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Part 1: Start With The Room

By Paul J. Stamler

 

This article is aimed at beginners—people new to this great adventure of home-based recording. But to the readers who have been doing this for a few years: stick with me, there’s plenty here that you can use too.

Here’s a bit of “inside baseball”, Magazine Division. In magazines like Recording, a type of article which appears regularly is the “How to Set Up Your First Studio” piece. We run such an article every few years, as new readers for whom it would be relevant arrive on the scene.

Typically these articles are written from the center of the system outwards—specifying the recording system (these days that means a DAW), then the interface (perhaps including a mic preamp), and finally the microphones. Often there’s a paragraph tacked onto the end that says, “Oh yeah, you’ll need some monitors and acoustic treatment too.”

Not this time. I’m going to start with the elements that are most often lacking in my experience of home recording setups, the room and the monitors. I’ll talk about some strategies to maximize results from these notorious weak points, without outspending the cost of a battleship or a hip replacement. (Trust me: these are comparable.) Only then will I spiral in to the microphones, interface and DAW.

Why this approach? I was motivated primarily by an exchange of messages that ran in the August 2013 issue: A singer in an a cappella gospel group was wondering why their home recording didn’t sound as good as a commercial recording of a well-known group which he attached. Well, the problem wasn’t talent: these guys could really sing. And while I could hear problems with tizzy mics and a low-caliber interface, that wasn’t the real issue. The mics and interface, though cheap, were plenty good enough to accurately reproduce the sound of the room in which they were recording… and that room was the real problem. It was boxy and mediocre-sounding—all too typical of the rooms in which many home recordists work.

That exchange affected me deeply, and I began thinking about advice I’ve given new recordists in the past, advice which was always centered around the equipment (mics, interfaces), rather than the places where investing some time and/or money might have made a bigger difference: room treatment and good monitoring, so the user can hear, and make decisions based on, a more-or-less honest portrayal of what’s been recorded. After all is said and done, a recording made with okay equipment in a good-sounding room will beat out a recording made with state-of-the-art equipment in a crappy room.

Not that I plan to recommend mediocre equipment when we get to that stage; I’ve got my eye on some gear that I expect will provide very good performance for the money. But we’ll start with the room (or rooms—don’t forget to treat the control/mixing room as well as the tracking room) and monitors, because they make the biggest difference.

Kef America LS50 – 728×90

 

Assumptions

Before getting started I need to list several assumptions which are built into this article; they’re true for many home recordists, but if they aren’t true for you, adjust accordingly:

  1. I assume you own the space in which you’ll be recording, rather than renting it. It makes a huge difference if you’re free to, say, build shelves onto a wall, because it belongs to you.
  1. I assume you’ll be recording mostly real instruments (things that make noise in a room) rather than virtual instruments (things that only make signals inside a computer).
  1. I assume that, like many home recordists, you’ll be layering one instrument at a time rather than tracking every member of an ensemble at once, each onto a single track.
  1. Along those lines, I’m assuming that one of the instruments you’ll be recording is a drumkit. To do that, you’ll need to record a mini-mum of three (and maybe four) mics at a time—left and right overheads, kick, and maybe snare. Alternatively, you may want to use a Glyn Johns-derived mic setup for drums, which also needs four inputs.
  1. Finally, I’m going to assume that you’re on sufficiently good terms with your neighbors that you can get away with tracking drums on a Sunday afternoon. If not, you’ll need to do the negotiating yourself, and good luck to you. Hint: a large pizza can smooth many ruffled feelings, but prevention is better than cure.

 

Room basics

At this point you may be wondering: how can this guy Stamler possibly give suggestions about how to improve my room, when he doesn’t know anything about my recording space, its dimensions or its acoustical qualities?

The answer is simple: I can’t, for your specific room. What I can do, however, is talk about some acoustical principles which apply everywhere, and identify pitfalls which may be waiting for you. I will also point you toward some excellent printed sources which can enable you to figure out some possible paths to a good sounding room if you have the raw space to work with, and some online sources than can actually enable you to plot out possible room designs. Finally, I’ll talk about some cost-effective room treatments I’ve used myself, and how you can build them. We’re not talking fine woodworking here; we’re talking about making do—champagne tastes, if you will, on a beer budget.

When we’ve done all of that, I’ll have some suggestions for affordable monitors, and finally some ideas about mics, inter-faces, and a DAW. That’ll be in Part 2, next month, which will give you some time to make a real difference in your room before you get seduced into buying gear.

