Without coming off as rude, but no foam at all? I'm only asking because I managed to find a guy on Craigslist selling corner bass traps for $15 a piece. They're similar to the Auralex LENRD ones. It would probably be a bit cheaper for me in the long run, but if not then I understand. Just wondering
Foam is fine... provided that it really is proper acoustic foam, and not some cheap imitation garbage. If you like the idea of foam, then there's no problem with using it, but ONLY buy it from a reputable acoustic manufacturer. Proper acoustic foam isn't cheap. If you like the idea of Auralex LENRDs, then buy them directly from Auralex (which is a reputable manufacturer, and does use proper acoustic foam for their products). The ones that guy has on Craigslist might well be "similar to the Auralex LENRD", but that doesn't mean that they actually
ARE Auralex LENRDs, or that they are made from real acoustic foam. Packing foam looks very similar to acoustic foam, and is MUCH cheaper... but is practically useless for acoustic purposes.
Unfortunately, there are a lot of unscrupulous people around on the internet, who make great claims for what they sell, but in reality are selling cheap and useless knock-offs of the real thing. And you'll never know until you actually get the product and find it doesn't work. And try to get your money back afterwards...
There's a very thin layer of foam that came with the speaker stands that the monitors sit on top of, but I doubt it's actually doing anything to isolate them. Would you recommend getting the speaker isolation foam or do you have something better?
The absolute hands-down best is Sorbothane rubber, but it isn't cheap. Once again, proper acoustic speaker isolators from a reputable manufacturer will work fine, but they also aren't cheap. You could try using EPDM rubber or Neoprene. Those are both reasonably good acoustic isolators, and not too expensive. EPDM is the type of rubber used in the seals around car doors and windows.
Each one of my monitors are exactly 26" away from the side walls, 8.25" from the front walls, and, from cone to cone, they measure 53". Does this seem desirable to you or should I move them around?
The recommended setup is have them the same distance apart as they are from your head. In other words, they are set up as an equilateral triangle, with all angles exactly 60° and all distances the same. That's the theory, but most engineers prefer a position that is a little closer to the speakers, and that works out perfectly anyway, since your head is wide, not jsut a single point. so if you sit at the position where the sides of that imaginary triangle are aiming at your
ears , then the apex will be a few inches behind your head, and your ears will be a few inches closer to the speakers than the distance between the speakers.
Also, your ears should be at roughly 38% of the room depth (distance from front wall to back wall). In your case, with a room length of 15.5', your ears should be roughly 5'11" from the front wall. NOTE!!! This 38% "rule" is not a rule at all: it's a guideline, a starting point. So try it out, then move forwards and backwards a couple of inches, and see if there is any improvement.
Also, both your ears and the acoustic axis of the speakers should be at a height of 1.2 meters above the floor (about 47-1/4"). Note! this is the acoustic AXIS of the speakers, not the top, bottom or middle. The acoustic axis is the point that the sound seems to come from, somewhere between the woofer and tweeter. Normally, it is much closer to the tweeter. Your speaker manual should tell you where it is on your speakers, but if not "guestimate" it by picking a point about 70% of the distance between the center of the woofer and the center of the tweeter, and you won't be far wrong.
So set things up like that: your head exactly on the room center-line (left to right), your ears at about 5'11" from the front wall, the speakers set up angled at 30° with respect to the center line of the room and in the location that points them at your ears while keeping that angle. This might mean that they'll be a bit further apart than they are now, but that's fine. The room is wide enough that you should be able to do that.
So, with the speaker geometry set up correctly, set the speakers to the exact same level, and play some good quality commercially recorded music at 85 decibels. No sit in your chair, close your eyes, and listen carefully. If it is set up correctly, you should clearly hear the "phantom center". It should sound like there is another speaker, directly in front of you, half way between the two real ones, and things that are panned to the center of the mix should be coming out of that "phantom" speaker. You should hear the vocals there, as well as the snare, and maybe also the kick and bass guitar, and anything else that is panned dead center, with all the other instruments spread out evenly to the left and right, ending exactly where the real speakers are. That is your "sound stage", and it should be even and clear: With your eyes closed, you should be able to point with your finger at the spot where each instrument seems to be coming from on that imaginary stage.
That's the normal way of setting up a room. But once you have done that, you can still tweak things a bit, if you want tom by moving your listening position a couple of inches forwards or backwards and repositioning the speakers to compensate, or changing the angles of the speaker to be a bit more than 30° (so the angle of intersection behind your head is greater than 60°), and see if you prefer that. Etc. Nothing is written in stone, so experiment a bit if you want. Or if you like the way it works out with the ITU / EBU recommended position (as I described above) then stick with that. Especially if you will also be working in a pro studio somewhere: they most likely do have their room set up correctly.
