Wavelength and reinforcement!
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Gold Member Username: Thx_3417Bournemouth,... Post Number: 1539 Registered: May-05 | You've got the matching three-screen in place you've done the basic test tone test using the (wideband pink noise) and now you're about to play the first of many demonstration test films all seams well you're friends come around you place the same film in the DVD player the show is running smoothly but one of you're friends is untested by the sound? Afterwards you ask him did it sound good, and the answer was something was missing? You're slightly puzzled as to why? what could possible be wrong with the placement of the three-screen loudspeakers there brand new they have fairly large drivers in a large enclosure, what could be wrong and the answer is staring straight at you! Play a sine wave tone in the low range between 60 and 100Hz over the left and right separately they should equal the same SPL db level when read by an SPL db meter, say 80dbc for example! Now play the same tone over the matching centre channel, the signal should read a rather less reading on the SPL db metre, and if so don't worry. Now place the centre channel in the same position as the one of the left or right loudspeakers. Now play the low frequency sine wave tone and note the SPL db level on the SPL db meter, it should read the same level! Now this is due to wavelength of the frequency and it's placement in 3-dimensional space across the front, plus the basic limitations of the loudspeaker dynamic frequency range to reach the listen position with very little strain place upon it. Now you could move the centre channel back up against the wall, this will magical increase the wavelength and maximise the reinforcement of the centre channel, how it is placed and what it is placed on including the other two matching loudspeakers placed on the left and right is entirely up to you. trueRTA http://www.trueaudio.com/rta_abt1.htm If you don't have a test CD or DVD with sine wave tones, please click on to this rather basic (trueRTA) analyzer, it's got it's own sound generator and you can key in any sine wave from 0Hz to 25.000KHz not that you're going to hear the very high frequencies or the very, very low infer sonic frequencies, so just keep it within 20Hz and 16khz that's an average listen range   |
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