Seeking feedback on acoustic treatment and design

[Krakadon]

I'm really sorry guys, but I see so many people chasing their tales, especially using ease in venues. They wander around waving their mics, making odd noises and producing wonderful graphs, waterfall plots and determine that this wrong, that is wrong and to cure it we need to do this, and that, and usually spend money. Many are very old listed buildings and then the people come in, and the acoustics change and suddenly get hugely better. The Victorian architects didn't have prediction and measurement software, just ears and experience.

What I meant with my glib comment about what does it sound like is that what it sounds like often argues with what it looks like!

Does the room sound dull or bright, obviously heavy at the bottom or missing the bottom totally - does it sound just dull, or have peculiar nodes where the sound changes with just a bit of ear movement. I always listen to every space I work in, and my ears tell me what it's likely to need to tame it. If you see a small room with parallel walls and surfaces that are hard you know it's going to sound boxy - I looked at all those wonderful plots and just thought that I had no idea what it sounds like. I cannot (what is the audio version of visualise?) imagine what it sounds from those. Confused? Yep, unbalanced, unfocussed, weird stereo image as the response clearly changes with frequency - but I have no idea if I could live with it.

Uhm...yeah. Here is where your comment has merit. Having good ears and instincts (which really are insights gained over time) is very important. Most importantly, what you hear over and over is that reference monitoring is the best tool, especially if there are some songs you know really, really well.

Relative to your comments about measurements and treatment, ah physics is physics even if you don't understand it. There are before and after examples all over the internet that show how a space was improved and almost any professional will say you need to work in as accurate a room as possible.

 

[rob aylestone]

Indeed - totally agree, but doing an analysis of food ingredients to find their spectrographic spikes, then repeating the test once the food has been cooked will reveal the damage it's doing to your kidneys and arteries - but it is totally useless at telling you what it tastes like.

I appreciate my view isn't what you want, clearly you prefer to rely on formulaic analysis of a space. However, very few spaces I have recorded in over the years would look good from the data. We all know of nice spaces to record. I just worry that nowadays we spend more time installing treatment than we do in designing the rooms. Designing a tuned trap to remove a problem frequency in a poorly designed room works, but usually removes more than you want of frequencies around the resonance which you then try to liven up.

I spent a long time with a home cinema guy who was designing his acoustics by software and maths. 32 band eq on every speaker channel, and looking at the curves he'd set up it was no wonder it sounded dreadful. I fiddled for half an hour, and he came in to have a listen. "Not perfect, but a hell of a lot better, what did you do?" I switched all the eq out, and turned the bass down on the usual sloping knob down a couple of notches. I played my favourite reference material (Alan Parsons Sound Test) and it sounded pretty well what I expected. He played his and he liked it. However, when he plonked the reference mic into his listening position he was almost in tears - it's a wreck he said. He simply couldn't balance what he heard with what he saw. He saw errors and he wanted them to be gone. I prefer to make my final decisions on the merits of what it sounds like. If I hear a nasty resonance, then the software tells me what frequency it is, and I can have a think on either soaking it up, or eqing it out.

Maybe I'm old fashioned in my approach, but it's worked for me for a long time. I even built a studio once with a large control room that had movable non-parallel walls that we could adjust with a pry bar, and it was amazing to hear what difference even a one inch spread did to the sound. Eventually we got a sound we could happily work with, and then we finished the construction. We borrowed (being a college) some gear from a partner uni, and these small changes were so obvious on the screen, but just sounded better/worse, but the one with a confused spiked and 'busy' spectral display on the time and frequency scales did not always sound bad, just different.

For me, I'll trust my ears to make my decisions.

 

[miroslav]

However, very few spaces I have recorded in over the years would look good from the data. We all know of nice spaces to record.

That was my point earlier...if you had the opportunity to see test measurements of many pro spaces...they would not all look super impressive, but many of the rooms still sound quite good and yield good results.

