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Recording Professional Vocals At Home; Isolation
With the current pandemic keeping the majority of us musicians at home, this is the prefect time to write and record some new music. The greatest benefit to recording at home is of course saving money but what you probably save in money, you lack in a purpose built, acoustically treated room or vocal booth. Recording a great vocal track is without a doubt the one thing that separates the amateurs from the pros. Vocals are the focus of the entire track, usually sitting on top of the music and naturally produce the frequencies our ears are most sensitive to. Choosing the proper microphone to record with is a huge part of the production puzzle but without the right space, any microphone you use is only going to highlight all the little nasties in your room, drawing attention away from your vocal and leaving listeners underwhelmed. Even if all you have is your bedroom or living room, we'll show you a few ways to make the most of your space and up your vocal game!
The biggest difference between your bedroom and a pro vocal booth is isolation. If you've ever found yourself constantly messing with the EQ on your vocal just trying to carve out all the room sound, that's a dead giveaway you're in serious need of some isolation. Real studio's spend thousands of dollars to make sure reverberation is kept to a minimum which ensures the only thing the microphone captures is your pure vocal. This way, the mix engineer can add delay or reverb that suits the song, in post. We'll discuss a few ways in which you can accomplish this at home and which methods work best and why. We're also going to dive into some acoustic theory to explain our reasoning, but don't worry. If you get lost you can just read the cliff notes in the review section at the end. Quick tip before we take off, though......stay out of your closet! And here we go!
THE QUICK FIX
If you've ever looked at images of home studio's on Instagram or Pinterest, you've no doubt seen a microphone shield. With dozens of brands and styles at various price points, these portable isolation shields provide the quickest way to help isolate your microphone. Typically built in a semicircle and outfitted with some type of absorptive foam, they attach to your microphone stand and are meant to soak up your vocal directly behind the microphone, keeping your vocal from reaching the walls of the room and reverberating.
Pros:
• Provide immediate absorption in a less than ideal room
• Portable
• Relatively inexpensive
• Can be used in conjunction with other methods
• Fantastic for use with microphones with an omni or figure-8 pickup pattern
Cons:
• Thinner shields typically only absorb mid-range frequencies and up, allowing low-mid frequencies to muddy or darken the vocal (read more about absorption and the 1/4 wavelength rule below)
• Still allows reverberation from behind the singer to enter the microphone (very apparent with a loud singer)
MORE EFFECTIVE
For some creative ways to deal with those pesky reflections let's learn a bit about absorption and how to use your microphone to do the work for you!
Just like in the pro studios, our goal is to maximize our signal-to-noise ratio, that is our direct vocal to reverb ratio. We want the most direct vocal and the least reverb possible (well, to an extent). If you have no reflections at all your vocal will sound super lifeless and unnatural (we'll go over optimum reverb times below). The best way to achieve this is to soak up or absorb the reverb. To do this, you need absorptive material and the proper thickness. Pillows, mattresses and other soft surface materials absorb sound and hard surfaces reflect them. Thicker absorptive material will absorb more frequencies. So to take our shield from above as an example, if it's foam is 1 inch thick, it will absorb all frequencies above about 280Hz. That seems pretty good unless your voice goes lower than that. The average female's vocal range goes down to 140Hz and the average male's range goes down to 85Hz. That means if you're female, you most likely require absorptive material at least 2 inches thick and a whopping 3.3 inches thick if you're male (we'll show you how we came up with these numbers below).
THE CORNER BOOTH
One of the most effective DIY vocal booths is to throw two mattresses up into a corner. They provide plenty of absorption for vocal needs and though they may not look professional, can deliver the results you're after. BUT - don't sing facing the mattresses! This is by far the biggest mistake people make when attempting the corner booth. To make the most of this setup, you want to physically stand between the mattresses and sing facing out into the room. It feels a little unconventional at first. You're still singing into an open, untreated room and creating reverb, right? Right! But, remember when we said you could use your microphone to do the work for you? This is where that comes into play. Most microphones used for vocals pickup sound in a cardioid pattern, meaning it picks up sound really really well wherever it's pointing, and it rejects sound at it's sides and rear. SO...if you point the rear of the microphone to the open room, the microphone will automatically reject all the reverb in the room. And you don't have to worry about the reverb bouncing off the walls behind you and getting in the front of the mic because they're covered....literally.....with mattresses.
Notice how the slap-back reflections (red & blue) are immediately absorbed upon their return after entering the rear of the mic, which is negated due to the cardioid pickup pattern. The longer reflection also enters the back of the mic but with the added benefit of traveling a long distance which means it has a much, much lower volume.
Pro Tip: Try to avoid recording in small spaces. The reflections in small spaces such as your closet don't have enough time to reduce in volume before getting back to your microphone. We'll introduce you to the Inverse Square Law to explain this further below.
Pros:
• Absorbs all necessary frequencies for vocal recording
• Uses microphone pattern to assist in reducing unwanted reflections
• Can be used in conjunction with other methods
• Free if you have unused materials lying around
Cons:
• Takes up a good bit of space
• Unsightly
• A hassle to move
MOST EFFECTIVE
So you're ready to take this whole "tracking vocals from home" thing seriously and don't ever want to go back to another studio. We gotcha covered!
