inSync Tech Tip of the Day
There are so many elusive elements affecting our ability to make recordings we like that it’s hard to know which direction to turn for making an improvement. Do you buy that new gizmo that is all the buzz in the ads in hopes that it’s the missing ingredient, or do you just need to go learn how to be a better engineer, or do you give up and turn to writing an Internet column? Just kidding there, my studio is actually very successful, but there are still tons of things even the most seasoned professional can learn if he keeps a learning mindset about him. One of the biggest mistakes I see people make is to become too confident in what they think they know. It shuts down the opportunity to learn (besides making them seem like jerks). We ALL have more to learn and it is sometimes surprising where we can learn things. Sometimes someone just has a different way of looking at seemingly obvious things, a way that can open a new reality for someone else. You never know where it will come from if you are open to it.
That is the philosophy behind our inSync Summits. Long standing inSync readers will recall our past summits ( Piano Miking ,Guitar Miking ,Once Piece… , and Vocal Recording ) and the valuable information they brought to light. Many of our inSync readers are highly technical and experienced in various fields. I wish all of you could see some of the amazing e-mail we get. There are some folks out there who really know their stuff and it sure keeps us on our toes. Similarly a lot of our readers have very creative and original ideas that work in the real world of actually doing things. Sometimes a mind uncluttered with the facts about how you’re "supposed" to do it can come up with brilliant ideas. In the inSync Summits we are able to benefit from the best of both worlds.
In this Summit we delved into the world of acoustics and sound treatment. We asked people to respond with tricks and methods for the acoustic treatment of their studios. We were looking both for solutions in effective soundproofing as well as solutions for creating a good acoustic space. It is possible for anyone to open a book on acoustics, and there can be a lot to learn in those books. We highly recommend them. But what we wanted to know was what has worked for our readers and how they deployed their methods. If those happened to originate in a book that was fine. We wanted to know why they chose that method and any tips and tricks they may have picked up along that way, especially those that may not appear in books.
Below you will find the various responses we received. These have gone through some minor edits for punctuation and spelling, but the style of each writer and almost all of the content has been retained. We hope you enjoy it and learn something.
David S. (not your inSync editor)
After walling off the end of a long garage and getting an electrician to put in a power box and convenient studio wiring, the resultant "echo box" required lots of help. Discarded carpet from a neighbor was glued to the cement floor over used padding from the dumpster of a carpet store. (It's better to get permission!) And we didn't forget to pad the door. A neighbor with an upholstery business provided foam chair pads for the ceiling--gluing them from a ladder was a trick requiring many poles to hold them up to dry. Discarded church bench pads were screwed into the wall studs. My daughter collected egg cartons from the store she worked at to fill in the rest of the spaces. For bass traps, rolled carpet padding stuffed in burlap bags and set upright did the trick, but took up a lot of room. By now the room was very, very quiet, almost like stepping inside a place of worship. To beautify our ugly creation, used stage curtains from a local curtain business were cut and draped from the walls, and a donated foam hospital mattress with added velcro strips made a quick and removable window cover. The only cost was for two tubs of non-toxic, quick-dry linoleum glue. And we didn't forget to clean the carpet, both walls and floor. The sound? We had to crank the amp to get a rush, but it's good enough to finish a mix--if you don't mind an overhead light humming along with you.
||Wanting to achieve some balance in my studio for a minimal cost, I came up with 3 very effective and low cost ideas:
||Fastened drop ceiling panels flush to the ceiling in both rooms with adhesive and sheetrock screws in a staggered pattern with 1/2" space around all edges of each panel, (to trap sound waves) then caulked the screw holes. This ended any ceiling bounce.
||Found and purchased some industrial rubber backed carpet (a remnant from a big hospital job) and wall to walled it in both rooms, with a removable square in the studio room to reveal the hardwood floor when a little brightness or bounce is required, like a more "lively" acoustic guitar sound. Total combined materials less than $500.00; I get a lot of compliments about my sound
Then, There was Sound Audio Productions
Before my bedroom became my recording studio, it was home to my futon mattress and my drum set. The hard, drywall walls created a terrible "live room" every time I sat down to play the drums. As a solution, I went to Target and purchased (ironically, they were on sale at the time) egg-crate foam mattress pads. I cut them to fit the walls and ta-da, no more loud, reverberant drum chamber (Oh, by the way, I stapled the foam to my walls-I'm dreading the day I have to pull all of that stuff down!). The room (now my recording studio) actually sounds fairly decent. I've had a number of people comment on how they liked their sound in the room.