Again...not saying that trying for perfection with treatment and measurements is a bad thing to do...just that at some point you kinda hit the limit of what you can do in a room without tearing it down and rebuilding from the ground up, but that shouldn't mean your room will totally suck or that you can't get good results in there once you learn it.
Shoot for the best treatment you can do and afford....but don't get totally dejected by non-perfect measurement results.

 

[Krakadon]

Gentlemen, thanks for the input. I agree. Your ears are the judge. At the end of the day the space is what it is, now get in there and make great records. Most spaces aren't perfect. That isn't the point of this thread. I never want to talk about acoustic treatment again for as long as I live. I want to optimize my design and move on. Let's just focus on optimizing the design.

 

[Mack Caster]

I never want to talk about acoustic treatment again for as long as I live. I want to optimize my design and move on. Let's just focus on optimizing the design.

Don't get discouraged. You were smart enough to use a process, that 90% of people just don't comprehend. Sometimes people fear what they don't understand. This is simply human nature. If you were smart enough to complete this process, and you are, then you are smart enough to sift through the information on this thread, take what you want, and simply ignore the rest including any advice I gave as well.

Now, go mix some original audio and link it back. That is going to help you the most. I am off to delete every thread I am subed to as I got close to 200 e-mails today and only 5 or 6 was worth reading. See, we all have our limits. ;-)

 

[miroslav]

I want to optimize my design and move on. Let's just focus on optimizing the design.

I think some of the posts here have been about that...ways to improve your setup, but TBH, I get the feeling like your more interested in why your current setup isn't giving you the measurements you expected.
Also, you do seem to be "set" in how things are now arranged...so I'm not sure how else you expect to optimize the design without some involved re-configuring...unless you're thinking about just adding more on top of what's already there...?

Don't get discouraged. You were smart enough to use a process, that 90% of people just don't comprehend. Sometimes people fear what they don't understand.

...yeah, OK.

 

[Krakadon]

I think some of the posts here have been about that...ways to improve your setup, but TBH, I get the feeling like your more interested in why your current setup isn't giving you the measurements you expected.
Also, you do seem to be "set" in how things are now arranged...so I'm not sure how else you expect to optimize the design without some involved re-configuring...unless you're thinking about just adding more on top of what's already there...?

It's not that I am set. There are practical constraints. This isn't a purpose built room. Closing off the doors isn't an option and I can't have people squeaking past my $1,500, excruciatingly carefully placed, studio monitors 30 times a day. I don't know why you feel I am inflexible or otherwise married to the design. Understanding the root causes of the poor performance is elementary in devising solutions. I have already implemented recommendations I have receive and am in the process of implementing more. The old design is in the past.

 

[Mack Caster]

I have already implemented recommendations I have receive and am in the process of implementing more.

Please keep me posted here or by PM if you would. I going to be working on some of my panels this weekend, maybe.

Me: Hey babe, you want a skylight before I put the roof on the new screen porch? Wife: No, I don't want one. The day before I picked up the shingles. Me: Hay babe, you sure you don't want a skylight? Wife: Ya, I'm sure. Three days after I had the roof finished. Wife: Hey babe, how hard would it be to put a skylight in? Any way, I would love any input you have once I get everything situated and run my mic tests.

 

[miroslav]

It's not that I am set. There are practical constraints. This isn't a purpose built room. Closing off the doors isn't an option and I can't have people squeaking past my $1,500, excruciatingly carefully placed, studio monitors 30 times a day. I don't know why you feel I am inflexible or otherwise married to the design. Understanding the root causes of the poor performance is elementary in devising solutions. I have already implemented recommendations I have receive and am in the process of implementing more. The old design is in the past.

I can appreciate the concern about the monitors, having recently spent a very substantial amount on a pair myslef...though in my case, I don't have people coming in/out of the place 30 times a day like in your situation. I thought yours was also mainly a personal/project studio where you worked solo for the most part.
That said...again, just looking at the width of your couch which doesn't appear to block the doors or create an obstruction...I thought your setup would fit easily in that same footprint.
The main reason that was suggested was due to the odd angled corner created by the fireplace, seeing how the monitors are currently firing back into that end of the room. Flipped around, they wouldn't have that.

