Advice Needed: Treating room, Tuning Room w/ Sketchup files

I use the DBX measurement mic - the one's they use for the Drive Rack.

That's actually a pretty good measurement mic, so that isn't the problem. The pre-amp should be pretty flat too, so it's a mystery where the low roll-off is coming from. Do your speakers have a low frequency "roll-off", "tilt" or "room correction setting"? If so, it might not be set correctly. As a quick test, set all controls on your speakers for flat response (no boost, no cut) and do one REW run like that, then set them back they way they wer (since you are probably accustomed to that sound at present. You'll have to re-train your ears for the room once it is completely treated correctly, but for now it's not worth doing that yet). Is there something else in the signal path that could be rolling off the bass? Console? Sound card settings on your DAW? Are you using a sub for those tests, or just the two main speakers? What speakers are they (make, model)? If you have a sub, did you try inverting the signal on it? Often flipping the phase inversion switch can have good consequences. If you have two subs, try all combinations: both 0°, both 180°, and each one flipped to 180° individually with the other set to 0°.

Do you have any guides for repeatable measurements?

I'll send you (PM) the setup instructions I give to my paying customers when we are about to start tuning their room, so you can follow those. Basically, you calibrate REW for your sound-card following the built-in manual, then you do the additional steps I outline in the notes, which is setting things up the the recognized "standard" calibration level of 86 dB and setting up the mic at the correct location, which is the middle of where your head will be while mixing, pointing directly ahead, and angled upwards 60°. Some acousticians say 90°, but I find that makes it too sensitive to the ceiling-floor axis, and not sensitive enough to artifacts coming off the desk and first reflections off the ceiling, so I prefer 60°. You then carefully measure the exact location of the tip of the mic in the room, such that you can always get it back to that exact spot, within a few mm (1/4"). You need that precise location for repeatability of the tests, so you can validly compare graphs at different points in time. You might also need to measure in other locations, but you need to be able to get back to that one consistently, so use measurements points on the walls, floor and ceiling that won't be covered with treatment at some point, making it hard to measure. I often put gaffers-tape on the floor and mark the spot directly under the tip of the mic with a fine tip permanent marker, and use a plum-bob to position the mic tip directly above that point, then measure the height with a tape measure.

The SPL suggestion makes sense.

86 dBC is the level you want with all speakers running, and since REW uses coherent sound for its tests, you need to calibrate each speaker up at 80 dB if you are just using two mains, or 77 dB each if you are using two mains plus a sub, or 74 dB each if you have two mains plus 2 subs. Use full-spectrum pink noise to set the level of the mains, and HPF filtered pink noise to set up the sub levels. REW can play both types of calibration signal for that. (if you set up your individual speakers to the correctly level, then the combined level will automatically be correct too. Do not adjust any settings between tests! And leave the room for each test: use the "Start Delay" setting in REW to give you time to get out.

But keep in mind that the ONLY LF treatment I have in the design doesn't exist yet, so there is NO LF treatment.

When I tune a room, I normally start with the bass trapping first, for three main reasons. 1) The bass junk in most rooms is so huge that it masks most of the mid-range issues. You need to get rid of that first, so you can at least see the mid range. 2) Bass trapping takes up a LOT of space, so it's best to get that in first, then fit the other treatment around it. 3) Bass trapping often does good things to the mid range and not-so-good things to the high end that you might need to compensate for. So I start out with the room totally empty, fo my "baseline" REW tests, then add the basic bass trapping and do another REW test, to check that it worked and see how much more I will need. Then add a second round of bass trapping, check, rinse, repeat. When the low end is under control, I look at the highs to see how bad I made it, and either modify the bass traps to fix that, or add other treatment. Then I go for the mids, which are often the hardest to deal with.

There are 6 VPRs in the design which are proven devices in lowering decay times in LF and improving FR as well, and that's ultimately my goal.

