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>>>>>>>>>>>>>>>>>>>>>>>> Document for THE LISTENING ROOM <<<<<<<<<<<<<<<<<<<<< REGISTRATION................................................................. $30 to Sitting Duck Software at the address shown at the bottom of this document. Upon registration you will receive the latest version of the program which includes the ability to provide a frequency plot of your loudspeaker system AS INFLUENCED BY THE NEARBY ROOM BOUNDARIES. The distance between the speakers and room boundaries cause peaks and dips to appear in the overall response curve. Judicious speaker and listener placement can help avoid the worst of both the standing wave and room boundary effects. WHAT THIS PROGRAM DOES.............................. LISTENING ROOM is software designed to minimize the effects of standing waves by determining desirable speaker and listener placement within the audio environment. Sitting in room locations where hot spots or nulls are absent provides a more natural, smoother response, removes the need for excessive equalization and reduces transient decay time. ============= THIS PROGRAM IS NOT FOR USE WITH DIPOLE RADIATORS! ============ MACHINE REQUIREMENTS................................ The Listening Room runs on any IBM compatible machine with DOS 2.11 or better, 256K of RAM and Hercules compatible, CGA color, EGA color and VGA color monitors. --------------------------------STANDING WAVES-------------------------------- Due to the nature of home listening environments, low frequency standing wave patterns develop within the room which alter the apparent FREQUENCY RESPONSE and TRANSIENT DECAY TIME of the audio playback system. Standing waves exhibit themselves as pockets of low and high acoustic pressures and may be readily observed by walking around within the listening room while steady state, bass rich material is being reproduced. The response variations, which can exceed 25 db at different listening positions, cannot be properly compensated for by an electronic equalizer. Of the various solutions to the standing wave problem, adjusting the loud- speaker and listening positions is the least expensive, most practical and often the most effective solution for the average homeowner or apartment dweller. If you are currently considering extreme measures to improve what your believe to be a problem room, use this program first. Many times, no further work will be required. Optionally, the software may be used to intentionally place the listening position in a standing wave "hot spot" for the LOWEST frequency to help compensate for speakers with poor low frequency response although the result will not be the same as that provided by a system with inherently good low frequency response. Additionally, using the program to locate the NULLS for low frequencies and placing your turntable at the calculated location will help to minimize acoustic feedback. Sadly, a traditional "along the wall" turntable position is among the worst locations while an intrusive "center of the room" placement is often the best. Note that a corner location is usually the worst of all. When determining the turntable location with this program, mentally replace "listener" with "turntable". Most often, the ideal turntable location is near the center of the cube defined by the room boundaries. This site places the turntable halfway between the floor and ceiling, an arrangement that you'll probably not select. ----------------USING THE STANDING WAVE PORTION OF THE PROGRAM-------------- This program assumes that your speakers will be placed symmetrically, and equidistant from the side walls and that the listening position will be on a line perpendicular to one drawn between the speakers and parallel to the side walls. Note that some standing wave nulls for the width cannot be raised in the symmetric mode. An asymmetric mode of operation is available for those who desire it. Starting with the speakers in the corners and the listener against the back wall, use the indicated keys to move the speakers and listener to positions which satisfy your personal tastes and environment. Make adjustments, compromising to the degree which you are willing, until the maximum number of markers are grouped around any horizontal line, preferably in the 0db to -10db range. Two or more ADJACENT markers which stray upward from the grouping, two or more markers for the SAME FREQUENCY which stray upward from the grouping or OVERLAPPING markers which stray upward from the grouping should be avoided. The markers symbol indicates whether its position on the grid is due to the (L) length or (W) width or (H) height of the room. There may be more than one set of acceptable positions. If used for locating the turntable, the maximum number of markers should be toward the bottom of the chart. Screen prompts provide the necessary keystroke information to make adjustments and enter the room dimensions. There is also a small help screen. Dimensions displayed are in inches, measurements from the speakers are taken