Donny's Acoustics Project

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
This past weekend, I began fabricating some acoustic treatment for my mixing environment.
The dimensions are as follows:

14' 6" L x 12' 3" W x 7' 11" H

I am lucky that during construction of this room (back in 1944) the carpenters did not square the walls to each other. With the exception of the ceiling height, which remains constant (hence, squared with the floor) the walls on both the L and W dimensions vary from end to end by up to two inches, so the longest dimension in length is at 14'6 on one end, and 14' 4" on the other end.

In the Width dimensions, at the widest point, the measurement is 12' 3" at one end, and
12' 2 1/2" at the most narrow end.

I have absolutely no idea if this splay is enough to help, in terms of parallel surface created issues..

The treatment I chose was a combination of absorption and diffusion.

This included Roxul material for bass traps in three corners, ( the 4th corner has yet to be treated. I cannot do so at this time, as that corner is behind an entry doorway).

I also incorporated a broadband cloud, using OC 703 / 2". I was able to suspend this, leaving a 1 3/4" gap between the top of the cloud and the ceiling. During fabrication, I allowed enough wire to alter this drop height, if I find the need; as an example, if I wanted to lay insulation in that gap, or, if I wanted to lessen the gap.

I didn't have to frame the cloud; I was able to pull wire through the material at 6 points: 2 on each end, and 2 in the center, offset towards the center of the panel, and attach these wires to 6 hooks, which were attached to the ceiling using anchors. It was placed directly above my mixing position.

I then wrapped this with a dark blue muslin.

My next step is to finish up a 2x2 "Skyline" Diffuser, which I plan to hang on the on the wall directly behind my mixing position. I have the pieces cut, I just need to adhere them to a base plate from which I can hang it horizontally on the wall behind me. This is going to be tricky, because it is heavy.

I haven't actually measured the extent of the change, although I'll say with confidence that I can now hear things in my mixes that I wasn't able to hear previous to the treatment being installed.

The low end now sounds tighter and more defined than it used to be, and I can now hear details in the top end that were hidden from me before the treatment.

I mixed a song last night, played it back on 3 different systems - 1. In 2 different cars, and 2.Thru a Home Theater System. Translation to these different playback mediums was very accurate. I heard no substantial gain or attenuation of any frequencies, other than what the various playback systems - such as the hyped low-end on a home theater system with a sub - would offer inherently.

At no point was any Auralex or Sonex foam used. I still have quite a bit of reflective surface remaining. And, at this point, I'm not quite sure that I really need to treat those areas, although I have enough 703 remaining to build two 2' x 3' panels for each side wall (on either side of my mixing position) if I want, or if needed. I'm just not sure if I need them or not.

I don't want to make the room too dead.

Implementing these changes has given me more confidence in how well my mixes will now translate.

Just thought I'd share.

FWIW

d/

:)
 

audiokid

Chris
Moderator
Joined
Mar 20, 2000
Location
Nanaimo BC, Canada
Cool, this will make big changes in your enjoyment and sound! I could be way off on this but, if you feel you aren't tight enough and can't get more treatment, mix at lower volumes. Works wonders.
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
I could be way off on this but, if you feel you aren't tight enough and can't get more treatment, mix at lower volumes. Works wonders.

It's not that I can't get more treatment, it's that I'm not sure if I need anymore, although guys like Ethan Winer will tell you that you can never have enough bass absorption. ;)

And I've always mixed at volumes much lower than most of my peers, turning up occasionally to check certain details in the mix, but then I'm back down to around 75 db again.
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
I guess my question at this juncture is if I do in fact need to add more treatment?

If my mixes are translating well to other playback mediums outside of the control room, wouldn't this be the best indicator, the best proof that what I've done is effective?

I have treatment material left over. I just don't know that I need it, if what I'm hearing now sounds as good as it does.

Isn't the whole goal of acoustic treatment to insure that what you mix and hear in your environment translates accurately to other outside systems?

