"First reflection"...what it means, why it's importat, how to find it

Discussion in 'Listening Spaces' started by tomlinmgt, May 29, 2012.

  1. tomlinmgt

    tomlinmgt AK Subscriber Subscriber

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    :thmbsp:
     
  2. GuyK

    GuyK Addicted Member

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    How did you end up implementing things?
     
  3. armyslowrdr

    armyslowrdr I don't want one..LOL

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  4. NH-MAN

    NH-MAN AK Subscriber Subscriber

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    I am not arguing anything said here but my mind wants to think reflections (to a point) aid in depth and soundstage? Like real life< ie a concert
    I guess when I listen it seems like it does, or maybe the size of my room is just in a way as sometimes i can hear instruments next to me, or below and to the side, or right next to my head which is pretty cool.
     
    Last edited: Apr 21, 2017
  5. tomlinmgt

    tomlinmgt AK Subscriber Subscriber

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    And you'd be correct...sort of. Image and sound stage resolution are "encoded" in the recording by way of spatial cues that the microphones pick up or the recording engineer creates with phasing, panning, etc. Those spatial cues in the recording are "decoded" by the equipment used for reproduction. Provided the fidelity of said equipment is sufficiently high enough, all this sonic information will come out as it went in and the ears/brain will discern/compute the spatial cues so dimension, proximity and localizable content are detected/perceived in the playback by the listener.

    The next hurdle is overcoming what the room does with this sonic information as it makes it's journey from the speakers to the listener. Reflections from hard surfaces that arrive at the listener within a certain time gap after the primary wave that arrives at the listener directly from the speakers can blur or smear the spatial cues that are in the recording which contribute to sound stage and image resolution (comb filtering). That's why there's a distinction between early reflections and late reflections. There's something called the Haas effect that describes this...and the simplified version states that any reflection arriving at the listening position within 15 ms of the arrival of the primary wave (sonic energy dispersed from the speaker directly to the listening position) is an early reflection and will cause comb filtering. Late arriving reflections, which arrive at the listener more than 15 ms after the primary wave, will help (re)create the sense of ambiance and space of the venue where the recording was made or whatever sense of ambiance and space the recording engineer has deliberately created in the recording. So late reflections...more or less what you are touching on...are a good thing. And that's primarily the function of diffusers...to create (predictable) late arriving reflections which in turn unlocks the sense of ambiance and space in the recording.
     
    Last edited: Apr 21, 2017
  6. NH-MAN

    NH-MAN AK Subscriber Subscriber

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    So would I be correct in thinking since my listening room is only 12x12 speakers at one end (a few feet from the side walls) and me at the other (laying in bed) that its all hitting me at roughly the same time initially as it is a small space?
    The reason I say this I have put treatments on the walls with no notable difference except for a decrease in soundstage: i am taking just a little. I would be at a sweet spot I think for sound reflecting off the walls. Maybe if studios were not putting so much crap in them, the newer sound wouldn't be so artificially bright as they are absorbing a lot of the highs? I have seen many recordings being made in studios that were nothing special as far a sound treatment goes that sounded great. I am sure we have all seen pics and videos and saw nothing special going on in the control room except a sound board and a couple speakers. I am not debating the fact that one can change how their room sounds with the gear they have and treatments but it also been known for a long time speakers and walls are used in conjunction to enhance the sound from the speakers. Remember this is just my observations.

    In my experience having a speaker that does not have a say a loud tweeter or something if you put it near a bright reflective surface it enhances the sound. I guess from my experience,( which I admit I do not spend to much time worrying about), unless there is a major issue going on in a room I think someone could hurt the sound/sound stage with treatments in a particular application. I think most of us know just angling the speaker up or down or side to side even just a little can make a very noticeable difference in how sound waves reflect in a room. I just cant stand generalizations (which is rampant) thats all, and how they may take people on journeys the don't need to go on..
     
    Last edited: Apr 21, 2017
  7. tomlinmgt

    tomlinmgt AK Subscriber Subscriber

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    I think it is highly unlikely that the reflections from every boundary layer in the room are hitting you at the same time (would only know for certain if I had more information..but you've given enough that I can make some safe assumptions). The ceiling reflection and rear wall reflections are almost certainly arriving at the listening spot (your head) at a different time than the reflections from the side walls since the ceiling and rear wall first reflection locations are a different distance from the speakers and your head than the side walls' first reflection location. You'd be much better off in terms of nullifying the effects of the early reflections in that small space if you were listening in a near field configuration...like 4-6' feet away from the speakers. Of course, this would change the presentation of the sound stage considerably compared to when you're at the other end of the room and laying in bed (and I have to wonder how you're getting much sound stage resolution when laying in bed...unless your speakers are suspended or up pretty high off the floor), and if the speakers are a large, mulit-way design may not sound very good at all close up. Regardless, you may like it, you may not...but simple physics dictates the behavior of the sonic energy and how the room's acoustic profile will manipulate it. You hear what you hear, and you've made some conclusions and shared them here, but I'm not really convinced you've attempted to implement a proper acoustic treatment scenario. That's not an attempt to chastise you or anything...it makes no difference to me or anyone else and if you like what you're hearing then that's cool. But having said that, I'm not sure what the absorption devices were that you tried or where you located them, but from the information you've shared I'm led to believe the absorption devices weren't broadband absorbers, weren't located properly to absorb the early reflections, or both.

    And there are no generalizations happening in this thread. Just the sharing of proven and practiced science which many, including many in this thread, have applied to their listening spaces with very positive results. If you're happy with what you have then more power to you...no need to rebut with a flat earth argument. There are scores of others who found that taking the time to understand the physics behind room acoustics and using that understanding to implement a proper acoustic treatment scenario in their listening space took them on a journey that was profoundly worthwhile.
     
    Last edited: Apr 22, 2017
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