Room Treatment

I'm sure the first thing people will mention is bass traps! A typical sized bedroom should have a minimum of 8 traps.

Yeah, I guess the ceiling is a factor as well. In my case, I have a vaulted ceiling. The high portion is over my mixing area. It's flat for about 3' and then slopes back from there going from approximately 12' to 8' in height. Not sure if this is a good thing or bad thing in regard to acoustics.

I've got 12" of 703 over my head. I was getting significant interference from the ceiling reflections, and though that's a lot of trappage up there, it was one of the largest contributors. In that other thread, I mention some measurement hardware you might want to get.

You would want to fix the room for mixing purposes generally. It may or may not make it a better recording room. It'll make it generally a bit deader sounding. But, if the room isn't that great, that's not so bad a deal. Go ahead and pimp it out with plenty bass traps go get it sounding right for mixing. Close mic and use artificial reverb where you need ambience, and just try to remove the room from the equation as much as possible.

I don't think that it would have much to do with upper mid type frequencies though, so you may not really be needing bass trappage if all you are doing is vocals and accoustic, though according to how it's recorded the accoustic can have some fairly strong low frequency content.

Put a frequency analyzer plug on the accoustic track and see what it looks like. Do you have any big peaks anywhere or is it reaonably flat and falling off on low and high end?

The thing I've been doing is, when I get in a new bunch of traps, I set up the measurement stuff, and start stacking the new ones on top of the existing ones, to see if the problem is not enough in a particular position. For the ceiling it's hard because I have to hold it up there during the measurement which is rough on the arms. But when you are dealing with stuff below 100Hz, it can take a lot o' trappage to handle a wicked reflection, so it can take a lot sometimes. I hugely smoothed out my response with the last batch when I doubled up 2 6" ones on ceiling and 10" worth behind the speakers. Clearly these were big contributors. And I dont' stack up a little, because I want to know for sure if there's any difference in a given position, so throwing a new 6" there or two of them, in addition to what's there, should make some sort of clealrly measurable difference if there is any to be had at that position anymore, even for really low frequency problems.

It's boring and you'll be stone deaf from sitting in the room with the measurement tones for hours, but with enough trial and error you can generally find the problem spots. So far, I've not been able to get any measurable difference with traps at the back of the room. So it just doesn't seem like I'm getting much from there. The shape of the room means that the rear corners cannot reflect back to me, so it could only be directly off the back wall or from the wall/ceiling corner back there. But I've tested with a fair amount of traps back there and never saw any difference. I'll give it another go with the next batch comes in next week and see what happens.

My big problem remains this seemingly intractable cancellation at the 65 to 75'ish range. I'm going to get that guy taken care of one way or another, if I have to fill the whole freaking room with 703 and mix from the next room through RDP.

You spend so much time tuning and restringing the guitars that you don't have time to worry about the other stuff.

ORIGINAL: Jamz0r
I'm sure the first thing people will mention is bass traps! A typical sized bedroom should have a minimum of 8 traps.

I'm pretty sure you are right about the first thing people will mention... what I really want to know is why?

Why does everyone assume, without any information, that a small space requires bass traps?

One of the most well behaved control rooms I've ever worked in was barely big enough to the gear and two people. I haven't been there in years, so these are estimates based on my memory, but the rough dimensions were probably about 16 feet wide, 7 feet high, and 10 (at most) feet deep. Not a big room at all, and very little absorption added, and no diffusion (cause it would not have worked!)

The room geometry and the placement of the equipment and people took care of all the acoustical issues.

Anything mixed there translated to the rest of the world with no problems. I loved that studio!

Indeed, if the room is sufficiently small the resonances are moved up, but then you also lose support for lower frequencies, so like everything else it's a trade-off!

I'd extend your first sentence to say something to the effect that you can actually have fewer problems in a well designed space<G>...