I've been using standard 2" thick Roxul Rockwool insulation.
That's fine, but 4" would be better. Or you can double up (two layers of 2").
However, 703 is supposed to be easier to work with
Yup! That's one of the big advantages. You can cut it with an electric bread knife, and only need gloves, a mask and eyeware. No need to wrap up more than that.
most people I've talked to have said that there isn't much difference between the Rockwool and Owen's-703 when it comes to acoustic treatment.
There are differences, when you look at the actual acoustic laboratory tests. And "Rockwool" covers a large range of things! It's a trade name: the generic term is "mineral wool", but even within the Rockwool brand there are several different products, with different characteristics.
Just curious, but what makes it undesirable? Too big? Too small? The more I know, the better I'm off.
It's the ratio of height to width to length. There are "good" ratios and "bad ratios". I'm sure you know that for each frequency (tone) the associated sound wave has a specif "wavelength", which is the distance in air between the peak of one cycle and the same peak of the next cycle. If a complete cycle of a specific tone fits in exactly between two walls in your room, then that tone will set up a "standing wave" in the room. In other words, it the walls are exactly a half wavelength apart, then the room itself resonates at that frequency. That is called a "mode". Obviously, there is one exact frequency associated with every single distance, so all rooms have many, many "modes". For example, in your room the mode associated with the length of your room, at 15.5 feet, is 36.5 Hz. Every time the bass guitar hits a low D (36.7 Hz), that mode will be "excited", and the room will play along with that note.
The problem is, as that wave bounces back and forth between the two walls, it reinforces itself, since it is always in phase with itself on every bounce, so it creates this "standing wave" pattern in the room, which you can actually hear: if you play a perfect 36.5 Hz tone on only one speaker in your room, and move walk around, you will clearly be able to hear places in the room where that tone is much louder, and other places where ti is much quieter. Those are the peaks and troughs of the standing wave.
The other problem is that the standing wave sorts of "stores" energy at that frequency (not really, but it's an easy way to think of it), so that if the note suddenly stops, well the energy carries on bouncing around for a wall in that standing wave: so the room carries on playing that note even after the speaker stopped making it! How long that "reverberation" lasts depends on many factors.
So the issue with modes is firstly that they create these loud-and-quiet patterns in the room, and second that they carry on "ringing". The purpose of acoustic treatment is to help with both of those, but there's another problem here, which happens in small rooms.
To make this more complicated, this doesn't just happen in one dimension: There are three dimensions to the room, so you have this "mode" thing going on with all three axes, all the time. Those are the "axial modes", that bounce back and forth between two surfaces (fornt and back walls, left and right walls, or ceiling and floor). But it turns out that there are other ways for standing waves to form in a room: it is also possible for a wave to bounce around between any four surfaces, and those are called "tangential" modes. And to really blow your mind, there are even ways that standing waves can form between all six surfaces of the room, and those are called "oblique" modes.
So there are obviously thousands of possible modes for any given room. In your room, for example, there are 139 possible modes, just below 250 Hz! So it gets very complicated. But that's actually good! It there were one mode for every frequency, then it really wouldn't matter, as all frequencies would be affect equally. But the problem is for low frequencies in small rooms, there just are not vary many modes at all, and THAT is the problem. For example, in your room there are only 9 possible modes below 100 Hz, below 70 Hz there are 3, and below 50 Hz there is only one single possible mode. So here's the problem: the smaller the room is, the fewer low frequency modes it can support.
Therefore, it is a really good idea to chose dimensions for your room so that those few modes are spread around the spectrum as evenly as possible, not all clumped up together in one place. For example, if you have a room that is exactly 8 feet on each side, then ALL the modes in ALL axes occur at exactly 70.6 Hz, 99.9 Hz, etc. So when you hit a C#, ALL THREE of the axial modes for 70.6 Hz light up, and now that mode is three times more powerful! So you REALLY hear it. But then there is no other mode at all until 99.9 Hz. So no other note reverberates at D, E, or F, but the G smashes out again at three times the power... You get the picture. If you could choose dimensions a bit different than 8 feet on each side, then the three modes would not pile up on each other; they would be spread around. And if you could choose dimensions such that there were also modes close to D, E, and F, then you don't have a problem any more, sine there is a mode for each note!