from the geometric center of the driver that is reproducing the frequency of interest (usually the woofer) and measurements from the listener are taken from the center of the head. If your system has several drivers in a vertical array which cover the the 20-220Hz range, the distance from the floor should be set to the middle of the array. With MANY drivers in a vertical array you may safely ignore the height altogether. You may also ignore the height if you have a large panel radiator such as an electrostatic system. Locate your speakers at least 24" from each of the nearest walls to minimize early reflections and allow a believable sound stage to be established. If you are placing your speakers asymmetrically, press <A> for asymmetric operation. In this mode, you may move the left and right speakers independent of each other, by using the keys as shown in the prompts. Asymmetric operation will display two sets of L's and two sets of W's and will require more time to find the best positions. For single-woofer positioning, as with a sub woofer, use the symmetrical mode and ignore one of the speakers and its distances to the boundaries. Depending upon the crossover frequency of your single woofer, you may have to do the woofer and satellite positioning as separate exercises. Some room shapes make excellent listening environments, others may be less satisfactory. In any case, the use of this program will provide an audible improvement. Final results will always be better than displayed because furniture and openings such as doors, help to break up hot spots and nulls in the overall response, particularly for frequencies toward the right side of the chart. The chart markers indicate the relative standing wave intensity for a particular room dimension and frequency. Only the AXIAL standing waves (those traveling from front-to-back, left-to- right and ceiling-to-floor) are considered, since these are the most significant. No attempt has been made to combine the standing wave activity with the DIRECT response from the speaker to the listener's ears. The displayed chart, therefore, should not be taken for a true frequency response curve. In practice, a null in the standing wave will usually mean a perceived reduction in bass at the given frequency rather than a complete absence of sound. Using this program to determine the preferred listening set-up will take some effort. Much less effort, however, than the time honored process of moving, listening... moving... listening......which always leaves the question, "Is this really better?" If you are equalizing your system with any of the several techniques available, be sure to locate your speakers prior to the procedure. Equalizing to correct erroneous speaker placement is not the path to take for quality reproduction. Do not waste your time trying to get everything within a few db. If you can get most of the markers between +2 and -10 on the standing wave graph, you have accomplished your task. Note that just a few inches one way or the other can sometimes make a significant difference. Using the asymmetric mode, even if your final set-up will be symmetric, makes it easy to compare one set-up curve with another. If your set-up is asymmetric, do not believe that +4 on one channel will properly compensate for -4 on the other. Try to keep the curves on the boundary plot as closely matched as possible to maintain L-R channel balance. This will be difficult and possibly suggests that a symmetrical set up may be preferable. As an instructive example try the following set-up: Room: 180" x 144" x 102" Operation: Symmetrical Speakers from front wall: 60" Speakers from side wall: 48" Speaker height: 20" Listener height: 35" Listener from rear wall: 34" None of these dimensions would be unusual for a typical room and this set-up and would provide acceptable results. Less than 20 minutes was required to juggle things into place for this example. Naturally, you will want to take a look at your current set-up. Who knows, it may already be perfect. --------------------------------SOME EXAMPLES------------------------------- The explanation of the standing wave portion spoke of grouping markers about a horizontal line. In the example below, the area bounded by +2 and -6 contains the majority of markers. This grouping is quite acceptable despite the W's at the bottom which are unavoidable in a symmetrical set-up. Tighter groupings are possible but often do not coincide with a reasonable listening configuration. +-----------------------------------------------+ | +6 | R +4 | e +2 | l 0 L W L | a -2 H L | t -4 L W | i -6 L H | v -8 | e-10 | -12 | P-14 | r-16 | e-18 | s-20 | s-22 | u-24 | r-26 | e-28 | |-30 W W | | 1 1 1 1 1 1 1 1 1 1 2 2 2 | | 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 | | 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 | +-----------------Frequency in Hz---------------+ The example below shows an unacceptable grouping. One L and one W marker are needlessly located at the bottom and a particularly nasty sounding potential problem is indicated