Room treatments

[Steve81]

OK, so one thread here inspired me to start delving into a topic that I've not really pushed into a whole lot before: room treatments.

As it stands now, I don't have any dedicated treatments, though by some sheer dumb luck and a little intelligent design, the placement of the furniture in my room has yielded what I'd qualify as respectable results.

So what do I have now? Well in the rear of the room, I've got a rather large shelving unit plus some other assorted furniture which ought to act as a half decent diffuser. The side walls are largely bare, but on the left side of the room, I've got a recliner placed right at a first reflection point, and on the right side, a piece of my sectional also pushes into some first reflection points as well. My thought here is that a couple of well placed heavy quilts could be useful in helping to absorb some of the mid to high frequencies. Outside of that, I'm contemplating a few acoustic panels for absorption to help cut down on the decay, although the prime spots where I'd think to put them are already covered with the aforementioned furniture, and I'd rather not spend large sums of money on nice looking treatments for little to no worthwhile effect.

In terms of low end response, I think I'm fairly lucky with respect to my listening position. Response from 100Hz on down is reasonably flat, with a slightly rising low end. I can live with that and I've never really had big complaints with the decay time of the bass in my room at my listening position. Probably the biggest issue in my book is a bit higher around 150Hz where the front stage of speakers exhibit a moderate dip (somewhere on the order of 10dB, though I've found that Audyssey does help a little with this, probably by boosting the heck out of it). My main concern with bass trapping to attempt to fix this is that I'd risk screwing up everything else. Also well...bass traps are ugly and I don't have a lot of corner space to put them.

Any thoughts?

 

[ImcLoud]

If you are happy with the sound leave it alone... I am a believe in if its not broke don't fix it, I know in this hobby its hard to admit when its done, but sometimes it is done no matter how much more money you can throw at it...

but anyway, throw some pics up here and Im sure someone will have a bunch of ideas for you to spend your money

There are a ton of videos showing how to use mirrors and masking tape to find out how to place treatments...

I thought about room treatments, but 2 factors steered me away
1-my wife, I dont want to argue about triangles in the corners....
2- Cost, IMO the stuff is expensive, your talking $1500 to do a good sized room with good looking decent stuff, that is a lot...

If you are in a studio or have a designated listening room with egg cartons on the ceiling that is one thing, but if you are like me and need to use this room as a living room and entertain family and friends in it, than doing more than letting room treatments sway your decision on curtains or no curtains is kind of crazy... I know my uncle is nuts with his living room, he actually returned a coffee table and chair because they glass top and wood railings were interfering with the sound, I heard it before and after and noticed no difference... He also added about $1000 of panels and traps, {and paid a guy to come and tell him what and wear} and I honestly liked the bass sound before more than after.....

But anyway, I will agree its a better investment than a $1000 power conditioner and $800 speaker cables...

 

[anamorphic96]

Room treatments where the best money I ever spent aside from good speakers. It can also be done for pretty cheap if your creative. It can also look good. Most of the time you don't have to treat the whole room. Just getting the back wall and first reflection points can make a huge difference.

I treated my room for less than 300.00. Check out ATS acoustics they have some great panels for around 30.00 a piece. There well built and offer lots of different styles.

Acoustic Panels by ATS Acoustics

 

[Steve81]

A few pics; excuse the mess

 

[Steve81]

If you are happy with the sound leave it alone... I am a believe in if its not broke don't fix it, I know in this hobby its hard to admit when its done, but sometimes it is done no matter how much more money you can throw at it...

I can empathize with this sentiment a lot, and really I'm a little weary of going down this path too heavily. The room is clearly a living space, not a recording studio, so there are limits as to what I can do from an aesthetic standpoint. Further, I am very happy with the sound I'm getting now. My wife and I can easily spend an afternoon/evening watching movies in the basement, so I'm clearly not getting fatigued by all the reflections. Still, I'm curious...

 

[jostenmeat]

Hello Steve, I'm a little unclear on the layout (which way is longer, etc), particularly in regards to last pic, sideways pics might confuse me a bit, but regardless . . .

You can't screw it up with bass traps, there is a saying that you can't go overkill with them. Except perhaps for killing the "liveliness" of the room, which you very well might not want to do. But not as far as FR or anything like that. So, outside of getting some standard bass traps, other possibilities:

Off the wall idea #1, it would need to be a very large (floor space? huge double-purpose coffee table? A hulking column standing in the corner?), and I'm not just how large, but a Helmholtz resonator is interesting because it can target a very, very narrow freq range. (I believe you can tune it exactly to the freq you desire, and the possibility that it can be invisible is interesting, if size allows.) The application is used in the automotive industry (exhausts, etc), and yes, also in high end HTs (whether as dual purpose risers, or using floor space with an inconspicuous vent/hole cut somewhere). There should be many threads on the subject over at AVS.