So that's the general idea: choose dimensions so that the modes in your room are spread around evenly, not clumped up together. Several scientists have already done that for you, and figured out that it isn't so much the actual dimensions that matter, but rather the
ratio between the dimensions. So you'll sometimes see reference to names like Sepmeyer, Louden, Bolt and others, and you'll often see folks saying they are basing there room on "Sepmeyer's best ratio", or something like that. It just means that they are using a ratio of height to width to length that Sepmeyer found to be the a good ratio, in his studies. The ratios are normally specified as something like "1 : 1.3 : 1.8", which would mean that that room is 1.3 times wider than it is high, and 1.8 times longer than it is high. The first "1" is always the height. So if that room were 10 feet high, it would be 13 feet wide and 18 feet long.
Your room ratio is 1 : 1.25 : 1.93, and the closest "good" ratio is Louden's second best ration, at 1 : 1.3 : 1.9. If you cold make your room 15'3" long and 10'5" wide, then you would hit Louden's second best ratio spot on. as you can seem you aren't very far away, but those few inches can make a difference. However, your ratio is not bad at all: it could be far worse, so don't sweat it too much. Especially seeing that you can't change it! If you ever do move or want to build a better studio, then you can take that into account more seriously, but for now, don't worry too much.
By the way, modes is also the reason for the recommendation of the 38% seating location: Theoretically, that's the position in all rectangular rooms where the modal patterns are least objectionable. In theory!
Anyway I could alleviate this without completely changing the room? Moving the acoustic panels in the room and "boxing" in the vocalist has helped in removing echo so far, but I don't want to muffle the room TOO much.
You cannot get rid of room modes with treatment. Not even by moving walls, adding panels, etc. The ONLY way to get rid of all room modes, is to take away the room! That's why recording in the open air sounds so great: no modes!
Of course, that's not feasible in reality...
So why treat then, if it doesn't kill the modes? Well, it attenuates them. If the sound wave has to go through thick acoustic absorption as it approaches the wall, then go through it again after it bounces off the wall, then it has lost some of its energy to the absorption. In other words, it bounces back at a lower level. Still the same frequency, still the same direction, but quieter. That's why there are graphs of how each type of acoustic treatment affects each frequency band.
But you still can't kill the mode. For example, even 703 has an absorption coefficient of 0.84 at 125 Hz, meaning that it absorbs 84% of the incident energy for tones around 125 Hz. You think "Great! So it gets nearly all of it!". Well, not really. 84% isn't much. That's roughly 4 decibels of sound power, or 8 decibels of sound pressure. So if you measured the level of that wave going in at 89 decibels (for example), it comes out at 81 dB. That's not a huge amount of difference. And that is for 4" of 703 spaced away from the wall, where it is most effective.
That's why you need a LOT of bass trapping in a room: a little but doesn't do much to low frequencies.
Of course, if you put stacks of 703 in your bathroom, you might be able to get the modes and reflections under control, but as you correctly pointed out, you'd also kill the high end. Absorption that is thick enough to have a decent effect on low frequencies is way, way, waaaaaaaayyyyy thick enough to totally destroy the highs. The easy solution is to put thick plastic across the front of your bass traps, to reflect the high frequencies back into the room, while still allowing the lows to get through and be absorbed. Depending on the room and other factors, you could use something as thin as 6 mil polyethylene plastic sheeting, or as thick as a layer of thin plywood or perforated panel. It all depends on how much of the highs you need to keep in, and how much of the lows you want to treat.
So that should help a bit to get your head around some of the basics of acoustics, and the reasons behind the recommendations you see on the forum. There is solid science behind all of this, unlike some other forums on the internet where the "advice" seems to be based on emotions, guesses, or "I used to date a girl who's third cousin had a friend that knew a guy who once worked cleaning the floors in a studio, and that's how he said they did it, so it must be right"!
That's the kind of place where you'll see them using egg crates on the ceiling and carpet on the walls, and thinking that they did something wonderful to the room, and now have perfect acoustics!...
The thing is, sound waves don't actually behave the way people assume they behave, so acoustics isn't very intuitive at first glance. But once you "unlearn" the common assumptions and understand how sound REALLY works, then it all starts making sense.
- Stuart -
) Ummm, yup, I noticed your mattress: it isn't doing much at all to help you. The little bit of effect it has is most likely due the cloth covering and underlay, not to the foam itself. Mattress foam is commonly closed-cell foam, which is worthless for acoustic treatment. You need open-cell foam, or fibrous materials, like fiberglass insulation and mineral wool. It works by the tiny fibers / pores absorbing the sound as it passes through. With closed cell foam, the sound wave cannot pass through, because the cells are closed! There is no way for the sound to get through!
Ummm... it has a square section! 8 feet long and 8 feet wide. That's bad. About the only way it could be worse is if it were also 8 feet wide.