Well, yes, VPR's can do that, but they don't necessarily smooth out things evenly. Your goal should be to meet ITU BS.1116-3 spec, or maybe EBU TECH-3276 specs. Those are the ones that are normally used for precision tuning of control rooms. It's not just about overall decay times, or overall frequency response.

But I am in a transaction currently which would allow me to purchase this property as my home.

Cool! That means you can start from scratch, and get the entire room properly designed as a control room. I would strongly suggest that you do it as a true RFZ style room, due to all the major benefits that can provide. If you do it right, you can get excellent results. Remember that room whose graphs I showed a few posts back? The owner just replaced his old speakers with new Eve SC-407's, which we flush-mounted in custom-designed isolated soffits that I designed for him, then we spent a couple of weeks re-tuning his room. This is where we are right now: That's smoothed 1/3 octave, as he wants to make sure it meets BS.1116-2. Full-spectrum frequency response is within +/- 1.7 dB of flat. Low end waterfall: That's the entire low end response, up to 500 Hz, un-smoothed graph. Flat and even decay times across the board. And the spectrogram for the low end: Also unsmoothed, also 20 Hz to 500 Hz. That's not how the final tuning will be, as he wants to add his house curve to that, which is similar to the old B&K curve, but we went this route first as "proof of concept" that we can get it dead flat and as smooth as mill pond on a calm day. Perfectly flat response isn't nice on the ears, but that's what it looks like if you want it. OK, so his room is bigger than yours, and was designed and treated from the start as a control room. You won't be able to get yours that flat, and neither should you try, but you can still get it much better than where it is now. I wanted to show you that so you don't get discouraged! There is hope... :) Follow the procedure logically and carefully, starting with an empty room, and you can get it really good. Randomly trying things that you find on half a dozen different web forums and manufacturer websites, won't get you there. You need to ditch that approach, and just follow one simple procedure, slowly, step by step, testing at every step. If you note in the FR graph above, that result is for "test number 127-Y"... (and we aren't done yet...) - Stuart

Testing Details: As stated in my previous posts, the difference in the placement of the mic axially varies quite widely due to ignorance. This ultimately taught me about placement of not just speakers, but also mix position. So the latter treatments, about half way down are actually pretty consistent in mic position. Consequently, the mix position, speaker placement, mic placement and also many of the treatments moved around during these tests as that is the purpose of these measurements - to see how it improves with changes. Most of these I tried to clean out, and attempted to keep only major movements for historical reasons. So these measurements unfortunately because of the revolving changes are not 1:1, but not that far apart either. I think that major, large wavelength issues will still do the same thing relatively speaking, so they are still at least valid if only abstract. Again, these are mainly for historical documentation for me to learn as changes are made, but again, the latter few are pretty much identical with the changes being in traps and so on, so the last third set is pretty valid with only exception being SPL varying a bit. About the speakers: My speakers are Focal Solo 6 BE LTD - FR of 30-40K The speakers have shelving EQ on HI and LOW bands. I don't know where they start/cut off, but most of the measurements have the speakers at 0-0 meaning no boosts or cuts. The first few measurements had, from what I remember, a HPF on my Console which I didn't notice was engaged. I noticed this later, but only the first lets say 1/3rd of the measurements may potentially be hurt by this. By the latter set of measurements I know for a fact that apart from SPL matching, everything else was verified to be the same. However, I really think I re-did the measurements when I learned my blunder, so the LPF may or may not be valid anymore - I just don't remember! But again, the last third is accurate. No sub, and no phase flip on either. Nothing else in the path, again the HPF was potentially engaged for the first few, although I feel like I re-measured without. I CAN however tell you that once the speakers were flush to the front wall, LF improved dramatically. And I also seem to need another +2dB boost on the back of the speakers to get a balanced LF audibly. However, as noted, the measurements were at 0-0. Regarding your graphs: Wow! I did not think that is possible! Looking at these measurements just completely blew my mind! Granted, I get that it was probably ideal in dimension and a build and so forth, but still, that is impressive!