What else could I do that wouldn't perhaps start to become a detriment? While Ethan has stated many times that it's not possible to ever have too much low end treatment, I know it's true that you can in fact have too much of mid and hi frequency absorption. I want an accurate environment, but I don't want an anechoic chamber, either. And, I don't want too top end absorption where I could get to the point of having my mixes come out as hi frequency heavy, either, which could happen, if I had too much absorption at those frequencies...

Just kinda think' out loud, here...

d/
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
its a nice change isnt it?

i wrapped mine in guilford of maine cloth, and they look identical to the GIK panels they are "copying".

tape op had a design for a cheap diffuser out of 2x2's and a backing board. mayby try those along the longer more open areas?

http://tapeop.com/articles/83/diy-diffusors/

I've already got a diffuser built, Josh. It's a 2 x 2 skyline RPG pattern, using various lengths of 2" x 2" pieces, from 1" to 4" high, placed (attached) to a 2'x2' base-plate. This was based on a design I downloaded about a year ago, and it may in fact have come from TapeOp. I think it may have even originally been a Massenburg design.

IMG_0227-1024x768.JPG


Although, my recent research has shown that diffusion is not always a "must have". It depends greatly on the dimensions of the room, and what frequencies are still problematic after absorption treatment has been installed. So, there's a chance I might not even end up installing it.

By professional standards, my mixing room is quite small - 14' 6" L x 12' 3" W x 7' 11" H - and as we all know, the smaller the room, the harder it is to successfully treat.

But, I am happy with the results I've gotten so far.

I have not sound PROOFED the room. Honestly? I don't even have any plans to do so. This would involve rebuilding the room from a structural and material replacement level, and not only do I not have the funds for that, it's really not a major concern for me. I'm far less concerned about sound leakage and transmission than I am with creating an accurate mixing environment.
I honestly don't care if a truck goes down the road in front of my house and I hear it, nor do I care about sonically isolating myself from my neighbors.

I'm still researching. I'll be glad to post updates and explain what I've done - both positive and negative, if you guys want me to.

:)

d/
 

audiokid

Chris
Moderator
Joined
Mar 20, 2000
Location
Nanaimo BC, Canada
I have 13 RealTraps plus foam and could have double the traps but I'm happy with what I have now. Where I sit or move around my ring is great. Thats how you will know. If I walk around my room is sounds pretty consistent everywhere too but there are still spots where I hear the bass needs more. Everything from treatment to where you position monitoring and sitting position counts. Use a measurement utility to see how it scopes out.

Here's how my room looks ( at mixing position) with 13 Traps. My room isn't ideal either.
slide-image-acoustics.jpg
 

Josh Conley

Well-Known Member
Joined
Mar 27, 2014
Location
Toledo
pretty sweet looking.

how much does that thing weigh, and how do you plan to mount it?
Did you attach each piece to the one next to it, or just to the backing board, and how?
Since I'm an engineer (no, the other kind) I'm very curious about how much that backing board will flex with all that weight attached to it, expecially considering it will be built laying flat, but it will be hung -bascially sideways- for many many years.

I've been thinking about making one since I read that tape op article, so maybe I'll get to it in the next 5 years ;) lol.
 

kmetal

Kyle P. Gushue
Well-Known Member
Joined
Jul 21, 2009
Location
Boston, Massachusetts
Cool stuff D. I'd say now is a good time to test the room, or if your are thinking of more broadband bass traps, put them in. anything beyond the mirror points and any addition broadband bass, is going to be unique to your room, and probably more narrowband in nature. this is where your talking resonators, and other traps of this nature. also dont forget the poor mans bass trap, the open door and window.

as far as sound "proofing", the better your isolation, the worse the acoustics. the typical air gaps, and thin walls, in residential construction, let the mids/highs out, and the walls aren't massive enough to contain the lows. so from an acoustic standpoint, its not a bad thing that your in a room like yours.

