I've been in a band all but two months of my bass career. I played in a band called Karetaker for almost 20 years. We were a very serious band. We worked very hard to be the best. Our originals were very intricate and complex. We were a three piece band that played out constantly for many years. After a while it just wasn't fun anymore. The guitarest and myself started moonlighting with other bands. I joined a band which is now known as Steel.
We have a lot of fun in Steel. We are currently playing the clubs almost every weekend. The guys in the band are all very tight and very good friends... it's great! We do original material and covers by: Maiden, Priest, Rush, Dio, Sabbath, Queensryche, Led Zep, Uriah Heep, just to name a few. Playing bass is fun again. We drink plenty of Heineken
when we play and make no apologies about it. Like I said, we have a lot of fun. I figure I have at least 10 good years left to play, and I intend on enjoying every minute of it. It's been one hell of a ride so far... but I'm not ready to get off this ride just yet.
Keep rockin'... and if you live in PA or MD come check out Steel some night. Were not the only ones who have a good time at our gigs!
Articles & Writeups I've posted in Fretbuzz:
To Compress or Not to Compress, That is The Question
How to be a Good Opening Band (Detailed Explanation)
Pyrotechnics & Indoor Firworks Safety
An Aritcle I Had Published in Play Meter Magazine
The Gig With Great White
Yngwie's in a Mood (We Opened For Yngwie Last Night)
If you don't want to read all I have written about acoustics and just want info on building absorbers and diffusers you can click on the links here:
I will add to the list as I get more written.
Questions About Acoustics, Helmhotz Resonators, Absorbers, Soundproofing, ask
What is your question about?
Acoustics, a Collision of Art and Science
By: Dave Magaro
I was crusin along at 100 m.p.h. traveling from Mechanicsburg, PA to Rockville MD.
The year was 1984 and I was on my way to Venemans Music. I had $4,500 cash on me
and I was looking to buy an eight track reel to reel and a mixing console for recording. I
made it to Rockville in my 1978 Trans Am in 45 minutes. The trip should have taken
almost two hours. I arrived at the music store and a few hours later I was heading home
with a brand new Tascam 38 eight track reel to reel, a Ramsa WR8816 board, tape, and
the cords to hook it up. I got it home hooked it up and started playing with it immediately.
This was pretty much the beginning of a long journey for me. I had made a bunch of band
tape using cassette decks to record. Some were good, some were all right and some were
just awful sounding. Now that I had this new gear it would have to be impossible to make
a bad recording.
A few weeks later I took my board and reel to reel over to our practice room to record a
demo tape for us. I had no real plan I was just making it up as I went. I set up the mics for
the drums. Once I had them set visually I never touched them again. I started going
though the kit with the drummer. I was spinning eqs only having a vague knowledge of
what I was doing. Instead of moving the mic I just kept twisting the eq till it sounding like
something I wanted to hear. I never considered the acoustics of the room we were
recording in either. I was too excited for such trivial things. I panned his double kicks hard
right and hard left (what was I thinking, lets not put the critical kicks dead center). I filled
six tracks with drums and then bounced them down to two track stereo. Then I recorded
bass and guitar. By the time I finished them I had to bounce down the bass, guitar, and
drums to two tracks. Strange things were beginning to happen. Even though I only knew
about half what I was doing the drums didnt sound to bad at first. By now they were third
generation and getting washed out. The bass and guitar lost some edge as well but not as
bad as the drums. I noticed quite a bit of tape hiss building up but what could I do at this
point. I pressed on and recorded the vocals. The only effect unit I had at the time was a
delay. I used that thing within an inch of its life. I recorded all kinds of stereo delays onto
two tracks. Then I mixed it down to cassette for a master copy. The content was good,
but the sound was not. I asked myself where I went wrong. The answer was just about
everywhere. I thought the same thing that most people think. If I have the gear it will be a
piece of cake. With the whole computer recording explosion people are getting software,
mics, and other gear. The idea is to record your music yourself. It certainly seems like a
good idea, and it is. However, it cant be approached in the way that I approached it at
first. It takes practice like anything. You also have to know what you are doing to get a
quality recording or even live sound. I am certainly not an expert on this realm. I do have
a wealth of information to share. That is why Im writing this. Perhaps I can help make
your journey a much shorter one than mine was. After years of recording and running live
sound you get to know a few things. The difficult thing is to give enough information that
its useful without getting too deep into the very complicated technical aspect. What the
Hell, lets just dive into the whole thing and see where it takes us.