I'll send you (PM) the setup instructions I give to my paying customers when we are about to start tuning their room, so you can follow those.

Thank you - that's very generous and kind!

When I tune a room, I normally start with the bass trapping first

I do as well, but in this case different vendors and subsequently "path of least resistance" won out first in that parts and labor to build thick Roxul absorbers and QRD diffusers was lower, so they came first. The problem with VPR's is the specificity of the components. Allot of research was needed to understand exactly why and how VPR's function, which dictates the very specific ways in which they must be built - namely the plate thickness, but more importantly the adhesion to the Carruso ISO Bond and also which absorber material will work best given the complex eigenmodes of the resonating plate - the winner being CIB of course. Not only is the design incredibly specific, but materials are not exactly "down the street", where the treatments which have been completed thus far pretty much are! So that's why broadband absorbers and diffusers/scatter devices were built first.

I would strongly suggest that you do it as a true RFZ style room

In theory I know what that means, but it sounds like this is more of a philosophy of implementation that I need to really absorb. I'll start looking into the ideals of "true" RFZ room design and see what I can learn. You mentioned "custom designed soffits" and I thought about this as my previous "proper" mix room from years back in Cali had these. The soffits were made with absorption at the back, concrete encasement for speakers, and hangars at the bottom from the top of my head. And I liked how that place sounded! I don't know if I want to do this same here though, cause I don't want to pigeon hole myself with my Focal's if I choose to augment, or replace these down the line. What are your thoughts on these?

the mix position, speaker placement, mic placement and also many of the treatments moved around during these tests as that is the purpose of these measurements - to see how it improves with changes.

To a certain extent, yes. But there's a basic set of "rules" for getting things to the starting point, that saves you a lot of hassle. And time. From that initial position, you normally only need to check maybe a range of a +/- one foot forwards/backwards for the mix position, and maybe +/- 5% of the room width for speaker position. That's it. The rest all falls into place, pretty much automatically. It isn't necessary to "re-invent the wheel" by trying dozens of positions that won't work. It's unfortunate that you found the forum so late in the game! We could have saved you lots of trouble if you would have found us right at the start of your quest.

I think that major, large wavelength issues will still do the same thing relatively speaking, so they are still at least valid if only abstract.

Right, but once you start getting up through the mid range and into the highs, small position changes can make big measurement changes. And even for the low end, it's surprising how much difference a small move of the mic (or speaker) can have. For the same room above, we did a series of tests with the sub, sliding it in steps of 3 inches at a time. Sometimes we got rather interesting changes from one step to the next, and moved down to 1" steps. And that's for a sub that cuts off at about 100 Hz! Wavelength 135 inches... We also did tests moving the mic all the way from the mix position to the back wall in 6" steps, to clearly identify which issues were SBIR, which were modal, and which were reflections. There's actually big differences in the low end between adjacent 6" locations.

My speakers are Focal Solo 6 BE

Nice! but the response I am seeing in those graphs is not the response I would expect from those speakers in that room.

I don't know where they start/cut off,

According to the manual, if you set that to -6, the low roll-off starts at about 1kHz and hits the -3 dB point at about 200 Hz.

I CAN however tell you that once the speakers were flush to the front wall, LF improved dramatically.

Yup. That's where speakers need to be in a small room like that. If they are moved away from the front wall then you start getting pretty serious SBIR issues. The bigger the gap, the lower it goes, and the larger the problem. You need to get it a couple of meters away before it goes off the bottom end... and that isn't possible in a small room. So the only place is tight up against the front wall, except for just enough separation to get the necessary absorption panel in there.

Wow! I did not think that is possible! Looking at these measurements just completely blew my mind!

Yup! Those are nice graphs, aren't they? Thanks for the kind words. Not everyone appreciates just how hard it is to do that. This is the actual room: That's the way it was before we replaced the speakers and started re-tuning. It's still a work in progress, but this is how it looks right now, with the Eve SC-407s in place: It's a bit messy: Speaker surrounds not finished yet, etc. Should be done by next week, hopefully.

