The outer frame serves to cover up the staples/fabric as well as provide some additional structure to this (heavy) gobo.  I opted to NOT use any glue or adhesive when attaching the outer frame or base.  Why?

This way the gobo is serviceable. You can access the fabric and innards just by taking out screws (rather than having to hack through dried glue/adhesive).  The gobo is plenty strong without the outer frame, so screws should do just fine by themselves.  The first time someone puts a mic stand through the front fabric, it won’t ruin the gobo.  You can take it apart in a few minutes, replace the 10$ worth of fabric and be as good as new.  I’m sure these things will take some abuse in the studio (as most equipment must), so I hope it proves to be a good idea.

Ok – so the outer frame is pretty easy.  Measure and cut the wood accordingly (to fit snuggly around everything) and just put on one piece at a time.  I opted to put the top and bottom on first, then the big sides.

Now the outer frame is on. Just a few steps left until a completed gobo.

When putting multiple gobos together, an “airtight” gap between them is ideal.  Since these are designed to be put together at angles (plus the fact that lumber is not always perfectly straight), I needed something plyable to join multiple gobos together.  I found some thin, “D-shaped”, non-porous weatherstripping that I am going to try.  It was approximately 6$ for a pack (which will cover both sides).  There’s no way to really test it until I build another one of these and put them together (plus to see if the stripping can take some abuse), but it looks promising so far.  (This is the only close-up I took of it, sorry).  Its just self-adhesive, and I ran it down both of the “absorptive-side” edges.

Now to get the base on.  First, I had to cut it out of plywood.  Its an octagon.  The center section is the wdth and length of the final base, and the edges come out at 45 degree angles.  I just marked up a piece of wood with a pencil and straight edge and cut it out freehand with a circular saw (rather than busting out a table saw).  If you go slow and are careful, you can get straight and accurate cuts.

Now I also decided to put carpet on the bottom (through the advise of others) so that it would slide on hard floors (as well as help keep the wood in good condition).  I had some scrap carpet around, so I just traced the edges of my base and cut it out with a knife.

Now time to screw the base on and attach the carpet.  Put the gobo on its side, then you can just screw the base right in.  (Again – I chose to not use any adhesive so I can take this thing apart if need be).  I think I used a dozen screws or so just to make sure it was REALLY on there.  For the carpet attachment, I used PL375 (the “heavy duty” construction adhesive).  I loaded it up, especially around the edges, and pushed the carpet on.  After using a somewhat mantis-like position hold on the carpet while it set for a few minutes, I quickly grabbed some extra wood and a bunch of clamps to hold it on while it dried.  I actually just left it like this for about an hour and then flipped the gobo upright (the weight of the gobo will hold the glue in place).  I did this rather than screws or carpet tacks because this is going to get dragged all over wood floors.  A stray end of a nail/screw with a 100 pounds pushing it down could bring HAVOC to floor in seconds.  I’ve been pushing this thing around my garage and the carpet seems to be holding just fine with the glue.

And finally ::drum roll::, the finished gobo!  I need to build another one to really field test it, but from my scientific initial “walk by it and hear what it does” test, I can say that this thing blocks some serious sound.

C

The Studio Files

So at the end of the last post, I had built the inner frame and attached the plywood backing.  Next up is the two layers of 5/8″ drywall.

Unfortunately, I forgot to grab my camera until after the drywall (and insulation support braces) were already in… Cut out two pieces of drywall (one will be ~2′x4′ and one will be ~2′x2′).  Lay down a bit of construction adhesive (I used PL400) and press the drywall on top of the plywood.  (Repeat for the second layer).

Then I caulked the edges (again, acoustic caulk is the best, but Alex Plus will work on a budget) and used a few 1″ drywall screws to better connect the two layers of drywall.  I would suggest leaving the box as I have positioned here (this side up, flat on its back) while the caulk sets.  This will allow gravity to pull it down into the seams a bit more.

