Attempting to understand how to treat my room

[kabletx]

Howdy,

I'm new here, but I'll do my best to adhere to the rules posted at the top of the forum. First, I'm glad I found this resource teeming with acoustic geniuses because I'm certainly punching above my weight!

I've set up what was intended to be a basic demo studio in a vacant bedroom in my home and it's worked well from a creative standpoint, but now I'm looking at tracking some vocals and I'd like to try and get some treatment up in my room to, at a minimum, cut back on reflections. I know I'm highly unlikely to replicate any intentionally planned rooms, but if I can improve this enough to get workable results I'd be very happy.

I know about a few of the rote basics, like the mirror trick for first reflections, but I'm not sure where to proceed from that. I attempted to use the Bob Gold Room Mode Calculator and mostly dark green (which I assume is good!), but I'm not sure it can accurately account for some of the stranger features of my room, as indicated in the attached file.

For the record, the strange box section of the room on the right is an open closet, although it's filled with Elfa shelves and clothing. No door. The door at the bottom right leads to a hallway. Volume is not a meaningful concern.

SO, I guess my question is how I should start to accumulate the needed information to properly begin treating my room. I've looked at a few of the "acoustic room eq" software packages, but I confess they mostly left me utterly confused. Any suggestions that could point me in the right direction would be much appreciated!

Thanks a ton for your time and willingness to read this post, and I hope all is well with you!

[Soundman2020]

Hi there "kabletx", and welcome!

It sounds like you have a reasonable and attainable goal, and a small but usable room to work with.

I attempted to use the Bob Gold Room Mode Calculator and mostly dark green (which I assume is good!),

IT looks pretty good, actually: The Bonello diagram is smooth, the ratio is close to a known good one, and the modal spread looks to be fairly even. You shouldn't have any unexpected or unusually complicated modal issues.

For the record, the strange box section of the room on the right is an open closet, although it's filled with Elfa shelves and clothing. No door.

It's probably not doing any harm, and might even be helping, acting as a sort of bass trap.

I would start by setting up your speakers and listening position correctly. There are a few rules of thumb that you can follow to get you in the ball park. First, get the speakers off the desk and onto stands behind the desk. The stands need to be very massive (heavy), such as hollow metal filled with sand, or even stacked concrete bricks, and even then you should try to decouple the speakers form the stands, with a layer of sorbathane under the speaker. That will accomplish several things, among them: preventing the speakers from causing the desk and/or console to vibrate, thus muddying up the sound and imaging; reducing the possibility of reflections and comb filtering artifacts associated with the surface of the console and/or desk; getting the speakers further apart (improving imaging) and as close to the front wall as possible (reducing artifacts), and a few others.

It would help to know what speakers you are using (brand and model), in order to see how you need to set them up to compensate for the power balance issues by having them close to the wall. That's both a good things and a bad thing: ideally, the speakers should be as far away from all walls as possible, and at least 2m in all directions, but if that isn't possible then the next best is to put them right up against the front wall, to force all the interference, combo-filtering, phasing and reflection issues up into the high frequency part of the spectrum, where it doesn't matter so much. But in doing that, you also eliminate a problem that is already resolved in the speaker design itself: the baffle-step or power imbalance issue. Since the speaker itself has a very small front panel or "baffle", there is an inherent power imbalance in the way the highs and lows come out of the speaker, and the designers accounted for that in the cross-over circuitry inside. But if you put the speaker up against the wall, the wall acts somewhat as an infinite baffle for low frequencies, so the power imbalance issue is no longer there. In other words, the speaker crossover is now compensating for a problem that no longer exists. Most good quality speakers have a control on the rear so you can correct this situation, by rolling off the bass response, which in effect is eliminating the internal correction, and allowing the speaker to work the way it should. So there should be a control on the rear of your speaker that cuts the bass response by up to 6 dB. It might be called any of several names, but check for that, and set it accordingly. If it is a switch with several settings, try -4 dB and -6 dB, to see which works better. Theoretically it should be -6 dB, but the rest of the room might be doing other things that would make it better at -4 dB.

OK, so now set up your chair so that your ears are about 56" from the front wall. That's the 38% point of your room depth, which is theoretically a good starting point for finding your best listening position. Now set up the speakers on their stands about 24" from the side walls, and angle them 30° inwards, so they are aiming at where your ears will be, when you are seated at the console. The should also be st up so that the acoustic axis of the speaker is 1.2m above the floor (about 47"). Note! the acoustic axis is NOT the top, bottom or center of the speaker! It is the point on the front baffle where the sound "appears" to emanate from, and should be shown in your speaker manual. If not, then there's a method for estimating it.