by the group of three markers around +4 and 190Hz. Room transient response suffers and an equipment problem may even be suspected. +-----------------------------------------------+ | +6 W | R +4 L LH | e +2 | l 0 L | a -2 H | t -4 | i -6 | v -8 | e-10 W | -12 | P-14 | r-16 | e-18 | s-20 | s-22 | u-24 | r-26 | e-28 H | |-30 W L W | | 1 1 1 1 1 1 1 1 1 1 2 2 2 | | 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 | | 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 | +-----------------Frequency in Hz---------------+ Note: Which horizontal line you choose to group the markers around is not as important a keeping the markers grouped together. Markers which stray UPWARDS from the grouping indicate the most severe problems. The well known "Rule of Thirds", where the speakers are in from the front wall 1/3 of the room length and the listener is in from the rear wall 1/3 of the room length does indeed put most of the markers on the -6 line. Its drawbacks are; the 1 (sometimes 2, depending on room length) stray markers on the +6 line and the fact that is cannot be usefully applied to the width and height of the room. The "Rule of Modified Fifths", where the speakers are in from the front wall 1/5 of the room length and the listener is in from the rear wall 2/5 of the room length, provides somewhat better results but may still result in a stray marker at +6. We have yet to find a simple "rule" that provides good results. In the Symmetrical mode, you may use <F2> or <F3> to set the markers and distances to the Rule of Thirds or the Rule of Modified Fifths. Despite the drawbacks of the two rules, they do make good starting points for you to work from. <F4> applies the Rule of Modified Fifths to the length and the Rule of Modified Fifths to the width. There is a rule based on 7ths but it does not provide satisfactory results. Below is an example of one possible near ideal situation. The asymmetric mode must be selected in order to move all the W markers into the grouping. More markers are shown in this example because the asymmetric mode doubles the number of markers necessary. Figure on spending a great deal of time to produce similar configurations, especially if you intend to get the boundary plot as nice! +-----------------------------------------------+ | +6 | R +4 | e +2 | l 0 | a -2 | t -4 LW H H L H L W | i -6 LW L H L H W L W | v -8 L W LH | e-10 LH | -12 | P-14 | r-16 | e-18 | s-20 | s-22 | u-24 | r-26 | e-28 | |-30 | | 1 1 1 1 1 1 1 1 1 1 2 2 2 | | 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 | | 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 | +-----------------Frequency in Hz---------------+ GETTING HELP If there is something about the program that you do not understand, feel free to call Sitting Duck Software during the hours of 8:00 A.M. to 10:00 P.M., Pacific Time. If there is no answer, try again later. We are glad to answer your questions and provide any advice in areas which we are knowledgeable. ERRORS and UPGRADES If you find any errors in the program, let us know immediately. We want to fix them for the benefit of new users. Purchasers of The Listening Room are always entitled to the latest version at no additional cost beyond a $1 shipping and handling charge. THE PHILOSOPHY OF SITTING DUCK We have no axes to grind nor are we interested in exercising our egos. The code of the Listening Room program has been arranged in a manner that will present to YOU an easy to understand and use distillation of the facts. If you don't believe we have done our job, let us know. CONTACT US We would like to hear about your experiences; before and after using this program. You could provide important information that will allow us to make operational, instructional or user interface improvements. No need to be tactful; you may hide a significant point. We are also interested in how many users have a math co-processor. We want to make this program as useful and easy to use as possible and will listen to all suggestions. There is a possibility of a professional version of the program; for this to become a reality, we need to know what you, as professionals, wish in the way of features and abilities. Thanks, regards and good listening from the co-authors; Bill Fitzpatrick, programming & interface Ralph Gonzalez, math, spatial geometry and nitpicking The program is compiled with the Microsoft BASIC 6 compiler. Assembler routine library from Crescent Software of Stamford, CT The Listening Room (C)(R) 1989 All rights reserved Sitting Duck Software POBox 130 Veneta, OR 97487 (503) 935-3982 As of 5 May, 1990 we would like to thank the following for their efforts in helping to promote The Listening Room: Audio Concepts Quality drivers and loudspeaker kits. CD Review "The" magazine for CD buyers. KLH Research & Development Loudspeaker manufacturers. Stereophile Respected "Underground" review publication. As ridiculous as it may seem, I believe we have to say: Microsoft is a registered trademark of Microsoft Corporation. IBM is a registered trademark of International Business Machines.