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The causes of poor Room Acoustics are :
- Bass Standing Waves / Room Modes & SBIR -
cause peaks and dips in bass response and boomyness at certain frequencies (ie.. long decay times). These issues lead to an un- even & ill defined low frequency response (‘mushy’ bass, boomy bass, or bass that’s lacking punch and definition). - Mid and High Frequency Reflections-
cause comb filtering when the direct and reflected signals are combined, which in turn leads to inaccurate sound reproduction and poor stereo imaging. A reflective room causes poor music and speech intelligibility due to long reverb times (RT60) and loud reflections.
For detailed explanations about Room Modes & SBIR and Mid and High Frequency Reflections
for Studios and Home Cinema -
ACOUSTICS EDUCATION
Working out what treatment your room needs :
Bass Frequencies :
Excellent improvements can be made to a room’s acoustics via the use of mode calculations to predict bass resonances, which in turn provides the information needed to determine where best to install bass traps and what type of traps to use.
However, if using a space for professional purposes (production, mix or mastering
rooms), or when a very accurate and great sounding space is wanted (eg high-
Mode calculations will give a list of the predicted bass resonances / problem frequencies. From experience in testing rooms and comparing the real world test results to the predicted mode calculation results the problem bass frequencies identified in room testing are usually close or very close to the predicted problems.. so mode calculations are a useful method of homing in on which frequencies are most problematic in a room (and therefore what treatment should be used to control them).
Here are couple of good online room mode calculators -
Bob Golds Room Mode Calculator
Or email us your room dimensions and we’ll run the mode calculations & come up with a treatment plan for you.
Please see our Room Modes & SBIR Explained section for detailed information.
Simple Customer Room Testing for bass problems :
Customers can run simple tests to identify which bass frequencies are problematic and where to trap for best results. This information then forms the basis of the advice given and specifically which of our products should be used where in your room.. ie targeted room treatments.
The most simple bass test is to download this pink noise file :
And play it back through your system at an average listening level (so that the bass
is driven as per usual listening levels -
• Vertical corners
• Floor / Wall junction corner
• Wall / Ceiling junction corners
• Also check rear wall (behind listening position) and front wall (behind speakers)
Basically a full sweep of all the room’s boundaries should be undertaken while the
pink noise is playing back. Where the bass is loud is where to install the trapping
for best effect. An SPL meter (set to C-
Because low frequency bass peaks and dips (sub 100hz) are usually the most problematic and difficult to treat issues the best approach is firstly find out what the lowest frequency problem is that your room has, and then treat corners using products that are effective to that frequency. To identify which frequencies are building where in the room steady or swept sine waves can also be used. Please contact us for links and details for performing sine wave testing.
Mid and high frequency reflections are very easily controlled using correct ‘reflection
point’ treatment, so the bass end is the proper starting point when deciding on which
type of treatments need to be used where for a given space -
If you happen to have room test data available we’re happy to do a free / no obligation
basic analysis on it to form the basis of treatment advice -
Please see the link below for details of how to perform room testing, as well as some helpful links to youtube videos for both setting up and running tests with RoomEqWizard and Fuzzmeasure :
YouTube video on Calibrating Soundcard in REW
YouTube Video on Setting Levels in REW
Youtube Video on Making Measurements in REW
Youtube Video on Fuzzmeasure Basics (with links to how to set up, set levels and make measurements)
Please note that Calibrating isn’t 100% needed to get started with room testing initially.
Also, unless you have an SPL meter you can skip setting the levels -
The speaker output volume should simulate normal listening / working levels in order
to drive the room as per day to day conditions. This should ideally be done using
an SPL meter to set speaker volume at 79db (spl meter set to c-
For rooms where exact / repeatable measurements are required an SPL meter will be needed.
Please see our room testing page for a step by step guide. The Consultancy and Acoustic Testing Guide pages may also be of help / interest.
Low Frequency Treatment :
Bass Resonances / Room Modes are usually the dominant problem in most domestic / studio control room sized spaces, and are therefore the best place to start when planning to treat a room.
The optimum places to treat to properly control bass response and decay times are :
• Room Corners -
• Rear Wall -
• Front Wall -
• Ceiling for room height related modes -
* Example Room Plan showing Bass Trapping Treatments only :
For more information on bass treatment please see our Room Modes and SBIR Explained page.
Further information can be found in our Acoustic Testing Guide.
The Solutions
Working out what treatment your room needs :
Mid and High Frequency Reflections :
Loud mid and high frequency reflections that bounce off reflective room surfaces and arrive at the listening position out of time / phase with the direct speaker signal cause poor frequency response accuracy and poor stereo imaging.
Treating mid / high reflections is very straight forward using thin panels -
To give sufficient coverage a minimum of a 4ft x 4ft treated area should be located
at each reflection point (eg 2 x BF-
- Wall behind listening position
- Left & right walls
- Ceiling
Finding reflection points :
The best method to find the exact locations of loud early arriving reflections is via the use of the ETC in room testing software. However a more simple approach, which will usually deal with the worst / loudest reflections, is the ‘Mirror Trick’.
To use the mirror trick sit in your listening position and ask a friend to hold a
mirror against side walls, ceiling and back wall (concentrate on one surface at a
time). If you can see a speaker in the mirror you’ll get a reflection from this area
-
You will usually end up with treatment in the locations shown in this plan :
Be aware that corners pose particular issues in mid and high frequencies too -
Adding in the corner traps gives a fully treated acoustic solution :
Mid & High Frequency Reflection Treatment :
Treating mid and high frequencies and controlling RT60 times is a straightforward
task using either 3” (BF-
For critical listening spaces (studio control rooms and hi-
Main reflection points are :
• Left and Right walls as facing speakers -
• Rear wall
• Ceiling between listening spot and speakers
Example Room Plan showing Mid / High Reflection Point Treatments only :
For an in-