My room treatment is very low impact, yet reasonably effective in my suburban project studio. Even for renters, these techniques are so low impact that only the pickiest landlord would complain. In the windows, I use a product called R-matte Plus. This is basically about 5/8" of stiff foam sandwiched between two sheets of aluminum foil. It is available from hardware stores in 4' x 8' sheets for less than $10. Cut the panel to fit the window and position it so that it doesn't actually touch the glass or the frame. Then caulk all the way around it to seal it completely. You might have to caulk twice to ensure a complete seal with no leaks (check for leaks by turning off the lights on a sunny day). When I move, the caulk easily comes off the painted surfaces (cheap caulk is easier to remove). After a fresh coat of paint the window is no worse for ware. For the walls, I put the proverbial mattress foam on the most offending wall surfaces. This cuts down flutter and deadens the room somewhat--enough to suit my purposes. I use a common office stapler to staple it in place to the drywall walls. Here again, when I move, a little spackling, sanding and a good coat of paint will hide the staple holes. I wouldn't recommend using mattress pad (or egg cartons, etc.) for the entire room. These are not acoustically "flat" and too much can cause more problems than they fix. There is a reason professional absorptive foam costs so much--because it is (more) acoustically flat. I also have a decorative and thick blanket hanging on one wall. On the door, I added closed foam "peel and stick" weather stripping on the sides and top of the doorframe, and throw a heavy towel or blanket for the bottom. As I stated in the " One Piece of Gear " summit, the one piece of gear that made the most improvement was that I built movable sound absorbing panels (AKA gobos). For less than $75 I cut a 4 x 8 x 3/8 piece of plywood into unequally-sized rectangles, built a frame around the edges with 1 x 4's, stapled burlap to the front and stuffed common rolled insulation (remove the paper backing) inside. Then I used 1 x 4's to build stands for the three panels. Now when I record, I place one panel behind the microphones and a panel on either side. This decreases the undesired room effects from the recording and lets the source more clearly shine through. "Steady-state" noise, such as the air conditioner, ceiling fan and refrigerator, are tuned out using Sound Forge Noise Reduction. I also built a bass trap out of shep-tube (this is the heavy cardboard tubes used when pouring concrete posts, etc. It comes in a variety of sizes and is commonly available up to 12" diameter). The bass-trap did not completely flatten a bad peak that I have at around 65 Hz., but it did help. I have some corner diffusion already and one day I hope to get around to finishing my corner diffusers. Sound gets built up in the corners and even a small amount of diffusion is a great help for adding clarity in monitoring (near field monitoring does NOT eliminate all problems!).
A relatively in expensive way to start is to make rolls of carpet (shag maybe?) and stick them up on the walls. Not just flat against the wall, but actually on the wall in rolls. It makes for a decent combination of diffusion and absorption, plus it actually acts as somewhat of a bass trap.
The beginning acoustician might enjoy the "Handbook for Sound Engineers - The New Audio Cyclopedia 2nd edition", published by SAMS (a division of Macmillan Computer Publishing). LOTS of good info. Relative to the question of how carpet absorbs sound, Chapter 5 briefly discusses carpet, plus foam, Fiberglas(tm), etc.
Tom Kiser, Brooklyn
I took the following steps to treat my old solid wood panel door.
||Put on rubber weather-strip where door meets doorstop.
||Put weather-strip where bottom of door meets doorjamb.
||Glued Styrofoam on panel in middle of door to make the center of the door level with rest of door (Styrofoam does't do much to soundproof but was a lightweight and cheap filler).
||Measured from hinge side of door across to trim molding surrounding door.
||Cut 1/4 inch rubber roofing that was 3 inches wider and taller than door.
||Cut Soundboard that was also 3 inches wider and taller than door.
||Glued Rubber roofing to Soundboard
||After removing handle, Glued and screwed Soundboard/Rubber roofing composite to Door. This extended Three inches above door and 3 inches out from the handle side of the door over the trim molding that surrounded the door. (Use as few screws as possible as they transmit some sound)
||Reinstalled handle with longer shaft would reach through extra inch added to door thickness.
||Attached Rubber Seal onto Trim Molding that surrounds door. This creates a second seal that makes contact with the 3 inches overhanging the original door.
Results: Transmission levels cut way down. It is not totally soundproof but it does a great job cutting out most of the noise that is generated by my Seven Children.
I’ve always had good results just by putting a few pieces of foam around my control room in strategic locations. I usually attach a few pieces to the walls and ceiling near where my speakers are and then some more on the back wall behind the listening position. It’s amazing what eliminating just a few reflections can do and it costs next to nothing.
DAS, Sweetwater Sound
The main idea behind using acoustic foam is to absorb primary reflections that would otherwise interfere with accurate monitoring. In many cases, it takes a surprisingly small amount of foam to make a significant difference in the acoustics of a room, especially if near field monitors are being used.