First, the print sources. Run, don’t walk, to your local public library and look for books by F. Alton Everest, the source for information about small, budget-priced DIY studios. Some representative titles are How to Build a Small Budget Recording Studio from Scratch with 12 Tested Designs and Acoustic Techniques for Home and Studio. (Don’t start with Master Handbook of Acoustics—that’s postgraduate stuff; begin with one of the simpler titles.) If your local library doesn’t have them, talk to the librarian about inter-library loan. You can also find these books at such used-book sources as www.abebooks.com. They’re well worth buying, and will pay dividends for years in better-sounding recordings.

 

Stand and wave

The most basic acoustical facts about a room are its dimensions—the height, length and width of the space. In some ways, the proportions of the room are even more important than the absolute size. To see why, we need to take a short detour into the world of standing waves.

To keep the detour short, I’ll simplify the issue to this: standing waves develop in any room with parallel walls, at particular frequencies defined by this equation:

Frequency (in Hz) = 1130 / room dimension (in feet) 1130 feet/second is the typical speed of sound in air.

That defines the lowest-frequency standing wave, but there will also be standing waves at integer multiples of the lowest frequency. So a room which has one dimension (say, ceiling height) of 10 feet will have standing waves at 1130 / 10 = 113 Hz and integer multiples of that frequency:

2 x 113 = 226 Hz, 3 x 113 = 339 Hz, 4 x 113 = 452 Hz, … and on up.

Sounds whose frequencies fall on those standing-wave frequencies will be reinforced; sounds whose frequencies fall between them will not.

Now think about a room that has identical dimensions on all three axes—height, width and length. Say it’s 8′ x 8′ x 8′, a perfect cube. It will have standing waves at 141.25 Hz, 282.50 Hz, 423.75 Hz, and so on. But here’s the thing: it will have three sets of them, as the standing waves from the three dimensions all reinforce the same frequencies, providing a triple whammy of bad sound.

The same thing will happen when room dimensions include integer multiples of one another—say, 8′ x 12′ x 24′. The 24′ dimension will have standing waves at 47.08 Hz, 94.16 Hz, 141.25 Hz, 188.3 Hz, etc. Meanwhile, the 12′ dimension will have standing waves at 94.16 Hz, 188.3 Hz, etc., and the 8′ dimension will have standing waves at 141.25 Hz, 282.75 Hz, etc..

Note that the 24′ and the 12′ dimension both have standing waves at 94.16 Hz and 188.3 Hz, while the 24′ and 8′ ones both have standing waves at 141.25 Hz. This “pile-up” of standing-wave-induced frequency reinforcements is the principle reason small rooms tend to sound “boxy” and amateurish—many rooms are built with these sorts of proportions.

There are certain “magic” sets of proportions that, over the years, acoustical designers have found work well in avoiding this “pile-up” of standing waves; you can find some of them in Everest’s books.

A quick google search on “standing wave calculator” or “room mode calculator” will find you online or downloadable software to calculate these basic (longitudinal or axial) standing wave frequencies, as well as some more complicated forms of standing waves I haven’t mentioned, called tangential and oblique (or skew) waves. (Never mind what these are; they’re generally less intrusive than longitudinal standing waves anyway.)

 

What’s to be done?

So you’ve looked in Everest’s books, you’ve run the calculator, and you’ve figured out that your room is a screaming (or standing) mess. What can you do about it?

One thing is to move—not necessarily to another house, but at least to a different room. Maybe the rec room is a better choice than the laundry room or the garage for tracking, or maybe you persuade your Significant Other to let you record in the living room, sometimes.

In extreme situations you may need to decamp. If you remember those gospel singers whose query started this discussion, Mike Metlay and I recommended that they look for an old-fashioned style church in which to record, one with a lot of wood in it. (In my experience, old-style churches with wood in them make better recording venues than more modern, unadorned churches.)

An alternative strategy, if you have a room that has bad dimensions, is to change the size of the room. The easiest way to do this is to build a new wall.

But, you cry, I’ve never built a wall before. Neither had I back in 1985, but (with much help from back issues of The Old House Journal) I built one. Now, I am about the least handy guy imaginable; up to then, hanging a picture in the middle of an exist-ing wall was more my speed, and frankly a challenge. But I bought a bunch of 2 x 6s from the lumber yard, framed it out, drove in a bunch of toed-in nails (no nail gun), stuffed in some R19 pink insulation, nailed up the drywall and mudded it into place. I had built a wall!

