Room Treatments/absorption panels / home-made bass traps

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SYN ACK

[H]ard|Gawd
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so i picked up a pair of GIK 244 4" bass traps for the time being that are being used as absorption panels behind my bookshelves:

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i dont have a sub, hence the reason the bass traps aren't in the corners at the moment...just being used to absorb the rear wall and actually made a pretty noticeable difference.

now i want more.

looking to add some 2" GIK 242 (or equivalent) abortion panels at the first reflection / side walls for the mids and highs...but im also continaully looking to make the room a bit more dead...it's a large, open 1room studio/loft...so even talking in a low volume can be fairly loud at times.

any acoustic treatments i do for audio also get the added benefit of overall sound of the room (e.g. talking/random house noises/cooking/etc)...

now, i have a lot of vertical space to play with, and only recently have moved in. now that im getting settled im looking and playing with room setup / adding new furniture/etc.

i came across the Ikea Epedit bookshelves in which i'll probably pick up a 4x4 unit to start with this weekend:
http://www.ikea.com/us/en/catalog/products/80071357

all Epedit's:
http://www.ikea.com/us/en/search/?query=expedit&pageNumber=0

great for record collection storage, and will allow me to consolidate all my other crappy bookshelves into these...and can add more / stack as i need in the future.

so that got me thinking one step further, what if i filled any empty spaces in these units with OC703 fiberglass and maybe FRK (i think it's called) on the front (to reflect a bit of the mids/highs)...and kill 2 birds with 1 stone? the bookshelves are deep enough i could have 4-6" of fiberglass, and still a huge air gap before hitting the wall itself.

has anyone done this or any recommendations/advice? probably would need to treat quite a few spaces in the bookshelf to be effective (sq area)...but in my situation i think it might work out better (and look better) than buying a bunch of bass traps/absorption panels and hanging on the wall.

interested in any comments/input,
 
If you know you're going to have a lot of space left over in the bookshelf, then I would suggest you get something smaller, and use the saved money to buy proper panels. If not, then keep the same bookshelf, and still get proper panels. lol.

I myself plan to go the DIY route with materials from http://www.atsacoustics.com. They have really good prices, and a lot of people are happy with the results. The only thing I would probably buy from them is the acoustic panels themselves, as other things like wood, cloth, and adhesive spay can be had cheaper locally.

Also, do you have windows in that apartments? If you do, you might consider getting curtains to add, or use instead of, regular shades. That's because they are cheap, and they help a lot in adsorbing sound.
Also, after everything is done with the panels and curtains, you might want to invest in a carpet. Not for the whole room of course, but a small one for the little section section where you would keep the speakers. But that can wait of course, as wood floors are not as bad as ceramic floors some people have. I have ceramic floors in this new apartment, and the echo is terrible.

Good luck.
 
echo isn't all that bad...doing a simple 'clap' test (i dont have a mic..but i do have FFT software for my iphone :LOL:)...i dont get too bad an echo after that pair of bass traps...it really helped with the rear wave / near-field ... i was surprised a pair did so much..can't wait to add more.

echo isnt a massive deal, but i know it's there...acoustics are great in near-field (where i sit at my desk)...im kinda doing it 50/50...50% for acoustic treatment and the other 50% for overall room treatment (e.g. speaking/talking, containing loud sounds / overall sound of the room).

here's some pics of my place for reference..i have blinds over my windows now but really not hurting much as far as i can tell...think ill keep them for the time being. but more panels are def on my want list...
http://img268.imageshack.us/gal.php?g=94983734.jpg

im still thinking about room arrangement (once i build a loft for my bed) so nothing is too permanent yet..but i def want to focus next on the 2" acoustic panels to absorb mids and highs (stop flutter/reflections)... i dont crank the bass too much (no sub at the moment), so the bass traps arent an absolute necessity.

i was thinking about putting a 48"x24"x4" corner bass trap (white) on top of my cabinets there in the corner in the first pic by the furnace vent..and then a smaller 24x24x4" corner bass trap under my tv (against that corner)..cant do 48" because it's too tall / obstructs windows. the wall behind that is mostly flat...no corners.
 
can't remember if i mentioned it yet or not, but you have large areas of hardwood floor, so you'll be getting a lot of floor > ceiling waves, kind of like an auditorium. You may benefit the most from absorption/diffusion on the ceiling, especially considering the depth of the walls.