Off the wall idea #2, grab cute little critter in last pic, perch on shoulders. Floyd Toole supposedly has a chart somewhere of a clothed human's absorption in sabines, I'm not sure about 150hz, but I was told it was around 5-7 sabines for the 1khz-4khz range. Upside: this is free, and immediately removable. Downside: unexpected startling sounds from an unintended rear 6th channel human baby speaker.

Ok, a bit more seriously, Off the wall idea #3, there appear to be other bass trapping techniques. Maybe a possibility is the membrane trap, it might possibly succeed in being a bit thinner than some other kinds, while also absorbing a particular freq range (though maybe not quite as narrow as the Helmholtz). I'll paste an excerpt that I just found right now, by Ethan Winer, regarding this. I've taken the liberty to boldface some parts for you.

Another type of tuned bass trap is the membrane absorber, also called a wood panel bass trap because many designs use plywood for the front panel. Wood panel traps are a mass-spring system, where the panel is the mass and air trapped inside a sealed box serves as a spring. Figure 19.7 shows a cutaway view of a typical wood panel membrane trap, built directly onto a wall. When a wave within the effective range of frequencies reaches the front panel, the panel vibrates in sympathy. Since it takes energy to physically move the panel, that energy is absorbed rather than reflected back into the room. Even though the fiberglass doesn’t touch the plywood front panel, it damps the panel so it doesn’t continue to vibrate. Were the panel allowed to continue vibrating on its own, less energy would be needed to keep it moving, so it would absorb less. Further, a panel that continues to vibrate after the source sound stops adds resonance into the room rather than removes it, which obviously is not desirable.

One advantage of wood panel membrane traps is they don’t need to be thick to absorb very low frequencies. Like all pressure traps, they work best mounted directly onto a wall or ceiling, rather than spaced away as benefits porous absorbers. The center frequency absorbed by a wood panel bass trap is a function of the panel’s mass and the depth of the air gap, which serves as a spring. A trap four inches deep with a 1/4-inch-thick plywood front absorbs 100 percent at around 90 Hz, which is more than the same thickness of rigid fiberglass at that frequency. The audible bass range spans several octaves, and panel traps absorb only part of the bass range. Therefore, a mix of traps is required, with some tuned to absorb the lower bass frequencies and others for the higher bass range. Besides absorbing low frequencies very well, the wood front on a panel trap is reflective at higher frequencies. So installing enough of them to make a real improvement at low frequencies will not make the room too dead-sounding.

http://audioundone.com/do-it-yourself-bass-traps

 

[Steve81]

Appreciate the input JM,

Hello Steve, I'm a little unclear on the layout (which way is longer, etc), particularly in regards to last pic, sideways pics might confuse me a bit, but regardless . . .

The first shot is head on into the front stage from the main listening position. The second shot is taken from the right side and capturing the left speakers/wall. The recliner is covering some first reflection point territory, and I think a heavy quilt folded over a couple times tossed on top of it could have some beneficial effect. If nothing else, it won't be terribly costly nor will it be an eye sore. Third shot is taken from the left side and capturing the right side of the room. Again, the sectional does push into first reflection points, and since that one is likely to be more reflective, some heavy quilts there could be useful I think. The last shot is the rear of the room from the perspective of the main listening position. With all the stuff back there, it should act in my little pea brain as a poor mans diffuser. I'm aware the big lightly covered window isn't exactly ideal, and the wife unfortunately isn't interested in heavy drapes (nor am I for other reasons, namely the glass break sensor on the security system).

Dimensions of the room are ~24Lx~13Wx~7H plus another few feet of width for the stairwell. Room is arranged so that speakers are firing down the length of it, with the listening position a tad under 10 feet from the front wall.

You can't screw it up with bass traps, there is a saying that you can't go overkill with them. Except perhaps for killing the "liveliness" of the room, which you very well might not want to do. But not as far as FR or anything like that.

Well that's somewhat comforting at least.

