The outdoors is the worlds best natural absorber. No reflections except from the ground. Why do you think ABSORPTION is rated in SABINES...1 Sabine=1 sq ft of ....well, OPEN WINDOW!!
But have you ever heard music recorded outdoors. Its DEAD. FLAT. LIFELESS...why do you think they call a room with good recording acoustics, a "live" room?)The fact is, tests over the years have confirmed, people subjectively LIKE certain types of reflection when it comes to listening to music. However, it is the QUALITY of the reflection that people like...which for live music, is referred to as a "diffused" sound. The study and analysis of the worlds greatest "music halls" have confirmed that it is this "diffused sound" which gives it its "quality". But without understanding what it is that is "diffused", you can't understand "quality", or what creates it.
This is a very difficult subject. But let me touch on a few of the important issues concerning recording/mixing spaces.
When an indoor space is "excited" by sound, some interesting things take place. When sound encounters a boundary such as a wall, some of the energy is absorbed by the boundary, and some is reflected at an "incident" angle, which is similar to a billiard ball bouncing off a pool table bumper(ray effect). However, a room has SIX boundarys, all of which are the recipient of DIRECT sound waves as well as these REFLECTIONS off adjacent and parallel surfaces. As it takes time for sound to travel, and sound looses energy proportionately to the distance traves, as it bounces around the room, it slowly looses the ability to excite your ear drum. In other words, you can't hear it anymore. This DECAY of the sounds energy IN AN ENCLOSURE, is refered to as a rooms RT-60....which is the TIME it takes for sound in a room to DECAY 60db. It is this decay which we call...REVERBERATION.
However, because of a rooms dimensions, the RATES of decay for different frequencys can drastically change the QUALITY of the RT-60. Let me explain some things to you. When a sound is introduced between TWO PARALLEL surfaces such as walls, if the distance between these two surfaces MATCH a WAVELENGTH of sound, a "resonance" or...STANDING WAVE will occur.
And because all SMALL rooms have 3 dimensions(width-length-height) which match the WAVELENGTHS of some Low Frequencies, these frequencies create whats known as ROOM MODES. And these MODAL frequencies are the most troublesome because they are RESONANT...in other words, they "dominate" the RT-60 of the room. Not only that, but because frequencies with ONE HALF wavelengths matching a rooms dimensions, create a NULL(or anti-node)at exactly ONE HALF(1/4 wavelength the dimension of the room...ie..NO SOUND!(not completely correct but good enouigh for this explanation) you now have TWO problems with low frequency wavelengths whose RT-60 DECAY is contributing to the overall "quality" of the soundfield.
The THIRD problem in small rooms is the MODAL occilation. Because room modes terminate in CORNERS(wavelength vs dimensions)it is the corners of the room where low frequencies "collect"...not a completely accurate term, but..good enough. Ha! Hence "bass trapping" in corners. However, lets look at the RT-60 decay characteristics of a room designed for "quality".
When one looks at a modern visual representation of a SMALL rooms RT-60, such as found on modern room analysis tools, a graph is displayed of a broadband(white noise) sound DECAY, which shows the various frequencys starting point(in time and spl), and the time it takes for the various frequecies to decay 60db. It has been discovered that the RATE of decay for different frequencies do NOT occur EQUALLY. Because of this, typically, small rooms exhibit a "boominess" in the low mid/low frequency RT-60. This is why small rooms do NOT have a "diffused" sound field, as it is DOMINATED by low frequency DECAY. Hence, recordings made in these rooms typically are also endowed with the footprint of the room. Needless to say, the holy grail of small rooms is this HOMOGENEOUS DECAY...ie. DIFFUSION...but alas..physics being what they are...
those of us who do not have a 5000 cubic foot room to record in are left to scratch our heads about what the hell is the problem.
Hence this forum.
But there is MORE. When a Microphones diaphram is excited by sound in a room, it not only reacts to the DIRECT sound, it also reacts to the sounds that have reflected off nearby surfaces..be it a table, floor, ceiling, wall..whatever. However, BECAUSE there is a difference in the PATH LENGTH between a direct sound and the reflected wave of the same sound, the reflected sound arrives at the diaphram can arrive OUT OF PHASE with the direct sound. The result of this creates a "reinforcement/cancellation" of various frequencys.
This effect is called COMB FILTERING. You can EASILY discover and hear this effect by talking into a mic while wearing headphones. As you speak or sing, start in the middle of the room, and slowly walk towards a wall untill you are directly in front of it. You will hear the sound change. Hence the importance of understanding "comb filter effects" on your mic placement.
Needless to say, recording outdoors offers no advantage other than absorption/lack of comb filter effects. What it CAN"T offer, is a DIFFUSED RT-60..or QUALITY.