It was a satisfying feeling, it shrank my tracking room by a crucial 7 inches with an attendant big improvement in sound, and it even cut my heating bills a tad—this project was built on a north-facing outside wall, and that R19 insulation did its job admirably. If I could build a wall, I suspect you could too.

Neumann TLM107 728×90

 

Absorb and diffuse

Okay, you’ve found a room with acceptable dimensions (or perhaps made a room acceptable). How are you going to treat it for good sound? Elsewhere in this issue, Bruce Black offers a DIY solution for tweaking low end via a Helmholtz resonator; I’m going to focus on the highs and mids in this next bit.

There are only two things a sound wave can do when it encounters an object: it can be absorbed, or it can bounce off. (Most likely it’ll do a bit of both.) In the 1970s, studio design was all about absorption, and we got a lot of dead-sounding rooms as a result. These days a combination of absorption and diffusion is considered preferable.

What’s diffusion? Diffusion is what happens when sound bounces off an object or surface, not in a single direction, but every which way. Smaller objects help sound become diffuse; the small decorations in old-fashioned churches (and concert halls) are a prime example. We’ll get to diffusion in a bit, but first let’s talk about absorption.

I’m going to oversimplify a bunch here, but basically absorption controls the reverberation time of a room—the time it takes a sound to decay to inaudibility, defined as 60 dB below its original level. A good number to aim for in a small recording studio is about 0.6 seconds, and in a control room probably 0.5 seconds will be appropriate. There are charts in Everest’s books that enable you to choose a reverberation time for various-sized rooms; my numbers are just ballpark figures.

The problem is, a given room will have different reverberation times at different frequencies, because most materials absorb different amounts of sound at different frequencies. If, for example, you line the walls, floor and ceiling with deep-pile carpet, you’ll do a great job absorbing high and high-mid frequencies, a poorer job absorbing low-mid frequencies, and a terrible job absorbing low frequencies. Result: a room that imposes a boomy, muddy, bottom-heavy sound on everything you record. Sorry, blankets do the same thing.

There are a couple of online resources that can help you plan out sound absorption for a better-balanced sound. I’ll start with a nod to a fellow Recording contributor, Ethan Winer, and the folks at RealTraps (realtraps.com), who present a great deal of material about absorption, including plans for some effective absorbers you can build yourself.

Another excellent resource can be found at sweetwater.com/shop/studio/acoustic-treatment/room_analysis.php, where you can download a form that gets you a custom-designed studio treatment from the makers of Auralex sound-absorbing foam (auralex.com). These sites will naturally emphasize the use of their respective products in designs, but that’s only fair; they have to feed their families too. Auralex, a large manufacturer of acoustically-absorbing foam, sells a kit expressly designed for home studios, the Roominators Project 2. The kit contains a broad variety of absorbent pieces, and some information on their use; you can also find information in Everest’s books, or at the online resources discussed below. The Roominators kit would be a good start for many rooms of average size, and I’ve made it the default acoustic treatment for our Startup Studio.

Auralex isn’t your only choice; foam isn’t the be-all and end-all for absorption by any means, and Primacoustic (primacoustic.com) offers an alternative set of packaged solutions in its London series of room kits, which use fiberglass rather than foam as an absorber (check out the London 12 kit as an example). My DIY alternatives also use fiberglass; I’ll get to those in a minute.

Don’t forget that, if your control room/mixing area is separate from your tracking room (it usually is), that will need some acoustical treatment too, along the same lines as the recording space. As I mentioned above, a reverb time of about 0.5 seconds is often appropriate for control rooms.

 

Build your own

Let’s say you’ve decided on your plan of absorption, but don’t have the money to buy foam or other products—or you want to keep this a 100% do-it-yourself project. Fear not; you can. Everest shows designs for some do-it-yourself absorbers in his books, and, as mentioned, there are some on the RealTraps website and else-where on the Internet.

I’ve written a couple of articles on sound treatment for this magazine in years past (“Build a Broadband Acoustic Panel,” Recording, August 1996) and “Sabins on a Shoestring,” Recording, January 1997) that provided designs for DIY absorbers which provided reasonably uni-form absorption down to 125 Hz or so. Both used Fiberglass insulation in 6″ thicknesses (R19) rather than 4″ (R11); the extra thickness makes a big difference down in the lower-frequency regions, around 125 Hz.

