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The causes of poor Room Acoustics are :


For detailed explanations about Room Modes & SBIR and Mid and High Frequency Reflections for Studios and Home Cinema - please see our guides : Room Modes & SBIR Explained & Mid and High Frequency Reflections Guide.


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-end hi-fi rooms) proper room testing is recommended, and will deliver a very ‘flat’ /  true, controlled (and subjectively fantastic) sounding space by ensuring the room treatment is suitable for the issues the room has.

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 - input your room dimensions and they will show the predicted bass problems that your room will have :

Bob Golds Room Mode Calculator

Hunecke 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 :

Pinknoise.mp3

And play it back through your system at an average listening level (so that the bass is driven as per usual listening levels - normally around 79db spl). While the file is playing back check ALL room corners for an increase in volume in bass frequencies. All corners meaning :

• 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-weighted slow) should be used for this test so that relative / accurate readings can be taken, but if you don’t have access to a meter ears work just fine. It’ll be very obvious when you hit on a loud bass zone.

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 - and all rooms are very different / unique acoustically.

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 - just attach the aiff, wav or RoomEqWizard files to an email. If using Fuzzmeasure please export the impulses as aiff and attach them so we can load them up at this end for analysis.

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 :

Room Testing Instructions

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 - just ensure that your speakers aren’t too loud when running the first tests, and increase the mic input gain and speaker volume until you get a good reading.

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-weighted slow), but if you can get in the ballpark on output level you’ll get a useable & useful test result.

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 - vertical corners are usually the best corners to treat first, but corners between floor / walls and ceiling / walls are also very useful (and sometimes critical) for controlling bass properly. BF-612, BF-850, BF-4040 or BF-1200 Traps are best used in corners (exact model to use is dependent on room dimensions and speaker system being used - please contact us for advice on the best products to use for your room).

• Rear Wall - length modes dominate here so thick trapping is normally recommended. ideally BF-175 type.

• Front Wall - behind speakers for Speaker Boundary Interface Response (if required, BF-125 or BF-175 type).

• Ceiling for room height related modes - BF-125 or BF-175 type ceiling clouds are suitable for ceiling treatments

* 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 - although ideally BF-125 type traps should be used as these provide excellent absorption to low mids and below (whereas thin acoustic panels or foam etc may not).

To give sufficient coverage a minimum of a 4ft x 4ft treated area should be located at each reflection point (eg 2 x BF-125s). The main reflection points are :

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 - which means it should be treated. The middle of any treatment used should ideally be located at ear height.

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 - they can cause nasty ‘pingy’ reflections, which will also cause issues in accuracy and imaging. So the use of broadband bass trapping in corners will deal with both bass control, and corner related mid / high problems.

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-075) or 5” (BF-125) deep panels and / or diffusers located in the correct areas of the room.

For critical listening spaces (studio control rooms and hi-fi listening rooms) the main areas to treat are Reflection Points.

Main reflection points are :

• Left and Right walls as facing speakers - the areas between listening spot and speakers

• Rear wall

• Ceiling between listening spot and speakers

Example Room Plan showing Mid / High Reflection Point Treatments only :

For an in-depth explanation of Mid and High Frequency Reflections please see our Mid and High Frequency Reflections Guide.