(In these pictures, you will already see the wood cross braces, which I will discuss next… sorry)

Next, I need to install the wood cross pieces that will help keep the air gap between the 703 and the drywall (as well as provide additional structure and support).

I used a T square to measure down 4″ from the top of the frame (since I know that I will be putting 4″ of 703).  I cut five ~24″ pieces of 1×2.  Measure across the box for each of these pieces!  Wood is not an exact science, so there will be slight variations. I spaced them out evenly (3 in the big section, 2 in the small) and attached with a bit of wood glue and a screw on each side.  Just make sure that the top edge of the brace doesn’t go above 4″ down from the top so you have enough room for the insulation.

Now in the next picture, notice how the cross braces are not laying on the drywall.  They are only attached to the sides of the frame.

After the cross braces are in, it should be a breeze to just drop the 4″ of 703 in.  The large section of the gobo should fit two pieces exactly if you build the frame correctly.  For the top half, just carefully slice one piece in half with a razor (I used my level as a straight edge).

Ok – now all the insulation is in.  Time to wrap it with fabric.  There are a lot of options for fabric, a lot of which can be decided merely by budget.  Guildford of Maine fabric is probably the ideal fabric.  Unfortunately its 4-6x more $$ per yard than other average fabric.  If you have the cash, get that.  You can also go with a burlap or muslin covering.  I went with something a little different.  I grabbed some fairly low thread count cotton/synthetic blend that had a little stretch to it.  I did almost get chased out of JoAnn fabric because I was taking dozens of fabrics and blowing through them… which didn’t make the sales lady that happy.  This fabric passed plenty of air but seemed like it could take abuse.

Now – one thing this fabric is missing – anti-flammability.  If you don’t treat this fabric, your gobo could become a giant match in a split second.  Unless your fabric is pretreated, just grab a can of fabric fire retardant and spray it down.

2.5 yards will cover your gobo.

Covering these with fabric is a bit of an art form, and you will get better at it with practice.  I chose to lay the fabric down over the box and staple the top side completely across.  This will give me something to pull on as I (slightly) stretch the fabric around.  Note – I did give the frame a very light sanding job beforehand, in hope that no sharp edges would damage the fabric. After you get one side stapled, its a matter of working your way down opposite sides, pulling out any wrinkles as you go.  I put a lot of staples in, in somewhat of a random fashion.  Since I am soon going to be covering these staples with wood, I thought spreading them out would help defeat any tilt that might be imparted (and it did).  As I got more staples in, I just cut away the extra with a knife/scissors.

In the next post, I’ll show you the outer frame and the base. (aka the finish line)

C

The Studio Files

]]> http://thestudiofiles.com/?feed=rss2&p=810 0 http://thestudiofiles.com/?p=801 http://thestudiofiles.com/?p=801#comments Wed, 18 Mar 2009 18:06:27 +0000 http://thestudiofiles.com/?p=801 The start of the gobo: the inner frame

The inner frame is made of the 1×8 board.  If you look at the original Sketchup drawing, you will see that the inner frame is essentially divided into 2 sections – a 4′ tall and 2′ tall section. Each of these sections is backed with plywood.  Now unfortunately its not as simple as just making the box and dropping the plywood in, especially since I am using store-bought sections of plywood.  Although they are sold as 2×4′ and 2×2′ pieces, they aren’t quite that dimension.  Measure each board, and design your frame around the plywood. The long sides are approximately 74.25″ long (48″ plywood+24″ plywood+3 board widths). The top, bottom, and center support are ~24″ long.

You can see in this picture that I have the plywood on the ground and am building the frame around it.  Note: The plywood is NOT attached to the 1×8 frame at this point. It is merely a reference to make sure I am making the frame correctly.  I used some wood glue and a few wood screws to make the corner, leaving the clamp on until its at least partially dry.

Here is a close up of the corner

When I put the other sides on, I did have the 2×2′ piece of plywood and center brace in there.  I took them out at this point to sand an edge down.