theres really no way to recommend more treatment, w out knowing what needs to be treated, frequency-wise.

ive never heard any acoustician say you could have too much bass trapping in small rooms. i think off the top of my head, in general its something like 20-35 percent, of the surface area in a CR should be absorption, which some people find a bit too dead, thats a rough quote from rods book, which i don't have w me right now. ill have to double check the number, but it seems like your happy w the mids and highs, and questioning bass. ?

i would imagine, the safest way to go w no testing, would be more bass traps.

that diffusor looks awesome man. great work!

the best sounding CR ive been in is the one, in my icon pic, it has 8 ft of bass trapping area behind the rear wall.

honestly, the most noticeable thing about it, is the imaging. it holds up very well, pretty much anywhere in the room. as well as the bass. i dont have any test data yet, so i cannot comment on its actual response, but the consistency is quite remarkable.

ive had the privilege of listening in this room through the project as the equipment moved in, and monitor controllers, and EQ on the mains. i very very strongly disagree w/ a senior co worker (former owner) that his use of EQ actually improved the sounds. this is from a listening perspective, not mix, and the eq while, technically made the room flatter according to the RTA device, it made things just sound wierd. granted, this guy has insane peaks and valleys on the eq, which, of course isn;t generally whats recommend w eq. it should be only a couple of frequencies, and not much at all of it, if you use it at all. frankly, it sounds better, (more full, and more like the outside world), and its an expensive EQ but i think this guys looking to reinvent the glory days, and also, just be able to say the room is 'flat''. when i finally finish up the re model, l'll post some tests, cuz i think are much more reliable testing methods, than an RTA from the 80s, which requires you to wwave the test mic (earthworks) in a circular polishing motion, while it quantifies.

glad to hear your liking your room improvements!!!!!!!
 
Last edited:

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
What I noticed right away was imaging and detail - for the better... far better. ;)

I'm hearing things that are now far more defined and detailed, particularly down low with the bass guitar and kick, as well as in those upper esoteric areas of "silk" and "air".

Also, one other result I hadn't counted on - or had perhaps forgotten - is that I'm using far lesser amounts of changes to get the desired results than I used to. For example, cutting or adding EQ by just the slightest bit can be heard very clearly now, as opposed to my untreated area, where it sometimes seemed as if my changes weren't even doing anything.

Now, after treatment, if I sculpt tones in the low end, or, add silk in the top, I can hear the results far more easily, quicker, and am using much less of it to get the desired results.

I really am very happy with where I am right now...and I'm not sure I'm concerned about low end at all, really. I have an open doorway behind me, and a window in front of me that I can open at any time.

My statement of there not being such a thingas having too much bass trapping came from Ethan Winer. Now to be more accurate and to put it into the correct context, what he actually said was that in a room as small as mine, there was no such thing as having too much bass trapping.

I've read that having these open areas will provide up to 1 Sabine of low frequency trapping, with the Sabine being the measurement relative to absorption coefficients, which are measured in increments from 0 to 1. 1.00 indicates a value relative to full absorption . Now, I don't know if that's true, I'd have to wait for Rod or Space or one of our other bad ass acoustics experts to chime in on this... but, there's nothing I can do about the doorway anyway. It's an old house with "coffin shaped" doorways from room to room. I suppose I could get a custom cut door installed, but again, not sure I'd really want to, especially if the open door or window is providing that much efficiency in low end absorption.

This has been a cool project and I've earned a lot through research and application. It's very cool when you do a project like this and can actually hear the results, and brother, I'm not just talking about minimal results, either. The sonic difference in this room is like night and day. It's not even the same room anymore.
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
pretty sweet looking.

how much does that thing weigh, and how do you plan to mount it?
Did you attach each piece to the one next to it, or just to the backing board, and how?
Since I'm an engineer (no, the other kind) I'm very curious about how much that backing board will flex with all that weight attached to it, expecially considering it will be built laying flat, but it will be hung -bascially sideways- for many many years.

