help new audio setup for recording classroom

[iASR]

Hi have been recording lectures for students.
Setup is really basic : iphone 12 with Rode AI micro with Sennheiser MK200 in right channel and DJI mic (gen 2) RX in left channel.
Would put DJI TX on the speaker with onboard recording and that's basically it...
This very often causes audio drift issues (all smartphones recording in VFR) and also doesn't capture the questions of the classes very well.
So am looking to upgrade this to a semi-professional setup.
Surely i well keep a lav mic for the speaker, but may want to change the DJI mic to maybe a more professional brand like the Tentacle Track E (32 bit) ?
I suppose I'll also need an external bt TC generator.
What would your suggestions be ?
But for the class, i was wondering whether i could use choir mics. Only found out about their existence recently.
Advantage is they easily cover about 20 voices, which is the standard number of students in most cases.
Was tinkering with the idea to either fix one (or two) from the ceiling or on the side walls above the student's heads.
You can see the layout of the class in the picture. With three possible placements for the choir mics in blue, red and green.
Will need i suppose an audio mixer between the XLR choir mics and the iphone (which i might change to a mirror less camera in order to have CFR) and if so, what would your suggestions be ?
I would like the teacher and student mics on a separate mono channel.
If the mixer could come with integrated automixer (and battery), that'd be a plus, as that's less work in post (and we also suffer sometimes from very short power cuts).

 

[Philbo King]

The biggest problem is that classrooms are very reverberant causing poor clarity.

 

[kemmler3D]

Is recording to a laptop an option? If so, I'd get 1 or 2 choir mics for the students and 1 lav mic for the lecturer. Put those into an analog mixer, pan audience left and speaker right, then you can use any 2-input USB interface to record. Quick mix to mono in audacity or whatever software you want and you're good to go. The laptop does not need to be high spec, anything from the last 10 years will be fine.

If power cuts are an issue then you might be able to get a bus powered interface with 4 inputs and record directly from the mics, with everything running on laptop battery.

 

[G|force]

Choir mics might be a good solution but they usually are condenser type so you would need phantom power. Maybe ditch the phone all together and use a Zoom or Sound Devices recorder- Battery powered with on board mixer and phantom power.

 

[G|force]

Is recording to a laptop an option? If so, I'd get 1 or 2 choir mics for the students and 1 for the lecturer. Put those into an analog mixer, pan audience left and speaker right, then you can use any 2-input USB interface to record. Quick mix to mono in audacity or whatever software you want and you're good to go. The laptop does not need to be high spec, anything from the last 10 years will be fine.

That's another good idea and very likely less expensive. The mixer could be a small sub $100 Behringer.

 

[iASR]

The biggest problem is that classrooms are very reverberant causing poor clarity.

that's true, especially in our case, where the whole left side of the classroom is basically made up of windows...

 

[iASR]

Is recording to a laptop an option? If so, I'd get 1 or 2 choir mics for the students and 1 lav mic for the lecturer. Put those into an analog mixer, pan audience left and speaker right, then you can use any 2-input USB interface to record. Quick mix to mono in audacity or whatever software you want and you're good to go. The laptop does not need to be high spec, anything from the last 10 years will be fine.

If power cuts are an issue then you might be able to get a bus powered interface with 4 inputs and record directly from the mics, with everything running on laptop battery.

hi and thx for the feedback. Per se laptops are possible, although I'd like not to leave too much gear around in the classroom after recording and iphones are less bulkier than laptops. What would a laptop solve compared to an iphone ? I would also be interested in having some concrete suggestions as to decent analog mixers and input USB interfaces to record. Can you recommend any ?

 

[iASR]

Choir mics might be a good solution but they usually are condenser type so you would need phantom power. Maybe ditch the phone all together and use a Zoom or Sound Devices recorder- Battery powered with on board mixer and phantom power.

yea and what would be the best placement for choir mics ? Normally they're placed facing a whole choir, whereas i suppose here it'd be better to put either a single one in the in front of the student's rows (would that suffice to capture a whole class ?) or two mics, each one in front of a row of students. I'm afraid putting them in the middle of the class facing the students laterally the mics will capture the speaker's voice too.
Would you have any suggestions for choir mics ? I see their price range can vary between 300-1500EUR or more. A YT reviewer liked both the DPA 2011C twin diaphragm cardioid microphone compact and the Rode NT5.
I could (and was thinking of) connecting the choir mics to either a Zoom or SD recorder-mixer, but at the end i also need to connect those to my cam (iphone or other cam).
Any suggestions for fitting zoom or SD device ?
At the end i basically need 3 mono tracks maximum right ?

 

[iASR]

That's another good idea and very likely less expensive. The mixer could be a small sub $100 Behringer.

ok not familiar with the brand. Can you point me to a specific model ? As I said, would be nice the audio mixer had an integrated automixer, which would greatly speed up post.

 

[G|force]

I found this on Thomann.
More than $100, but this one has a USB interface built in.

Since you probably will be editing and mixing on a computer anyway, (I would)
I would use a laptop to record too as Kemmler3D suggested. SD recorders are neat but are more geared to portable field recording, so please disregard my previous comment on them.

I would forget about "automixing" in this context, as this is a misnomer.

The hanging mics I've used are from Audix and Audio Technica. I don't remember the model numbers as it has been ~10 years since I did that type of work, but they were around $300. It's best to not go cheap on these as you will need a lot of preamp gain to get useable signal, and the cheap ones will make a lot of self noise before you get adequate signal. Heck, even the good ones will get unusably noisy if you gain them up too much.

In general ONE in front of the front row on center is best unless the room is exceptionally deep, where you may want a second one centered half way back. You aren't trying to capture stereo effects, so center mono capture panned L/R is the way to go. The problem using more than one front to back or two L/R is delay, as multiple mics will capture sound and generate more gross signal, (good) but proximity effects between the individual mics can/will diminish intelligibility.

The best thing you could do for intelligible capture is pass a handheld wireless mic to whoever is speaking (could be it's own nightmare if the students aren't adults) and put a lav or even better, a headset mic like a countryman on the lecturer.

Hope that helps!