Finally, I put the plywood back in (for measuremeant purposes only!) and add the center support.

The plywood is still NOT attached to the frame.  I am waiting until the frame dries and is strong.  I found that it is much easier to get the plywood flush with a strong, dry frame.

Once dry, I used wood screws and glue to attach the plywood to the frame (flush with the back edge).  Then I caulked the inside edge.  Using true “Acoustic Caulk” is best for this – this type of caulk never becomes rigid (it stays rather squishy forever), but if you are on a tight budget, using a very elastic caulk (such as Alex Plus) should be OK.

Next – fill the frame with drywall.

C

The Studio Files

First was the design stage.  I like to use Google Sketchup for design work of this type (its a free program!).  I knew my design needed to

• Be sound isolating, and probably about 6 feet tall (so I could group several together for a quasi vocal booth)
• Be able to join multiple gobos at a variety of angles
• Have the option for a gobo with a window

I also wanted the gobo to have one absorptive and one reflective side (for added flexibility of use).

The most important property of sound isolation is MASS.  Typically, more mass means better isolation.  However, more mass means heavier and harder to move.  I decided that a layer of plywood and a few layers of drywall would be a good start for the “massiveness”.  The plywood would be exposed (for the reflective side), and the other side would be 4″ of Owens Corning 703 insulation.  An inner frame of 1×8 lumber will hold the “innards” in and be covered with fabric on all sides, except the plywood side.  Then an outer frame will go over that, for increased strength, as well as to cover the staples and fabric.  Again, this gobo design is purposely adapted for the use of multiple gobos at once.  This is why the gobo is only ~2′ wide.  This way, I can make multiple gobos and have them arranged in any arrangement I need (plus moving a 2′ wide gobo is a lot easier than a 4′ wide gobo).

I would use spacers to hold the 703 up as well as create an air gap in the middle (which should help slightly with the control of lower frequencies as well).

The pictures will show you the reflective side, the absorptive side, and the innards.  I do have a model of the gobo with a window as well, although I am not currently building that one.

The odd hexagonal base was chosen so that I can put two gobos together at up to a 90 degree angle without the bases sitting on top of each other.

Materials Cost:

• 3x ten foot, 1″x8″ boards  $25
• 1x eight foot, 1″x8″ boards $7
• 2x 2′x4′, 3/4″ birch plywood boards $30
• 1x 2′x2′, 3/4″ birch plywood boards $8
• 5x 2′ long, 1″x2″ boards $6
• 1x 4′x8′ piece of 5/8″ drywall $6
• 3x Owens Corning 2″ pieces $24
• 2.5 yards of fabric (cheapest is likely burlap/muslin) $8
• Various tubes of Wood Glue, Construction Adhesive, Caulk $10
• Wood Screws (1.5″) $3

Grand total – $127, aka I can build 3-4 of these for the amoutn of $ I’d spend buying one.  Plus, its more fun to make your own.

Its even a good deal if you don’t have all the necessary tools.  Even if you have to buy a circular saw, clamps, and a drill, you’ll spend less than buying a gobo.

The next post will show the start of the frame.

C

The Studio Files

Your room’s acoustics are extremely important!  Even the most expensive signal chain in the world can be greatly hampered if not used in a great sounding room.  Project and home studios can benefit greatly from even a small investment in treatment (such as absorption for first reflections and parallel surfaces plus bass trapping)

To make your acoustic dollars stretch even further (and to have a bunch of fun!), you can build the treatments yourself.

So what tools do you need to make your own treatments?

A lot of the treatments are fairly similar in construction.  You can make absorptive panels, clouds, and bass traps out of basically the same materials: wooden frame, filled with Owens Corning 703, wrapped in fabric.  Therefore, the most important tools will be those used to construct the wooden frame.  I actually built some today; here are the tools I needed:

• Saw – A circular saw is a great start (especially if you are experienced), but also having a miter saw around is really my preference.  For quick cuts (and, of course, miters) a miter saw is really convenient.
• Drill – Any solidly built, cordless drill will do just fine (not pictured, sorry)
• Clamps – I like to have a few small 90 degree clamps, a few medium alligator clamps, and some larger clamps available just in case
• Ruler, T, and level
• Wood glue (I like Liquid Nails for wood)
• Sandpaper, utility knife, pencils
• Hearing protection! (especially for cutting wood, its loud!)