In the example above of my first real recording mistakes where plenty. Lets start with the
room in which the drums where recorded in. This information will be handy if you plan on
recording, or even if you are just trying to get your practice room sounding great. The
room that I recorded the drums in was 16 feet long, by 8 feet wide, by 8 feet high. That
comes out to 1280 cubic feet. It had carpet on the floor and a drop ceiling. The walls
where wood paneling. This is where the problem began. 1,024 cubic feet is just too small
of room to overcome the standing waves that will exist. So, I guess you want me to
explain to you what a standing wave is huh? Isnt it too soon for you to be this
Lets look at the room I recorded the drums in. 16 x 8 x 8. First
let us look at the 16 section of the room which were the east and west walls. Sound
travels at 1130 feet per second in average conditions. (about 770 miles an hour).
Therefore, we can see that sound would have a finite time to make a round trip from one
end of the room and then back to where it originated from. So we can look at this as 2L
feet. So its a simple calculation that would look like this: 1130/2L Hz. So if we look at
our two walls 16 feet apart we can do a simple calculation as seen above: 1130/2x16 =
Hz. So we simple multiply 2L or 2x16=32 feet. Because it will take our sound 32 feet to
make a round trip. Now it looks like this 1130/32 = 35.3125 Hz. So we will call it
approximately 35.3 Hz. The 35.3 Hz is a standing wave. Now that we got through that
you can start to gain an understanding of a standing wave. What this all means is that
sound will resonate between these two walls at 35.3 Hz. But it doesnt end there. For it
will also resonate at every multiple of 35.3 Hz. Ive heard these multiples referred to as
harmonics. Although thats not the case I cant find a better word to describe it so Ill
just use it. Our walls16 apart which where east and west for those keeping score will have
a fundamental resonance of 35 Hz as stated. They will also resonate at the harmonics of
70.6 Hz, 105.9 Hz, 141.2 Hz, 176.5Hz, and so on. That is what a standing wave is.
Great so now we know what a standing wave is. How do we use this to our advantage?
Well, for starters we only looked at one wall. One wall with resonating frequencies is not
going to be much of a problem for us. However, we need to calculate the other two wall,
and the ceiling and floor. If we want to get really crazy we can calculate the Tangential
(two pairs of surfaces), and oblique modes (involving three pairs of surfaces) as well. If
you want to get the far into it you really should buy a book on acoustics. I dont feel you
have to get that far into it unless you are planning on setting up a multi-million dollar
studio. The axial resonance will serve us quite well.
Now that we have the east and west walls calculated we will move onto the north and
south walls. The north and south wall are 8 feet apart. So we use our handy dandy
calculation above to find the fundamental resonating frequency and all the harmonics of it.
1130/16 = 70.625Hz. So we will call it about 70.6Hz.
Then there is the ceiling to floor calculation to be done. This was also 8 feet from floor to
ceiling. This being the same distance as the north and south wall will give us the same
fundamental frequency of resonance of 70.6Hz.
So now that we have this information what do we do next? Now we are going to plot a
chart. This will let us know if their are areas of concern within our room. This might
sound like a huge chart at first. Plotting out all the frequencies from the fundamentals on
up though the spectrum of human hearing could take all night. Fortunately the only area
where standing waves are a problem is in the low end. Our biggest area of concern is
below 200Hz. If there is a stacking of standing waves this is the area that will most likely
be audible. From 200Hz to 300Hz the resonating frequencies will not as much of an issue.