I've been thinking about making one since I read that tape op article, so maybe I'll get to it in the next 5 years ;) lol.

The backing board you currently see holding the various sized pieces of wood is not the one I will use - at least not alone - to attach to the wall. This was used strictly as a template from which I followed the blueprints of where to place and attach each piece.

The template board will be attached to a piece of 3/4" ply, which will then be anchored - (heavily anchored, LOL.. I was jackpot lucky and found two verticle studs on 16" centers) to the wall with a piece of acoustic rubber under-layment between the diffuser and the wall itself. I didn't just randomly choose this material... this was what was recommended with the diffuser plans.

This is a web picture of the type of insulating material I will use between the wall and the diffuser.

716774006_613.jpg


But.... here's the thing, after all of the labor it took to make the thing, I'm still not 100% positive that I need it. If I end up not using it, I guess I can always sel it, but this beast isn't going by standard USPS Ground.

I haven't weighed it yet, but it's not light. A wagered guess would be 75 lbs, more or less. Before I hang it, I'm gonna need to get an exact number (after I attach the piece of 3/4" ply to it) so that I can get the proper rating for the right type of anchors.

FWIW

d./
 

RemyRAD

Well-Known Member
Joined
Sep 26, 2005
Ain't making your own acoustic stuff for your studio fun? Far more gratifying building it than just buying it. I think? I had to come up with some new ideas when my SONEX finally rotted and turning to dust after about 15 years. And I had no budget. Like zero. So ya go to industrial centers/complexes and retail shopping centers and start combing through trash dumpsters. It's amazing the quality materials you can find! And the best of recycling and lowering our green footprint. There is no shame in doing that. It's something to be proud of in fact for doing. At least in my book. The more we can recycle. The happier I get. The more prebuilt stuff ya buy? The more concerned I become for the planet's well-being. Sure everybody needs to make a living. But figuring things out for yourself is the mark of a real engineer and not a wannabe knob twiddling, computer gaming, adolescent. It's becoming something of a lost art. Like actually playing music that doesn't require software to fix. Like singing in tune because you are good and not a fraud like so many.

Guys like Ethan and Rod, no doubt, know, good from bad. They know acoustics. And their knowledge, services and experience are therefore ya if ya need it. Not all of us need it. No we don't do everything right. I'm not an acoustic engineer. I'm a hack. But I'm a good hack. So is Donny. So are many others here like Mad Max, Boswell, Chris and many others here. All professionals. All people I hold in high regards and esteem. They are all far more knowledgeable about accuracy than I am. But that's okay. In many ways, really nothing much matters except your skills. The equipment is actually secondary though others will certainly argue that. And their arguments are valid. But I don't live that way myself. I want to live longer LOL. So I don't stress over that which I can't fix or can afford to fix. That's where I shine. I'm the Queen of workarounds. No LOL... I'm not gay but I could be even if I'm not. But I am a Queen for lack of a better term. Maybe JAP à la Jewish-American Princess even though I'm an agnostic LMAO. Yeah I could lose a few grounds there. And a facelift wouldn't be bad either. But my facility is more important. I like to ingratiate myself with things and be a narcissist. But that doesn't really get ya anywhere. Well... maybe it does for the Kardassians? Especially when you marry a wrapper I mean, a rapper. (He is wrapped with money)

