RPG Room Sizer Software Many audiophiles wonder, \"What's the perfect sized room\" Is it the golden ratio or something else Room Sizer has been developed to enable the optimization of small room dimensions for improved low frequency performance. The criteria for room size being to minimize the coloration effects of low frequency modes monitored by a predicted modal response. The method is an improvement on previous methods in that the theoretical basis is a more accurate model of the room response than examining the modal spacing in frequency for a rigid box. The system is flexible in that it can search for the best dimensions within constraints set by the designer. Furthermore, the procedure has flexibility in that as better prediction models of rooms become available, they can be used in the general optimization design procedure. Results demonstrate that the new search method produce room sizes that match or improve on the room ratios published in current literature.
With an attractive user interface, easy-to-understand instructions and a host of useful display readouts, the freeware Room EQ Wizard is a must for every studio owner who wants to improve room acoustics, or hi-fi users who would like to tweak their room's sound with a parametric EQ.
If you want a sobering experience after installing your expensive new monitor speakers, try moving them to several different positions in your room and playing back the same CD tracks. Even if you listen from the same spot in the room each time, the bass end will probably sound hugely different with each speaker location, while if you walk around the room listening you'll probably notice even bigger variations, with huge amounts of bass at some spots and almost none in others.
This sort of variation makes a mockery of critical mixing decisions, and explains why so many mixes don't 'travel' (don't sound good on lots of different playback systems), yet many musicians still avoid acoustic treatment because they think it's too complicated. Fortunately, there are various PC utilities that can help you decide what to install and where to put it, and you needn't wait until your gear is in place before you consider acoustic issues, either, since other utilities can help you decide whether or not a particular room will be a good shape acoustically or will be a pig to work with. Even if you're considering building a studio from scratch, you can benefit from such utilities, since they can suggest slight changes in dimensions that will benefit you in the end.
The reason for this is that each of the room dimensions (width, depth and height) will encourage certain frequencies whose wavelengths are related to them. For instance, if your room is 8 feet in length you'll get a set of 'modes' at 70Hz and the harmonics of 70Hz (140Hz, 210Hz, 280Hz and so on), a second set for the room width, and yet another for its height. To stand a reasonable chance of achieving good acoustics, you should try to choose a room whose combined modes are reasonably well spaced across the frequency range, particularly below about 300Hz (above this it's comparatively easy to deal with them using acoustic tiles).
You can calculate your room modes by hand (each lowest Mode Frequency = 6720/Dimension in inches), but why bother, when Ethan Winer has written the freeware PC Modecalc utility (www.ethanwiner.com/Modecalc.exe), which displays the first 10 modes for each dimension of your room and then plots their frequencies across the bottom of the window
There are various 'Golden Ratios' of width, depth, and height for rooms, that space the modes more uniformly and therefore sound better, and Modecalc displays some of these. However, RPG's Room Sizer utility (www.rpg-europe.co.uk/Products/software/software.htm), which runs on Windows 95/98/2000/NT/XP, offers a rather more sophisticated approach with more accurate predictions. After you enter the smallest and largest dimensions available for your room, it will search for the best room within these limits and then display the frequency response results between 20Hz and 300Hz for the best and worst dimensions in your range. If you're choosing between several existing rooms, you simply input identical smallest/largest dimensions for each room in turn and Room Sizer will predict how they will perform, so that you can decide which is going to be easier to work with. Obviously, modal pile-ups are bad, but this utility cleverly tells you how much they will affect frequency response.
This 'boundary interference' is responsible for many frequency-response dips between 50Hz and 200Hz in smaller rooms, but once again Ethan Winer has a handy PC utility you can download (www.realtraps.com/sbirlbir.htm). The DIY-er can use SBIRLBIR.EXE to find out whether a particular dip in room response is due to boundary problems. You can enter a problem frequency and the utility will tell you what distances it relates to, or enter a particular distance (between your head and the rear wall, for instance) and it will give you the series of related frequencies. Once you've found a correlation with your room's response (most easily measured by playing a vanilla sine-wave synth patch from a keyboard and listening for those notes that are significantly louder or quieter than the others) you can try moving your speakers or changing your listening position to reduce the problem.
The height of your speakers from the floor needs to be such that the tweeters are pointing at your ears for the best high-frequency response, so this depends to some extent on whether you're sitting on a sofa or at a mixing desk. Meanwhile, the horizontal spacing of the speakers should be symmetrical about an imaginary line drawn down the middle of your room from front to back. Their spacing will also depend to some extent on how far away from them you're sitting. Most experts recommend an equilateral triangle arrangement, with the speaker distance from your ears the same as the distance between the speakers.
RPG's Room Optimizer can help you avoid lots of 'equipment shuffling' by telling you the best locations for your loudspeakers and listening position.As you can see, just plonking your ears and your speakers at the most convenient spot in your studio can seriously affect what you hear, and therefore your mixing decisions. Even once you understand all the rules it's still difficult to decide on the best positions for everything. Good rules of thumb are to place your ears 38 percent of the distance from the front or back walls, since this avoids the major modal null points, and to place your speakers either several metres into the room or very close to the front wall, to avoid the worst boundary effects.
By playing back a suitable test signal through your loudspeakers, and placing an omnidirectional microphone where your head normally is when mixing, you can capture and analyse the sound of your room. If an SPL meter is used instead of a microphone (lower diagram), you can dispense with the mic preamp.
Once you've run a level check and then the actual test signal (which lasts just a couple of seconds), an Impulse Response measurement appears in the main window. It's tempting (particularly for the novice) to leap straight into the various frequency-response views, but the Impulse Response display can tell you a lot about what's happening in your room: the main spike is the initial direct signal from the loudspeakers, while any other (hopefully much lower-level) spikes that arrive later on are reflections arriving after the sound has bounced off your walls, ceiling, mixing desk and so on.
When you do start examining the frequency response of your room, you'll probably be shocked by how lumpy it is, particularly the low-frequency response between about 20Hz and 300Hz. However, the low-frequency 3D waterfall response displaying the same information over time will be even more of a shock: you'll see how the various room modes 'ring' like organ pipes, the worst ones possibly ringing for several hundred milliseconds. Any bass notes that use these frequencies will not only sound louder than the rest, but also boom like crazy!
Now you can start adding bass traps in the corners of the room to see how much they 'dry up' the ringing and smooth the low-end response by damping peaks and raising troughs. For me, one of ETF 's best features is its 'Sequential Data Acquisition'. Any of its displays can be updated in real time every couple of seconds, so you can move your bass traps around the room while watching the frequency response of your room change, to find their most effective position, or shift your speakers or listening position a little to see if the response becomes flatter.
Once you've captured one or more room responses, you can start to experience the benefits of the sophisticated click-and-drag zoomable display of this software. It's possible to continue taking extra measurements and get them overlaid on the same display, which makes comparisons a lot easier than with ETF5, and you can also average up to 32 measurements, so you can move the microphone around to get more of a feel for room trends. Like ETF5, RPlusD has various smoothing options that modify its graphs to be closer to what the human ear hears, as well as an intriguing new psychoacoustic option, which takes that idea even further.