Granted, I get that it was probably ideal in dimension and a build and so forth, but still, that is impressive!

It's a reasonably big room, yes, and the best part of it is the height. That always makes it easier. But the shape is not that good. Unfortunately, I was only brought in once the basic shape had been built, with no possibility to change it, so I had to live with it. The room was intend to face the other way, bu that was not going to work at all, so I had to flip it around, which left me with a strangely angled back wall. A nice challenge! :)

So that's why broadband absorbers and diffusers/scatter devices were built first.

You probably don't want to hear this, but I'm not at all convinced that you need those "diffusers/scatter devices" in your room... I suspect that some of your problems are actually being caused by those things, not solved by them... Those are apt for much bigger rooms. Small rooms and QRD's do not play well together. That's not just myu opinion: it's the opinion of the guys who wrote the book on QRDs, and came up with the math that describes how they work, and how to design them. I suspect you'd get better results without those, or at lest without some of them.

In theory I know what that means, but it sounds like this is more of a philosophy of implementation that I need to really absorb.

The basic concept is not hard to follow: you angle the surfaces forward of the mix position such that all first reflections go past the head of the mix engineer by a wide margin, and end up at the back of the room to be absorbed (small rooms), or absorbed/diffused/scattered (larger rooms). The room in the photo above is RFZ-based. Most of the rooms I design are.

he soffits were made with absorption at the back, concrete encasement for speakers, and hangars at the bottom from the top of my head.

That's one way of doing it, yes. I use a different approach, but the results are the same. Two main methods for doing it, that end up at the same finality.

And I liked how that place sounded!

I bet you did! To my way of thinking, its the best possible way of building a room, since it takes the speaker completely out of the room, acoustically speaking. So you get none of the artifacts from having the speaker in the room. That's a major plus. In addition you get a free LF boost (since the soffit baffle solves the power imbalance problem), and it looks cool as well.

I don't know if I want to do this same here though, cause I don't want to pigeon hole myself with my Focal's if I choose to augment, or replace these down the line. What are your thoughts on these?

For the room above, the owner originally had the Genelecs as his mains (now on stands behind the desk), but always planned to upgrade at some point. So I designed the original soffits with the speakers mounted in "trays" that can be unbolted and pulled out completely. I made the trays larger than the largest speaker he ever thought he'd use. That was three years ago. So when the time came to upgrade, I re-design the tray innards for the Eve's, and all he had to do was pop out the tray, modify the tray interior, and pop it back in again. In reality, he ended up building new trays to save time, and minimize downtown, so it became a "slide out, slide in" speaker swap. I designed the trays in advance to make that possible, with a complex internal suspension mechanism, so the entire speaker actually "floats" inside the tray, and is fully decoupled from it. I'm not sure if he'll allow me to share the details of how I did that, since he was the one who paid for the design, but I'll ask. Anyway, that's what I would do for your room too, if you wanted to soffit mount but aren't sure what speakers you might end up with. An interesting aside: for those folks who say it is not possible to soffit mount rear-ported speakers, look at the pics! Those are Eve SC-407's which are rear ported, yet there they are, soffit mounted, and performing fantastically. The head designer at Eve Audio gave me some info that helped to do that: it actually wasn't that hard! :) So it can be done. Soffit-mounting and RFZ style design sound daunting, and they do have their complexities, but with careful design and a bit of experience, the results are well worth the effort. Another interesting aside: I have never even been inside that room personally! All of the design, treatment and tuning have been accomplished purely by "remote control", over the internet. (It's amazing what modern technology allows... ) - Stuart -

