Interesting; so does that mean that the length of the cables can affect the quality?
Yes. Balanced (three conductors: positive, negative, ground) can run longer distances without added noise or risk of RF interference. Unbalanced (two conductors: positive, negative+ground) can only run a few feet before there’s a risk of added noise floor and increased risk of picking up RF bleed.
Balanced audio can run 200’. Unbalanced shouldn’t run longer than 10’, and shorter than that is better.
Context is certainly important, especially when it comes to mics. Here goes... format is most always interviews for my own podcast & YouTube channel. Production locations are either indoors seated in someone's living room, or outdoors moving around in the field; two people - interviewer & interviewee.
So you have two very different scenarios. The first rule of thumb is, “Whenever able, use a cable.” When everyone is seated for a locked-down interview, wired lavs on both host and guest are a great way to go. Record them to separate channels and control the mix between the two in post. If that leaves cables across the floor that will be in the shot, two boomed mics (on stands) can give you the same end result. One mic over the host, one over the guest. Record separately, mix in post.
For walk-and-talks, that’s a very different beast and hard-wired lavs (even a hard-wired handheld) are impractical. This is where wireless systems with lavs come in. Or, if you want to simplify things, one wireless handheld in the host’s hand... but that constricts movement a bit.
I have learned, unfortunately through trial & error, to use multiple mics as backup in case one has a problem. When I have given interviewees a handheld mic (in this case the Zoom H1), & they are not used to speaking into a mic, they tend to wave their arms & I lose the audio. I now know not to ever do this unless someone is experienced using mics. When my interviewer holds the mic, the results have been much better; that said, sometimes there is fidgeting noise with the handheld & sometimes she's paying so much attention to the interviewee that she forgets to move the handheld mic from her mouth -for the question- back to the interviewee's -for the answer.
First, I’d
never give a handheld mic for an interview to the interview
ee. That’s the job of the host/reporter/intervewer.
Second is that for the interviewer, it requires dedicated practice learning how to use a handheld efficiently. Under most circumstances, an omnidirectional interview mic is also going to be helpful as it is a little more forgiving if the mic accidentally tilts off-axis.
Third, using a handheld recorder with the on-board stereo mics as a handheld interview mic is just a recipe for disaster under any circumstances.
All that said, & now that you know the specifics, let me pose a slightly more hypothetical question:
A hypothetical case calls for a lavalier microphone to be used. The sound person has a professional brand mixer. This mixer has a balanced phantom power XLR mic input. This same mixer has a unbalanced low voltage plug-in power 3.5mm mic input. This sound person has two lavalier microphones which are the same brand & model lav mics. Each of these lavs are able to be used with this same mixer. There is one difference between the mics... one lav has an XLR connector, the other lav has a 3.5mm connector. Which one does the sound person go to? Why?
You’re seeking a simple answer to a complex issue, so I’ll give you a most unhelpful word of an answer: it depends.
A good sound kit has lavs termiated for XLR connection for running wired direct to the mixer/recorder/camera, and lavs terminated for wireless transmitters (which can vary based on the wireless system used). If the interview is seated and the sound person is going for wired lavs, the XLR-terminated lavs allow the cables to run across the studio or location without issue. If the interview is a walk-and-talk, the sound person is probably going to go wireless: the lav is terminated for 1/8” (3.5mm), or TA3F (mini-XLR), or 4-pin Lemo, or _____... whichever matches the wireless transmitter used. The wireless receiver will connect to the mixer’s XLR inputs.