Room Acoustics

Discussion in 'AV Receivers' started by WendyS, Apr 1, 2004.

  1. WendyS

    WendyS Stunt Coordinator

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    I'm not sure which forum to place this in.
    I've had 3 different systems over the last 15 years and have never been happy with the sound I'm getting.
    I'm starting to wonder if it's the room!!!
    The room is located in my basement....approximate size is 16x26x7. The floor consists of pine planks suspended on concrete subfloor using 2x4's.....so there is air space between the floor and concrete.
    The bottom 1/3 of the walls is natural wood wainscotting.....the rest drywall. The wainscotting seems to be installed directly on the wall studs....no drywall behind it.
    So.....about 50% of the surface area of this room is wood.
    The ceiling is the tbar/tile drop type...more air space but great installing and hiding speaker wires!!!
    One of the corners of the room which I have my HT setup is a stone wall behind a cast iron wood stove.
    Isn't wood considered a soft surface when it comes to acoustics? In other words......a good?
    What about all this air space in the floor and the ceiling?
    Except for my back surround which are wall mounted about 18 inches from the ceiling, my speakers are all floor standing.
    Any thoughts?
    Could this room be the cause of my disappointment?
     
  2. Wayne Ernst

    Wayne Ernst Cinematographer

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    It very well could be. Personally, I have a room that is 15 x 21 x 8' high. When driving my 5 speakers and 2 Shiva subs in this room with my H/K AVR-7200, I never had the music level beyond the -30 mark as the music would be rockin' the place. My walls are drywall and I have carpet on 100% of the floor which covers and cement base floor.

    I think the wainscott material might be bouncing off lots of your sounds because usually it isn't a very absorbant material - when compared to something like drywall with paint on it.

    To cheaply test and revise the acoustics in your room, you might look into some home-made acoustical panels to improve some of the sounds.
     
  3. Wayne A. Pflughaupt

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    Wendy,

    You didn’t exactly tell us what you find “disappointing” about the way things sound in your room, but I think I can take an educated guess from the information you provided.

    Not at all. It isn’t as bad as concrete, but it’s still a fairly hard, “live” surface. You didn’t say what kind of material is being used for the ceiling tiles, but usually they aren’t overly absorptive either.

    Bottom line: It looks to me like you have way to many reflective surfaces, with minimal-to-no absorption or dampening – walls, floor and probably ceiling. Doesn’t leave much, does it? [​IMG]

    I think the first thing I’d do is carpet the floor, if not wall-to-wall (preferable) then at least a huge throw rug. I’d also apply dampening materials to at least 50% of the wall surface. If you don’t have any draperies anywhere, some framed panels with carpet in the center, placed on the walls at regular intervals, will do the job.

    Regards,
    Wayne A. Pflughaupt
     
  4. Brian OK

    Brian OK Supporting Actor

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    Wendy,

    If you ever entered my dedicated basement HT from the stairs and looked into the room you would scream in horror at how ungodly ugly it looked with all the room treatments in place.
    Large rolls of insulation stacked 4 high up to the ceiling covered with Jute. Not unlike the bales of hay you see in fields at a distance wrapped in white plastic - except mine are upright.
    Wall panels 6" thick spaced 4" away from the wall, again wrapped in jute. Triangular pillows in all the corners, again wrapped in jute. And those square convoluted "thingies" on the walls (diffusors) that stick out like camel humps and dinosaur scales.

    Are you sure you want your room to look like my basement eyesore in order to get good sound ?
    Just a thought.

    Wayne has excellent advise. Rugs and wall hangings (wool with polyester batting are an easy combo) are a great start. If you hear the differences for the better, then take it a step further. Before I even started on messing up the looks of my room, I paper clipped about 2-3" of poly batting to a wool Mexican floor rug and tacked it to the first reflection points on my side walls. Bingo. I could head mid-bass..... yahooo !!!!
    You guessed it, that was the start of my room treatment nervosa.
    Experiment with this first reflection point and listen in your sweet spot for instruments never heard, notes never struck, smoother HF signals, less harshness, a little deeper soundstage......etc. If you hear the subtleties, and like the improvements, then remove the paperclips and sew until it looks just cheeky.

    You get my point.

    Good Luck

    BOK
    2 typo edit...
     
