Worship Musician Magazine December 2021 | Page 134

THE BASS TRAP By now , it ’ s probably clear that low frequencies pose the most looming problem in our quest for perfect sound . In large acoustical environments , the low frequencies are often the most destructive . That they contain impressive proportional energy , and that they are dominant in the acoustical environment makes them difficult to overcome .
If the resonances and nodes are controlled in any acoustic environment , the sound is much

Convex

Slatted Wall

Dense Fiberglass
more intimate , and the mixes created are more
pleasing and less imposing . The bass trap is
designed to address these issues .
There are basically three types of bass traps :
• The Helmholtz resonator
• The panel trap / membrane resonator
• The broadband bass absorber
The Helmholtz resonator is simply a large , tuned box with a hole in it that resonates at a specific frequency . Much like a flute , pan flute , or pop bottle , this resonator responds to one frequency . That it resonates at a predetermined frequency , which ideally corresponds to a problem acoustical frequency , helps minimize that frequency in the ambient room sound . Because it takes energy to resonate the box , that energy is diminished in the room . The Helmholtz resonator can be designed for one specific frequency or for a broad band of frequencies .
The panel trap is essentially a wood frame with a thin plywood ( or similar material ) front panel . Fiberglass insulation is often placed in the panel to help increase absorption . The frequencies affected by the panel trap are dependent on size and material density . It ’ s typical to incorporate panels that absorb frequency bands centered at 100 and 200 Hz . This is an efficient way to control modes in the trouble frequency range below 300 Hz .
The broadband bass absorber utilizes a rigid fiberglass material about four times denser than fiberglass insulation . It is often placed behind a
This broadband bass absorber design includes deflection , absorption , and trapping . The angled wall
constructed of wood boards provides reflection control , the dense fiberglass provides absorption , and the
slots between the boards let sound in without providing a direct path for reflection to re-enter the room .
wall or other structure . I have used an effective design that incorporates an angled back wall made from varying sizes of wood boards spaced at somewhat random distances from
sessions . Whether tracking or mixing , address these issues so your music can have the best possible chance of impacting the listener with the power and emotion you know it deserves .
each other ( between 0.5 and 1.5 inches ). In this
design , the boards act as random resonators , the heavy fiberglass ( often Rockwool ) absorbs efficiently , and the slatted design allows low frequencies to enter the void behind the boards . The low frequencies are effectively trapped and absorbed .
MONITORING : TURN IT DOWN
In a live show , the volume is guided by management , leadership , or any number of other factors . However , in the studio , the louder your system is , the more opportunity there is for destructive acoustic interaction .
The sheer amount of energy in any acoustical
TUBE TRAPS
environment determines how strong the
Physical
structures
within
the
acoustic
modes and nodes are . If you monitor at a
space provide the best diffusion of otherwise detrimental waves . Though soft surfaces
minimal listening volume , the effect of your room is minimized .
dampen high frequencies , the low-mids , which
can be most damaging to sound , must be diffused or deflected to ensure a smooth , even frequency response .
Of course , as indicated by the Fletcher-
Munson curve , we hear the most accurate balance of high and low frequencies when
we listen at about 85 – 90 dB . But , this takes
When absorption panels are hung on the studio walls and tools like the Studio Trap or
into consideration that the listener is in a wellcontrolled and acoustically trustworthy room .
baffles are used to confuse standing waves , the
sounds you record are easier to mix . Suddenly , your recordings sound more like the hits you hear on professional recordings . To overlook these considerations is to create a troublesome situation for your recording and mixing
Many highly experienced and successful mix engineers monitor at a minimal volume for most of the mixdown process , turning the system up to 90 + dB only occasionally to check the low-frequency content . Turning the
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