Firstly, I feel like I need to donate to this site, and I will ASAP. I am very thankful for your info, and it's hard to find level-headed, KNOWLEDGEABLE, no BS people which one can learn from - so thank you! Now on to the other stuff. You've piqued my interest with a few of your claims, so let's go through some of them! 1. I agree about the Frequency Response of these speakers in this room. It was a "what the!" from day one! A bad "what the"! :D 2. So you're a proponent of absorption behind the speakers? Interesting! There seems to be so much contradictory information out there, allot of people explain, for good reason I think, that broadband absorption is pointless behind the speakers because even at 1/4 wavelength touching those SBIR frequencies is not possible with your standard broadband trap. I do however believe in proper "powerhouse" (diaphragmatic/pistonic or helmholz) absorber, that can actually absorb LF, being placed behind speakers, and it is why I have 2 VPRs in my initial design behind the speakers and 2 to the sides. I know this room enough through experimentation and measurement that I reason in having these VPR's back there would really help keep those modal issues and more importantly SBIR at bay. And I think that the shear pressure behind the speakers, and to the sides as well would really excite the eigenmodes of the metal plate of the VPR's which would should theoretically make them work incredibly efficiently! They are pressure activated devices after all, and so they work in high pressure areas. So theoretically the problem frequencies would really light up the plate, and thus cause high absorption coefficients. I really love the explanation that ASC, makers of Tube Trap, put in their whitepaper when defining what I am experiencing - they call it "head end ringing", and I feel that is a phenomenally accurate description of the problem I have. The front part of the room rings like all get out without treatment, and as soon as one back's up in the room, it tames, with the exception of the "expected" LF buildup at the back. So I feel that after many moons of gray-hair generating frustration, that VPR's are a definite and proven solution for my so called "head end ringing". Of course this is just theory, but one I feel very strongly about due to experiential and empirical evidence that I have access to. YMMV 3. Regarding the diffusers, you already had convinced me way back to get rind of them up close, even though they are already built. The scatter devices are as a direct "knee jerk" reaction, if you will, of the "deadness" of the room. And FWIW, so were the QRD's, but because of the phase issues with diffusers I figured scattering is wiser? :) This room has slapback and ringing like all get out, without absorption or diffusion! So having untreated parallel surfaces is really a bad idea in this room, much more than any room I've ever "treated" before honestly. For instance, with 3" of Roxul, I found that it is not enough to stop the ringing/slapback at those mid frequencies. The scattering devices, specifically those half cylindrical shape ones are really quite good from my experience at controlling the slapback! Because they absorb using Roxul with cut poly slats, covered by fabric and cylindrical wood micro poly's, which scatter/diffuse - they are pretty "invisible" sounding, if that makes sense, but more importantly they are really quite good at dealing with those paralel slap back on the side walls. They are away from my mix position though, so I doubt they are affecting anything at mix for the ranges they work in. Like I said, they "sound invisible". For instance, an absorber "sounds" like a black hole, I think anyone can relate to that. A diffuser, generally, sounds like a bigger room. But these scattering devices sound like.....nothing. It's kind of like a half way point between a bigger room and a black hole, so I kind of like what they do. Because they dont just piss out the energy back into the room, the absorb a good part of it, and control the rest of it. I hope that makes sense! The benefit is that I get complete control of slapback (which is hard to do with flat absorbers, you need the really thick stuff covering huge parts of the wall), and I don't add to the problem of over absorption on the wrong end of the scale. But if I wind up building the room, honestly, I'll build all this stuff into