Take a look at where your monitors are placed, and at the flat, hard surfaces that are near them. Typically, these will be the side walls of your studio, the top surface of your mixing console or desk, any gear around you and the monitors, and to a lesser extent the ceiling above you. If any of these are at such an angle that they will reflect sound directly to your ears, they are causing problems.
At this point, enlist the aid of a friend, family member, shrieve, or other easily conscripted lackey. Have them move about the room, holding a mirror against the possibly offending surfaces while you relax comfortably in your normal monitoring position, possibly sipping a cool beverage. If you can see a reflection of your monitor's tweeters in the mirror from the monitoring position, have your assistant mark the spot as one requiring acoustic treatment.
You can even go one step further by attaching this foam to panels that you can hang down from the ceiling a few inches from the walls. This produces some diffusion and a bit of a bass trap to even out the effects of the high frequency absorption.
For mixing console and gear surfaces, covering them with foam may disrupt the manufacturer's intended ergonomic design. Try changing the angle of the mixer slightly, or moving things around in other ways to minimize unwanted reflections.
Richard, Paris France
RPG brand acoustic treatments are definitely not the cheapest way to go, but if you are serious about this it is worth the money. They make a variety of very effective materials for various acoustical problems. They are also very helpful in the design and decision stages.
|Editor’s Note: We use RPG materials in our main control room here at Sweetwater. They do work great. Check out our on-line white paper from RPG. There is a ton of useful info there. Additionally, there have been some tips in inSync before about treatment. Check out the TTOTD from 3/19/99.
Max, San Antonio, TX
I'm not sure this tip fits exactly in the studio acoustic treatment summit, but maybe it's close enough. I have had some trouble recording mic'ed electric guitar -- more from the amp noise than the quietness of the studio. Here's the fix I came up with to get the sustain I wanted and a quiet signal. I ran the preamped guitar signal into the board and then sent a line out from the board to the line in of my amp (to power amp and speakers only). Then I could turn up the volume on the amp to get the sustain/feedback I wanted and yet get a clean guitar signal that could be effected later. The same trick can work with monitor speakers in a pinch. The sustain/feedback is a little different from the more colored sound of the guitar amp speakers vibrating against the guitar strings, but it works ok.
This entry is actually a copy of an e-mail exchange I had with one of the readers about the concept of true acoustic spaces. While this wasn’t an official entry into the Summit the topic is relevant enough to include here.
from: Richard F.
Greetings. First of all let me again applaud the inSync staff for their highly useful on-line resource.
I have a fundamental question about room acoustics and monitoring that has never been fully answered to my satisfaction. I wonder if inSync would help me think through this question.
The industry seems to have an implicit understanding that to build a "good room" for monitoring (not recording) one should strive to eliminate primary reflections that would otherwise interfere with accurate monitoring. This notion is articulated in part (below) in your last inSync. You write:
"The main idea behind using acoustic foam is to absorb primary reflections that would otherwise interfere with accurate monitoring. In many cases, it takes a surprisingly small amount of foam to make a significant difference in the acoustics of a room, especially if near field monitors are being used."
I would like to open the question of exactly what we all mean in the industry when we say "accurate" monitoring. It seems to me that if one goes to elaborate measures (with foam, carpet and drop ceilings, etc.) to build a specialized room for "accurate" monitoring, one has surely created an acoustic space that is similar to less than 1% of the listening public's typical acoustic spaces (in their living rooms, cars and walkman headphones.) How many people do you know who put acoustic foam in their living rooms? Shouldn't the idea of "accurate" monitoring in a pragmatic sense correspond to what the average listener has in his living room, which is an imperfect (perhaps "inaccurate") acoustic space? There may be no right answer here, but I think the answer lies partly in who the recording musician decides is his primary audience, and this ought to be a conscious decision. Is the recordist trying to sound good in 99% of the world’s acoustic spaces (imperfect/inaccurate) or is he trying to please the true audiophiles (1%) with their foam listening rooms. It seems that the statement of an audience target is rarely done up front in a discussion of monitoring. Am I missing something here? Help me understand what is flawed in my thinking. How does a specialized "accurate" acoustic space for monitoring help the recording sound good in most of the world's imperfect acoustic spaces? Have studies been done on how to replicate the average imperfect/inaccurate space that most listeners actually have?
Thanks for your time.
to: Richard F
This is a great question and I hope to somehow address it in the limited space of inSync.
Yes, building an acoustically perfect space takes one further away from the "typical" listening environment. The problem becomes, "What is typical?" There is obviously no one answer to that question. A quick sampling of just a few people's stereo setup reveals all manner of configurations, most of which unnecessarily reduce the accuracy of the listening experience, each in its own unique way. Clearly many people do not know or care about the finer points of sound and just have things set up for convenience.