If you did everything right, then you now have your speakers and head set up in an equilateral triangle, with the apex a few inches behind your head, the speakers will be about 4'6" from your head and about 4'11" apart from each other, and aimed directly at your ears. If you play music like that, you should be able to clearly hear the "phantom center", as though there were a third speaker directly in front of you, from which the vocals, snare and other center-panned sources seem to be coming, rather than from the two real speakers.

OK, so with that done correctly, now you need treatment: First, thick absorbers on the front wall, directly between the wall and the speaker. Maybe 4" of 703 or something similar. Next, thick absorption on your first reflection points: Mirror-trick - both side walls and the ceiling. Once again, 4" or even more of 703 would be good. Next, the corners: Large Superchunks in all four vertical corners. The door at the right read is a problem, but you can put the superchunk for that corner on wheels, and roll it in front of the door for critical listening. Nest: the rear wall. The rest of the rear wall is going to need a thick layer or absorption, held away from the wall. For example, 6" of 703 in a frame spaced 6" away from the wall, or more if you can.

And finally, some more absorption, scattered around the walls, as needed.

What you should also do is to measure the room response at each stage, using REW. So first measure the empty room, then measure again after you install each set of treatment, to see what it did, and what still needs to be done. One caveat: you MUST get the microphone back to the exact same point in the room for each measurement. If you don't, then you cannot compare readings. Also, just use one speaker for all measurements: either left or right. Better still, take two sets of readings, once with just left, and one with just right.

I've looked at a few of the "acoustic room eq" software packages,

It is impossible to fix room problems with EQ. That's a myth, but a very persistent one that seems to be perpetuated by the internet, unfortunately. Room issues are most commonly in the time domain, not just the frequency domain, so there is nothing that an equalizer can do to fix that. For example, if you have a bass guitar playing an F# on your speakers, and that excites your 2,0,0 axial room mode at 91.9 Hz (yes, your room actually does have a mode there), then the standing wave will build up in the room over a few cycles, "storing" energy at that frequency. When the note cuts off suddenly, the energy in that standing will continue "ringing" around the room for a few hundred milliseconds, until it eventually dies away. Think about that: the speaker cone stopped moving, but the note carried on! So how can a graphic equalizer fix that???? The cone is not moving, so there is NOTHING that an equalizer can do to make the mode stop. A room mode is a time-domain issue, not a frequency domain issue. No matter what you do with your equalizer, the mode will still be there, and will still "ring". Even if you cut 92 Hz on your EQ, you still have not solved the problem: Sure, the note is no quieter, so the mode is less noticeable, but you have also distorted your system response now, so F# sounds lower than it should: You'll probably compensate for that subconsciously in the mix, and your mixes will sound terrible when played elsewhere (even though they sound fine in your room).

You also cannot fill a null with EQ: if your head happens to be in a null for C# (it will be) and you then boost 139 Hz on your EQ to "compensate", all that you will do is pour more energy into that mode, making it more intense, and in fact deepening the null and making it ring even longer!

Sorry for the rant, but EQ is not the solution for problems with the room itself, despite popular belief, and despite marketing hype from some manufacturers. At best, EQ can help to reduce really stubborn problems a bit, but even then it only works for one specific location in the room. As long as you never move your head, and never have anyone else in the room with you, then EQ can help a bit...

The solution to acoustic problems in the room, is acoustic treatment in the room. You cannot get rid of modes, but you can damp them, absorber them, diffuse some of them (not all) and fight back with certain kinds of device.

The solution to frequency domain problems in the signal chain is EQ. The solution to time domain problems in your room is acoustic treatment. They should be used together, but used correctly, each for the right purpose.

So that would be mu suggestion: first, set up your room geometry correctly (speakers and listening position), then set up your basic treatment, and analyze the room with REW. Then post the REW results here, if you still have problems, so we can try to understand what the issues are, and help you address them.

- Stuart -

[kabletx]

First, thanks a million for the extensive reply! I definitely appreciate you taking the time to share your knowledge with me. I will attempt to work through it in a logical fashion. And I'll even include images from FuzzMeasure Pro!

I would start by setting up your speakers and listening position correctly. There are a few rules of thumb that you can follow to get you in the ball park. First, get the speakers off the desk and onto stands behind the desk. The stands need to be very massive (heavy), such as hollow metal filled with sand, or even stacked concrete bricks, and even then you should try to decouple the speakers form the stands, with a layer of sorbathane under the speaker. That will accomplish several things, among them: preventing the speakers from causing the desk and/or console to vibrate, thus muddying up the sound and imaging; reducing the possibility of reflections and comb filtering artifacts associated with the surface of the console and/or desk; getting the speakers further apart (improving imaging) and as close to the front wall as possible (reducing artifacts), and a few others.

