. . . The thing that kills me is the people who always suggest the sound shields have NEVER played behind one to know what it's really like . . .
Are you sure of that? Do you ask them? Anyway . . .
I e-"stumbled" upon this article while doing research for DIY drum shields for private and professional use. I was amazed at the large number of inaccurate statements that I read. So, I decided to address some of them (even tho' I may be "resurrecting" an otherwise dead topic). Then, having addressed them--to my chagrin--I wiped out my comments by failing to log in.
. . . (I hate reading "nonsense" when I'm looking for sense, even when what I'm reading is "old" by "bulletin board" standards. I'm sometimes compelled to correct some of it.)
So, . . .
First: high frequency sound does not have less energy than low frequency sound. If you take a sound-level meter and measure a pure sine wave at 100 SPL dB(C) at 100 Hz and another at 100 SPL at 10,000 Hz, each measurement is denoting the same amount of energy, just for a different frequency. The frequency of the sound is completely independent of the amount of energy contained by the sound waves. This misconception that high frequency sound has less energy may be due to the fact that high-frequency horns are much more efficient at converting electrical energy into mechanical energy (sound) than lower frequency direct-radiators ("speakers"). Thus, much more electrical energy is used to amplify the "bass" than the "mids" or "treble".
Second: "mic-bleed" and "stage-'volume'" (correctly termed "stage loudness") are interrelated. Sound is simply a mechanical vibration propagating through a medium, or, in lay terms, a "wave" traveling through the air, through wood (in instruments, through a wooden stage floor, etc.), or some other medium (steel, water, glass, etc.). Higher frequency sounds tend to propagate ("move") in more directional patterns and lower frequency sounds tend to be more uni-directional in their paths of travel. Unwanted sound that travels from a source (a kick-drum, a bass-guitar amp, etc.) to a destination (a microphone, the stage under the microphone) is problematic because it: (1) interferes with "picking up" wanted sound (i.e., at the lead-vocalists mic 4' to 20' in front of the kick drum), and (2) gets "picked up" too easily causing feedback.
Third: Any object placed in front of a source of sound (i.e., a kick-drum) tends to: (a) absorb, (b) deflect, or (c) reflect some of the sound. That's all a drum shield is: an absorber (of higher frequencies more than lower), a deflector (of lower frequencies), and a reflector (of mid to high frequency sound).
Fourth: Plexiglass absorbs some sound energy at all frequencies (for this discussion, audio-frequencies, 20 Hz to 20 kHz). It absorbs a higher percentage of higher, treble sounds than it does of lower, bass sounds. BUT, Plexiglass does absorb some bass sound.
Fifth: Because bass sounds (kick drums, bass guitars, tom toms, etc.) are lower in frequency (usually, and somewhat incorrectly called "pitch"), they have longer wavelengths. Sound with longer wavelengths will deflect, will go around and over barriers as well as through them (albeit slightly attenuated). Thus, what bass is not absorbed by the drum shield will be transmitted through it or around it. Or, . . .
Sixth: . . . it will reflect off another surface, i.e. a back wall.
Some of you have noted some of these effects, albeit often naively and usually incompletely. But, to really understand how a drum-shield works (i.e. "The straight fact
"), you need to put it all together.
So, if much of the bass, lower-frequency sounds just go around the shield or bounce off other surfaces, then why do people use them? Because it's the mid and high ranges that are causing much of the problem.
Most microphones used on stage are unidirectional (tend to pick up from one direction better than all others). In fact, unidirectional mics have to be used to get any useful acoustical-gain (amplification) on anything but the smallest stages. But--repeat BUT--so-called "unidirectional" microphones are only moderately directional at the highest usable frequencies. The lower the frequency of sound gets, the more omnidirectional all microphones are. Thus, by combining the use of shields (the cabinet around the speakers in an amp are also a shield!) and directional microphones, placing each properly, properly tuning the PA, and EQing--cutting frequency bands where necessary--we obtain the best "signal-to-noise" ratio possible.
Now, "noise" is any unwanted sound. 4' to 20' in front of the kick-drum, all the sound coming from the kick drum that gets into the vocalist's mic is noise. There's not a lot that can be done about the bass, but deflect it a bit, make it bounce off a rear surface as far a way as possible so the distance attenuates it as much as possible (makes it softer). We sound-people (soundmen, soundwomen) try to turn the bass down as much as possible in the vocal mics. But, we can't turn down the upper-bass (for males), nor the mid-range and treble (for both males and females), otherwise the lead-singer's singing sounds like [expletive deleted]. They, the other band-members, and the audience, tend not to like that. But, along with that "boom, boom, boom" bass coming from the kick-drum, from the toms, from the bass amp, there's a lot of mid-range and treble in those sounds. So, we use directional mics and point them away from the drum set and the amps as much as possible, we stick all the amps in the back, etc. But, at some point, we're still getting too much noise into the vocalist's mic, so, we put up a drum shield.