Obviously, you’ll also need wood and insulation, but I’ll get into those specifics for each project.

In an upcoming article,  I will show you how to build is an absorptive panel (which I am going to wrap in fabric and hang for absorption above my mix position).  Alternatively, you could mount this on a side wall to tame reflections.  Later on, I’ll show adaptation for corner bass traps, and then I’ll give a step-by-step of my current gobo building project. EDIT: I’m actually going to start with the gobo due to a delay in getting some materials. As a quick teaser – the wood for the small cloud (2′x4′) cost around 8$.

Any questions on tools or techniques?  Ask them in the comments here -

C

The Studio Files

This is a number assigned to building materials to provide a means of comparing acoustical isolation properties.  The higher the number, the more isolation.  (For example, a CMU wall filled with sand would have a higher rating than a piece of drywall).  These numbers are important to acousticians when doing things like figuring out theoretical reverb time (RT60) calculations, among numerous other applications.

^^These are all things that people involved in audio (from beginners to professionals) should know.  This article will discuss comb filtering from theory to practicality.  (Including a preview of a MAX program I’m working on that will do all the plotting and calculations for you…)

So first off:  What is comb filtering and what causes it?

Comb filtering is a type of filtering that occurs when a signal is combined with a delayed copy of itself (or, if not the exact signal, something with similar frequency content).  The interference now caused by the difference in phase of the waveforms causes very deep notches to be taken out of the spectrum at regular intervals.  In between those notches, wide boosts of +6 dB occur.  In this picture, I have taken a L and R channel of white noise, delayed the R channel by a number of samples, and combined them.  This is a look at a linear spectrogram (not logarithmic, for this picture, it will look better):

Let’s compare this to what white noise normally looks like on a spectrogram:

Ouch, right?  So by the looks of it, we have some seriously negative EQ happening to the delayed and summed white noise.  (Its not necessary for the scope of this article, but) If you do the math, you will find out that the first “notch” taken out is at 3150 Hz, and the next “legs” of the comb filter occur every 6300 Hz (so at 9450 and 15750).  In between, we have some wide gain applied.

As a the delayed signal moves farther and farther away from the non-delayed track, the number of filtered bands goes up.  So, up there^^ we were delaying the signal in the R channel by 7 samples.  What happens if we delay it by 17 samples instead?  This is what we get:

Ouch more, right?  Now we have 7 notches taken out, starting at around 1.3K and occurring every 2.6K (again with gain in between).

So, before we move onto “Why this is relevant to recording?”, make sure its clear that this filtering is happening because a signal is present twice, and one instance of it is delayed;  when the delayed combines with the original, filtering occurs (based on the delay time).

Probably one of the prime examples of a “COMB FILTERING DANGER ZONE” is when recording a drum kit.  Here you have a slew of mics to place.  While ideally each mic would only pick up the drum it was aimed at, inevitably there will be bleed from mic to mic.

A great example of where to watch for comb filtering is on the snare drum.  Very often, engineers will place 2 mics on the snare drum (top and bottom mics).  So now we have two relatively similarly sounding tracks that are going to be combined.