AFA the root causes, it's not like there's some mystery there that is hard to understand. It's a small, kinda square-ish room...so without some major reconstruction (which you can't do since it's a rental)...I'm not sure what other options you have other than to stuff the heck out of it with more trapping...which may not improve the measurments a whole bunch, but it should help.

I think you should lose either the ceiling hard surface or the the floor...for the most part. That might help...and I think you also need more at the back wall, at least as much as you have at the front wall. Extra thick, absorption is the only thing that will help in a small space. The more you take the room out of the equation with absorption, the less issues...but then you could end up with a borderline "dead" room...so it's a lot of trial and error.
I think that was one reason for the question that was posed...."but how does it sound"?

AFA the doors...I have a similar situation, where at one of the back wall corners, is a door. Now the door is actually not a bad thing, and in your case, you should always work with both of them open so as to let the sound pressure and low-end escape as much as possible...but you still kinda want something there to help absorb the stuff that doesn't escape.
I made a bunch of "portable" low-end traps...they're gobo-like and free-standing due to their 7"+ depth (there's a thread here where I posted the trap build).
That way I can move them into position, in front of the door or how I like them behind me...and then move them out of the way when I'm not mixing, and I can use them for tracking as gobos.
One side has the OC 703 FRK with the aluminum backing facing out, and the other side of the traps is just 703...so I can spin them around for a different effect.

So what kind of changes/additions have you implemented or plan to in addition to what you show in the first post?

 

[Mack Caster]

...yeah, OK.

You can't mix what you can't hear and if anyone tells you different, I would not use their paid services. A blind man can walk up a set of stairs due to mussel memory, yet place a veteran mastering engineer in a dead room and ask them to produce a finished quality mix, is like driving with blinders on.

Understanding the root causes of the poor performance is elementary in devising solutions. I have already implemented recommendations I have receive and am in the process of implementing more. The old design is in the past.

You should know that manufactures are now designing software into their mixers that will allow the sound engineer to sweep the room for bad freqs. When the process is completed, it will custom build the eq based on the results. This will allow the live performance to sound the best it can, with the room dimensions it has to work with.

You already have what is needed to do this as well. Once you build the custom eq for your room, use it as a guide to show you what you can not hear or what is being reduced. Adjust accordingly.

View attachment 100847

 

[Krakadon]

The availability of room correction software should be common knowledge by now. It is ubiquitous. However it comes with its own set of flaws. It's not like professional rooms where they have phase coherent equalizers that cost many thousands of dollars. You need to correct as many room problems as you can before if and when you elect to use this technology.

 

[miroslav]

You should know that manufactures are now designing software into their mixers that will allow the sound engineer to sweep the room for bad freqs. When the process is completed, it will custom build the eq based on the results. This will allow the live performance to sound the best it can, with the room dimensions it has to work with.

You already have what is needed to do this as well. Once you build the custom eq for your room, use it as a guide to show you what you can not hear or what is being reduced. Adjust accordingly.

View attachment 100847

If you're going to dwell on the room nodes/nulls thing and say that "you can't mix what you can't hear"...then you can't in the same breath talk about EQ room correction.

If you have frequency nulls...you can boost the living shit out of those frequencies with any EQ and the nulls will still be there.
Anyone selling room correction EQ software is probably also selling wooden knobs for stereos, for the "warmth" they add to the sound.

The reality...the hard reality is that almost ALL rooms will have a collection of nodes and nulls. The better, purpose built rooms with purpose built treatment will address the serious stuff...but you can go run sweep measurements and use software to compute nodes/nulls using the room dimensions...and ALL rooms will have them to some degree.

