Need ideas to help me improve my low end response in a cubic small home studio (yes, I know)

[The_Ogre]

Hi folks.

Even tho I still can consider myself a noob, I'm on my journey to learn more about acoustics, even because I've already started treating my home studio (an spare cubic bedroom at my house).

I got an introdutory online course from a Brazilian acoustics company, I've also been Foruming/Googling/Youtubing for more info for a while, and just bought two gret recommended books about the subject (Rob Gervais' Home Recording Studio: Build It Like the Pros and Bobby Owsinski's The Studio Builder's Handbook).

However, I know, in advance, that it'll be kind of an ungrateful task, as we're talking about an small cubic room (3.00 x 3.00 x 3.00 meters) and it's one of the worst to treat, but it's what I had available, at least to start. I've already installed some panels using 35kg/m³ PET wool (three 0.60 x 0.60 x 0.15 (6") meters clouds, two 0.60 x 0.60 x 0.20 (8") meters panels at the wall/ceiling junction in front of me, two 1.00 x 0.60 x 0.20 (8") meters panels at the superior trihedral corners in the front wall and thirteen Elgato Wave panels at the front wall, behind the desk/monitors). The first reflection points at the sides have (now) one Elgato Wave panels with an extra layer (2") of PET wool, but as soon as possible I'll add 0.80 x 0.60 x 0.15 (6") meters panels there too. Still have two unused Elgato Wave panels (four, counting with the ones I'll take from the side walls).

My monitoring consists in a pair of JBL 104 and a Presonus Eris Sub8, and IK ARC Studio for the room correction. Each of the JBLs are sat above a metal support, with each support sat above four IsoAcoustics Iso Puck Mini, and their speakers are positioned around 88 cm from the respective side wall and 13 cm from the front wall, distant 127 cm from each other and 127 cm pointed direct to my ears. The Presonus Sub is sat above an IsoAcoustics Iso-200Sub, and its speaker is positioned around 75 cm from the left side wall and 70cm from the front wall, below the desk. My listening position is around 42% of the dimention of the room.

Due to the small room size, I have a resonance at 57Hz, and maybe due to SBIR/comb filtering, I have a deep at around 45Hz. And those are exactly my main focus now. Even tho I managed to correct a bit of the inconsistencies using ARC, I still have some excess in low frequencies in the room, difficult to solve with only porous absorvers (even using deeper ones, with a plenty of air gap behind them).

I think I should mention that I have a window at my left side too, and a bookshelf exactly behind me, on the back wall, and I can't change the position of the desk. I still can use the back wall (behind and above the bookshelf) and the back side of the ceiling to add more panels.

Any ideas on how to improve the low end response of this room? I'll add the current curves (REW) and a photo of the already done job (so far) as soon as I get home.

I'm leaving here some of the curves from when I started treating the room (with just the Elgato panels on the front wall) in comparison with the current state of both acoustic treatment and ARC 4 (measures made with the SPL reading around 84dB).

Thanks in advance.

 

[Curvature]

Due to the small room size, I have a resonance at 57Hz, and maybe due to SBIR/comb filtering, I have a deep at around 45Hz.

hunecke.de | Room Eigenmodes Calculator

SBIR is usually between 100Hz-300Hz. Below 100Hz are room modes, to do with the dimensions of your room.

Generally you need to use EQ, multiple subs, heavy and large panel based traps or a combination. None of the velocity based absorbers you have will do anything meaningful below 200Hz.

 

[kemmler3D]

You need membrane traps or helmholtz traps, look into VPR. I often suggest BAD facings for Rockwood panels to deal with bass but I think your problem frequencies are too low for that.

 

[The_Ogre]

hunecke.de | Room Eigenmodes Calculator

SBIR is usually between 100Hz-300Hz. Below 100Hz are room modes, to do with the dimensions of your room.

Generally you need to use EQ, multiple subs, heavy and large panel based traps or a combination. None of the velocity based absorbers you have will do anything meaningful below 200Hz.