Uh oh – If there is a delay present between these two copies of the signal, that we are creating a textbook definition of comb filtering. Why would there be a delay?  One common way this would happen is if the mics are at different distances from the drum.  If it takes longer for the sound to get to one mic, that mic will be delayed in relation to the other.  It may be prudent to make sure that the mics are equidistant from the drum (as to avoid filtering).  I’m not done with this Max/MSP program yet, but here is a screen shot from a program I am making.  Right now, you can choose the source material and then delay a channel by an amount of samples (and it does the calculations for converting that to milliseconds and inches).  Inches translates to how many inches your mics’ diaphragms would have to be “off” to cause this filtering (based on the speed of sound).  I’m hoping (once completed) that this program will be a good reference.  So, in this picture, notice that I am delaying 7 samples (notice the filtering) and also notice the number under “Inches”.  A difference of a few inches can make a big difference.  (Click to enlarge)

(Currently I’m working on getting MAX to plot the theoretical comb filtering function, rather than just tell you the primary frequency and interval.)

Despite all this, I wouldn’t get too neurotic about measuring the distance of every mic you place.  For starters, just use your ears when bringing up levels in the control room.  If things sound “phasey” or weird, then you know something is wrong.  Often this can be fixed just by flipping the polarity inverse switch (often mislabeled the “Phase” switch) on the preamp of one of the mics.  Sometimes comb filtering can even be a good thing…

Most importantly – be aware of comb filtering (and its causes) and always use your ears within this context.  When pulling up mics in the control room, listen for these cancellations.

I’m hoping to have this program done soon, and with some adaption, I would like to make it available for TheStudioFiles.com.  Its even good as ear training, as you can load up sound files and delay them to practice listening for filtering.

More on this as we begin to delve into drum mic’ing techniques…

C

The Studio Files

Working in an industry where it’s your job to listen to music all day, knowing the safe limits of our hearing system is really important.  You only get one set of ears, they need to last!

The ears can safely listen to a WIDE dynamic range of sounds.  However, the duration of this “safe” window decreases rapidly as sources increase in volume.  Many of us in the audio industry will be listening for the better part of a whole workday (say 8 hours at least), so its good to know how loud we can listen without damage.  The problem is that everything sounds better when its louder.

OSHA (the Occupational and Safety Health Administration) is a federal organization dedicated to safety in the workplace.  OSHA has generated a list of dB ratings with associated time durations which will not damage the hearing system.  Unfortunately, these figures are sometimes disputed.  OSHA first outlined that it was safe to listen to 90 dB sound for 8 hours per day.  However, many audio professionals think that the number should be 85 dB.

In my opinion, its better to operate on the safe side (right?), you won’t miss those extra 5 dB.  There is some debate on how long to listen to music at certain SPLs.  Taking in account factors such as the natural compression of the middle ear, the duration of breaks, spectral content of material, how our ears deal with loud sounds (vs. soft sounds), etc. can factor into these numbers (as well as the weighting of the SPL meter).  Here are some basic guidelines for listening levels (each of these being “per a 24 hour period”):

• 8 hours at 85 dB
• 4 hours at 93 dB
• 2 hours at 100 dB
• 1 hour at 105 dB
• .5 hour at 110 dB
• 15 minutes at 115
• Anything higher, get out immediately!

Also remember, these are over a 24 hour period.  Once you listen to 15 minutes of ~115dB music, you need to shut your ears off from the world for 23 hours and 45 minutes to ensure no damage occurs.

Another good thing to keep in mind is that relationships between decibel levels are logarithmic (not linear).  So if you jump from 50 dB to 110 dB, thats not 2.2 times louder, its 1,000,000 times louder (ONE MILLION!).  Crazy huh?

The moral of the story: buy an SPL meter and use it!

SPL meters are inexpensive, and can save your ears.  Keep one by your mixing desk and check it occassionally throughout the day.  Its also good to calibrate your listening system so that you know where certain levels are located on the knob (relatively close obivously).  Setting your “normal volume” to around 80dB will ensure that you are safe for the whole day.

Anyone working in a studio knows that sometimes during the day, its time to listen to the song really loud once through (not only to pump the band up, but also to hear what the song sounds like at that volume).  This is fine!  Just make sure it doesn’t drift above 100dB too much, and that you substitute some sub-80dB listening in parts of the day to make up for it.

More on SPL meters and decibel ratings in the future.  Any quesitons? Post them here.