THe bookshelf idea is a good one, and you definitely have the room for them. Every little bit helps :)

Oh, and get those speakers isolated from the desk.
 
aardvark sandwich said:
can't remember if i mentioned it yet or not, but you have large areas of hardwood floor, so you'll be getting a lot of floor > ceiling waves, kind of like an auditorium. You may benefit the most from absorption/diffusion on the ceiling, especially considering the depth of the walls.

THe bookshelf idea is a good one, and you definitely have the room for them. Every little bit helps :)

Oh, and get those speakers isolated from the desk.
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refresh my memory on what isolation will gain me - besides an obvious early/first reflection off my computer desk (e.g. if wall mounted or mounted on stands)

the speakers are 20lbseach on those crap rubber feet...ive felt around and didnt feel any movement when they were turned up a notch.

i know you dont want your speaker to be unstable / any slight movement could be devastating...
 
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SYN ACK said:
refresh my memory on what isolation will gain me - besides an obvious early/first reflection off my computer desk (e.g. if wall mounted or mounted on stands)

the speakers are 20lbseach on those crap rubber feet...ive felt around and didnt feel any movement when they were turned up a notch.

i know you dont want your speaker to be unstable / any slight movement could be devastating...
Click to expand...

Better bass. Bass frequencies will travel in to the desk/floor/whatever and turn it in to an unwilling resonator. That'll lead to worse sound. The better isolated they are, the less of the problem. Now, with rubber feet, they may already be plenty well isolated. There are diminishing returns as with anything else. Most important is just to not have them laying directly on another hard surface.
 
^^ that. Shared vibration = distortion. Plus it should sound better if its as close to ear-level as possible, so putting them on something like mopads or the primacoustic pads will raise them about 2 or 3 inches. Probably not enough elevation, but I'd imagine it'd still be an improvement.
 
right - tweeter is already at about ear level.

these bookshelves (jbl L820s) are made to be wall mounted (surrounds) - so most of the abs-pads out there arent made to fit these (their 15" wide and only 5.5" deep)...guess i could get my own material and cut to fit ..
 
Sycraft said:
Most important is just to not have them laying directly on another hard surface.
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regardless of bass, im actually more concerned being near-field and having an early reflection of the mids/highs coming off the desk itself
 
upon further testing, yes. ..i can feel bass transfer through my desk.
one more thing to work on
 
Well isolation won't help you with that. You could put an absorbent material on the desk,but that might interfere with usability. You could also get a receiver with MultEQ which can deal with some of the effects of things like that, but it is costly and I don't know how well it deals with near field work (it is designed for home theater).
 
For isolation form the desk, Auralex Mopads should do the trick nicely. They are dense bunches of foam that don't transmit vibration well. They are also cut such that you can angle the speakers up or down a few degrees.
 
Sycraft said:
Well isolation won't help you with that. You could put an absorbent material on the desk,but that might interfere with usability. You could also get a receiver with MultEQ which can deal with some of the effects of things like that, but it is costly and I don't know how well it deals with near field work (it is designed for home theater).
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eq isn't going to help with early/first reflections.

nor do i think any type of material on my desk will fully absorb the first reflection. i think my best bet is to wall mount or mount on stands/off the desk...but that will come later.

the reflections arent obvious at the moment ... acoustics is fairly good near field; im rather impressed after just a pair of bass traps. but still looking forward to adding more
 
Sycraft said:
For isolation form the desk, Auralex Mopads should do the trick nicely. They are dense bunches of foam that don't transmit vibration well. They are also cut such that you can angle the speakers up or down a few degrees.
Click to expand...

none of the ones i originally looked at fit my bookshelves (15" wide x 5.5" deep)

they were all more for standard narrow/deep bookshelves.
 
