[Richard Crowley]

It gets difficult to talk about this as pure theory. Can you put a sample up somewhere we can hear it? Do you have anything on YouTube or Vimeo, etc? Did you mention what gear you are using now?

[Richard Crowley]

The “dynamic range” refers to the range between very quiet sounds and very loud sounds. The range between low frequencies and high frequencies is called “frequency response”.

Indeed, less expensive microphones frequently have narrower frequency response than more expensive models. Note, however, that for picking up speech/dialog frequencies, an extended low frequency response is often more trouble than its worth because those low frequencies are almost always undesirable noise that you must get rid of anyway. And very high frequencies also pick up sibilence and noise that you must filter out.

We don’t know the bigger picture here, so it isn’t clear whether a microphone with a wider frequency response would be better or worse for whatever you are doing.

[Richard Crowley]

It seems possible that you could improve the “quality” of the audio performance, depending on what parts of the performance you are talking about and whether it/they are influenced by the microphone, or by the rest of the audio chain.

It is not at all clear that “the size of a microphone’s diaphram affects the quality of the sound”. Some extraordinarily high quality microphones (such as those from DPA, etc.) are also extraordinarily tiny. And again, unless you can better define the term “quality” it is indistinguishable from ordinary free-floating anxiety.

[Richard Crowley]

No, I did NOT say that the 2.4 GHz systems were NOT USEFUL in RF-crowded situations. They may very well be brilliant. But they have been out a very short time and we have not heard any significant number of reports back from users whether they are good or bad. So at this point we just DON’T KNOW YET.

As Mr. Reynolds said, it is very rare that when you are watching TV, that you will EVER hear audio from a camera-mounted mic. And you can be sure that if you are in a theater watching a feature film, you will NEVER hear audio from a camera-mounted microphone.

Unless you are quite (uncomfortably) close to the guest subject (significantly less than 3ft/1m) a camera-mounted mic will give you pretty “diffuse” coverage and it will sound like amateur-hour off-mic. And especially if you are in a busy city street, etc with lots of ambient noise.

You don’t have to take our word for it. And only YOU can make the final trade-off decision of whether the audio is “good enough” for your purposes. When you get your camera, spend an afternoon out on a busy street and see what you get from the on-camera mic.

[Richard Crowley]

Either of those cameras are probably fine for your application. Assuming you aren’t expecting to be shooting in moonlight or candlelight or anything silly.

Yes, putting a wireless lav on the main character seems logical and sensible. NOTE, however, that wireless kits < $650 are generally considered to be temperamental, unreliable, fiddly, disposable, plastic toys and typically NOT RECOMMENDED.

Some very recent exceptions to that benchmark may be the 2.4 GHz (“WiFi”) digital wireless kits like the AudioTechnica System-10, the RodeLink, and the Sennheiser D1 (although the Sennheiser does NOT have a compact, camera-mount receiver). A caution with the 2.4 GHz band new devices is that the bandwidth is shared with WiFi, BlueTooth, and even microwave ovens, and reliable use in populated areas (i.e. any city in China) has not been well established yet.

You said that the main character’s mic would handle “most of the talking” but you did NOT identify what the other sounds are that you think you can capture from the camera-mounted “shotgun”. Note that the mics that come with the cameras (and even the 3rd party “video mics”) are more like plastic cap pistols compared to true professional shotgun mics.

Note also that a microphone of ANY quality mounted ON the camera is RARELY in a position to capture decent quality audio. But perhaps your audience will forgive the audio quality considering that it was a “guerrilla production” in hostile territory?

ALWAYS remember to MONITOR your audio. Maybe you don’t want to attract attention wit a big pair of over-the-ear headphones like the industry-standard Sony MDR-7506 or something, so a GOOD pair of ear-buds would be a camouflage substitute.

[Richard Crowley]

If you were THAT close, then your microphone may be broken, or the battery may have reached its end of life. It would be beneficial to know something about “gain staging” even if audio is not your specialty:

TIPS AND TRICKS – GAIN STAGING 101 https://www.alesis.com/tipsdec08

[Richard Crowley]

Yes, the distance between the microphone and the subject is critical. Even a microphone that costs as much as your car isn’t going to work worth a diddle over 3ft/1m. And especially in hostile ambient audio locations.

The length of the cable is of almost zero concern unless you have a really terrible cable.

Generating the 24 or 48V required by the phantom power specification understandable eats up a lot of power from a few AA batteries which are also powering your mixer/recorder. Clearly, a microphone that operates from its own internal battery will likely eat up fewer batteries than if you were using phantom power.

OTOH, the better-performing (more “professional”) microphones tend to be the ones which only operate on phantom power, and have no provision for internal batteries. So there will always be a tradeoff decision to be made there.

It looks effortless in the movies and on TV. But they go to great cost to achieve that good quality audio. Those “reality” shows may have $30,000 worth of wireless mics on all the participants. And another $20,000 worth of mixing and multi-track portable recording. And then a multi-person audio mixing crew that works for many hours in editing.

And you can be sure that the production audio person went along on the location scouting tours to ensure they weren’t trying to capture audio along a busy interstate highway or in a boilerworks, or at the end of the runway at the international airport.

And for feature films, it is still not unusual for the actors to spend hours in the ADR studio, “looping” (replacing) their dialog lines that were too noisy from the original shooting.

[Richard Crowley]

I have heard no credible evidence that the Tascam DR-70D fails to produce proper 24V or 48V (switchable) phantom power sufficient to operate any microphone. I have a DR-60 and have no complaints about it. The DR-70 appears to be a reasonably well-regarded product.

Now, if you are asking whether the DR-70D has enough low-noise GAIN to use with the NTG3 (or any other shotgun mic) that is a DIFFERENT question than any discussion about phantom power. I think it is safe to say that in the hands of most amateur users, those commodity digital recorders are marginal if you are operating at the edge of reasonable performance.

IMHO, most amateurs seem to think that shotgun microphones have magical properties that exempt them from basic laws of physics and what kind of reasonable working distances and signal-to-noise ratios you are shooting/recording in. No shotgun mic is a “zoom lens” for audio.

I must say that many (most?) user comments and “reviews” (and I use that term with great reservation) in mass-market websites like Amazon and even B&H appear to be written by people who have no clue what they are talking about.

[Richard Crowley]

No you cannot do that.
Because nobody really wants to do that
Because it is typically “mixed” during post-production editing.

If you want to mix the two microphones together in real-time during shooting, then you will need a mixer. Note, however that is exactly what most of us try to AVOID doing. Because mixing live in real-time is something best left to an experienced audio person. And something tells me you don’t have a dedicated sound person.

[Richard Crowley]

WOW, that SD 688 looks fantastic. Those guys are geniuses.
Wish I could afford something like that.