Yeah! Room modes mostly, indeed.

I've been studying how to add another sub to the layout, but still not figured it out how to connect both using an interface. Right now, the cables goes from interface to ARC Studio, then to sub, and then to monitors.

You need membrane traps or helmholtz traps, look into VPR. I often suggest BAD facings for Rockwood panels to deal with bass but I think your problem frequencies are too low for that.

Yeah! Tuned traps. I'm trying to find reliable sources of data to learn how to build them myself, as there isn't many possibilities available in our local market, and importing isn't an option (due to costs of importing).

And I just perceived that I forgot to post the image of actual state of the home studio (attached).

 

[kemmler3D]

I'm trying to find reliable sources of data to learn how to build them myself,

There are a few threads out there (one or two here) on how to build a VPR. it's not tuned per se, it uses the dense vibrational modes of a big thin sheet of steel to absorb bass. I looked into it and they should be pretty cheap to build if you can get the steel sheet at a decent price.

I think membrane traps using mass loaded vinyl need to be tuned but I'm not totally sure how to do that.

 

[The_Ogre]

There are a few threads out there (one or two here) on how to build a VPR. it's not tuned per se, it uses the dense vibrational modes of a big thin sheet of steel to absorb bass. I looked into it and they should be pretty cheap to build if you can get the steel sheet at a decent price.

I think membrane traps using mass loaded vinyl need to be tuned but I'm not totally sure how to do that.

I knew about membrane and helmholtz resonators, but haven't heard about VPR before. Will check it.

 

[Duke]

Due to the small room size, I have a resonance at 57Hz...

57 Hz is the lowest standing-wave frequency of your 3 meter dimension. And frequencies that low (wavelength = 6 meters) are difficult to absorb. You might try tuned Helmholtz absorbers.

Another possibility is a distributed multisub system. I would suggest three or four small subs distributed in all three dimensions. You might try this: Each sub a DIFFERENT distance from its nearest corner (maybe even stagger those distances in a golden ratio), AND each sub as far away from the other subs as is reasonably feasible. The idea is for each sub to interact with the room differently, and the sum of these three or four different room interactions will be smoother than any one or two subs alone.

A distributed multisub system reduces the bass frequency response variation from one location to another, such that any remaining anomalies (like your 57 Hz resonance) are likely to be present throughout the room. This way, EQing the response for one particular location does not simultaneously make the bass worse elsewhere. This "reduced spatial variance" characteristic of a distributed multisub system is probably more beneficial for a multi-listener stereo or home theater setup, but it's not a bad thing even if you're always going to be sitting in the mix position, and it might give you a bit more flexibility in WHERE to locate your mix position.

You might try setting up your main speakers on a diagonal, or just off the diagonal by a few degrees, to see if this gives a bit better results than setting up "normally". What you want to do is, have as many of the first wall bounces "miss" the mix position as possible, and then treat those reflection zones where the reflections arrive after only the one bounce.

Very best of luck with your challenging room!

Disclaimer: I make a commercial embodiment of the distributed multisub concept, but I think my subs are bigger than you need and I think you can get there for a lot less money via three or four small subs. I do have one (happy) customer who mixes with my four-sub system in a square room, but it's not a fully cube-shaped room.

 

[DVDdoug]

You can tame the bump with EQ, and the bumps tend to be the more annoying than dips. You can't really fix dips because it takes "infinite power" to overcome the wave cancelation.

Of course if you are producing rather than listening for pleasure, it's more important to smooth them both.

Bass traps trap the reflected bass so they can smooth-out the dips and the bumps. But I believe you need to cover a significant percentage of wall space.

Ethan Winer is one of the owners of RealTraps. They sell the "thin" membrane bass traps and he has an article (that I've never read) about building your own mass trap.

..If you look at the pictures on Ethan Winer's website or the RealTraps site, you'll see a TON of treatment.

 

[kemmler3D]

You can tame the bump with EQ, and the bumps tend to be the more annoying than dips. You can't really fix dips because it takes "infinite power" to overcome the wave cancelation.