SYN ACK said:
eq isn't going to help with early/first reflections.

nor do i think any type of material on my desk will fully absorb the first reflection. i think my best bet is to wall mount or mount on stands/off the desk...but that will come later.

the reflections arent obvious at the moment ... acoustics is fairly good near field; im rather impressed after just a pair of bass traps. but still looking forward to adding more
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I can help to a degree. When you are talking reflections that close, there's little time difference between the signal and the reflection. Sound moves at around 34cm/ms. So at the kind of distance you are looking at you are talking maybe a couple milliseconds between the direct and reflected wave.

Also advanced systems like MultEQ are actually FIR filters, which operate in the time domain. They can deal with reflections and so on to a degree.

You can also check and see if you can find out what the dispersion of your tweeters is like. Depending on the tweeter and the baffle of the speakers, you can get real different dispersion patterns. Often speakers try to optimize for a small amount of vertical dispersion and a wide horizontal dispersion. In that case, you'd probably not have a ton reflections off the desk. It might require reorienting your speakers though (turning them so the long edge is vertical). You'd have to find out.
 
should be picking up some ikea epedit bookshelves this weekend and then find out how much space i have to work with - using those unused spaces to stuff with OC703 fiberglass.

keep everyone posted/take photos as i go...
 
Sycraft said:
I can help to a degree. When you are talking reflections that close, there's little time difference between the signal and the reflection. Sound moves at around 34cm/ms. So at the kind of distance you are looking at you are talking maybe a couple milliseconds between the direct and reflected wave.

Also advanced systems like MultEQ are actually FIR filters, which operate in the time domain. They can deal with reflections and so on to a degree.

You can also check and see if you can find out what the dispersion of your tweeters is like. Depending on the tweeter and the baffle of the speakers, you can get real different dispersion patterns. Often speakers try to optimize for a small amount of vertical dispersion and a wide horizontal dispersion. In that case, you'd probably not have a ton reflections off the desk. It might require reorienting your speakers though (turning them so the long edge is vertical). You'd have to find out.
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well, it's still an early reflection even if it's only 5ms difference from the source.
the brain can't determine that it's a different source for what, 25-35ms? so early reflections can still damper clarity. - although like i said, there isn't any obvious issues from what i can tell...but just by looking i know they're there.

really not interested in EQ for the most part - rather get my room sounding right/treated and then work from there.
 
anyone else help me find some isolation pads that will fit my bookshelves (e.g narrow and wide...15.5" wide 5.5" deep).

thanks
 
Sycraft said:
For isolation form the desk, Auralex Mopads should do the trick nicely. They are dense bunches of foam that don't transmit vibration well. They are also cut such that you can angle the speakers up or down a few degrees.
Click to expand...

yeah, looks like ill just use a pair per speaker (to support the width) ... cool
i don't want the ones that angle downwards, though - just flat/level.
i can't tell if the mopads allow this or not (are they all tilted/angled? or is that an option

where the hell can you buy those? im seeing dealers/distributors on their web site:
http://www.auralex.com/sound_isolation_mopad/sound_isolation_mopad.asp

edit: looks like amazon.com has them / google is my friend.

but where can i purchase online?
i hope they are sold in pairs - buying 4 (2 per speaker) could get expensive quick!


what's the difference between the mopads and the speakerdudes?
http://www.auralex.com/sound_isolation_mopad/sound_isolation_mopad.asp
http://www.auralex.com/sound_isolation_speakerdudes/speakerdudes.asp
 
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The angle is an option. More or less they have some angled cutouts and depending on how they are inserted you can have 4, 2, 0, -2, -4 degrees of tilt.

They are sold in quads actually. The intent is that you will use two pads per monitor, so the 4 pack is enough for two speakers. I use 4 on my centre speaker, since it is quite large. However an option on many speakers is simply to leave space between the two pads. The less contact the better, over all, so long as it can still support the speaker.

I haven't encountered the speaker dudes, they seem new. From looking, I think the only difference is they are bigger. Everything form Auralex is more or less the same material. It is just a dense foam that doesn't transmit sound/vibration very well.

