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"First reflection"...what it means, why it's important, how to find it
- Thread starter tomlinmgt
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GuyK
Addicted Member
How did you end up implementing things?
armyslowrdr
I don't want one..LOL
Subwoofer left of stereo rack, subwoofer rt rear corner of room.
For tune placement see the current 1st 3 photos at my flickr stream at https://www.flickr.com/photos/armyslowrdr/
For tune placement see the current 1st 3 photos at my flickr stream at https://www.flickr.com/photos/armyslowrdr/
NH-MAN
Addicted Member
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.
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.
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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.
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NH-MAN
Addicted Member
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..
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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.
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armyslowrdr
I don't want one..LOL
Changed the room and gear a lot since this thread--I'll add a photo or 2 but will be stretched as I used wide angle and fish lens. Major change is that the huge computer and multi monitor set up is out of room and moved to loft.
And done! I ordered 3 art panels and 6 bass traps from John at GIK today after swapping emails and photos and room diagrams all week.
And done! I ordered 3 art panels and 6 bass traps from John at GIK today after swapping emails and photos and room diagrams all week.
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armyslowrdr
I don't want one..LOL
And that is why my art panels and rear bass traps are having scatter plates installed--as John at GIK says--so as to ensure the room is still lively...which is what I am used to.
AvFan
Super Member
This has been a good thread to read. Like many my stereo is in our living room that by default has lots of stuff that interferes with good sound. There are comprises being made at many levels! I currently try to tame first reflection points by stacking pillows in front of a piano (yes, I tried to find it a new home and the idea was rejected) and sofa/wall and it works OK. However, is there a reason you don't want to absorb the sound from the speaker headed towards the first reflection point closer to the speaker?
I have some 2" OC 703 fiberboard and put two 2' x 4' panels immediately to the outside of both speakers. FYI 2" OC 703 absorbs pretty much everything above 500Hz. I noticed a difference in the L - R balance that was a little disorientating at first and the soundstage was just the speaker-to-speaker width. Obviously more listening is needed but the sound seemed to be more coherent too. I don't want my system to sound like headphones but what is lost by absorbing the sound that will be reflected closer to the speaker? Here are some photos.
Right speaker with couch:
The real problem in the room...the left speaker near the piano (see the pillows stacked on the cover for the keys etc):
I can make some covered frames for the OC 703 and bring them out for serious listening sessions. Oh, I did put the the OC 703 behind the speakers (they are rear ported) and there weren't any easily noted L-R changes but the sound was more coherent.
I have some 2" OC 703 fiberboard and put two 2' x 4' panels immediately to the outside of both speakers. FYI 2" OC 703 absorbs pretty much everything above 500Hz. I noticed a difference in the L - R balance that was a little disorientating at first and the soundstage was just the speaker-to-speaker width. Obviously more listening is needed but the sound seemed to be more coherent too. I don't want my system to sound like headphones but what is lost by absorbing the sound that will be reflected closer to the speaker? Here are some photos.
Right speaker with couch:
The real problem in the room...the left speaker near the piano (see the pillows stacked on the cover for the keys etc):
I can make some covered frames for the OC 703 and bring them out for serious listening sessions. Oh, I did put the the OC 703 behind the speakers (they are rear ported) and there weren't any easily noted L-R changes but the sound was more coherent.
Wow...this is a very interesting scenario you have going on here. Raw 703 panels in a tidy and very nice looking room with some great gear and very, very intriguing speakers (just heard Selah's curved line source a few weeks ago) that I'd definitely like to hear more about (I think I'm smitten!).
Ok...lots of stuff to touch on here. First...those raw 703 panels HAVE to be shedding fibers with nothing to contain them (I'm getting all itchy just looking at the pictures!). Until you can get some proper absorption panels built, I think I'd wrap the raw 703 in bed sheets or some kind of thin fabric and seal it shut with fabric glue or tape or whatever you can come up with...then I'd vacuum the living hell out of the carpet anywhere those panels stood at rest. But honestly, at this stage, I'm not so sure you need them because....
Second...you run into issues with early reflection energy at the listening position when you have a fairly large, flat surface at the early/first reflection location. It looks to me like your early/first reflection locations have room furnishings which will be diffuse to the left (piano with hard, irregular surfaces) and absorptive to the right (couch...fabric covered cushions). This could cause some image shift or just a general degradation of image and sound stage resolution, but with the pillows stacked on the piano and bench it seems to me you've addressed this issue. What do you hear when you remove the pillows from covering the piano?
You pretty much answered your own question regarding having the absorption panels right up close to the speakers when you described the results you heard...noticeable improvement in sonic clarity and image/sound stage resolution, but at the expense of sound stage width. If I were you, I might try letting the couch handle absorption to the right (when you're wanting to do some serious/critical listening, stack some pillows on top of the backrest of the couch to create absorption higher up on the wall) and stick with the stacked pillows on the piano and bench or drape a heavy bed comforter over the piano (double it over for added thickness). You don't want to contain all of the sonic energy to just the width of the speakers. You want to allow it to fill the room so it can create late arriving reflections at the listening position from surfaces that are not early reflection locations. This is how a sense of space and ambiance is created in the reproduction. With the panels up so close to the speakers, you're practically mimicking a room is overly absorptive/dead.