Of course if you are producing rather than listening for pleasure, it's more important to smooth them both.

Bass traps trap the reflected bass so they can smooth-out the dips and the bumps. But I believe you need to cover a significant percentage of wall space.

Ethan Winer is one of the owners of RealTraps. They sell the "thin" membrane bass traps and he has an article (that I've never read) about building your own mass trap.

..If you look at the pictures on Ethan Winer's website or the RealTraps site, you'll see a TON of treatment.

Yes, even with VPRs you need a lot of coverage. An 8' x 4' (24 square foot) VPR might eliminate around 3dB from a dip if you are lucky. If this sounds disappointing to you, well... other types of traps I've seen don't even do this much in the <80hz range. If you are willing to cover a lot of the walls and maybe even ceiling, you may be able to beat it into submission, though.

 

[MKR]

57 Hz is the lowest standing-wave frequency of your 3 meter dimension. And frequencies that low (wavelength = 6 meters) are difficult to absorb. You might try tuned Helmholtz absorbers.

Another possibility is a distributed multisub system. I would suggest three or four small subs distributed in all three dimensions. You might try this: Each sub a DIFFERENT distance from its nearest corner (maybe even stagger those distances in a golden ratio), AND each sub as far away from the other subs as is reasonably feasible. The idea is for each sub to interact with the room differently, and the sum of these three or four different room interactions will be smoother than any one or two subs alone.

A distributed multisub system reduces the bass frequency response variation from one location to another, such that any remaining anomalies (like your 57 Hz resonance) are likely to be present throughout the room. This way, EQing the response for one particular location does not simultaneously make the bass worse elsewhere. This "reduced spatial variance" characteristic of a distributed multisub system is probably more beneficial for a multi-listener stereo or home theater setup, but it's not a bad thing even if you're always going to be sitting in the mix position, and it might give you a bit more flexibility in WHERE to locate your mix position.

You might try setting up your main speakers on a diagonal, or just off the diagonal by a few degrees, to see if this gives a bit better results than setting up "normally". What you want to do is, have as many of the first wall bounces "miss" the mix position as possible, and then treat those reflection zones where the reflections arrive after only the one bounce.

Very best of luck with your challenging room!

Disclaimer: I make a commercial embodiment of the distributed multisub concept, but I think my subs are bigger than you need and I think you can get there for a lot less money via three or four small subs. I do have one (happy) customer who mixes with my four-sub system in a square room, but it's not a fully cube-shaped room.

Class act as always @Duke , thanks for your outstanding contributions to ASR and your consistent impeccable transparency

 

[The_Ogre]

There are a few threads out there (one or two here) on how to build a VPR. it's not tuned per se, it uses the dense vibrational modes of a big thin sheet of steel to absorb bass. I looked into it and they should be pretty cheap to build if you can get the steel sheet at a decent price.

I think membrane traps using mass loaded vinyl need to be tuned but I'm not totally sure how to do that.

I found some info on VPRs. Seems interesting, but I don't know if I'll be able to find somewhere nearby that kind of big sheet of steel. Not aware of a any metalurgics around here. But it's indeed an option. Thanks for the tip.

57 Hz is the lowest standing-wave frequency of your 3 meter dimension. And frequencies that low (wavelength = 6 meters) are difficult to absorb. You might try tuned Helmholtz absorbers.

Yeah! Every online acoustic calculator I tried had already pointed me in this direction, and I'm being able to feel it in person. OK, It's is a fact that I managed to get rid of a lot of stuff after doing the treatment I've already done, and also after using ARC. And I know it still has some room for improvement, even if it wouldn't end being the best studio ever. There are things we can't fight against, and an small cubic room is an small cubic room. But I'll do my best to make it works the best it can.

Another possibility is a distributed multisub system. I would suggest three or four small subs distributed in all three dimensions. You might try this: Each sub a DIFFERENT distance from its nearest corner (maybe even stagger those distances in a golden ratio), AND each sub as far away from the other subs as is reasonably feasible. The idea is for each sub to interact with the room differently, and the sum of these three or four different room interactions will be smoother than any one or two subs alone.

