rzdz@fluke.UUCP (Rick Chinn) (02/14/85)
Since this old subject has reared its ugly once more, I feel compelled to add my 3 cents worth. First, kudos to Dick Grantges (hound!rfg) for his comments on phase shift, etc. It's nice to see the horse pulling the cart. Now its time to dispell some myths: 1. yes, an equalizer will help you flatten the frequency response of your system. 2. yes, a real-time-analyzer (rta) will help you adjust your equalizer to attain flatness. 3. both #1 and #2 can improve the loudspeaker/room/listener interface. 4. contrary to popular belief, flat is not beautiful, nor desireable. 5. if you simply equalize your system to flat using an rta and an equalizer, you won't like the sound. Here's what you need to do (if you feel you must): 1. hook everything up. turn it all on. 2. pick a reasonable volume level for the pink noise. it should be high enough to overcome any local ambient noise. 3. use the crossover controls on your speakers to level the curve out as best you can. 4. now use the equalizer to further smooth the curve. Start at the largest peak (note *PEAK*). You may have to use two adjacent sliders to remove it if it's bandwidth is greater than the bandwidth of an individual band on your equalizer. 5. ignore any dips in the response if they're greater than 6 dB. fortunately (for you), the human ear hears excesses better than it hears absences. Going after huge dips wastes power and causes excessive phase shift. If the dip is caused by diaphragmatic absorption in your room, then you could pour tons of energy at it without appreciable benefit. (the dbx automated equalizer doesn't know this.) 6. now that your system is relatively flat, introduce a controlled hf rollof into the overall response. there is a lot of discussion over where to begin the curve. I'd say between 3 and 8 khz, around 1 to 3 dB/octave. Try using the tweeter level control on the speaker first. If your crossover is in the midrange, then this could be an easy way to introduce the required rolloff. Otherwise, do it on the equalizer. 7. Remember flat isn't beautiful, but smooth is the name of the game. 8. If your listening room is an acoustical toilet (cesspool, etc.) then what you need is dynamite rather than an equalizer. Sorry to burst the bubble, but someone had to. I have many equalizers and a spectrum analyzer (rta). I use the equalizers to "fix" bad recordings and the specrum analyzer to observe the spectral balance of program material. I don't really care if it is *flat*, just smooth and listenable (and occasionally very loud). Rick Chinn John Fluke Mfg. Co MS 232E PO Box C9090 Everett WA 98206 {ihnp4!uw-beaver, ucbvax!lbl-csam, microsoft, allegra, ssc-vax}!fluke!rzdz (206) 356-5232 <--------------- listen to the music ------------------------------------>