Although my drawing doesn't do a very good job of showing it, my speakers are at least somewhat decoupled from the desk at the moment. Rather than sitting directly on the surface, they are actually on rack stands that connect via a small metal bracket on the back. They then sit on Auralex foam pads, although those my be of dubious use. The cones are 27" inches from the wall behind them, 32" from the wall on either side, and 38" from the center of one another. The use of stands would either put the speakers right against the wall and behind my monitor or push me into the center of the room. I've attached a picture indicating the current situation. Given that 2 meters definitely won't happen, you think I'd be better off just moving the desk completely against the wall?

It would help to know what speakers you are using (brand and model), in order to see how you need to set them up to compensate for the power balance issues by having them close to the wall.

Adam A7x.

Most good quality speakers have a control on the rear so you can correct this situation, by rolling off the bass response, which in effect is eliminating the internal correction, and allowing the speaker to work the way it should. So there should be a control on the rear of your speaker that cuts the bass response by up to 6 dB. It might be called any of several names, but check for that, and set it accordingly. If it is a switch with several settings, try -4 dB and -6 dB, to see which works better. Theoretically it should be -6 dB, but the rest of the room might be doing other things that would make it better at -4 dB.

I believe I understand the concept of this, but not certain I get the execution. Be interested to see if my attached FMP3 documents have any influence on what I should do here.

OK, so now set up your chair so that your ears are about 56" from the front wall. That's the 38% point of your room depth, which is theoretically a good starting point for finding your best listening position. Now set up the speakers on their stands about 24" from the side walls, and angle them 30° inwards, so they are aiming at where your ears will be, when you are seated at the console. The should also be st up so that the acoustic axis of the speaker is 1.2m above the floor (about 47"). Note! the acoustic axis is NOT the top, bottom or center of the speaker! It is the point on the front baffle where the sound "appears" to emanate from, and should be shown in your speaker manual. If not, then there's a method for estimating it.

So I actually already have almost all of this in place. As noted before, my speakers are 32" inches from the side walls, but I did that so that my head could be at the peak of the equilateral triangle while still able to reach my desk. I do have plenty of room to move them further out, however. Would you recommend doing so?

If you did everything right, then you now have your speakers and head set up in an equilateral triangle, with the apex a few inches behind your head, the speakers will be about 4'6" from your head and about 4'11" apart from each other, and aimed directly at your ears. If you play music like that, you should be able to clearly hear the "phantom center", as though there were a third speaker directly in front of you, from which the vocals, snare and other center-panned sources seem to be coming, rather than from the two real speakers.

Based on what I'm reading here, you answer my question above. Yes, move them out. Doing so now.
...
...
Just tested with Radiohead's 2+2=5 and it definitely sounds much better. Gonna have to bump up my computer resolution though!!

OK, so with that done correctly, now you need treatment: First, thick absorbers on the front wall, directly between the wall and the speaker. Maybe 4" of 703 or something similar. Next, thick absorption on your first reflection points: Mirror-trick - both side walls and the ceiling. Once again, 4" or even more of 703 would be good. Next, the corners: Large Superchunks in all four vertical corners. The door at the right read is a problem, but you can put the superchunk for that corner on wheels, and roll it in front of the door for critical listening. Nest: the rear wall. The rest of the rear wall is going to need a thick layer or absorption, held away from the wall. For example, 6" of 703 in a frame spaced 6" away from the wall, or more if you can.

All makes perfect sense. I'll be forced to deal with the equipment I have in the room, namely a guitar tower rack and a 4 tier synth stand, but I'll probably just have to accept their influence on the room to some extent

What you should also do is to measure the room response at each stage, using REW. So first measure the empty room, then measure again after you install each set of treatment, to see what it did, and what still needs to be done. One caveat: you MUST get the microphone back to the exact same point in the room for each measurement. If you don't, then you cannot compare readings. Also, just use one speaker for all measurements: either left or right. Better still, take two sets of readings, once with just left, and one with just right.

Loading up FMP3 right now. I will attach the results to this post. I'd actually run one set, but with the new, wider speakers I"m going to give it another go.

I've looked at a few of the "acoustic room eq" software packages,

It is impossible to fix room problems with EQ...

My fault for poor choice in language. "acoustic room eqs" actually referred to the REWs and FMP3s of the world. I definitely know EQ can't fix genuine acoustic issues.

So that would be mu suggestion: first, set up your room geometry correctly (speakers and listening position), then set up your basic treatment, and analyze the room with REW. Then post the REW results here, if you still have problems, so we can try to understand what the issues are, and help you address them.

Thanks Stuart. I've attached the FMP3 results from the room pre-treatment (orange is right, blue is left), as well as a few pictures of the space as it look at the time of testing. This is a link to the project file from FMP3. I can't express enough gratitude for the time that you've shared. I greatly appreciate it, and I look forward to sorting this out with your help!