  5. WendyS

    WendyS Stunt Coordinator

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    Why are many theatres and concert halls richly decorated with wood? Sound booths in recording studios? This is what made me think that wood is good. LOL
     
  6. Brian OK

    Brian OK Supporting Actor

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    Wendy,

    Those halls were built by acoustical engineers with "mad science" !!!!
    Seriously, halls like those are designed with ceiling and wall dimensions to fit a certain sound decay level. It is formulaic for sure, but it is a science and sound waves are predictable.

    But keep in mind that the damping factor and decay is predicated on a hall full of warm and clothed bodies sitting in seats. We are not covered in jute though :*0

    Ever hear live music played in an empty concert hall ? Rings/reverbs and echoes like hell. Just not pleasant.
    Recording studios nearly invented the stuff we call treatment... hoarders of foam.

    BOK
     
  7. TimMc

    TimMc Stunt Coordinator

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    Brian - camel humps on the walls? You are one sick cowboy...

    Wendy - the best part is that he's pretty much right on. Maybe not with the fashion statement part, but some room treatment stuff really can be significant. I haven't gone to the stacked bales of insulation yet (although I do make the family wear Jute Suits in "the listening room" ;~). But I had caught some of Brian's earlier posts and figured out how to test some of the room treatment stuff out. I can't exactly go all-out "anechoic modern" but we are now carpeted & have overstuffed fabric furniture and some foam-backed curtains. I started figuring out some of this with towels & blankets, of all things. You can approximate Brian's camel humps with some folded towels and you can hang a couple of blankets together on a wall to deaden the wood or wallboard. And it works OK, without commiting to camel parts (and the camels will thank you for that)...

    PS - I was also listening to Studio 100s this past week in a Paradigm dealer's smaller audition room. Very bluntly, they were terrible - but mostly because of the room. Downstairs in the anechoic foam-treated room things were much, much different (bordering on spectacular). I came away w/ it's much easier to try this room treatment stuff that buy new gear or a new room (but YMMV).
     
  8. Brian OK

    Brian OK Supporting Actor

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    Tim,
    Yeah, the Auralex diffusors.. aka "camel humps" are the thingies. Auralex calls them "mini-fusors" and they are a 9"x9" polymer plastic which can be placed literally anywhere in a room. I filled their cavity with minimal expanding foam (in the can @ HD) per Jon Risch's recommendation in order to allow them to absord some lower frequencies.
    I have added some MUCH LARGER Auralex T-Fusors (foam filled again) recently in the rear of the room and they have helped tremendeously.

    Room treatments are a double edged sword. If you want to spend mega-bucks you can go for ASC tube-trap stuff. The best out there commercially. Proven and copied by all.
    Or, you can approach it from the deranged "cowboy" angle and save cash but achieve 80% of the ASC model.

    But diffusion, IME, is only part of the treatment approach.

    Absorption is the first step. Just causing decay of the first reflection points from the front L,R speakers can make those speakers image more accurately. Bass traps (and I know this is the WAF "no-no") are the biggest sonic return for the time and money spent. Jon Risch's "Quick and Dirty" recipe (the stacked insulation which I follow) will get you to 80%, or so, of the ASC model. And as odd as they look in ones room, they honestly battle the nasty room modes that hang out in your corners and can literally snap your midrange into immediate focus while calming the HF (the jute is used because it is acoustically transparant and it actually hides 2" of poly batting which is wrapped around your insulation bales so as to handle the HF hash).
    In a nutshell, a couple of wall hangings and some absorption in your rooms corners can transform your room into a pleasant listening environment. Throw a plastic fica plant here and there and you have some diffusion.

    Speaker placement and listening position are also HUGE, repeat ENORMOUS factor regarding your rooms sonics (this goes without saying)...... but that is real science and another volume.

    Think twice about "upgrading your various components. There is a wealth of info out there about room acoustics... all there with a little effort .
    It's the ROOM.

    Thankfully, my wife just smiles and walks by. She can't hide her smirk though ;^)

    BOK

    typo and edit
     
  9. Steve Adams

    Steve Adams Second Unit

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    BOK, hit the nail on the head. do some research about room sonics and treatments and you will have a better sounding room for not a lot of money and some elbow grease.

    Im in the process of building a new house with a new home theater. The room will be a theater only no ohter purpose in life. I am currently figuring out how to build a proper theater and im learning lots of different things. But I have narrowed it down to using insulation, resiliant channels and double layers of gyproc. then a few wall difusors and Im set.

    Good luck wendy!
     

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