[Richard Crowley]

By “sync” they are probably referring to sound clips that are synchronized to the video/film. If the scene is an actual live performance, then the “sync” track will be what was actually recorded while shooting the picture. Or if the scene was lip-synced to an original recording, then the “sync” track was the audio track they were performing to, but it is referenced to the picture (by the clap-stick or the timecode or whatever method they used).

A “stem” is a group of mixed down tracks that typically logically fit together. Like a sound effects stem or a Foley stem or a music stem or a dialog stem, etc.

Ref: https://en.wikipedia.org/wiki/Stem_(audio)

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Remember that here in the US, wireless microphones that operate in the 600 MHz service band (the 617-652 MHz and 663-698 MHz frequencies) will be required to cease operation no later than July 13, 2020,
That is a major reason why heaps of very good 700MHz and now 600MHz gear is being dumped at fire-sale prices. 🙁

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

[clyde villegas] “The RF signal in the receiver remains on even when I unplug the microphone from the transmitter. But it goes off when I turn off the transmitter.”
OK. That would suggest to me that the microphone is more likely to the the source than the transmitter/receiver.
[clyde villegas] “Is it possible that the receiver has a noise gate that’s why it’s so silent when mic is unplugged? Though I think this is impossible for this mic system at this price point. What do you think?”
Yes “squelch” (where the audio signal is muted or gated when the radio signal drops) is quite common. I would expect that even this gear would have proper squelch function.
[clyde villegas] “Will try to connect the lav mic directly to my GH5 and Zoom H5 and see what happens.”
Yes, it is always good to try different combinations to discover where a problem is coming from.

Even expensive wireless kits come with a microphone that isn’t very good. It is very common for professional users to buy a better microphone for their wireless kits. So, for such an inexpensive kit, it wouldn’t be very surprising to discover that the microphone was the weak link.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Yes, I agree that the transmitter may be muting when it senses there is no mic plugged in.
Does the receiver have any indication of the signal strength of the radio signal?
Does the RF signal shut off (and “squelch” the receiver) when you unplug the microphone?
Else perhaps it is an indication that the Transmitter->Receiver link is actually quiet, but the mic is noisy.
Is there an way of testing the microphone in some other device? Camcorder?, cell phone?, recorder?

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

While that video was a good test to demonstrate the ability of the microphones to distinguish between the voice and the ambient noise, the ambient noise obscures the self-noise of the microphones. It would have been very helpful to hear all those microphones at the same gain into the same recorder, but in a noise-free environment. Perhaps buried inside a great pile of pillows and blankets inside an interior closet at midnight.

One of the risks of buying inexpensive gear like those microphones is the possibility that the performance may not be consistent from one year to the next. As sources of parts (especially the commodity condenser mic capsule) may come and go. The only reliable method of determining actual performance might be to actually try it for yourself if you can get your hands on them to test. Of course, higher-price, “mainstream” microphones would have a better expectation of consistency.

I would have somewhat higher expectations from JK than from some of the “no-name brand” products.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

The only “K&F Concept wireless lav system” I can find is the M8 with one transmitter and one receiver for $130
https://www.kentfaith.com/USKF10.002_m8-uhf-wireless-lavalier-microphone-for-dslr-camera

IME, you can’t expect good signal-to-noise ratio (SNR) or low noise-floor from any $130 wireless microphone of any brand or model. Here in the 21st century, you may get better performance from a more modern design like one of the digital wireless mic kits that shares the 2.4 GHz band with WiFi and Bluetooth, etc.

I would expect even a very budget kit like the “Azden PRO-XD 2.4 GHz Digital Wireless Lavalier System” ($200) would have a better SNR than any budget UHF system.

If you are in the United States, note very carefully that all wireless microphones in the 617-652 MHz or 663-698 MHz frequency bands will become illegal to operate after July 13, 2020 And in some cases even before that date as the 600 MHz band is auctioned off to mobile wireless users (i.e. cell phones, etc.) I wouldn’t buy any 600 MHz wireless mic at this late date.

It is pretty easy to discover how much of your noise floor is from the transmitter-receiver link vs. how much is from the microphone. Simple listen to the system in a noise-free environment. Perhaps an interior closet with the microphone burred inside a mound of pillows and blankets. You get the idea. Then simply unplug the microphone and compare the noise floor. That will demonstrate how much of the noise floor was from the microphone.

You are correct that selecting a low-self-noise microphone is very important in achieving low-noise wireless performance.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

What happens if you try recording somewhere else away from your roommate? Are you saying that you hear things upon playback that were inaudible during recording? It is unlikely that recording in MP3 will yield any different result. But only you can do this experiment under such unusual circumstances. I would separate myself from such a joker.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Alas, modern, inexpensive consumer products are often more expensive to repair than to replace. They are designed for inexpensive assembly, not for “repairability”. Service information is no longer published as it was in former times, and fewer people are left who still do this.

It would not be surprising that if you find someone to take the job, just the cost of looking at it to determine whether it can be repaired can amount to a large portion of the cost of a new (or used or refurbished) replacement.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

My first step would be to contact the person who made the recording.
They would seem like the most likely to both identify the problem, and have the gear to resolve the problem.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

You didn’t mention budget/schedule? I agree that “stick-built” ordinary wood stud construction is probably a waste of money. I would think that “tilt-up” solid concrete or at least concrete-filled cinder-block construction would be necessary for attenuation of mid/high frequencies. Note that reverting to a conventional “stick-built” roof will rather negate the attenuating effect of the solid concrete walls.

Low frequencies (coupled through the ground) will be more difficult without extreme methods like “floating” inner floors, etc. However, if you are doing interviews (or vocal music) recording, then you can roll off low frequencies since you don’t need to record them anyway. Note also that using close microphone techniques (like headset mics) will greatly increase the signal-to-noise ratio of the desired signal (the speech) vs. the noise levels.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.