So, outside of getting some standard bass traps

I'm actually not entirely opposed to something akin to this (of course whether my wife is opposed is another matter) up in the rear top corners of my room, but I do wonder just how much it would accomplish at the same time:

RealTraps - Tri-Corners

Off the wall idea #1... Ok, a bit more seriously, Off the wall idea #3

Interesting possibilities, but unfortunately (and I should have mentioned) DIY territory is where I'm well...incompetent

Off the wall idea #2, grab cute little critter in last pic, perch on shoulders. Floyd Toole supposedly has a chart somewhere of a clothed human's absorption in sabines, I'm not sure about 150hz, but I was told it was around 5-7 sabines for the 1khz-4khz range. Upside: this is free, and immediately removable. Downside: unexpected startling sounds from an unintended rear 6th channel human baby speaker.

Nice

 

[jostenmeat]

The first shot is head on into the front stage from the main listening position. The second shot is taken from the right side and capturing the left speakers/wall. The recliner is covering some first reflection point territory, and I think a heavy quilt folded over a couple times tossed on top of it could have some beneficial effect. If nothing else, it won't be terribly costly nor will it be an eye sore. Third shot is taken from the left side and capturing the right side of the room. Again, the sectional does push into first reflection points, and since that one is likely to be more reflective, some heavy quilts there could be useful I think. The last shot is the rear of the room from the perspective of the main listening position. With all the stuff back there, it should act in my little pea brain as a poor mans diffuser. I'm aware the big lightly covered window isn't exactly ideal, and the wife unfortunately isn't interested in heavy drapes (nor am I for other reasons, namely the glass break sensor on the security system).

The danger with the boldfaced ideas is that they would probably do exactly opposite of what you want. They would probably absorb plenty of the lively HF that you apparently are totally fine with, and do absolutely zilch for the problem freq(s) that you were originally concerned with. Hence, the term "broadband" is rather important for many applications.

Dimensions of the room are ~24Lx~13Wx~7H plus another few feet of width for the stairwell. Room is arranged so that speakers are firing down the length of it, with the listening position a tad under 10 feet from the front wall.

Getting pretty warm to that "starting 38% of room length" for balancing out axial modes in a rectangular room.

I'm actually not entirely opposed to something akin to this (of course whether my wife is opposed is another matter) up in the rear top corners of my room, but I do wonder just how much it would accomplish at the same time:

Those are so small, that I nearly consider them as accessories; add-ons. Nothing beats mass. Sure, a bit of air gap lets the treatments be a little more efficient. Now, the corners are definitely a bang for buck place, but with those things, I'm not sure you could even discern a difference. The thing with treatments is that they are a cumulative effect. While it's quite rare that just a couple/few/several can make a significant discernible impact, I have once experienced that. However, it was because of something that I'm certain that was inside* the wall that was getting "excited".

Interesting possibilities, but unfortunately (and I should have mentioned) DIY territory is where I'm well...incompetent

I'm terrible too, generally speaking. However, I love the idea of hiring people for these situations. What could be a great possibility if that was my room, is to hire one friend to help build the membrane trap (of course after plenty of research; also curious as to weight and thickness of various possibilities of wood/membrane), and then another friend to turn it into a piece of artwork. (I'm lucky to be friends with two pro artists; I'm sure we could work out a favorable agreement.) In the best case scenario, it could be a fantastic piece of artwork, made to order, just maybe sticking out an inch or two more than you would typically see, but where any given guest wouldn't have a darn clue it is masquerading as freq(s)-specific bass trap. Just a neat idea I guess.

That all said, maybe something more massive than that RT Tri Trap? Perhaps this GIK tri trap, in a lighter color to blend with wall, somewhat hidden next to the subwoofer (which would have to scoot away from corner a tad bit to allow it)? I have both brands, btw, RT does have better fit and finish, but GIK does provide nice value. I didn't check out much with either, short on time.

Corner Bass Tri-Trap : GIK Acoustics

Gotta run, had less time to compose this email than anticipated. Cheers!

 

[Steve81]

Getting pretty warm to that "starting 38% of room length" for balancing out axial modes in a rectangular room.

Goes back to that sheer dumb luck thing; the layout happened to work rather well for the room as the front half is HT area and the back half is the wife's craft area and kid's play area.

Those are so small, that I nearly consider them as accessories; add-ons. Nothing beats mass. Sure, a bit of air gap lets the treatments be a little more efficient. Now, the corners are definitely a bang for buck place, but with those things, I'm not sure you could even discern a difference.

That's about what I figured, but I thought I'd ask.

Perhaps this GIK tri trap, in a lighter color to blend with wall, somewhat hidden next to the subwoofer (which would have to scoot away from corner a tad bit to allow it)?