I'm not suggesting they be ignored, but I think for most home studios there is a point of diminishing returns and you'll be either wasting time/money and/or ending up with a room covered in traps everywhere...and it will STILL have nodes/nulls.
So the point is...do the basic acoustic treatment stuff, the common sense stuff that will provide the most improvement...and then go make some music and put away the measurement software and all the acoustics theory.
I mean, great music has been recorded and mixed in some pretty basic rooms...people don't need to lose their minds over perfect acoustics (which they will not get anyway).

 

[Mack Caster]

If you're going to dwell on the room nodes/nulls thing and say that "you can't mix what you can't hear"...then you can't in the same breath talk about EQ room correction.

They are designing this into their software so they can product the closest sound the room could produce if it was designed properly to begin with.

If you have frequency nulls...you can boost the living shit out of those frequencies with any EQ and the nulls will still be there. Anyone selling room correction EQ software is probably also selling wooden knobs for stereos, for the "warmth" they add to the sound.

Yes, especially when they are know for cutting edge design concerning live mixing software & hardware. Yep, that's how they built their impeccable reputation, by misleading the professionals in the audio field and we were just dumb enough to believe them.

The reality...the hard reality is that almost ALL rooms will have a collection of nodes and nulls. The better, purpose built rooms with purpose built treatment will address the serious stuff...but you can go run sweep measurements and use software to compute nodes/nulls using the room dimensions...and ALL rooms will have them to some degree.

Of course they do and nobody has ever said any different. The goal is to level them, not remove them.

I'm not suggesting they be ignored, but I think for most home studios there is a point of diminishing returns and you'll be either wasting time/money and/or ending up with a room covered in traps everywhere...and it will STILL have nodes/nulls.
So the point is...do the basic acoustic treatment stuff, the common sense stuff that will provide the most improvement...and then go make some music and put away the measurement software and all the acoustics theory.

Well, now you are back on topic and that is what this post has been about the entiretime. From the OP:

I rented a small duplex and have a 13'10"x13'10"x8'9" room with a hard floor (all of the details are in the subsequent slides). Clearly there are limitations with this small, somewhat cubic room. Also, as a renter, I can't make any structural changes. I spent a long time researching and planning the Acoustic Treatment, and ran the plans by some folks who said they looked good. I spent about $2,500, and a huge number of hours, designing, constructing and installing the treatment. When I took the REW measurements, I was quite bummed at the results. I’m seeking feedback on the design and results and any recommendations for improvements. Thanks in advance to anyone that can help me out.

The point being that when everyone starts suggest they start building this or buying that, they really need to do their own homework before they have people waist their money or as you put it,

you'll be either wasting time/money and/or ending up with a room covered in traps everywhere...and it will STILL have nodes/nulls.

I do get tired of everyone screaming bass traps have to be installed first, as 9 times out of 10 times, that is the worst thing you can do in a small room and 9 out of 10 times is simply a waist of money.

 

[miroslav]

The goal is to level them, not remove them.

There are several big name software companies churning out apps that either let you simulate a perfect room on your headphones...or that try to EQ out the issues of your room....etc...but those things don't fix the problems in the room.
There's a lot of very professional snake oil out there...and people who will buy into it.

I'm still not seeing how software is going to "level" a room node/null. The only thing that would do that is a change to the room.

That brings it back to the original topic and that you kinda will hit a dead-end in most home studios...and there's only so much that you can do, and no amount of measuring or adding more traps and diffusers inside the same space will make a significant change.
I'm just saying that when you hit that point...you should move on and work with the room, learn it...or go find another room. I think you can make yourself nuts just running sweeps and adding/re-positioning traps..etc.

 

[Mack Caster]

I'm still not seeing how software is going to "level" a room node/null. The only thing that would do that is a change to the room.

The program does two things.

1. If you are running live audio, it will show you how to set your eq to provide the best listening experience for your audience. Most high end home theaters sound system will have an eq that the homeowner can adjust. Back in the day, everyone would make a slow sweeping "V" and thought they were doing something good. This is incorrect. Since all rooms will have bad areas as far as listening from and frequencies that will be affected due to room size, the eq is used to either cut or boost that frequency that is affected. That's what this software does. The more bands the eq has, the better sound it will produce.