C

The Studio Files

This academic stuff is a tough sell.

But!  As boring as this stuff can be, its really important.  I’m going to breakdown the complicated human hearing system into three parts to give you a basic understanding of what’s going on.  I’m writing this article as sort of a preface to some upcoming posts (about things like safe listening levels and how to protect your hearing).  Honestly, if you are working in audio, you should have a basic understanding of your own hearing system.

It’s best to think of the human hearing system as having 3 distinct sections: The Outer Ear, Middle Ear and Inner Ear.  (click for fullsize pic)

(“Ear.” Wikipedia.org. 20 Nov. 2008 <http://en.wikipedia.org/wiki/ear>. Colored lines added)

The Outer Ear (RED)

The outer ear is comprised of the Pinna (the outer part of the ear), the Auditory canal (ear canal), and the surface of the tympanic membrane (ear drum).  The Pinna directs sound into the auditory canal, which in turn begins to vibrate the ear drum.  Simple enough right?  Its good to note that at this point, the energy from sound is acoustic energy until it hits the ear drum (tympanic membrane)

The Middle Ear (BLUE)

The middle ear is made of the tympanic membrane and the ossicles (three bones of the middle ear: malleus, incus, and stapes).  There are other parts to consider (Eustachian tubes, labrinyth, etc…), but the ones I listed are the most important.  The middle ear’s job is to convert the acoustic energy coming in from the outer ear into mechanical energy.  The ear drum (or tympanic membrane) moves back and forth, causing the three bones to vibrate in turn.  The final bone, the stapes, is connected to the inner ear (at the oval window) where the energy will be converted into electrical.

The Inner Ear (GREEN)

The inner ear is the most complicated part of the ear.  Its most important parts (for this discussion) are the oval window, the cochlea, and the basilar membrane (which is located inside the cochlea).  We know the stapes connects to the cochlea at the oval window, vibrating it back and forth.  The cochlea is a spiraled, fluid-filled bone cavity.  Running the length of the cochlea (inside) and dividing it lengthwise is a thin membrane called the Basilar Membrane.  On the basilar membrane, you will find thousands of tiny hairs, which are one of the most important parts of our hearing system. The hairs, among other things, aid in the process of translating the mechanical energy into electrical, which can then be sent to the brain. The vibrating stapes causes the fluid to vibrate, which excites areas of the basilar membrane.  The basilar membrane also responds to frequencies at different areas along its length (more high frequencies at one end, more lows at the other).

Phew! Got through it.  Here’s a summary

• Sound comes in ear, makes the ear drum vibrate.  Ear drum vibrates the 3 bones (ossicles) of the middle ear.  The last bone (stapes) pushes in and out on the cochlea (at the oval window).  The now vibrating fluid inside the cochlea excites the basilar membrane (and the hairs on it), and transmits that data to the brain.

In upcoming articles, there may be some references to information in this article (such as when I do the article on protecting yourself form hearing damage).

If you have any questions on the material here, OR if you would like deeper information on any part of the hearing system, please post in the comments.

C

The Studio Files

You’ll notice in these pictures I have made some pink diffusers for the ceiling. If you really want to know how to make them, I will share them in another article, but I will warn you: they take like 6 hours a piece to make, they are super annoying, and your hands will hurt very badly when you are done… That being said, they work extremely well and cost about 14$ a piece (for materials). Post in the comments here if you want a full article on them.

First the pictures, then let’s talk technique.

Matt (the drummer) had a 3 tom setup with a fair amount of cymbals. His drums sounded OK, but we spent about an hour tuning them, adding moon gel to the toms/snare, tuning the kick, adding more padding, etc… As far as “acoustic treatment” for the room (and I use that term with caution…), I started with the ceiling diffusers, then added some pillows to the bay windows. Across from the drum set (not pictured) about 14 feet back is a big, flat wall. This was going to be a huge “slap” problem, so I took a big mattress and propped it on top of a couch (long ways), and it effectively blocked the whole wall with padding (worked great!!). The big pink things on the windows are just extra foam I had leftover from the diffusers. My hope was that by hanging them at opposing angles, they would help the slap off of the windows. I think they helped.