How close is the rear wall to the listening position?
Michael
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AvFan
Super Member
@tomlinmgt : Thanks for the response. First up, the uncovered OC 703 panels were in my living room for about an hour while I listened to a couple of records and you are right, that stuff is nasty so a good vacuuming is in order. But I needed to see if this idea of putting the panels relatively close to the speakers had any merit before going to the trouble of making some frames and covering them with speaker cloth. I also tried out the OC 703 behind the speakers.
My room is irregular to say the least. I live in a mid-80s Southern California tract house and the floor plan/cathedral ceiling style was pretty common amongst all the builders. My floor is concrete slab with carpet. Here are some photos of my challenge...
Taken from the right speaker for @totem...The Poang chair is my sweet spot.
Panning to the right from the right speaker...Note the piano.
Now from the dining area back to the stereo...
The pillows on the piano and on top of the sofa are at the first reflection points. The piano finish was an excellent mirror! Removing these pillow yields a muddy mess that, for example, makes it hard to set ant-skate on my TT. Also, the center image seems to move randomly without the pillows at the first reflection points. This room rings, so our next steps are...
We are going to add two sound absorbing items. First, my wife is a quilter and she is going to make a quilt to hang over the sofa. I have some 1" OC 703 that I can frame and seal behind it to help with room reflections. Second I'm going to replace the group of four pictures on the wall behind the listening position with a large canvas box photo with OC 703 inside. But there are just too many hard surfaces in this space and I can't treat them all. And to what effect? I doubt there is any software that could even approximate the acoustics of my living/dining room. It certainly doesn't help that we don't have drapes over the windows and the cathedral ceiling changes height over the width of the speaker's soundstage. I looked at putting the stereo on the sofa wall but it didn't work well as a living room so that idea was discarded.
Hence my idea to cut off the sound from the first reflection points closer to the source. All ideas are welcome!
My current Selah Audio speakers are five years old and, unfortunately, are no longer available due to a change by the mid-range manufacturer. They are rear ported and have a RAAL tweeter, Accuton ceramic mid and two 8" aluminum cone woofers. My system has changed a lot in the last five years but not the speakers. Rick Craig is a joy to work with and custom built these speakers even down the type of finish I requested. So you must have been at the Lonestar AudioFest?
My room is irregular to say the least. I live in a mid-80s Southern California tract house and the floor plan/cathedral ceiling style was pretty common amongst all the builders. My floor is concrete slab with carpet. Here are some photos of my challenge...
Taken from the right speaker for @totem...The Poang chair is my sweet spot.
Panning to the right from the right speaker...Note the piano.
Now from the dining area back to the stereo...
The pillows on the piano and on top of the sofa are at the first reflection points. The piano finish was an excellent mirror! Removing these pillow yields a muddy mess that, for example, makes it hard to set ant-skate on my TT. Also, the center image seems to move randomly without the pillows at the first reflection points. This room rings, so our next steps are...
We are going to add two sound absorbing items. First, my wife is a quilter and she is going to make a quilt to hang over the sofa. I have some 1" OC 703 that I can frame and seal behind it to help with room reflections. Second I'm going to replace the group of four pictures on the wall behind the listening position with a large canvas box photo with OC 703 inside. But there are just too many hard surfaces in this space and I can't treat them all. And to what effect? I doubt there is any software that could even approximate the acoustics of my living/dining room. It certainly doesn't help that we don't have drapes over the windows and the cathedral ceiling changes height over the width of the speaker's soundstage. I looked at putting the stereo on the sofa wall but it didn't work well as a living room so that idea was discarded.
Hence my idea to cut off the sound from the first reflection points closer to the source. All ideas are welcome!
My current Selah Audio speakers are five years old and, unfortunately, are no longer available due to a change by the mid-range manufacturer. They are rear ported and have a RAAL tweeter, Accuton ceramic mid and two 8" aluminum cone woofers. My system has changed a lot in the last five years but not the speakers. Rick Craig is a joy to work with and custom built these speakers even down the type of finish I requested. So you must have been at the Lonestar AudioFest?
AvFan
Super Member
A little more info...I may be able to move the piano and there is a remote possibility I can put the stereo on the sofa wall. Doing so would eliminate a potential issue with the ceiling height not being symmetrical with the direction of the direct sound but will probably create other "opportunities to excel". Does anybody think the sloped ceiling is a significant issue when it varies in height across the width of the speakers?
armyslowrdr
I don't want one..LOL
1st of 6 cartons from GIK Acoustics arrive tomorrow. Rest later in week.
armyslowrdr
I don't want one..LOL
GIK Acoustics items installed. Room's rockin'.
Excellent. Whatcha think now that the room is decked out with acoustic treatments?
armyslowrdr
I don't want one..LOL
Sounds fabulous. A significant improvement in bass and even vocal clarity.