Unless you add ambience via electronics...OR, simply like a DEAD quality, then recording in an enclosed space is the method of choice for most people.
However, understanding WHY and HOW the room effects the recording is paramount to creating "quality" sound ON the recording. This understanding gives you the tools to MODIFY the room in order to improve its SOUNDFIELD as well as Mic placement techniques.
But there is even MORE.
Lets say you are one of the typical recording enthusiasts who are only endowed with ONE ROOM in which you must "host" the musicians, as well as MONITOR the sound you are recording. As most "home recording" enthusiasts know, this is difficult at best, as feedback between Mics and monitors(speakers)prevents listening to the sound over speakers. Not to mention trying to deciper the "monitored sound" from the "live sound". Therefore, the method of monitoring is reduced to monitoring LIVE sound over headphones. Now, most HR wanabe engineers have discovered, that even in headphones, HIGH SPL sound bleeds into the headphones. Even acoustic sounds can overcome and blend with the sound in the headphones. Hence the desire to "isolate" the LIVE sound from the monitoring environment, which is a no brainer why another room is chosen for this environment, as it places a barrier between the live and monitor soundfields.
Most of us HR enthusiasts are lucky enough to have ONE room, but having TWO rooms at our disposal is a real luxury. If you are so endowed with this luxury, you go about setting up this "monitoring environment", thinking WOW! Now I can hear the sound in the "studio", without the "live" sound affecting what I hear on the monitors. TRUE RECORDING NIRVANA!!!
BUT, as many of you know, you soon discover that even given this new found "isolation" freedom, something is amiss...something is still missing(or added) to the recordings, as when you playback these recordings on ANOTHER SYSTEM, in a totally different room, something is DIFFERENT than you heard in your OWN monitoring environment...ARRRRGGGRRRRRRRRRR! WTF!!!! And no matter what you do, you can't seem to "EQ" the mix whereby it has this "elusive" quality when played on a target system. You know what that is ...right? No...well, your TARGET is the CONSUMER!! RIGHT? Hmmmm, wait a minute...if the CONSUMER is the FINAL ARBITER of the sound he hears, AND he can EQ it to fit his own SUBJECTIVE approval, WHAT the fuck are we trying to do???
My friend, welcome to the land of engineering CONFIDENCE.
Well, maybe thats not the correct term, but it will suffice. This is the point. If we have NO confidence that our recordings TRANSLATE EQUALLY, to a variety of systems and room types, then we are constantly fiddling with the mix trying to find that ELUSIVE quality that DOES translate. And what IS this elusive translation quality?? What do you think the point of this and other forums on this BBS IS??
In that context, let me offer this last bit of "studio building and display" insight. When you are monitoring in a seperate control room, and are lucky enough to own an isolated environment whereby the transmission of sound from the live room to the control room is good enough that you ONLY hear the sound of the monitors, you have now hurdled but ONE of the many paths to "translation nirvana".
In light of this aquired ability to monitor the studio sound, independently of the studio sound, you go about your business of recording only to discover this new found freedom does little to the final result, other than give you proof that it has had little effect on your ability to "affect" the final result. And why is this? Without writing a book on the subject, which I'm by no stretch of the imagination an expert on anyway, lets look at what is happening in this "independent" monitoring environment. As you listen to the monitors replication of the "soundfield" in the adjacent room, guess what is happening in the control room? You got it. The same things that are happening in the "studio" room. Reflections, standing waves, comb filtering, modal response and RT-60 UNEQUAL decay. Amongst others.
And that is the point. IF, the control room ACOUSTICS, masks the STUDIO acoustics, you have NO WAY of hearing the TRUTH. If it lies to you DURING the recording, then it also lies to you during MIXDOWN. Its like this.
If, you have control room reflections(comb filtering) off the sidewalls, ceiling, floor, rearwall and console face, that effectively arrive at your ears PRIOR to the comb filtering you are TRYING to hear IN THE STUDIO, then you can't hear them truthfully as the control room acoustics are MASKING the comb filtering taking place in the studio. If the control room RT-60 is LONGER than that of the adjacent studio, then how can you tell what it sounds like in the studio? Comprende? And then you have the mixdown. If the control room acoustics LIES while you are recording, it lies to you during mixdown AGAIN!!
Suffice to say, its beyond the scope of this reply to delve into the various solutions to these problems. All I can say that hasn't already been said a million times, is you MUST TRUST YOUR MONITORING environment. If you can't, then welcome to the land of disheartened HR enthusiasts. Otherwise, do yourself a favor and start reading about these subjects. You will discover, there IS a land of HR NIRVANA. And btw, ABSORPTION is your friend in small rooms.
Now my disclaimer., I ain't no stinkin expert, and ALL opinions expressed are subject to correction and displeasure from those who ARE!! nuff said.
fitZ