However, that doesnt mean you just ignore them if there is a stacking of resonation
between this range. So lets plot this chart and see what we come up with.
Axial Resonating Frequencies
| E-W WALLS
|| N-S WALLS
Looking at this chart makes me want to go tear down that room. This room is riddled with
standing waves. It is very problematic indeed. Heres a chart that better shows the
Axial Resonating Frequencies
| E-W WALLS
|| N-S WALLS
You will notice from the table above that we have standing waves that are piling up in
many areas. Notice on the east-west wall that we have a standing wave at 70.6Hz (shaded
in red). The 70.6Hz standing waves are also present within the north-south wall and the
floor-ceiling. It doesnt end there for us as we also have problems at 141.2Hz (shaded in
pink), 211.8Hz (shaded in blue) and 282.4Hz (shaded in yellow). So whats the solution if
you are recording in a room like this? The answer is find another room. This room is less
than 1500 cubic feet and is a standing wave nightmare. The problem with this is that you
may not have another room to record or practice in. This is what you have so if you cant
move then you need to treat the room. As if we didnt have enough problems with this
room heres another little fact that hurts. Where we have the standing waves we will have
an unnatural boost in these frequencies. To add insult to injury there is separation of the
frequencies as we move away from the standing wave frequencies. What this all means is
that we will get and unnatural boost near the resonating frequencies, and as we move
away from it will become unnaturally depressed (much like the author of this).
In the above example we can clearly see that we have an extreme problem. The solution is
that we need to diffuse the problem areas. High end is easy to diffuse. Its small
waveforms are diffused easily by carpet and many other materials. The higher frequencies
are simply to get under control. The carpet and drop ceiling did just fine in our example
room. The standing waves in the low end are the real issue with this room. Is all of this
giving you a headache? Maybe you dont want to have to be a mathematician to solve
your rooms problems. Then the answer for you is to build some wideband absorbers and
some simple low end diffusers. Wideband absorbers are simple to build and they do a great
job. They will absorb frequencies for 125Hz to 4kHz. These things work great! I think
they should be in every practice room there is. However, even if we built a bunch of these
and hung them in our example room it wouldnt help the 70.6Hz resonating frequencies. If
we truly want to address the problem in this case we would have to build a tuned
resonator. For this application we would be building what is know as a Helmholtz
Resonator. Personally I would be building tuned resonators for all our problem
frequencies in this room. However, I would start with the 70.6 and 141.2. I would hang
them and listen to the room. You cant just pull out a tape measurer and tune a room. You
have really listen to whats going on in the room. The current room we are practicing in
and recording in is a great example. The room was remodeled and we intended to get it
set up to record in. We were practicing in the room and I was really listening to the sound
of it. It was obvious at first that it needed some treatment. We started putting up
wideband absorbers a few at a time. We put them up until we were happy with that aspect
of it. Again we were playing in the room and I was really listening to how it sounded. I
noticed that my bass was getting an unnatural boost in amplitude at certain places on the
neck. This is when I broke out the tape measurer and did the calculation to find out if we
had standing wave issues. Sure enough we did at 100Hz and 145Hz. I checked to see if
this was indeed where I was hearing the unnatural boost with a frequency chart as I knew
what notes I was playing when I heard the boost. The 100Hz matched up with what I was
hearing and what I measured. I built two Helmholtz Resonators to overcome the standing
waves. One tuned to 100Hz and one tuned to 145Hz. Because of the wideband absorbers
we had built the 145Hz was not nearly as bad as the 100Hz standing waves. The one
Helmholtz Resonator at 145Hz was the icing on the cake. It did the job so we will not
tune another resonator in this area. However, the 100Hz remains an issue. I will be
building another Helmholtz Resonator tuned to 100Hz to address this problem. I will build
it, hang it, and then listen to the room for a while. After all, it is your ears that have to be
the final judge of what sounds good. I will go over all the how to build resonators,
diffusers, and absorbers later on in this write up.