Could it go in the corner diagonal to the sub? The white box above the sub is the breaker box, so I'm not exactly keen on covering that up.

In the best case scenario, it could be a fantastic piece of artwork, made to order, just maybe sticking out an inch or two more than you would typically see, but where any given guest wouldn't have a darn clue it is masquerading as freq(s)-specific bass trap. Just a neat idea I guess.

Definitely an interesting possibility. I could probably even pull off such a thing with the wife, depending on how big we were talking. Of course, if I were really going to do this, I'd probably contract it out to a pro who would come in, take measurements, etc. That'd be a much longer term project than just buying a couple corner traps

 

[ImcLoud]

Honestly by looking at the pic, and judging by your comments, I would take the money and go buy the baby some toys, he looks like a little brute, so a football may be a good investment ...

But seriously, I have played with room treatments, and in some rooms they will be a huge plus and well worth the investment, but for a room like yours that is for living, just enjoy what you have...

Plus it looks like you use it primarily for HT, and imo room treatments are best for music listening where you will be critical, with a movie you shouldnt be sitting there pulling acoustics apart....

Anyway, congrats on the nice system and good looking baby

 

[Steve81]

Honestly by looking at the pic, and judging by your comments, I would take the money and go buy the baby some toys, he looks like a little brute, so a football may be a good investment ...

Ohh yeah... At last check, he was 85% percentile on height for his age, and 100% percentile on weight for his height. He's starting to level off in the weight department, but he's in 24 month clothes, and has been for a little while.

Plus it looks like you use it primarily for HT, and imo room treatments are best for music listening where you will be critical, with a movie you shouldnt be sitting there pulling acoustics apart....

Anyway, congrats on the nice system and good looking baby

Appreciate the input; I do generally agree, I'm not sitting there going gosh, I've got a dip at 150Hz during Skadoosh (Kung Fu Panda) and other such scenes, I'm going OMG OMG!!! Still, was worth getting opinions. Sounds like it might be more than I'm willing to chew on at this point.

 

[fuzz092888]

Appreciate the input; I do generally agree, I'm not sitting there going gosh, I've got a dip at 150Hz during Skadoosh (Kung Fu Panda) and other such scenes, I'm going OMG OMG!!! Still, was worth getting opinions. Sounds like it might be more than I'm willing to chew on at this point.

I think you may be approaching acoustic treatments for movies from the wrong angle. It's not so much for that hump here dip there type of stuff. It's to keep any nasty room induced spikes or dips from influencing the sound. Obviously RC helps out a lot, but the flatter you get your room to start with, the more RC can do it's magic. It'll help make bass tighter and more defined, gunshots really snap and decay, dialogue come through crystal clear. I'm not even claiming the acoustic treatments will make a huge difference. It all depends on how your room was to begin with.

 

[ImcLoud]

Ohh yeah... At last check, he was 85% percentile on height for his age, and 100% percentile on weight for his height. He's starting to level off in the weight department, but he's in 24 month clothes, and has been for a little while.

He looks healthy, my 13 year old has shoulders wider than most of the male teachers at his school, and my 11 year old weighs over 130 lbs with no belly.... But rite now he practices with his older brothers team since he is over the weight limit and under the age limit, but its making him into a monster, he hits so hard for a little kid, you ever see a 135lb 11 year old do 9 pullups? lol I think he is going to be bigger than me {I'm 6'5" up to 290, and still run the 40 in 5.05} {well the shoulder surgery has me in rough shape since I'm sitting on the laptop talking about stereo systems instead of working and hitting the gym 9 times a week....} But thats the price you pay when you want to get one more rep out, even after you feel a hot pain following a loud crackle right next to your left ear...

 

[agarwalro]

Probably the biggest issue in my book is a bit higher around 150Hz where the front stage of speakers exhibit a moderate dip (somewhere on the order of 10dB

Sounds like floor bounce effect originating from the ceiling. You can use this tool to verify the calculation, Floor/Ceiling Reflection Calculator

If verified to be the cause, the 150Hz adoptive panel will be mounted at the first reflection point on the ceiling.

 

[Steve81]

I think you may be approaching acoustic treatments for movies from the wrong angle. It's not so much for that hump here dip there type of stuff. It's to keep any nasty room induced spikes or dips from influencing the sound. Obviously RC helps out a lot, but the flatter you get your room to start with, the more RC can do it's magic. It'll help make bass tighter and more defined, gunshots really snap and decay, dialogue come through crystal clear. I'm not even claiming the acoustic treatments will make a huge difference. It all depends on how your room was to begin with.

