shielded), meaning that an outer conductor wraps around the others conductors to shield them from electromagnetic interference. The outer conductor may be made of various materials such as wire braid or metal foil.

The components inside a cable

In most cases, the outer conductor is connected to ground so that any induced currents (due to interference) will flow directly to ground rather than being mixed with the audio signal. However, this is not a perfect solution, which is why balanced signals were introduced.

In an unbalanced cable, there is a single inner core (conductor) that carries the audio signal while the outer screen act as the ground cable. The screen also doubles as the signal return path, hence any interference induced will cause the audio signals to be mixed with the interfering currents. These unwanted interferences are more prominent in long cable distances or where there are nearby sources of strong interference (e.g. dimming circuits).

Even in long distances, balanced cables are resistant against such interferences. As compared to its counterpart, a balanced cable has two inner conductors, commonly known as positive and negative. Similar to an unbalanced cable, the screen conductor is grounded but no signal will run through this path. Balanced audio transmission relies on Common-Mode Rejection Ratio (CMRR) to cancel out any interference picked up in the cable. A differentiating process will be implemented at the input stage of the receiving end to cancel out any noise. If any interference makes it through the screen conductor, it is likely to have the same influence on both the positive and negative conductors, thus the CMRR will reject any interference common in both conductors (positive and negative).

As mentioned, CMRR is based on the premise that unwanted external interference is being induced into both signal conductors equally, but is there any way to minimise the susceptibility of interference pickups to maximise the benefits of CMRR? Decreasing the distance between the two conductors by twisting them together helps to equalise the coupling effect of the interference with the audio signal.

A "loop antenna" is formed when two conductors have a spaced gap between them. Therefore, the farther apart the two conductors are, the large the antenna will be, thus picking up more interference along the line of transmission. Minimising the area between the two conductors helps to reduce unwanted hum and buzz from this type of interference, which the cable shield is almost ineffective against. The distance between the twists is called the lay of a pair. Shortening the lay by increasing the number of twists will improve not only the CMRR but also cable flexibility. Do take note that by shortening the lay distance, it would require more material (wire) and machine time, thus increasing hardware cost.

Understanding the characteristics of a good quality cable is vital in system building, as it determines the signal integrity carried through the medium. As a rule of thumb, if there is no option for a balanced output, I will usually not have any unbalanced cable of more than 5m, any more than that would require a Direct Injection (DI) box to transform the unbalanced audio to balanced. The above characteristics have been proven to help sustain signal integrity in real world practices and investing in a bunch of good quality cables is certainly wise.

YWFU

"I'll fix it in post"

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"I'll fix it in post" is a common phrase we hear in recording projects. This refers to the editing works required to fix a particular track after the recording phase. In many cases, tracks that are heavily post-processed lose its signature characteristic and often do not live up to what the editor hope to craft during the post-production process.

I am not expressing any displeasure in post-production editing / mixing, as one of the most crucial processes in any music production is to really craft the song into something iconic and polished. Maybe many have heard of extraordinary stories in the production magic audio engineers have used to create wonderful sounding vocals even though the vocalist is totally out of tune. In today's technology, something like this is possible to polish into a fine piece of music (for this case, with the help of Melodyne). However, in my own opinion, it will rarely become a piece of music that impact the listeners' emotions or last through the test of time.

Funny video that exaggerate the "post-production magic" 

A particular phrase is often quoted in the industry for people who are practicing recording arts and that is "Garbage in, Garbage out". This crude sounding phrase refers to the idea where if the recording element does not sound good in the first place, it will never ever sound good after it is being produced. The recording process is the time where the engineer and artiste will try and capture the best performance possible and not be contented for second best.

As a recording engineer, always try and experiment with the hardware you are working with to get the sound characteristics that really define the song. This includes trying out different miking techniques or miking up with different microphones. Miking techniques you get from course books or online forums are a good starting point if you have no experience with the instrument. However, these techniques are best considered guidelines and you should not follow them blindly. The recorded sound should determine the actions you take. If the sound is not to your liking, then something can be done to improve it before you even start recording. In my recent post of the "Wonderwall" cover, the kick drum was miked up with an SM 57 instead of a Beta 52 as the drum kit originally sounded very fat in the low end and the Beta 52 was not able to provide the attack I needed. By switching it to a SM 57, I was able to pick up more attack as the microphone has more "bite" in its frequency response—a simple and easy way to rectify a problem.

Of course, there are plug-ins that lets you modify the attacks or bass resonance characteristics of a kick drum in post-production, such as the Waves MaxxBass. However, the purpose of post-production mixing is to enhance / craft the recorded track, not to "reproduce" a sound because the recorded track was flawed.

The cost of recording has dropped significantly as you practically have an unlimited amount of recording takes due to the available storage space inside a computer. This might be one of the reasons why people might not pay much attention to recording anymore, as the cost of a recording is simply just the duration of time spent. Having a test record is understandable as that gives you a good gauge in terms of your recorded signal strengths (make sure they are at healthy levels) and your sound pickup. A recording should be done when both the engineer and artiste are on form, where each individual have practiced their parts and are ready to deliver the job well. Although having multiple takes of a song is common in order to capture the best representation of the music, having a second take in a live event / performance is often impossible as that will disrupt the show. Ironically, sometimes the flaws captured in the recording during a live show will be the iconic part of the recording itself.

Recording is the art of capturing the moment, the performance, and the emotion of the artiste at that particular point in time. Post-production should only then enhance and craft out the iconic parts that will signify the song.

YWFU