Im going to sidestep from the whole acoustic discussion for just a moment. I dont want
you to lose site of the forest through the trees. This is obviously going to be a long write
up about acoustics. It is a very complex issue that I am desperately trying to simplify. Bear
in mind that in my first real recording the room was not the biggest factor in the poor
quality recording. I could have been making that recording in the best sounding room in
the world and it would have still sounded bad. It may have sounded better, but still not of
the quality that it could have been. A good sounding room will not make up for poor
micing technique and haphazard equalization. A good sounding room can not overcome
poor planning and execution. A good engineer can overcome much. The two most critical
tools at an engineers disposal are his mind and his ears. On the flip side of that I dont
want to make it sound like the room sound is unimportant. A good sounding room is a
critical part of making a high quality recording.
Acoustics, Legend and Lore
In the example room of my first recording something really jumps out at us. The
north-south walls are the exact same measurement as the floor and ceiling, each at 8 feet.
The east and west walls are a multiple of 8 at 16 feet. This is exactly the kind of room
you want to avoid for recording. It would have been a problem if only two were either the
same as or one was a multiple of the first. So if you are playing in a square room you are
going to have standing wave problems with the room. If you have two walls 10 feet apart
and your ceiling is 10 feet high its going to be a problem for you.
In the past some people have splayed or skewed walls. For example: Say we decided to
skew our west wall in our example room. We decide to skew it one foot. One end of the
wall would be our original 16 feet, and the other end would now measure 15 feet. We just
put the wall on an angle. Is going to help? It will reduce flutter echo and may help to some
degree with the degeneracies (coincident frequencies). However, it will also shift our
modal frequencies to some unknown realm. Walls are generally splayed between 5 degrees
and 12 degrees. 5.7 degrees and 11.3 degrees are the most commonly used in studios to
my knowledge. I wouldnt recommend this unless you are building a studio from scratch.
We can solve the standing wave issues with absorbers and diffusers. Although our
example room is riddle with problems, chances are that your room will not be the drastic
of a case.
- The best way to hear flutter echo is to go into a large room with
hard reflective surfaces. Clap you hands and you should be able to hear the flutter
afterwards. Flutter echo in a studio will increase the reverberation time in a room.
Also know as our Coincident frequencies. This is just a fancy way
of saying the frequencies are piling up. Look at the chart below. 70.6Hz, 141.2Hz,
211.8Hz, and 282.4Hz would be our Degeneracies, or Coincident Frequencies in our
Again refer to the chart below. All the other frequencies
would be our model frequencies. On this chart they would be 35.3Hz, 105.9Hz, 176.5Hz,
Axial Resonating Frequencies
| E-W WALLS
|| N-S WALLS
Back in the good old days studios where large areas. They were predominantly large
rooms where the recordings where done. As multi-track came along things changed.
Studios started going with small rooms and isolation booths. Drum booths became all the
rage. This was a bad idea from the start. As weve plainly seen small rooms are just far too
troublesome to record in if we are shooting for a high quality recording. Most studios
have turned those drum booths into vocal booths to record singers in. I walked into an old
home recording studio years ago. When I walked into the recording room the only word I
can use to describe it is groovy. This studio had shag carpeting on not only the floor,
but on the walls and ceiling as well. There were no absorbers, or diffusers of any kind. Just
shag carpeting everywhere one looked. If you are checking out a studio to record in and
you see this scenario I have but only one word of advice for you. RUN!
If you walked into a room that had concrete walls, a concrete floor, and a concrete ceiling
it would be very reverberant indeed. If you had a small rubber ball and you threw it on the
floor at a certain angle it would bounce off the floor at the same angle that you threw it at.
Light waves will do the same thing, and so will sound waves. Sound waves are rising and
falling above and below atmospheric pressure but they follow this same basic principal.