the walls which may mean no scatter devices, or not! Who knows where that'll go, I am playing with concepts now. 4. I like your concept of "deflect and absorb at the back". This is what we did in the room in Cali. See pictures below of the room there. So theoretically speaking, you're not a fan of flat slatted wood panels over large absorption surfaces? I see allot of conflicting info here as well, because there are guys from the likes of "Acoustic Fields" which argue that the decrease in SQF and thereby volume of the room of slanted wall builds is not as welcome when comparing to just treating the parallel walls appropriately - in other words the benefits are not huge, but the cost is pretty high regarding angled walls. And to some degree, obviously presuming that the absorption is at the correct "rates and levels" as he says (meaning frequency and coefficients) slanted walls are not all that big of a benefit - I kind of agree with that, because honestly it makes sense! I mean the way I reason it is, I am already in the lower end of the scale for room size. It's not a TINY room, but it's not a large room either, so lowering the SQF in this situation seems to be counter intuitive to some degree. The sound proofing effort will already do that with floated floors, ceilings and walls, so doing more would really start to hurt both size wise, but more importantly volume wise. Your thoughts? 5. "Because it takes the speaker out of the room..." when I saw that I freaked out! Like WHAT!? :D To me, a direct translation of that means "NO SBIR". Is that kind of.....right? Because holy flying squirrels batman! If we can resolve that, the modal issues of this room are a joke to get rid of. Even me, at my current knowledge level can relatively easily handle the rest of the modal issues in this room IF SBIR is largely eliminated! I feel I have currently, largely already dealt with the natural internal modes of the room with thick absorbers. Obviously the low end is the exception, and I feel that most of the LF problems are largely caused by this damned SBIR! I think that the SBIR in my room are causing huge oscilations in the walls themselves, which is a big reason for why that FR in my room looks so retarded! Honestly the more I know about this property I am in, the more I am thinking that the biggest problems I have are caused by the walls actually ringing themselves, because it simply doesn't make sense otherwise. Meaning the drywall and studs are resonating because of piss poor build quality. Even though it is to code, I think that cavities in the walls, and the drywall and stud choice together are causing allot of these issues. Which is why I am more and more motivated to burn it down (proverbially speaking) and build it from studs! But if I build it up, the soffits are definitely an option, pretty much everything within reason is an option at that point. I don't want to commit to anything yet, because I don't know if this transaction will go through, allowing me to own the home, and second I don't know if Ill be able to front the 10-15 grand out of pocket. I don't run a commercial studio, so I have basically no clientele for the audio division of my business yet, which means nothing but my own funds would finance this. It's basically a glorified home theater and office at this point, which I want to turn into a proper mix room simultaniously - thus the challenge! Buying a home, AND remodeling a room out of pocket in quick succession is pretty much out of the question of what I can support financially, obviously. So there are some logistical issues that have to be sorted well before I can commit to building it. What is positive however, is I have close professional friends which would work for pennies on the dollar to help me build this from a construction perspective, so that lowers the cost drastically from what commercial prices and costs would dictate. Basically that means this situation is a give and take. It has positives and negatives, but it is reasonably realistic! I am merely trying to upload this information so that once a move is made, the entire history and right turns of this project are documented for the help of others. So they can see where it started, and what it wound up being. Standby, I'll let you guys know what is happening in the next 2 months. By end of June I should know confidently what can happen. :blah:

Firstly, I feel like I need to donate to this site, and I will ASAP.

John will certainly appreciate that! It costs him money to run the forum, and he gets no return on that, except donations. Last time we spoke about that, he mentioned that donations only cover a fraction of the running costs, so I can tell you for certain he'll appreciate your donation!

I am very thankful for your info, and it's hard to find level-headed, KNOWLEDGEABLE, no BS people which one can learn from - so thank you!

:oops: Thanks for the kind words!

1. I agree about the Frequency Response of these speakers in this room. It was a "what the!" from day one! A bad "what the"!

Yup. The good news: I think it can be fixed. It won't be perfect, but it can be a lot better than where it is.

2. So you're a proponent of absorption behind the speakers? Interesting! There seems to be so much contradictory information out there, allot of people explain, for good reason I think, that broadband absorption is pointless behind the speakers because even at 1/4 wavelength touching those SBIR frequencies is not possible with your standard broadband trap.

Weeeelll.... take what you read on the internet with a grain of salt! :) The 1/4" wavelength thing is part true, part myth. Yes, porous absorption is most effective if it happens to be 1/4" wavelength away from the wall for the frequency you are targeting, and 1/4 wave thick. True. However, that does NOT mean that it won't work anywhere else! At 1/8 wave it is still 70% effective, at 1/16 wave it is nearly 40% effective, and even at 1/64 wave you still get a usable effect (about 10%). Another "however": all of the above is for normally incident sound (sound hitting the front of the absorber at 90°). For all other angles of incidence, the sound wave "sees" an even thicker absorber, so it is more effective than for normal incidence. For random incidence, you can get some very effective absorption for thicknesses and positions that would surprise you. In reality, it turns out that for normally incident sound, porous absorption can be 7% thick (7% of the wavelength) and be effective. For random incidence, it only needs to be 3.5% thick to be effective. Which is why superchunk bass traps work so very well down to low frequencies, even though they are not that thick at all, compared to the wavelengths: most of the sound is not normally incident to a superchunk. But we are not talking superchunks: we are talking absorbers behind speakers, just 10cm thick (4"). Here's the thing: 4" of suitable porous absorber against the wall actually has good effect down to about 120 Hz. (wavelength = 113", 3.5% = 4") for randomly incident sound, and about 240 Hz for normally incident sound (wavelength = 56", 7% = 4"). Since SBIR is normally incident, you'd think: "Darn! 240 Hz! That's too high. SBIR happens much lower!" ... well it would be too high, if the speakers were a long way away from the wall, and the SBIR was down low... But with the speaker tight up against the front wall, things are different! :) The cancellation frequency formula for SBIR is F=c/4dx. This is easier in metric, so: assume the front of the speaker is 35cm from the wall. Speed of sound is 343 m/s. So 343/(4x0.35)=245 Hz. Oh yeah! Now we are talking! :) So provided that you can get your speaker up really close to the front wall, which forces the SBIR null up into the low mids, then you actually can get a usable effect on SBIR with just 4" of suitable absorption. But for speakers that are more than a few inches away, it wont work. As usual, there is some small truth in the Internet myths, but only partial, and only under the wrong circumstances. Yes, "they" are correct in saying "you can't treat SBIR with front wall absorption". But "they" are ignorantly assuming that the speaker is away from the wall. But when the speaker is close enough to the wall, you actually can have some useful effect on that. The closer you get it, the better you can treat it. Plus you have the added benefit that SBIR in the mid range is much less objectionable psycho-acoustically than SBIR in the low end.

I do however believe in proper "powerhouse" (diaphragmatic/pistonic or helmholz) absorber, that can actually absorb LF, being placed behind speakers,

I wouldn't do that in y room. All those are resonant traps, and resonant traps have a bad habit: they resonate! :) I have a serious religious objection to resonant things in the front part of the room, as they can "color" the direct sound from the speakers. To my way of thinking, the direct sound field from the speakers is almost sacred: Don't touch it! After it goes past your head, do whatever you want, but in front of you, keep it as pure and crystalline as you possibly can. That's why you'll see in most of my designs I only use absorption and reflection up front: Resonant stuff can happen from the ears backwards, but not forwards. (Usually! But not always)

And I think that the shear pressure behind the speakers, and to the sides as well would really excite the eigenmodes of the metal plate of the VPR's

Oh yes, definitely! And that will make them ring and ding and zing very nicely, along with your music... :) You'll have a resonant chorus going on up front! :)

I really love the explanation that ASC, makers of Tube Trap, put in their whitepaper when defining what I am experiencing - they call it "head end ringing",

Mmm hmm! yup. I like that phrase. It really does describe what happens! I'm just not so sure if the cure will stop the ringing, or cause even more of it... :)

The front part of the room rings like all get out without treatment,

Yup. It usually does. Which is why you need to damp that ringing, or deflect it away from you, not add even more ringing to it...

3. Regarding the diffusers, you already had convinced me way back to get rind of them up close, even though they are already built.

Great! Save them for the day when you build a live room. They can do unusual things in live rooms, and that's actually good! Just not in small control rooms.

The scatter devices are as a direct "knee jerk" reaction, if you will, of the "deadness" of the room. And FWIW, so were the QRD's, but because of the phase issues with diffusers I figured scattering is wiser?