2. If you will be using a room to mix or master in, it will show you the frequencies that will be affected by your room. It is the same principal as number 1, but it is to make the person doing the mix, aware that if you are working on something that has a lot of high end, and your look at the reference that says your room will not properly play the high end, make sure you don't boost the high end to much, as it is already in the mix and you just can't tell, due to your room conditions.

As far as using the Room Mode Calculator goes, it is simple something that will tell you in advance whether your room is a candidate for being able to apply room treatment and get good results, due to being able to evenly distribute the modes. If your room does not meet the requirements, you will spend an arm and a leg and still not get what you may be looking for, as the OP has discovered.

The so called "Bolt-area" indicates a accumulation of good room ratios. If the red cross lies within this area you have a good chance of more evenly distributed modes.

The man that designed this system is a member of this community. I have an interview with him coming up in the next few weeks for a video I am doing. I have followed his work for years, long before I joined here. I regard him as the top expert in the field of acoustical science, as do many others. His articles have been peer reviewed and have passed with flying colors. When you have the AES backing your claims as well as your math, you pretty well have your ducks in a row.

I never have, nor will I ever tell anyone that trying to improve their room is useless, simply just as you stated above, there is only so much you will be able to do and then you will simply need to live with those results. You see, we are both saying the same thing, just from a different point of view. That's why it kills me when someone just jumps in recommending bass traps for improving your room.

If your room does not have the proper size to begin with as well as the proper material that it is built out of, you are better off letting the bass escape the room and dissipate, than trying to catch it in a small room and control it. One of the easiest things you can do is simply open the door to your control room and let it go. Why recommend the most costly thing you can do for sound treatment, when it will never produce the needed results to begin with.

In closing, I have been to your YT page, before we started posting on this thread. Some of the best I have ever heard Brother! I just wish you had more videos. ;-)

 

[miroslav]

If your room does not have the proper size to begin with as well as the proper material that it is built out of, you are better off letting the bass escape the room and dissipate, than trying to catch it in a small room and control it.

Yup...I was saying the same thing earlier (or maybe in another thread)...let it out.

I'm not saying don't use the mode calculator...just making the point that you can run that and also the sweep measurements in many pro studios and you will still see all kinds of "issues" according to the measurement results...
...and that those things shouldn't be "THE" deciding factor on going forward and using the room after applying the basic/common sense treatments.

I also know what you mean about the other software...I'm just saying that even when it tells you what wrong in the room, there no way that you can correct it with that software or EQs....you have to acoustically correct the room in most cases to really improve the results...but you get to a point where there's no place to go, without tearing the room down.
I'm sure many venues are not optimal, yet they are workable...same as many home rec spaces.

Point being...are you looking just how to build a perfect acoustical space...or to correct what you have to an acceptable degree so you can get on with making music...?

 

[Mack Caster]

Point being...are you looking just how to build a perfect acoustical space...or to correct what you have to an acceptable degree so you can get on with making music...?

The last part of your statement has been the number 1 goal from the git go and will always be my battle cry. Once you are informed of your limitations, do what you can, save your money, let the rest go, ROCK ON & HAVE FUN!

​

 

[Krakadon]

Update

UPDATE:

Completed:
• Repositioned broadband absorbers on front wall to be tight against wall
• Placed studio monitors per Soundman2020’s suggestion (i.e. 4” from back wall, 49” from sidewalls, acoustic axis placed at 50” height)
• Removed diffusion array from back wall
• Removed headboard from broadband absorber above former diffusion array position
• Replaced 3” 8 lb./ft^3 Roxul with 4” OC703 in rear wall broadband absorber and moved it down behind the sweetspot, just above sofa flush against wall
• Since I can’t put superchunk bass traps in left rear corner, I reused the two old bass traps in that location, removed diffusion grates and 6” of 8 lb/ft^3 and replaced with 8” of OC703. Still need to remove limp mass membranes on those two. Also plan to fit some OC703 scraps behind traps
• Took quick set of REW measurements (w/o sub)

