I recently had the pleasure of meeting a fellow forum member who expressed an interest in taking part in my test & assisting with the technical aspects. He proved to be rather well qualified for this as he is an electrical engineer with a particular interest in acoustic engineering & an array of very handy equipment to assist in the precise level matching that will be necessary to preclude the subjective bias that almost everyone experiences in preferring the louder signal. Indeed he suggested that we should aim for 0.1dB matching if practicable since there is some evidence that even differences in level below the 0.5 - 1dB change that represents the effective limit of our conscious perception can be sensed subconsciously and therefore invalidate a serious test. I'm happy to bow to his superior experience in this respect although it will take us some further trial & error at a subsequent session to find the best volume settings on my Transporter & DAC adjusted in tandem to achieve this. No problem.
He then came up with the startling (to me at least) assertion that after 30 minutes or so of acclimatisation our brains have the capability of ignoring static reflections in a listening room, together with some very plausible conjectures as to why this should be the case. I'll let him share these with you himself on the forum if he chooses, because he'll make a better job of explaining it than I would. Well, I'm always up for new ideas, so (with some difficulty!) I shut up for half an hour while he selected a wide range of recordings from my collection with which he was familiar and "dialled himself in". When he had finished, he kindly said that he found my system very musical, regardless of genre. This (apart from flattering me) suggested that I do at least have a system of sufficient resolution that differences might be discerned in the proposed double-blind test *-if-* they really exist. One of the things that we subsequently did was to load up a test disc containing a variety of system checks, one of which was a sweep tone test consisting of a series of constant amplitude tones each itself at a fixed pitch for about 10 seconds, but then followed by a subsequent tone at a lower frequency. The first thing that surprised me was that I heard the highest tone with 62 year old ears (it came immediately after a spoken introduction explaining the purpose of the test). The next thing that surprised me was that I heard each successive tone at the same subjective volume, except for the very last and lowest which was twice as loud, clearly hitting a major modal frequency (presumably concrete floor to beam & concrete ceiling, which is the shortest dimension as you would expect) in my room which is essentially a concrete box *-and which must therefore be full of reflected sounds which you would expect to affect some frequencies more than others, -*simply because of the room dimensions: it's almost square, just to make matters worse. I had been intending to invest in some acoustic panels on the assumption that my room must be too bright as is. But that (after a lot of listening over the years from my favoured position) is not what I actually heard, and it certainly made me at least take the proposition of echo suppression in our hearing sense rather seriously. Of course I could be deluded about this too, although it was absolutely not the result I expected so it could hardly be a simple case of "hearing what you want to hear". What I actually wanted was to get a sense of how much acoustic treatment my wrong shaped & constructed room really needed. It will be interesting to see if other test participants (after a suitable musical interlude) have the same auditory experience with the sweep test. One thing is for sure - my floor, walls & ceiling don't move (except for the extreme bass resonating with the ceiling which I'll have to try & fix before one of my neighbours murders me), so all the reflections would be of the static kind that it had just been proposed to me would be eliminated by my brain while listening to the direct sound from my speakers which of course reaches my ears slightly earlier than any reflections. I'm going to hold off plastering my walls with acoustic panels, although I'll probably need some on the ceiling to help absorb the resonant low bass frequency, and probably a bass trap to finish the job. The fact that I wasn't expecting the phenomenon just described at all made it more remarkable. But that's experimentation for you - sometimes you *-don't-* get what you expect. Further investigation warranted on this, I think... Dave :) ------------------------------------------------------------------------ Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