A distributed multisub system reduces the bass frequency response variation from one location to another, such that any remaining anomalies (like your 57 Hz resonance) are likely to be present throughout the room. This way, EQing the response for one particular location does not simultaneously make the bass worse elsewhere. This "reduced spatial variance" characteristic of a distributed multisub system is probably more beneficial for a multi-listener stereo or home theater setup, but it's not a bad thing even if you're always going to be sitting in the mix position, and it might give you a bit more flexibility in WHERE to locate your mix position.

You might try setting up your main speakers on a diagonal, or just off the diagonal by a few degrees, to see if this gives a bit better results than setting up "normally". What you want to do is, have as many of the first wall bounces "miss" the mix position as possible, and then treat those reflection zones where the reflections arrive after only the one bounce.

Very best of luck with your challenging room!

Disclaimer: I make a commercial embodiment of the distributed multisub concept, but I think my subs are bigger than you need and I think you can get there for a lot less money via three or four small subs. I do have one (happy) customer who mixes with my four-sub system in a square room, but it's not a fully cube-shaped room.

That's pretty iteresting!

As I said above, I'm not against this, and I've been trying to find how to add another sub to the layout, as I've already read a bunch about using more than one sub to try to tame the sub low frequencies inconsistencies, but still not figured it out how to connect two (or more) subs using an interface with single LR outputs. Right now, the cables goes from interface to ARC Studio, then to sub, and then to monitors. And my sub isn't that big (8"), so add another one to try to tame these inconsistencies might be feasible.

I just don't get exactly what you mean when you said "You might try setting up your main speakers on a diagonal, or just off the diagonal by a few degrees, to see if this gives a bit better results than setting up "normally"". How do I do that, exactly? Are you saying to put them 'outside' the equilateral triangle rule?

You can tame the bump with EQ, and the bumps tend to be the more annoying than dips. You can't really fix dips because it takes "infinite power" to overcome the wave cancelation.

Of course if you are producing rather than listening for pleasure, it's more important to smooth them both.

Bass traps trap the reflected bass so they can smooth-out the dips and the bumps. But I believe you need to cover a significant percentage of wall space.

Ethan Winer is one of the owners of RealTraps. They sell the "thin" membrane bass traps and he has an article (that I've never read) about building your own mass trap.

..If you look at the pictures on Ethan Winer's website or the RealTraps site, you'll see a TON of treatment.

Yeah! That's the point. As I'm using this room to produce and mix music majoritarily, I'm trying to make it the most 'neutral' it can get, even knowing it'll be an hard task, almost impossible, as it's a pretty challenging room. Looking at the curves attached in the first post, I've already tamed a bunch of the bigger peak around 57Hz, with the treatment already done and using ARC... but the dips are here, and ARC is no match for them.

I was planning to add a huge bass trap at the back wall (2.00 x 1.80 x 0.20 meters), but I don't know if it'll be that effective by having the bookshelf in front of it. But I can try to make a membrane bass trap to put there, above the bookshelf (of above this massive back bass trap). I was also planning to add thick clouds at the back of the room, just like the one above my listening point. Also, I'm planning to add at thick curtain on the window, (maybe) to help with reflections at the left side. And change the first reflection side panels for thicker ones too, like said in the first post above.

 

[The_Ogre]

One thing I forgot to mention on the first post is that I also added two 0.60 x 0.60 x 0.20 (8") meters panels at the superior trihedral corners in the back wall.

So, at least the four superior trihedral corners have some treatment installed.

 

[JTee]

May I ask, has anyone seen this design for a Limp Mass absorber? I was wondering about building these for my room and wondered if it would be helpful to you, Ogre. I can forward the link to the forum where this design was discussed, if that would be of any help? The man who designed them suggested that the size of the absorber, in terms of width and height, seemed largely irrelevant. Not sure if I believe that...