My first concern was getting a good overhead position. I was a little reluctant to do a spaced pair for two reasons: the diffusers stuck down too far (plus the low ceilings) and with the close walls, there’s a bigger chance for nasty reflections. I ended up sticking the two large diaphragm condensers in between the sets of diffusers and angling against each other about 105-110 degrees. (Picture 2) The room mics were a spaced pair of omni’s about 10 feet back as well as the stereo ribbon from Sontronics (which we ended up using in place of the omni’s).

The rest of the mics were fairly self-explanatory: MD421′s and the like on the toms (few inches off the head, usually angling somewhat towards the center of the drum), an SM57 on the snare top, and an SM81 on the bottom (also an 81 on the hat).  Kick drum was taken care of with a Yamaha Sub Kick outside and a Beta 52 inside, pointed at the beater.

As you will see in the “drum mixing” article which will follow eventually, I embrace a lot of the inevitable bleed.  I rarely use gates.  Given the circumstances (of recording in a basement), I found it better to go into the project knowing that I am going to be dealing with bleeding.  To me, with too many gates running, it sounds “fake”.  Bleed is inevitable, let it happen.  (That being said… a snare mic with more cymbal than snare is obviously less than desirable).

I am not on the computer with the audio files… I will try to get some examples of the drums up here tomorrow.

More to Come

C

The Studio Files

Questions/Comments? Post in the comments here or email me.

These tips will help you minimize those issues, so you can get more accurate mixes from your room.

When setting up your room, there is somewhat of an ideal spot to place yourself (if you have the liberty to do so). Try to place the listening position 38% of the longest dimension in the room (assuming it is a rectangle. That is, if your room was 10′ x 6′, you would want to sit 3.8 feet from either the front or back wall. This will help you “dodge” the nasty room modes which can ruin the low end of your spectrum.

Now, for speaker placement. Your speakers should be placed around the same height as your head is at the mix position. They should form an equilateral triangle with your head (and if you are getting really picky, the back of your head). So that means the distance from one speaker to the other should be the same distance as from your head to either speaker. If everything is in this equilateral triangle spacing, the speakers should also be at 60 degree angles towards you. If you have the space, try to keep your speakers as far away from the walls as possible. Obviously, sometimes space is limited so we have no choice. When speakers are placed too close to walls, they can start to build up low frequency energy, and cause inaccuracies in the room (especially the low end of the spectrum).

Parallel walls and small room dimensions can plague the home studio owner. However, with a small investment into some acoustical treatment, you can negate a lot of these problems. Try an Auralex Roominators kit and a pair of MoPads. Together, these cost less than $200, and can really help “flatten out” the response of your room. The roominators kit has enough panels (and glue) to treat the first reflection spots of your room (to help with flutter echo and other problems). Isolating your monitors with the MoPads will make your monitors much more accurate in the low end.

The easiest way to find your first reflection points is to find a friend and a small mirror. Sit in the mix position (with your speakers properly placed) and have your friend slowly hold the mirror against the side walls and slowly move it back and forth. When you see the reflection of your speakers in the mirror, mark the spot, because those are the points to treat with your Roominators Kit. I would start by treating the 4 walls of the room (leave the ceiling for another day).

If you’ve noticed, many of the issues I am discussing here deal with the low frequency energy that can build up in a small room. Many rooms need “bass traps”, which are specially designed acoustical panels (usually put in the corners of the room) that “trap” the low energy in the corners, thus preventing it from distorting the spectrum at the mix position. Many companies (like Auralex) sell bass traps, but it is also possible to build your own. (I opted to build my own, which I would be happy to share with everyone in another article some time).

All rooms and situations are different, so if you have a room that you need to treat, please feel free to post in the comments here, or email me with questions.

C

The Studio Files