For what follows, here is a major caution: WEAR RUBBER GLOVES THAT GO WELL UP YOUR ARMS, AND A BREATH-ING MASK. Fiberglass is nasty stuff; it provokes itching that rivals poison ivy, and it’s not at all nice to inhale.

Okay, here’s the more formal absorber. Build a 6″ D x  17.5″ W x 48″ H wooden frame from 1 x 6 lumber (the crosspieces should be 16″ long); nail and/or glue it to a piece of 17.5″ x 48″ chipboard (you can get 5 of these from a 4′ x 8′ sheet, with a bit left over). When the glue has dried, staple a 20″ length of picture wire to the back, so you can hang it from a hook on the wall. Fill the frame with unfaced R19 Fiberglass (remember the gloves and mask), then cover the frame with thin fabric. (The fabric used on the bottoms of couches is good for this application.) Staple the fabric to the sides or back of the frame, and voilá—you have a sound absorption panel.

Each frame will use one 1″ x 6″ x 12′ board; add in the fiber-glass and cloth, with a few pennies for picture wire, staples and nails, and you’re maybe looking at$12–18 per absorber, depending on the grades of lumber and cloth you choose.

What about the less formal alternative, bet-er known as the “padded cell” design? This uses all the ingredients of the formal design except the frame. Lay a 34″ x 72″ piece of thin fabric on the floor. Place a 15″ x 48″ slab of unfaced R19 on the fabric, centered (remember gloves and mask). Place an 18″ X 48″ sheet of chipboard on the Fiberglass; fold the fabric up over the sides and staple it in place, without compressing the Fiberglass too much. Staple a 20″ piece of picture wire onto the chipboard. Voila again: sound absorbers. Not formally beautiful ones per-haps, but they do the job. Expect to spend from $7–$12 per unit, mainly depending mostly on the cost of the fabric.

(Yes, those descriptions are terribly abridged. Go to recordingmag.com and get the original articles for a much more detailed story.)

 

Diffusion, by the book

Okay, you’ve put some absorption into your room and it’s sounding a lot better balanced than before. Now it’s time to add some diffusion.

I mentioned that smaller objects tend to create diffusion—lots of smaller objects. Contrary to the tale that is venerable enough to have attained the status of Urban Legend, the cardboard from egg crates will not work, ever. I’ve heard egg-crate studios for forty years, and they all sound like, well, no diffusion at all.

You can buy devices that create diffusion; gadgets that look like pseudo-random abstract sculptures, designed using abstruse mathematical formulas. Or you can buy molded plastic squares, designed for mount-ing on the wall or in a dropped ceiling. Both types of diffusers work very well, and will give you good results if your budget sup-ports it…

Or you can build a bookshelf.

I’m not joking; a bookshelf with a wide assortment of books on it makes an excel-lent diffuser. Here’s my favorite approach.

First, go to the hardware store and get enough wall strips and brackets, plus boards, to make a bookcase that covers a substantial portion of a wall. (It could even be the new wall you built in the room.) Put up the strips; you’ll need a stud-finder, and a cordless screwdriver plus soap on the screw threads saves wear and tear on your wrists.

Now fill the shelves with books—all sizes of books, with maximum variability in depth. Use hardbacks, paperbacks, old pulp magazines, even the odd VHS tape. Variety is your friend.

But how to afford all those books? If you’re anywhere near a metropolitan area the answer is simple: Book Fairs! The book fair has become an established institution, at least in the USA; in my medium-sized city there are frequent major book fairs put on by local not-for-profits. The key moment is “Bag Day”, usually the last day of the event, where the sponsors clear out all the unsold material that would otherwise be consigned to the landfill, typically for $5 per shopping bag.

Since your criterion for buying books is size, not content, Bag Day is your chance to fill your shelves at a discount price, though visiting friends may be puzzled by your ownership of four copies of Fighting Father Duffy. It’s all in the cause of diffusion, so pack those bags full; you might even help out a good cause in your community.

Oh, and if you’re a renter, you can accomplish much the same effect by lining one wall of your room with stand-alone bookshelves filled with books. It’s a bit more expensive, but has the advantage of being easily movable/removable when the time comes.

Okay, there’s your nicer-sounding room. Next time, we’ll put in speakers and fill it with the rest of the needed toys. See you then!

 

Paul J. Stamler (stamler@recordingmag.com) is a recording engineer, educator, and collector of interesting vintage audio, living and working in St. Louis.

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