I got a few acoustic panels - Where should I put them?

Discussion in 'Sound Science' started by noname2020x, Dec 30, 2017.
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  1. noname2020x
    40578321.jpg Hello all!

    I'm not looking for perfection, just some echo reduction.

    Here is my apartment. The green areas are the spots that are free to put the panels. The red are my speakers, the black is my tv.

    I think they will probably look best behind the TV but of course looks are secondary
    Thoughts?

    Thanks!
     
    Last edited: Dec 30, 2017
  2. bigshot
    where is your listening position?
     
  3. noname2020x
    Smack dab in the middle of the room on a couch.
     
  4. yage
    It depends. You can begin by treating the first reflection points in the walls and ceiling. You can find these by sitting in your listening position and having someone else slide a mirror along the wall or ceiling until you can see the speaker. If you have hardwood floors, try putting a rug in between the listening position and your stereo.

    If you need to reduce slap echo (e.g. the metallic zingy sound you hear after you clap your hands) then you can get away with treating one surface out of a pair of parallel surfaces. That should reduce the sound bouncing around.
     
  5. bigshot
    That's more of a problem than anything. The center of the room is where all the reflections hit. It's best to be either 1/3 forward or 1/3 back. If you can't change it, put panels at the primary reflection points. Figure sound is bouncing like balls on a pool table. Find the spot where a ball would hit the bank if it was shot from the speaker and bounce back directly to the listening point. Same thing on the roof and floor. Those are going to be your biggest problem. Second address the back wall. Lastly the front wall.
     
  6. amirm
    Why that? The worst sounding room is one without echo: an anechoic chamber! Echos (reflections) can be quite good.

    First you need to determine if the room is too live. You can measure that or just have someone stand where the speakers are and clap (do NOT do it yourself). Listen to see if there are secondary sounds. If it is just a dull thud, your room is probably too dead and I wouldn't put in any more absorbers in there.

    Assuming it is on a live side, your first tool should be to put a shaggy carpet on the floor. These have large surface area and as a result, quite effective. And floor reflections are one of the few that are not good. See https://audiosciencereview.com/forum/index.php?threads/perceptual-effects-of-room-reflections.13/

    If the room is still too live, then you can indeed put something behind the system as front reflections are not beneficial either.

    I wouldn't dangle anything in front of that window. You want the light in and not interfere with opening and closing of that door.

    Put some plants, bookshelves, etc. where you have the other two circles if the room is still too live.

    Note that all of this will make small differences. The biggest improvement will come from optimizing the bass response using DSP/Room EQ.
     
  7. amirm
    Unless you are mixing/recording music, or are part of the 5 to 10% exception, that is the opposite of what you want to do on walls. Modern psychoacoustic research shows side reflections to be absolutely beneficial. See the link I provided above for a tiny fraction of the research data that is out there on that.
     
  8. yage
    Interesting. I read through your link the and the very first reply was from Ethan Winer who disputed your conclusion. I've also come across the research on first reflection points by Toole et al. on Audioholics. I should've caveated my post by stating that the OP try to treat the first reflection points to hear how that changes the sound, whether for the better or worse. Maybe they're in the 5 to 10%.
     
  9. bigshot
    Ethan Winer has a great video on youtube on this subject
     
  10. amirm
    And what do you think Ethan does? Records music. As I said, that group is an exception.
     
  11. bigshot
    Ethan Winer is a pretty good resource for info on this stuff. Theory is theory. Application is the only difference. A recording studio requires tighter standards than a home, but the concept is the same. I have tremendous respect for him. He knows his stuff and he has a good perspective on how to apply it.
     
    Last edited: Jan 1, 2018
  12. amirm
    Ethan is a good friend and I have debated these issues with him at length over many years. As I mentioned, his frame of reference is different than vast majority of listeners. And no, studio needs are not at all what we want at home. A studio is a workplace. Home is for entertainment.

    Dr. Toole explains this conflict well in his book, Sound Reproduction:

    upload_2018-1-1_0-17-28.png

    As you see, when you use a room for work, your ears can get trained to hear reflections differently than others. And at the same time, there is a job to be done which is hearing effects of sound manipulations to make judgements. None of that is in play when we enjoy music at home.

    The research on benefits of side reflections is extensive and quite solid. I can quote pages of it if you like. What our intuition says about this topic is just plain wrong.

    As any expert acousticians the #1 problem they see in the field and they say DIY room treatments that result in very dead spaces. The first thing they do is rip it all out.

    Sadly in forums this myth that reflections are bad continues leading to tons of wasted money to buy acoustic products, leading to uglier spaces and rooms that at the end of the day, sound worse.
     