Bill

ORIGINAL: bitflipper

You can actually have fewer problems in a tiny room. It's because the resonant frequencies rise as the room dimensions shrink. You still have resonances, but they're at higher frequencies. The higher the frequency, the more likely that various stuff in the room will dampen it, including human bodies. But, like the OP, most of us are in bedroom-size spaces, with resonances starting around 50-60Hz or so. If we were in drastically larger or drastically smaller spaces, the problems we'd face would be entirely different.

The traps are only intended to make it sound right at the mixing position, so anywhere else in the room is a crap shoot and probably won't sound right. For a dip in the 60 to 70 range, you are going to have to find the location that is contributing to that cancellation and pile up a lot of trappage there. A 4" trap isn't enough to get down that low.

Ok...this is unorthodoxed, but I rotated everything so that I'm back against a corner. Before, there were some crazy peaks in the low bass that COMPLETELY smoothed out, especially with the sub off, but the bass is still alot smoother than before, even with the sub on. I dropped the crossover point on the sub and that helped too. The problem is that once I get to the mids, the levels almost double or more, and stay that way. So even though bass is smoother, it's response is way too low relative to everything else. You can really hear it too. 808 style kick drums are very thin and have no meat or thump, even with sub on.

I think it's the square room. This will be a bit of a hassle but I'm going to move my stuff into a larger rectangular room and see what happens there.

Traps are intended to dissipate energy. Broadband traps dissipate energy across a wide portion of the spectrum, tuned traps dissipate energy in a smaller portion of the spectrum. A properly trapped room will have reasonably well behaved frequency response throughout the space, but in an acoustically small space there will still be problem spots.

Sure, I assumed that everyone understood that I meant "the reasonable number of traps that we can afford are generally placed such that...." The standard placements are relative to the listening position and generally you are trying to optimize that position.

There probably is not one location that is contributing to the cancellation. The cancellation in the 60Hz-70Hz range is almost certainly due to either the room dimensions or the room geometry or the placement of the speakers and/or listener.

I mean where the reflections are coming from that are contributing to this particular cancellation. I've done enough testing to know by now that most of the peaks and cancellations have primarily been related to a reflection off of a given surface, or symmetrical surfiaces (left/right walls, ceiling/floor.) I've stacked up extra traps in specific locations and re-measured and I can see where the biggest contributions are coming from for a given peak or dip usually. This particular one may be a combination of one or more particularly bad reflections, or it may be strongly created by one or two of the corners/surfaces that I've not yet got a thick enough coverage to deal with an issue at that low a frequency. The 4" thick ones won't do anything at that frequency.

So I'll be experimenting when the latest batch of bags actually arrive, to see if I can find out where that particular issue is coming from. It's in there somewhere, so it's just a matter of finding who is reflecting back at me at that frequency and taking care of that reflection (or those reflections.)

My current guess is the corners behind the speakers. I only have 4" thick ones there top to bottom. My first experiment is going to be to stack up 6" ones in front of the 4" ones that are there and see what that gets me. If I get a significant decrease, I'll know. If not, then I'll start looking elsewhere. So basically I just take the new ones and move them around to thicken up various locations and see what the measured result is. If yo put 6 or 12" of trappage in a particular place, that's enough to definitely see a measured change if that particular corner or wall is a contributor to a problem.

I don't have any clouds right now, so I'm going to be trapping up there, hopefully tonight, and adjusting HF absorption on the walls a little bit. I'm really surprised though the difference subwoofer placement has made. Initial testing for improved portability are turning out really good. I had only one song out of about five that was off, and on that one the bass guitar was too low. On one other it was just a hair too loud. I didn't have any high pass filtering going on at all, so I think that will help some more too for better portability.

In summary, for those adding a sub, try a corner first and then test your room response. I'll be posting my graphs later today. They were really flat on my last measurement, so I'm hoping after these tweaks it will be even better.

Next project to take on is an air conditioner. It's GOT to be at least 85 in the room after gear has been running.