The ball would bounce around the room until it finally lost energy and came to rest. A
sound wave will bounce off the walls until if finally loses energy and the air molecules
(which are the medium in this case) would come to rest. If we take a tennis ball, a basket
ball, and a giant beach ball they all do the same thing. They bounce, lose energy and come
to rest. However, if we lay carpet on the floor and do the same thing. We notice that the
small rubber ball would lose much more energy than the tennis ball. The basket ball would
bounce about the same, and the giant beach ball would be unaffected. And yes a large low
end sound wave would bounce right off the carpet as well.
A dead room is not what we are striving for here. We do not want to fill the walls with
absorbers and diffusers. Worse yet we dont want to absorb all the high end and leave the
midrange with minimal absorption, and no absorption in the low end whatsoever as in the
shag carpet studio. Whatever room you are playing in right now has a certain unique
sound to it, a certain color if you will. The color of that room is going to be printed to
your recording medium (tape, computer, hard drive or whatever). As soon as you put a
microphone in that room to record something, that color is going to be there. I dont care
how loud you turn up, or how close you put the mic to the source the color of that room
WILL BE PRINTED TO YOUR RECORDING MEDIUM! So it only makes sense to get
the room sounding as good as it can.
Acoustics IS a collision of art and science. I like things to be precise. Its just not the way
in the world of acoustics. It drove me crazy at first. I couldnt stand hearing words and
phrases like: This is in the ballpark or This will get you close or Approximately. If I
was building some small wooden boxes to put on the wall for some diffusion. I would
want them all to be the same size and same distance apart. Then they would look all nice
and pretty. This is the complete opposite of what you should do. The boxes should be
built random sizes and placed random distances apart to achieve the best diffusion.
Random is the key. The exception of course is a tuned Helmholzt Resonator, where the
holes or slates would be precise.
Absolutely avoid concave surfaces. Did you ever see one of those guys at a pro football
game holding one of those microphones with what looks like half a bubble around it.
Obviously this focuses the sound into the microphone. You do not want to focus sound in
your room so avoid them completely.
Size does matter. Every room will have a cutoff frequency. In
the high end above the cutoff frequency is not the issue. The model frequencies become so
close together that they merge and will yield a smooth response. Below the cutoff
frequency on the low end is where the trouble can be. The model frequencies can become
too spaced out and yield an uneven responses. Larger less reverberate rooms will have a
lower cutoff frequency. I never calculated the cutoff frequency of our example room. But,
I can promise you that it was above 40Hz. If you were setting up a commercial studio this
is probably something you should know. For the rest of us I think we can get by without
knowing what our room cutoff frequency is. Again, if this is something you want to
calculate then you really need to buy a book on acoustics.
A snare drum is a great instrument to evaluate a room. It is a wideband instrument that has
a quick transient attack and quick decay. Have the drummer hit it as you stand at different
places in the room. Do you hear it bouncing off the walls? Maybe you need some
wideband absorbers in your room. Bear in mind that a snare is not helpful in determining
standing waves. It will just give you a general idea of what the room sounds like. If your
room is too reverberant you might even hear some flutter echo.
As I stated acoustics and sound are very complicated. I am just scratching the surface
here. I hope by now that you have a pretty good idea what Im talking about. But, now
weve heard enough talk, its time for some action. Its time to correct some of these
problems that up to this point weve only been discussing. In the next section Im going to
explain how to build some of these diffusers and resonators that Ive been talking about.
Building most of these things are not difficult. If you are a fair handy man you should have
no problems with their construction. Furthermore, where not going to break the bank with
these things. I know when people think about acoustic treatments they think they are
expensive. If youre buying them, they are. They sure dont cost much to make though.
