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Post by Hexspa on Apr 22, 2016 23:30:19 GMT
Is comb filtering and Node/Anti-node all the same? This article says that the best place for speakers are, after flush-mounted, are within a meter from the wall so long as absorption is behind them. Is that true? I thought you wanted them a few feet off, like around 4'. Thanks.
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Post by Hexspa on Apr 22, 2016 23:34:39 GMT
Oh, I guess if your speakers are rear-ported (mine are) you want them off the wall.
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Post by Hexspa on Apr 23, 2016 6:21:36 GMT
Also I've noticed you neglect the front wall. You mentioned dipole speakers and their relevance. I was under the impression that the front wall is indeed contributive to early reflections. In your Hearing is Believing video the front wall is well-treated. Now I'm under the impression that you prioritize for treating rear walls <10ft from listening position. Just wondering if you could shed light on this.
Thanks,
-m
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Post by Ethan Winer on Apr 23, 2016 16:09:35 GMT
Most loudspeakers are omnidirectional at low frequencies (only). So absorption on the front wall behind the speakers is useful, but only if it's thick enough to work as bass traps. The usual thin foam you see all over the front wall is a poor choice. More here: Front Wall AbsorptionFor my Hearing is Believing video we wanted to treat the room with as much bass trapping as we could manage, to show what's possible in a small room. All of the traps in front of all of the walls are 6 inches thick. --Ethan
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Post by Hexspa on Apr 25, 2016 4:35:33 GMT
Most loudspeakers are omnidirectional at low frequencies (only). So absorption on the front wall behind the speakers is useful, but only if it's thick enough to work as bass traps. The usual thin foam you see all over the front wall is a poor choice. More here: Front Wall AbsorptionFor my Hearing is Believing video we wanted to treat the room with as much bass trapping as we could manage, to show what's possible in a small room. All of the traps in front of all of the walls are 6 inches thick. --Ethan Ok, I see. That Front Wall Absorption article is interesting because I think I read in Sound on Sound that frequencies become "directional" (used for localizing sounds) above 750Hz. Though psychoacoustically this might be true, when treating a room for reflections and bass, the physical directionality of a loudspeaker (to include which direction it's facing) is also important. Thanks as always, -m
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Post by Hexspa on May 18, 2016 7:16:39 GMT
Ok, if I may add: I'm getting two disparate advices about speaker placement: 1. Place close to wall 2. Place far from wall These seem to reconcile this way: Far from wall: if boundary interference will be below a speaker's cutoff. For instance my HS50m is down 10dB by 55Hz. That would be a 10.29' boundary for a peak (1/2 wavelength) or a null at 22.5Hz (1/4 wavelength). Specifically the manual recommends "1.5 meters (about 5 feet)" which corresponds to the cutoff options on the mains and sub (around 100Hz). (Actually if you look at the response vs. their suggestion, maybe a 3dB increase from a single boundary could help in this case.) Close to wall: if the above isn't possible then you go the opposite direction and try to move the SBIR within the effective range of absorption. So a gap of 25cm (10 inches: 4" for the absorber, 4" for the air gap and 2" for heat/cables) will give you a peak around 680Hz and a null around 340Hz. Clearly far off the wall is more ideal given space and where flush-mounting isn't an option. So if the Grammy paper suggests a distance of around 7' between speakers that means a room would have to be at least 27' wide to accommodate all factors where flush-mounting is not possible. Oy vey. -m
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Post by Rock on May 18, 2016 12:56:59 GMT
Just one general concept. You've cited "frequencies become "directional" (used for localizing sounds) above 750Hz". I sure it's understood but I'd just like to interject anyway that in audio and acoustics in general, attributes like directionality and absorption for instance, occur and change gradually throughout the spectrum and not abruptly. I'm sure there are exceptions like sympathetic vibrations but in the case of directionality, I believe that, just from common experience, frequencies considerably lower than 750Hz can be localized to some extent...It's a matter of degree.
Cheers, Rock
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Post by Ethan Winer on May 18, 2016 16:40:18 GMT
Yes, changes are gradual.
There are arguments for close and for far. Closer raises the SBIR frequencies making absorption behind the speakers more effective. Farther away and the reflections are weaker, though you'd have to be 20-30 feet away for that to help much. As always, the only way to know where is best in your room is to measure the LF response at high resolution as you experiment. As you may know, the very best place for speakers is in the walls.
--Ethan
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Post by Hexspa on May 19, 2016 5:20:23 GMT
Thanks gentlemen.
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