OWENS CORNING 703
This stuff is the holy grail of absorptive material. We didn't go over noise reduction coefficients but they're just the measurement of how absorptive a specific material is. Each frequency is measured and is given a rating in Sabins from 0 (no absorption) to 1 (total absorption). Then all frequencies are averaged together to give the material a NRC (noise reduction coefficient). Owens Corning 703 & 705 are boards of rigid fiberglass insulation used in construction and duct work. You can purchase them in 2ft. x 4ft. sheets in thicknesses of 1, 2, 3 or 4 inches. You can also get them with a thin foil layer on one side or unfaced. Here's how these suckers stack up; yes some of them actually go above 1 Sabin of absorption in some frequencies.......crazy!
Check out this table from Owens Corning's website:
The other nice thing about this stuff is that it's super easy to cut. You can literally cut it with a knife into any size or shape you want. Once you have the shape you're after, just make a simple wooden frame to keep it protected and then staple some fabric over it. Any fabric will do the trick! They're light enough to move around when needed or you can hang them on the wall for a permanent installation. We were able to make eight 2'x4' panels of 4" thickness for just over $200!
***Tip! We chose to combine two 2" panels of different types to maximize low end absorption. We used the 2" 703 Unfaced in front of the 2" 703 FRK (foil faced). The FRK type has a much better absorption coefficient at the 125Hz centered octave band.
Pros:
• Phenomenal sound absorption
• Portable
• Customizable look and easy to work with
• Can be used in conjunction with other methods
Cons:
• Must be made yourself (unless you spend $$$ for the pre-made versions)
• Take up a fair amount of space when storing them
• Overall, fairly fragile with fabric offering little protection (but, be gentle with them and they'll last you a lifetime)
• Material not always locally available - may have to order online
MORE TIPS
Sound doesn't travel linearly, it emanates spherically from the source, which means you also may need to tackle reflections from the floor and ceiling. A rug will help tame the floor and draping a blanket or comforter over some extra mic stands can manage those pesky ceiling reflections - just do go overboard with absorption; remember we want a natural sound.
Already have a mic shield but not getting the results you expected? Combine the mic shield with the corner booth to create the ultimate reverb fighting fortress!
REVIEW
We packed a whole lot of information in this post so for the sake of brevity, let's review. To get the most out of your home studio vocals, find a room with ample space. Closets and bathrooms are usually a no-no. If your room has a tile or hardwood floor, place a rug where you're setting up to help with floor reflections. A room with furniture will help absorb reflections. A makeshift booth can be made in the corner of a room by lining the corner walls with mattresses, pillows, or comforters. Standing in the corner and singing out into the room, though counter-intuitive, provides the best isolation when you are using a cardioid microphone. If your mic is omni or figure-8, the addition of a microphone shield to the corner booth will work wonders.
We hope this has been helpful and you make the most of your home studio by taking your vocals to a professional level! If you have any other suggestions, please leave a comment! We'd love to know how you made your vocal booth or if you are curious about how to improve what you already have! Until next time - enjoy quarantine!
RESOURCES - Lets Get Nerdy
The Quarter Wavelength Rule
Use this to determine the necessary thickness of material to absorb all sound above a specific frequency. The rule states that in order to absorb a frequency, you need a material that is 1/4 of the thickness of that frequencies wavelength. Example: if we use the lowest average frequency of female singers (140Hz) and divide the speed of sound (1125ft/s) by that frequency, we get the wavelength of that frequency. 1125 divided by 140 is 8. The wavelength of 140Hz is 8 inches. To absorb that frequency and all others above it, we need material that's 1/4 of 8. So 8 divided by 4 gives us 2. Try it out yourself - if you want to absorb all the way down to 40Hz, you'd need 7 inches of absorptive material! Can you figure out what the lowest frequency is your mattress will absorb?
The Inverse Square Law
One of our favorites and the best way to bust the "Closet Booth" myth. This law states that for every doubling of distance, sound drops by 6 decibels. To put that into context, 10 decibels is considered twice as loud or quiet. So.... if we clap our hands at 70dB, we'd have to be twice as loud to reach 80dB, then another twice as loud to reach 90! Now for some real world context: Let's say you sing into a microphone that's 4 inches away and we measure the volume of your voice at the microphone at 85dB. 8 inches from you, your voice would be 79dB. 16 inches from you would measure 63db. If we measure at a wall that's 10 feet away, your vocal will have dropped nearly 30 decibels! Can you figure out how loud it will be when it gets back to the microphone? This is precisely the reason closets cause so many problems. They simply aren't large enough to let the reflections decrease in volume without a ton of absorptive material. Remember, we want maximum dry vocal to reverb ratio.
What the heck is RT60?
RT60 stands for Reverberation Time 60 and it's used by acousticians to determine if a space requires more treatment or not. They blast white noise into a room at a specified amplitude, usually 85dB, and measure how long it takes for the reverb to drop by 60dB. A reading of RT60-7 means it took 7 seconds for the reverb to drop 60dB. For recording vocals, you'd definitely need some absorption panels. Maybe a shield too! Most pro studios aim for an RT60 rating of 0.5. That's a pretty dead room.