Appreciate the input fuzz.

I'm not really sure how to approach acoustic treatments, and that's what is warding me off from them the most right now. I mean, getting a couple artsy looking 2" thick panels and a pair of tri-corner traps and hanging them around the room seems like a piece of cake, but if they don't accomplish anything of great value, there's not a lot of point to it, and that's what I'm afraid of.

As mentioned in my OP, it seems like I've got some of the basics already taken care of with the placement of furniture and some dumb luck. I've got no actual complaints when listening to anything, which makes this whole thread more of an exploratory foray rather than an attempt to solve a specific problem.

 

[Steve81]

you ever see a 135lb 11 year old do 9 pullups?

I know very few that can do even one, which is a sad commentary in and of itself. Not that I've got a lot of room to talk; when I lived in an apartment, I had a pullup bar (you know, the iron gym from the infomercial) and had a good routine going. Then I moved to a freshly renovated house with mostly 7 foot ceilings, which made things a bit more difficult. Then the kid came along... Suffice it to say, I'm probably not as tough as I was two years ago.

lol I think he is going to be bigger than me {I'm 6'5" up to 290, and still run the 40 in 5.05}

Well, I'm the "little guy" on my wife's side of the family at ~5'8/180lbs. A couple of her cousins are firefighters that probably built like you. Suffice it to say, at the going rate, my son should exceed me in size pretty quickly. I'm hoping to train him to be better than the lazy kid I was too.

But thats the price you pay when you want to get one more rep out, even after you feel a hot pain following a loud crackle right next to your left ear...

Fortunately for me, I don't have that kind of determination Take care of yourself!

 

[Steve81]

Sounds like floor bounce effect originating from the ceiling. You can use this tool to verify the calculation, Floor/Ceiling Reflection Calculator

If verified to be the cause, the 150Hz adoptive panel will be mounted at the first reflection point on the ceiling.

Thanks for the tip. I'll do some measurements at home tonight. Just running some off hand guesses though seems like it would place it a bit too high in frequency though. I'm figuring about 2.5 feet (76cm) for driver height (probably midpoint of the 2 8" drivers), 40" for ear height (101cm), and 8.5 feet distance from the driver (259cm) which puts it at ~320Hz.

 

[agarwalro]

I'm figuring about 2.5 feet (76cm) for driver height (probably midpoint of the 2 8" drivers), 40" for ear height (101cm), and 8.5 feet distance from the driver (259cm) which puts it at ~320Hz.

Unless specified, the axis of the tweeter is the 'design axis' or the line along which acoustics related choices were made and related calculations/measurements had been done by the manufacturer. This is why popular convention goes thusly, "tweeter at ear height" or "angle the center speaker to point towards the primary seat". So, you need to use the tweeter height.

Also, since you are literally turning the calculation on its head, you need to use distance to ceiling, not distance to floor . Assuming you have an 8ft ceiling, that means you speaker height = ear height = 143cm and using same distance to driver gives a result of 135Hz. Adjusting for tweeter height by making distance to ceiling = 135cm yields a result of exactly 150Hz.

 

[Steve81]

Now that makes a bit more sense, and of course complicates things. The ceiling is a tad bit lower than 8 feet, so a conventional thick treatment isn't really ideal, so I guess if I wanted to fix it, I'd need something such as what jm mentioned. Hanging it from the ceiling ought to be fun; I'm sure the wife would be thrilled with the prospect too . Don't suppose anyone sells such a product.

 

[FirstReflection]

Yours is a case where you need measurements and analysis.

You've got a lot of stuff in that room. It's impossible to predict your acoustic response right now. And your main worry seems to be spending money on acoustic treatments, but hearing no obvious benefit from them.

I can tell you that you can most certainly benefit from acoustic treatments in that room. But the absolute highest bang for your buck is going to require measurements and analysis to identify.

So I'd highly recommend that you start by contacting Auralex and taking advantage of their Room Analysis services . In your case, I feel strongly that paying for the "Room Analysis Plus" service would be worth your while. But start with the free service. I mean, it's FREE. So why not, right?

There's no point in guessing blindly as to what sort of treatments will benefit you most, and where they should be placed. Gather your data first, have it analyzed by Auralex, then come up with a plan of attack from there

You can also get great advice from GiK Acoustics. Just talk to them on the phone and hopefully send them some photos and diagrams. They're extremely helpful at GiK