Scattering causes phase changes... :)

This room has slapback and ringing like all get out, without absorption or diffusion!

Yup. Small rooms generally do.

So having untreated parallel surfaces is really a bad idea in this room,

Again, that's pretty much always the case with small untreated rooms.

For instance, with 3" of Roxul, I found that it is not enough to stop the ringing/slapback at those mid frequencies.

What density Roxul? Where did you locate the panels? How big?

4. I like your concept of "deflect and absorb at the back". This is what we did in the room in Cali. See pictures below of the room there.

I'm looking, but not seeing! ? No pics? Also, do you mean "Cali" as in "California, USA", or "Cali" as in "Cali, Columbia, South America"?

So theoretically speaking, you're not a fan of flat slatted wood panels over large absorption surfaces?

Oh actually, I AM a fan of slats over absorption! Just not in the front of the room, Sides and rear? Great, Front? Nope. (For RFZ-style rooms, at least): I do use both tuned slat walls and un-tuned slats in many of my designs.

I see allot of conflicting info here as well, because there are guys from the likes of "Acoustic Fields" which argue that the decrease in SQF and thereby volume of the room of slanted wall builds is not as welcome when comparing to just treating the parallel walls appropriately -

Yup: Agreed. to kill flutter by angling walls, you need an aggregate angle of at least 12°. That takes up a lot of space. For control rooms, I tend to NOT angle the side walls (I keep the parallel), and only angle certain parts of the front wall, enough to get RFZ conditions.

in other words the benefits are not huge, but the cost is pretty high regarding angled walls.

Yep.

The sound proofing effort will already do that with floated floors,

Floated floors? :ahh: Nope! no no no. Nope. Baaaad idea. Floating a floor property is complex, and expensive. Floating it "non-properly" will make things worse than not floating it. Far worse, in some cases. Its not easy to do, requires a huge amount of mass, and eats up your head room. And is NOT necessary at all in the vast majority of cases. Nope. Don't even think of doing that in your room.

so doing more would really start to hurt both size wise, but more importantly volume wise.

Volume is key. Try to maximize the total air volume in the room, and the height of the room (especially at the rear). Those are your two best friends. Anything that takes away height or volume should be examined very closely, to see if the benefits outweigh the lost volume.

5. "Because it takes the speaker out of the room..." when I saw that I freaked out! Like WHAT!?

To me, a direct translation of that means "NO SBIR". Is that kind of.....right?

Sort of. It eliminates SBIR with respect to the front wall, 100%, and with respect to the side walls very greatly, but you still have the rear wall effect, as well as some of the ceiling and floor effect. What soffit mounting does do, is to kill all edge-diffraction artifacts, and all other artifacts associated with reflections form the front wall (early reflections, comb filtering, phasing, etc.), as well as to correct the power imbalance inherent to small speakers on stands, and a few other Really Good Things.

If we can resolve that, the modal issues of this room are a joke to get rid of.

Dont' confuse modal with SBIR! Two very different animals. Modes ring, SBIR does not. Soffit mounting is very useful for SBIR, but wont' do much for modes (except to avoid triggering some of them).

Meaning the drywall and studs are resonating because of piss poor build quality. Even though it is to code, I think that cavities in the walls, and the drywall and stud choice together are causing allot of these issues

Tell me more about those walls: how are they built? Layer by layer, including air layers, starting from the surface of the room that you see, and going outwards.... material, thickness, attachment, etc.

It's basically a glorified home theater and office at this point, which I want to turn into a proper mix room simultaniously - thus the challenge!

Yep! Control rooms and home theaters have rather different layouts, acoustically. Pretty hard to do both at once...

By end of June I should know confidently what can happen.

Hopefully, it will work out for you. And hopefully,you have a lot of musician friends who would love to cut their demo tracks in your room, and fork over a few greenbacks in compensation... :) - Stuart -