Absorption Panel Depth/Dimensions for Vocal Recording

Also remember,
Proper treatment behind the vocalist, facing the microphone, can be as important as what's behind !

Complete overkill if your only goal is to improve vocals.  Extremely large and thick panels would only be necessary if you're trying to block instruments with much higher power levels than the human voice.

Absorption isn't always about depth and overall size of the panel.   Placement is key.  

The second part you're likely not aware of is that distance is as important as panel specs.  If you place the vocal area in the middle of the room and place a few small panels in key areas (V shaped behind mic to cut reflections at the cardioid lobes, as well as one or two behind the vocalist, that could literally be all you need.  The distance from the mic to the panel cuts the incident signal before it can reflect, and the distance between the panel and the wall will reduce the power of the reflections so that the panel will reduce the reflection to almost nothing.

4" thick panel of medium density mineral wool would be plenty.  

What I ended up doing was making 2'x4'x4" panels and using conduit hangers and eye bolts to hang them on mic stands.  The stands make the panel heights adjustable and I can center the panel on the mouth-to-mic axis.

What svart said !

I have a large GIK portable folding panel behind me.

Imho, it’s what behind the vocalist that counts, way more than what’s behind the mic (unless recording with a ribbon or omni pattern LDC)

The mic is mainly “listening” to what’s in front of it, not what’s behind it.

Though in my case I have treated behind the mic too

Yes because first the radaiating pattern becomes Omni at any freq lower than a wave length longer than the baffle ( width of the head. Second absorption will not be greater than 80% .

My advice take some acoustical measurements, and either get a consult from Headback or advise from GIK. I keep finding that most rooms treated strictly based on dimensions seam to have some unforeseen problems. Also as far as absorbing bass freq. if you measure the room silent with an RTA or FFT you might find some unforeseen noise issues that some LF absorbers can at least help with. Do it with and without HVAC and if you have any major appliances near by measure nous with and without.

It’s going to be more of what initially wraps around your head and reflects off the back, I can’t find a formula for figuring out when a oblong baffle ( your head ) effects directionality. So I’m sticking with the basic flat baffle if your head was 12 in wide it would go Omni from about 950hz down.

You're over thinking it   If someone has their back to you, you can still hear them talking.  Sound waves aren't directional in the way that most of us visualize them.  In air they act more like pressure waves than laser beams.  Think about a light bulb and how it radiates light in all directions.  If you block the light bulb with your head, some light will still wrap around it.  

Sounds like 7-8 inches was overkill then, I'll probably just do two rockwool baffles thick which is about 4-5 inches. That extra inch so I can sleep at night...

I actually do plan on having it behind the vocalist - when I was writing the post I realize it sounds like the other way around. It makes sense that the mic (especially cardiod) would pick up more reflections in front of it rather than behind...

I also have a bunch of DIY tube traps to work with. It's crazy how different it sounds singing into a tube trap (just in front of it, not recording) with 2MM plastic film on versus no plastic film. Never thought the difference would be THAT audible. Seems like a great way to have more high end in the vocal with that diffusion side being used in the tracking area. Excited to experiment with those as well.

you want both, most cardiods are more of a notch than as directional as most think. Oh and once again yup varies with Frq. Do a 360 of your favorite mic with headphones, for even a better lesson download a Freq generator app and do it at different freq. Even Ward will tell you learning the real world polar patterns of all of your mics will make you a better AE, and help make better choices on the fly.

And yes as geeky as I am I did actually have a hot girlfriend in high school and still had time to do all this audio stuff, I just didn’t go to class.

There is a school of thought to put thin plastic film .02 ml inside a diffusser to promote its diffusion snd that is stuffed it will absorb as well ?

Re: off axis, that reminds me why when Seawell did his 87 shootout I tested them all with EQ. Boosting highs and mids on Neumann 87 is a different experience than a million other popular clones. They seem tighter and don’t have so much room mixed in, it’s closer to a dynamic in terms of signal to ambience, maybe how I’d explain it? My experiment helped me notice the Serrano as a standout. Bees knees was very good too in a different way. Small sample size but enough to know I need to be more discerning. Summary: a great mic might solve some troubling room issues

Reducing the bandwidth of absorption is the goal when putting a thin plastic barrier on the face of a trap. Depending on the design, some people glue craft paper to the front face of the traps, or use wood slats. The barrier reflects mostly high frequencies while still allowing low frequency waves to be absorptive.

You’re right though that at a certain point, if the barrier is too good the trap won’t work at all. But we’re only taking about a thin barrier covering only face of a trap so plenty of sound energy is still passing through the trap.