Look at pro shops to buy them, they are mainly a studio product. I bought mine at a local pro shop, but Musician's Friend will happily ship them to you.
 
You can use them sideways, shouldn't matter if you don't want to angle the speakers. Having gaps is not important, simply an option.

Buy from Musician's Friend instead, as they are $40 for a quad pack, which should be all you need for your speakers.
 
guitar center has them for the same price and there is a local store so i can pick them up tonight
nice - thx
 
SYN ACK said:
well, it's still an early reflection even if it's only 5ms difference from the source.
the brain can't determine that it's a different source for what, 25-35ms? so early reflections can still damper clarity. - although like i said, there isn't any obvious issues from what i can tell...but just by looking i know they're there.
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You're not understanding the concept. The total distance from the speakers to yours ears isn't what's important, only the difference in distance between the direct path and the reflected path. It's all about path length difference.

really not interested in EQ for the most part - rather get my room sounding right/treated and then work from there.
Click to expand...
Treating the room is the right first step, but EQ can be used to tweak it. Find the Sabine equation, then find absorption data for the different items and surface coverings in your room. You should also be able to find absorption data for OC703 or whatever absorbers you're planning on putting in. Build yourself a Sabine spreadsheet and you'll be able to calculate exactly how much absorption to put up to get the reverb times you desire.
 
RevMen said:
You're not understanding the concept. The total distance from the speakers to yours ears isn't what's important, only the difference in distance between the direct path and the reflected path. It's all about path length difference.
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i am talking path length difference - just in the time domain.


RevMen said:
Treating the room is the right first step, but EQ can be used to tweak it. Find the Sabine equation, then find absorption data for the different items and surface coverings in your room. You should also be able to find absorption data for OC703 or whatever absorbers you're planning on putting in. Build yourself a Sabine spreadsheet and you'll be able to calculate exactly how much absorption to put up to get the reverb times you desire.
Click to expand...

yes, that's my plan...load up on panels as best I can...but eq shouldn't even be a factor until after all that is done. what good is a -10dB max on an EQ when i have a 25dB spike? thanks for the continued input -
 
lol quality control? any idea if this is how they are supposed to come ???

92473461.jpg


36303723.jpg


41965863.jpg


the tweeters are now at ear level, and do sound a bit better in that regard...but the bass im not sure about...the mid does appear to sound a bit better, but not conclusive yet.

BUT,
im still feeling at least 75% of the original vibration on my desk!
 
RevMen said:
Is there a frequency domain for length?

So what is your path length difference? Have you measured it?
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im not trying to argue you here by any means (i really appreciate your input), but are you saying a early reflection off my desk is negligible/something i shouldnt be concerned with?

i haven't measured the path, but obviously the reflection off my desk to my ears is longer than the source to my ears.
 
The lopsided stickers aren't uncommon or anything to be worried about. So long as the foam is in good shape you are good. As for the vibration, well that sucks :/. As to what to do about it I'm not sure. All the other options I can think of wouldn't work on your desk setup or would raise them up way too high.

All in all though perfect is hard to achieve. You have to take what improvements you can get and deal with what remains.
 
SYN ACK said:
im not trying to argue you here by any means (i really appreciate your input), but are you saying a early reflection off my desk is negligible/something i shouldnt be concerned with?
Click to expand...
Correct. If the path length difference is sufficiently short, then the reflection arrives at your ears so quickly after the direct sound your ears can't tell them apart. In fact, it even reinforces the original sound.
i haven't measured the path, but obviously the reflection off my desk to my ears is longer than the source to my ears.
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Naturally, but the question is how much longer?

The term "early reflection" usually means a good thing. An early reflection is one that gets there in time to reinforce the original sound without muddying it up. A "late reflection" is what you should be worried about. Late reflections get there too late to reinforce the original sound and end up making it sound muddy or echoic.

This is the key to concert hall design (part of my job description, it turns out). I usually work with a maximum path length difference of about 30 to 35 feet. Remember that sound travels really, really fast. So if your path length difference is a matter of one or two feet it's extremely unlikely your ears will be able to tell.
 