I had fun watching that film by Dave Grohl called Sound City. It certainly presents some very compelling information regarding studio acoustics and who designs them or doesn't design them. Everything that was wrong with that room of that studio is what was right about it. It was supposed to be bad. It was bad. But it wasn't bad. In fact it was great for what it was doing and the people it was doing it for. There is haphazard acoustics at its best! All ya want is gigantic drum sounds. And that doesn't come from a dead box with foam thingies all over the place. It doesn't even necessarily come from an acoustically accurate room. Because it's rock 'n roll. And rock 'n roll ain't a Mozart violin Concerto. And even for that Mozart violin Concerto, you'd never do that in a dead box. Though George Massenburg did something like that with his studio, ITI, back in the early 1970s when he tried to record Baroque Bach harpsichord. What a horrible sounding POS that was! At the time his entire large studio was bright pink! And I wouldn't have suggested to anyone to even breathe in there. I mean, you know you're alive in the morning when you all wake up and take a nice big fresh breath of raw Owens Corning Fiberglas. Where the pink panther is smiling at ya because the pink panther likes to breathe pink fiberglass. And of course George is the world Superstar, expert. Guess not? So the guy in 1971 that didn't know how to record Baroque Bach harpsichor, Is recording opera today. Maybe I should give George a lesson? He doesn't have a Grammy nomination for recording opera. I do. And from 22 years ago when I was a much younger scalawag. In my early 30s. He's only now catching up. Think about it LOL. He, might even find out his own equipment doesn't sound good for that genre as it was made for rock 'n roll? So I'm looking forward to see what he comes up with his operatic work? It better not sound like Earth Wind & Fire, like the harpsichord recording, did.

Primal pontification
Mx. Remy Ann David
 

Space

Well-Known Member
Joined
Jun 26, 2007
"I'm far less concerned about sound leakage and transmission than I am with creating an accurate mixing environment."

Well, if you are going for Sun Records environment then stick with it.

Problem as I see it is simple. We live in a cluttered world truly filled with people. And people have kids and people with kids make noise and so do those that live next door to them.

Now I am not saying you need isolation, I am kinda saying you already knew your equipment and now you have touched on basic rfz techniques that allow for less interference of the actual room you are in. Wonderful thing, I remember when I had that experience.

But isolation is part of a good mixing environment. It isn't about leakage outward it is about leakage inward. In any event I am glad you are doing better in your room.

BTW...I am a moderator, not an expert.
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
BTW...I am a moderator, not an expert.

Well, if you're not an expert, then I don't know what the criteria for "expert" is. I've read many of your posts. You state the truth, you back it up with facts. It's been through the research and reading of your posts, along with Rod's - that I have learned the most, and have been able to actually apply principles that have shown obvious audible results.. ( yes, I'm a "lurker" in the acoustics forum LOL)

So, if you're not an expert, then you're certainly the most knowledgeable novice I've ever encountered. ;)

When I mentioned that sound transmission wasn't an issue, I should have elaborated further. I didn't mean to imply that I won't eventually get to that; I do think that it's important. Right now I've spent the funds I had available on the treatment of the room's acoustic signature; but I do have every intention of creating some isolation between me and the outside world as soon as I can afford to do so.

The good news is that I'm not a city dweller. I own my own home which is located in a rural setting, on several acres, so "noise pollution" to me isn't traffic, jack hammers, or even kids playing. My noise pollution is made up of the tree frogs and crickets in my pond out back, the owls that call to each other at night, etc.. My closest neighbor is 1000 yds away from me, and in 20 years of living here, along with rehearsals and recording, I've never had a noise complaint.

I guess what I'm saying is that at this point, my goal is more to be able to offer a well-balanced room in which to mix projects that have already been recorded, as opposed to doing any serious recording...so, at least right now, anyway, isolation is secondary in my hierarchy of needs. ;)

I do wish to express my gratitude to you for your posts, both past and present. I've learned a lot from reading them.

d/
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
Hello all..

I have been looking at signing up for night classes at a local university (Akron U) that would cover an introduction to acoustics.

The class I am most interested in is named - appropriately - "Introduction To Acoustics", and meets two nights a week for 2 hours, for 3 months. This class is part of a continuing education program, aimed at adults. Some classes are accredited, some are not. I'm looking for the knowledge - as opposed to the paper - so a non-credit course doesn't sway me.
Classes begin in September.

I realize that this is in no way similar to an actual degree in the science of acoustics, but I would like to take his class in the hopes of gaining more knowledge.

I am still trying to find out who the instructor is, and what his/her qualifications are.