  13. gregorio
    However, there are ALWAYS two sides to this coin. As with many areas of living, too little of something is bad but too much of that something is also bad, too little oxygen and you'll die, too much and you'll die but also, 5% oxygen would be beneficial to someone hyperventilating and 95% oxygen would be beneficial to someone with a condition restricting their ability to absorb oxygen, so what is the right amount of oxygen to give to a patient? The answer is of course that treatment only makes any sense if you know what the patient is suffering from. If you went to the doctor and they prescribed chemotherapy without first finding out if you had cancer or that it was a type of cancer which responds to chemo, you'd sue them. The first stage of treatment must therefore be diagnosis because only then can you know what treatment will actually work. This fundamental fact is often missing from audiophile thinking, simply buy a treatment and apply it, regardless of both what "condition/s" require treatment and of what condition their treatment is designed to treat. To make matters worse, there often seems to be the belief that music recording studios are designed to be quite dry/dead and therefore any and all absorbing treatment is always good, as it gets closer to that "ideal". I'm not sure where that belief has come from but it's false, recording studios are typically designed to have a reverb duration roughly comparable to consumer rooms!

    In short then, most of the advice given is purely speculative, no one here knows what problems you are actually getting at your listening position and yet they are providing absolute statements about what you should and shouldn't do? All the advice you've been given might work well, might not make any difference at all or might even make things a bit worse, depending on exactly what's wrong with your room in the first place. Additionally, you've just said "panels", which is relatively meaningless, it's like saying you've got some medicine; unless you know what's wrong with the patient AND what that medicine is designed to cure, it's meaningless. So, do you really need to reduce reflections or are you just saying that because you believe dryer/fewer reflections must automatically be better, what's actually wrong with the patient? And, what's the medicine you've got, what sort of panels, what are they designed to cure; are they absorption or diffusion panels and what frequency range are they effective at treating? You therefore really need to run some measurements and find out what's actually wrong, failing that, the next best advice I've seen so far is simply to get a couple of friends to hold the panels in various places and pick where sounds better to you in your listening position and to try various amounts of those panels (less/fewer can sometimes be more!). Blindly treating or not treating the primary reflection points (or anywhere else) is IMHO, the worst option!

    G
     
    Last edited: Jan 1, 2018
    jgazal likes this.
  14. amirm
    Really? So if someone says USB cables sound different and I said no, you would say the same thing?

    As to the rest of your post, I am unclear why you are addressing me. I didn't give the blanket advice to go after reflections. Indeed I said not to rush into that and provided a set of steps to evaluate the room.

    The latest topic is specific to the reflections being "bad." The research here is very conclusive conducted by multiple experts over some 40 years. Reflections are not bad. They increase sound power (total energy of what you hear) allowing better comprehension and extraction of information out of what we hear (think voices in movies and classrooms with students hearing teachers). Side reflections are beneficial because they turn the point source of a speaker into a wider area. Since that is how real life works, we appreciate and like that effect. Think of listening to a band on stage. Is the sound coming from a focused point or a larger diffused area where the band plays?

    On this front then, unless OP is outfitting a studio or is asking questions in the context of recording/mixing music, we can safely give advice to leave lateral reflections alone.

    Likewise floor reflections are shown to change timbre above 500 Hz so it is a safe advice to put a thick carpet there assuming the room is not overly dead already.

    Other solid advice is that frequencies below transition of 200 to 400 Hz are always distorted by the room so using DSP to fix the peaks there is always valid.

    Buy a good speaker with well behaved off-axis response, and blind controlled listening tests to verify its performance and you are golden!
     
  15. bigshot
    It's been my experience that in general terms, the needs of a studio and the needs of the home are basically the same. The only difference is a matter of degree. The basic concepts are the same. A studio just needs a higher degree of quality and is focused on a single listening position, and a home might need compromises to facilitate the quality of life in the space. But an unwanted reflection is an unwanted reflection. Generalized reflections are better than very specific ones. You use your ears and your brain and you figure it out. If someone wanted to create a room like a studio in their home, it would certainly work. It would just be overkill for the purpose of listening to music in the home. There's a lot of that going around however!

    A rug was helpful in my listening room because I had a concrete slab floor. A different kind of floor might be better without a thick rug. And off axis performance depends on whether there's off axis listening positions. In this particular case, I would bet that the floor of the apartment might be fine as it is, and there wouldn't be any off axis listening position in a multipurpose room that small. His biggest problem is probably going to be the reflections off the side walls, ceiling and the rear. I'm guessing there is tile in the kitchen area. Some listening and experimenting with placement of the panels he bought would help him figure that out.
     
    Last edited: Jan 1, 2018
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