These are by far my favorite so I will start with them. If youre not looking to be an
acoustitision and just want to treat a bad sounding room these are for you. If you are in a
room with a lot of hard surfaces I would recommend these to you. You can make them as
fancy as you want. The meat of these units will be the insulation that you use. For
wideband absorbers we will be using Owens Corning 703 insulation or the equivalent of
it. Its basically the same thing as normal insulation only it is compacted tightly. It is 3
pounds per cubic foot of density. Some may refer to it as rigid insulation. These things
will absorb frequencies from 125Hz all the way up to 4kHz! Hence the name wideband
absorber as they absorb a wideband of frequencies. Here is how to build a simple and
effective wideband absorber:
All you do is make a 2 foot by 4 foot frame out of 1x8s. Basically its a 2 foot by 4 foot
box. You can make it what ever size you want but this is a good size wideband absorber
to start with. If you want more absorption you can always build more of them. Now cut
out a piece of plywood slightly under 2 feet by 4 feet for the back of our box. You can use
a thickness of 1/4, 3/8, 1/2, or whatever you have on hand. The plywood thickness is
not a big factor. Make sure the frame is square. Use wood glue, and glue and screw the
plywood onto the 2x8 frame. This will be the back of the box. Once that is done flip the
box over. Now we are going to glue and screw 1x4s to the 1x8s on the INSIDE of the
box. Make sure the 1x4s are tight against the plywood so they wont vibrate and make
any noise. What the 1x4s do is give us a ledge for our insulation to sit on. Next you can
mount it to the wall or ceiling. You can just use long drywall screws and screw right
through the plywood into the studs in the wall, or joist in the ceiling. Just make sure you
hit wood when mounting these things. Next we cut out insulation to fit snugly inside the
1x8s and push it in until the insulation is resting on the 1x4s. This will give us airspace
behind the insulation. The airspace is critical for this thing to work properly. Be sure to
use gloves and a mask when working with the insulation. Its also a good idea to wear a
hat and long pants and a long sleeve shirt. Now all you have to do is cover the front of it
with a loose woven material. Burlap works great, but you can use speaker grill material or
any loosely woven material. You can simply staple the burlap right to the 1x8s. You can
make them as fancy as you want. You can use a piece of trim to cover the staples. You
can paint them, stain them or ever finish the 2x8 frame with Formica. But that is the meat
and potatoes of building a wideband absorber. If you want to make a 4 foot x 4 foot one
its almost as simple. Just add a 1x8 down the center of the box and put 1x4s on both
sides of it. Then basically you will have two separate 2 foot by 4 foot boxes in one frame.
Pretty simple hum? They really work well too. These are the first thing I always
recommend. If you are practicing in a place with concrete floors and walls these things are
going to be your best friend. They will really improve the sound of your room.
See I told you a wideband absorber would be easy to build. But, what if you dont want a
box sticking out off of your wall 7.5 inches (the width of a 2x8 piece of lumber). Can you
make it out of 1x6, 1x4, or even 1x2? The answer is yes. Can you use regular insulation?
Again the answer is yes. You can apply the same principals as we did with the 1x8 box to
a smaller box. What you will be sacrificing is some sound absorption. The same thing
applies to the airspace. The smaller the airspace the less absorption. The smaller the box
the less absorption, and of course the thinner the insulation, the less it will absorb as well.
However, all these sizes will work effectively. The larger ones will just have a greater
impact. If you plan on using normal housing insulation you may want to eliminate the
lumber on the inside that we used for a ledge for our rigid insulation to rest on. Instead
you can zig-zag wire back and forth in the box to insure that airspace will be left behind it.
I built some 1x4 absorbers this way and just ran wire back and forth at the half way point
of the box. A 1x4 is 3 1/2 inches so I just measured a line half way down at 1 3/4 inches
and zig-zagged wire back in forth the entire length of the box. Then I used regular
insulation instead of the rigid insulation. They work very well so dont be afraid to knock
the size down a bit if a 1x8 box is too much for your space. Always keep in mind that you
WILL be sacrificing absorption with the smaller box. The least critical factor of a
wideband absorber will the insulation density. There is little difference between 6 pound, 3
pound, or 1.6 pound per cubic foot of insulation. However, I would still recommend the
Owens corning 703 rigid insulation for a wideband absorber.
So, now you know how to build a wideband absorber. Like I said they are very simply to
build and very effective.