Sycraft said:
The lopsided stickers aren't uncommon or anything to be worried about. So long as the foam is in good shape you are good. As for the vibration, well that sucks :/. As to what to do about it I'm not sure. All the other options I can think of wouldn't work on your desk setup or would raise them up way too high.

All in all though perfect is hard to achieve. You have to take what improvements you can get and deal with what remains.
Click to expand...

no - why aren't the foam pads cut to the same height.
i got 1 box with 4 pads...the pairs dont match up...so now my right speaker is slightly higher than my left.

look at the photos again, see the gap???
 
RevMen said:
Correct. If the path length difference is sufficiently short, then the reflection arrives at your ears so quickly after the direct sound your ears can't tell them apart. In fact, it even reinforces the original sound.

l.
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that is complete opposite from everything i've read (from GIK / realtraps /etc)....which state that the brain *cannot* tell a difference in signal if it arrives under 25-35ms from the source - hence it does not 'reinforce' the sound, but causes clarity/disruption...and comb filtering.

the ears can't tell them apart - that's the point...but that's a bad thing, not a good thing..
 
RevMen said:
The term "early reflection" usually means a good thing. An early reflection is one that gets there in time to reinforce the original sound without muddying it up. A "late reflection" is what you should be worried about. Late reflections get there too late to reinforce the original sound and end up making it sound muddy or echoic.

This is the key to concert hall design (part of my job description, it turns out). I usually work with a maximum path length difference of about 30 to 35 feet. Remember that sound travels really, really fast. So if your path length difference is a matter of one or two feet it's extremely unlikely your ears will be able to tell.
Click to expand...

everything ive read says early reflections are bad! which is why you put acoustic panels (absorption panels) at the early/first reflection points! every home audio/studio does this.

late reflections - the brain can tell this is a reflection, and induces comb filtering (peaks/nulls)...but it's the early reflections that the brain cannot distinguish from the original source which causes clarity issues...

sound actually travels relatively slow in my opinion..

a difference of one or two feet can make a *big* difference in your setup. especially speaker placement (or sub) against boundaries (again, comb filtering).
 
http://www.realtraps.com/rfz.htm

http://www.realtraps.com/art_room-setup.htm

http://www.gikacoustics.com/education.html

When a direct sound is accompanied by an echo that arrives within 20 milliseconds or less, the ear is unable to distinguish the echo as a separate sound source. So instead of sounding like an echo or general room ambience, the sounds coming from different directions combine, which obscures clarity and confuses the stereo image. You can still tell when an instrument is panned all the way to the left or right, but the in-between positions are not as well defined. Put another way, listening to music in a Reflection Free Zone is similar to listening with headphones - musical instruments sound clearer, and their placement in the stereo field is much better defined.

Another important reason to control early reflections with absorption is to reduce comb filtering. This is a very specific type of frequency response error that's caused when a source and its reflections combine in the air. Depending on the difference in arrival times, some frequencies are boosted and others are reduced. The graph in Figure 1 at left shows the comb filter frequency response measured with and without MicroTraps at the first reflection points. You can learn more about this effect in the Comb Filtering video on our Videos page.
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The pads ought to be the same size. Mine were. Take them back maybe.
 
Sycraft said:
The pads ought to be the same size. Mine were. Take them back maybe.
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thanks - ill return and open the box before leaving next time :)

ive since turned the pads horizontal and i think that provides a bit better base for them (since my speakers are not deep at all - could easily tip)
 
I don't dispute that directionality can be affected by reflections. I do dispute that muddiness occurs from early reflections.

But don't just listen to people on the internet, give it a try for yourself. Put your speakers on the front edge of your desk and scoot your chair back an equivalent distance. Will it sound different? Probably. Will it sound better? That's completely up to you.

If desktop reflections are a real problem then that problem is so small that few people, if any, care about it. Do a GIS for studio mixing desks and see how many professional mixers or mastering engineers bother to put absorption on the top of their desks. I'll be surprised if you can find one.

But, again, whatever sounds best to you is what's right. If you can hear a difference due to either physical acoustics or, more likely, psycho-acoustics, then you should go with the sound you prefer.
 
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