Planned:
• Remove limp mass membranes from rear traps and add additional OC703 to fit gap
• Remove existing bass traps from front corners and replace with floor to ceiling superchunk traps
• Remove polysorbers
• Install some amount of superchunk bass traps in the wall/ceiling corners
• Upgrade RadioShack SPL meter and Behringer ECM8000 calibration mic
• Retest room
• Remove everything from room and do baseline characterization (this will take several days and take my studio off-line so I don’t know when I can get to this. All of the other stuff I can do in the margins so to speak).
• Solicit input for revisions

Questions:
• When I build superchunk traps, do I put a layer of plastic or craft paper over the insulation below the fabric to reflect some mid/high frequencies? I have read this in some places. Often, I have seen wood slats placed on the outside of the superchunks, i.e. facing into the room, presumably for some diffusion or reflection of mid/high frequencies back towards the mix position, yes?

 

[miroslav]

So would this be the "before" and "after" measurements?
Looking at all the different measurements in your first post...not sure if this would be the best one to compare to?

I'm also not sure if you're using the same levels in your measurements...seeing the difference between these two.
I would shoot for 80-82 dB SPL when you first calibrate your monitors.

Also...are you measuring one monitor at a time...Left and Right...or both at the same time?
It should be one monitor side at a time...and then you can average the two measurements.







So what do you think of your new setup and measurements?
Just looking at the graph....it almost looks like you now have more defined/deeper nulls/peaks, but I'm not sure if these two measurements were don't exactly the same way to make them a fair comparison.
Plus...the real comparison would have been the room without any treatment and then with treatment. Then you would know just how much the treatment is actually making a difference to the room.

 

[Mack Caster]

• Solicit input for revisions

The first thing you need to do is get your mid range decay under control. This is very easy to do, with what you have done already by simply re-positioning your absorption panels and if you need more, just BOAT it. (Bust Out Another Thousand). Once you do this, you will need to do the same thing for your low end, + 20% more. According to the math, you need to apply 123.8 square feet of absorption to fit your room size. This is based on over a million dollars worth of controlled lab experiments, done by people who have PHDs attached to their names.

I did not come up with or design the math for my answers to you. As JB states, "We stand on the shoulders of Giants that have come before us"! I mentioned this to you before in this thread, unless you are sitting in a concrete structure, the best thing anyone can do for their home studio, is to simply let the bass escape the room. Most of the time, extensive bass trapping is a waist of money, time and material. To use it for soundproofing, you probably will run out of room space before you stop the thumping from reaching the outside.

Since you mentioned nothing about sound proofing, I will stay on topic with simply using bass trapping for mixing/mastering situations. Think about the car coming down the road with their bass amp kicking. The bass always gets to you first before you hear the rest of the music and it sounds so good in the car, as once it hits your ears it just keeps right on moving away. Trap that same bass in the car and it will make your heart start skipping.

Two months ago myself and my wife had to leave within the first five min of a Christian Concert as the bass was triggering her pacemaker to kick in, as it thought her heart was beating irregular. This was coming from a stage sound system that was recently revamped for 1.4 mil inside of a 80 mil dollar complex. This was not a control room, the traps were designed to keep the bass in for soundproofing as it is located within 2 or 3 hundred yards from other commercial buildings.

Questions:
• When I build superchunk traps, do I put a layer of plastic or craft paper over the insulation below the fabric to reflect some mid/high frequencies? I have read this in some places. Often, I have seen wood slats placed on the outside of the superchunks, i.e. facing into the room, presumably for some diffusion or reflection of mid/high frequencies back towards the mix position, yes?

These types of traps are designed to allow for both absorption as well as reflection and if they are built at an angle, they also work for diffusion. That is why they have a angled hard reflective surface. If you build them properly, there is no need to apply a second layer of reflective material over the insulation.