"But, John, . . ." you say, "the bass just goes through or over or bounces around the shield". Yes, and we can't change that except for turning the bass down in the VOX mics as much as possible without changing the character of the singers' voices. BUT, the shield does not allow the mid-range and treble drum-kit sounds to travel around it (which is why the unmiced- or unamplified-kit sounds like someone is playing it from the bottom of a well, when listening from in front of the shield). The Plexiglas absorbs some directly and bounces the rest back. Sure, the drummer has to deal with that increased sound, but, better him or her than the lead vocalist (unless the drummer is the lead vocalist). But, if you've read closely--and some of you by your comments haven't--tho' some equally or more astute-and-less-verbose posters previously have noted--you will also note that you have to put some insulation around the inside of the shield's panels at the bottom, where it is less visually-objectionable. On a large open-air stage, with multiple mics on the drum in "close-miced" placements, the amount of sound bouncing back from the panels is probably less than that from the drummer's monitors. But, it's not as much a problem as there usually isn't a hard wall within a reasonable distance behind the kit. When it is a problem, those surfaces--on the shield bottom and the back wall--have to be insulated.
But that relative thin (by acoustical standards) shielding doesn't work well at any but the highest frequencies. Indoors, where sound can and does bounce around more, the solution--at least partially--is to make less of it, less sound and especially less noise. That means if you're having stage-loudness ("stage-volume") problems, you NEED to make less sound, and especially less noise and try to deflect, reflect, or absorb it only where necessary. So, if your church is contemplating a "Drum Booth", iso-booth, putting the kit in a separate room, etc. the first thing you need to do is to "TURN DOWN" everyone and everything, including your guitar amps, including your wedge-monitors, etc., including the drums.
But, you need to realize that sound-reinforcement (especially "transparent" sound-reinforcement) is a set of compromises. The noise on stage is the reason why live albums NEVER sound as good as good studio albums. Noise on stage can only be reduced. It can never be completely eliminated. Putting a recording booth onstage to quiet the drums may work acoustically (but not aesthetically, as so many of you have stated, some so none succinctly), but, it's a rather large expense and inconvenience. If just turning down isn't sufficient, then I'd suggest you try a few panels. If the drummer's feeling disconnected, try moving the back-line back so it's a true back-line: move the guitar and bass amps back so that they are behind the drummer (not directly behind; behind a line parallel to the front of the stage, which line is behind the drummer). Try 2 or 3 panels that shield the vocal mics in the front-line, but allow sound to travel straight out the sides (and vica versa) to the instrumentalists (if your bassists and guitar players also sing, then, make them stand in the front line by putting their mics up there, but, leave their amps in the back-line and keep them turned down. If that is insufficient, then add some more panels. Then, . . . a roof for the "iso-booth."
(Almost) Finally, IEMs are a necessary fact of 21st-Century life. We live with ear-damaging levels of noise,: traffic-noise, air-conditioner- and heating-system-noise, TVs and stereos and iPods and iPads and Walkmans (well, only for those MP3-challenged individuals). On any stage in any area where more than 50-100 people can easily congregate and easily hear unamplified instruments, amplifiers will be in use for electrified instruments (electric-guitars and -drums, keyboards, etc.). Any place where instrument amplifiers are in use, unless TURNED DOWN, singers will have to be amplified. Any venue large enough to require a PA--so some or all of the audience can hear--will eventually have a stage too loud (in terms of what is and isn't healthy for our ears). Thus, the best way to quiet your stage is to use In Ear Monitors. Even then, TURN DOWN the IEMs or you'll still go prematurely deaf. A good idea is to get a daily noise-exposure chart and abide by the limits therein (from the point of view of hearing damage, music is noise).
"But, John . . ." you say, " . . . I feel disconnected from my audience when I [insert choice of: (1) "use IEMs", (2) "play behind a shield", (3) any other excuse you think of]. I'll say--right back to you--"Feeling connected with your audience is as much a matter of your perception as it is of theirs. If you absolutely can't use IEMs because you have to hear your amp, then, at least tilt it back at your ears because you're NOT hearing what the audience is. And, if you have to have "more ME", "more my guitar" in the monitors, you may be experiencing temporary hearing loss. Temporary hearing loss--whether from the kid down the street driving up and down the street with his trunk lid flapping in the breeze of his 10kWatt car stereo system with 8 x 18" sub-woofers--or from you saying "turn me up"--that is repeated becomes permanent hearing loss. Learn to play in tune, learn to sing in tune, learn to play and sing in tune and in time with the rest of the worship band, regardless of whether you have to turn down, play in a booth or in the cry-room, etc. That will do more to connect you to your fellow band-members and audience than anything else!
And--even tho' I'm not a member of your church--remember that your church service is not a bar, not a club, not an open-air outdoor concert for which you generally have to buy tickets. It's a worship service and people don't worship well, nor as often, nor willingly, when they go home with tinnitus because you're too loud.
FINALLY: Use a shield! Use IEMs! TURN DOWN! (Use a condom. Brush your teeth. Eat three square meals a day. Take your vitamins, but not mega-vitamins. Etc.)
John Edward Lawton
PS At 58, I am a fledgling ("wanna-be/never-really-gonna-be") drummer, a singer, a fledgling (...) lap-steel player, an oookulele player, fledgling harmonica player, etc. I'm investigating building a shield so I can play e-drums longer, more often, and especially (as I'm a night-person) later at night more quietly, but, also so I can get better live sound onstage. While I love plugging my kit (primarily a Yamaha DD65 at the moment, due to space constraints) into a "stereo-pair" of JBL EON 315s (from my sound reinforcement company), I usually have to compromise and use a set of head phones. I prefer Shure SE215's good price-to-performance ratio.
JEL