If I were to do a mix ideally suited for my mother's stereo it would be best for me to somehow pipe the music in there and listen to it. Otherwise anything I do is just a guess for how it will sound in there. Since there is no way we can hope to be able to take into consideration all of the unique and special "flaws" of everyone's listening environment we must instead try to achieve an accurate mix. I mean a mix that is as "objectively" correct as we can make it. Speaking in terms of objectivity when it comes to something as clearly subjective as music mixing is almost funny. But the only way to accurately apply your (the engineer's) unique and presumably valid subjective take on what things should sound like is to have an objective representation of it from which you can make good decisions. This is the common reference point we are all striving for. Building a mix in an objective environment means that it can be played on each "flawed" system out in the world with somewhat predictable results. Each mix will be broken in the same way as other mixes on a given stereo. And since that person obviously does not find his stereo's sound to be a hindrance to his enjoyment of the music then having our mix broken in the same way as everyone else's is a compromise we must live with.
When we mix in an environment that colors our subjective objectivity we make decisions that become unique characteristics to our recording that we are not aware of. These characteristics may or may not show up on a given system out in the world, but there is a good chance that they can. I see two problems with this: 1) The engineer may not have wanted them there, which means that the monitoring space tricked him into leaving something in his mix that was undesirable, and 2) Even the listener of the flawed system may hear it as a bad recording because there could be a new tonality or mix that he has never before encountered on his system. Your mix sounds "worse than his other CD's."
For those reasons it is important to monitor in as accurate a space as possible. Not everyone agrees about what is accurate and produces the best mixes (surprise). Everyone generally does agree, however, that it is something to be concerned with and decisions should be made against the background of what the producer/engineer believes will allow him to make mixes that sound good in most systems in the real world.
Rap producers may monitor on huge $20k Genelecs, but they still test themselves on a common "blaster" because they know that's how their mix will be heard by most people. That's just the producer applying some common sense. It is still important to listen to the main studio monitors because they help hear things that may be hidden by some special acoustical function of the given blaster - things that might well show up in another blaster or in a car stereo.
Hope this helps.
In cases where one wants the ability to make temporary connections between rooms the solution is to install some PVC pipe fittings through the wall and use what plumbers call a "Tee - Wye" fitting with a threaded "clean out" on each end. This series of fittings can be "force fitted" into the wall with foam insulation or secured with silicone. Each side would have a hand tightened plastic plug so you can see what you are doing (straight line view through the wall with the plug removed) while passing the wires through, but the wires themselves would actually be going the indirect route via the "leg" of the wye section. After the wires are in place one need only stuff some foam rubber into the open pipe ends then screw the caps back on to minimize any direct sound transfer. These two fittings need not be directly connected to each other inside the wall and can have a small gap between them to keep the sound / vibration transfer to a minimum. The whole idea is just to have a sealed but neat looking access port between the two sides.
These fittings can be readily purchased in sizes from 2 inches on up to 6 inches (or larger if necessary) and they are fairly cheap. Bigger might be better considering that one day you might want to get a bunch of cannon plugs in there for that extra snake or the rare occasion that a 220 volt line (with a big plug) might be needed for an out of town act that brought their own equipment.
"I have just read through your Acoustics Summit (very helpful!). I am on the verge of renovating a basement area for recording. The open basement space will be turned into a control room and two studio rooms. While I have a fair idea of the type of construction I need for properly isolated walls, doors and windows, one thing that I am less sure on is the best way to pass wiring through a wall (staggered stud wall with insulation) in such a way as to not compromise the wall's isolating properties."
The two main things you can do is to make sure the entry points for the wire are not opposite each other on the two walls, and seal off the area around the wire. You just want to make sure that air can't transfer between the entry points. Making the entry points different is a matter of bringing the wire into the wall from one room, and then running it laterally through at least one of the wall studs before having it exit in the next room. The wall stud and wall insulation will help a lot in preventing acoustic transfer. You can seal the wires at either end with a variety of caulks or silicone based sealants.
I'd like to report on an inexpensive and simple method for removable installation of acoustic foam -- with carpet tack (aka carpet strip).
Carpet tack, used in the installation of wall-to-wall carpeting, is a four foot strip of wood studded with small nails (points up) and large nails (heads up). The points of the small nails hold the carpet in place while the large nails hold the carpet tack to the floor. Carpet tack is readily available at your local home improvement store.
A horizontal length of carpet tack mounted to a wall can be used to hang acoustic foam, even full sheets of 4" Auralex wedges. This same method also works great for hanging rugs for decoration and/or sound dampening. Neither foam nor rug are damaged by the carpet tack.
I recommend replacing the large nails in the carpet tack with drywall screws. With this method, removing both foam and carpet tack takes just minutes and leaves nothing but a few holes to spackle. As a further bonus, it's easy to lift the foam right off the wall to change room acoustics on the fly.