The counselor I spoke to told me that I should take a physics refresher course first, and this makes complete sense to me.

Should I also perhaps look at taking a course in geometry or another form of relative math first as well?

It's been a very long time since I was in college, and honestly, having graduated with a Liberal Arts BA (as an English Major) in 1984, I didn't take much math during this time, other than what the requirements stipulated. My grades in basic math - geometry, algebra - were average.

I am also willing to accept the fact that I may be way out of my league here, and that based on my intellect - or lack thereof - particularly in regard to advanced maths like Trigonometry and Calculus, taking these classes could be a lesson in futility. In short, if told by resident experts here that I should forget the idea, then I would take absolutely no offense.

I realize that acoustics is a very complex field of study, and that not just anyone can grasp it.

I really want to try, to at least gain a basic level of knowledge on the subject, but am willing to accept that it may simply not be something I could ever really understand.

My ultimate goal is to be able to understand enough about the subject so that I can apply the knowledge to my own recording and mixing environment. I have no illusions, at 55, of seeking a career in the field.

any suggestions, thoughts?

d/

An introductory class might get you the basics. But I would suggest that hunger is the best agent towards getting anything a person wants.

Are you still reading books? Do you buy books? Master handbook of acoustics, F. Alton Everest, is introductory all the way to the advanced and I do not know anyone that knows anything in this field that does not own a copy, myself included.

Get Rods book, its kind of a rule around here :)

It does not come fast and it does not come easy but contrary to the saying "acoustics is not intuitive" I say that it makes perfect rational sense once you know what it is you are looking at.

Other books I have and would also recommend:

Building a recording studio, Jeff Cooper (he has answered questions via email that I asked about his work)
Acoustic Design for the Home Studio, Mitch Gallagher
Sound Studio Construction on a budget, F. Alton Everest

If you can't get the basics out of these books, the acoustics 101, then read them again :) I still do :)

A big +1 to Rod's book and Everest and Pohlmann. Pohlmann did the 4th edition revision as Everst had passed away. An excellent text on architectural acoustics is Architectural Acoustics by Marshall Long. I just noticed while researching this post that there is a 2nd edition. Time to update my library. It is pricy (109$ at Amazon) and worth it!

In terms of practical texts, what ever that means, one of the great texts is Guide to Acoustic Practice by Rose. You can by used copies from Amazon etc for ~$150 or download a pdf copy here:
http://downloads.bbc.co.uk/rd/pubs/...tural-acoustics/bbc_guideacousticpractice.pdf

Enjoy!

Andre
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
As many here know, I've been in the process of trying to improve the acoustics of the current room I am in.

Last week, due to a family member moving back home (my mom is terminally ill and will now be in her own home with the aid of hospice and nursing) I now have another room I could use as an alternative to the room I am in now.

The reason that the new room interests me is that because measurement wise,
it seems to be fairly close to one of the Sepmeyer ratios; (in my case, it would be Sepmeyer's second ratio) which is:

H X W X L__

1.00 X 1.28 X 1.54


Here are the dimensions of the other room:

H X W X L
___
8' X 9' 7" X 11' 8'


Here are the resulting ratios:

H X W X L___
1:0 X 1.22 X 1:48


Ratio Differences:

H X W X L__

-0.00 X -0.06 X -0.06


As you can see, the ratios appear to be very close, BUT... I don't know that they actually are, because I don't know how crucial it is to be exact to these ratios... so that a difference of
something as seemingly small as -0.06 could be a mile off in terms of the equation...and this is what I don't know....is it close enough to consider?

Materials in the other room would be the same as the room I am in now; 1940's Gypsum Board on walls and ceiling, hardwood floors, 2 windows, one entry.

My question is, will moving into this other room be a better situation for me in terms of dimensions, and, would it provide enough of a noticeable benefit to make it worthwhile?

I know very little about "ideal ratios" (although I'm studying as much as I can) so I turn to the experts here to tell me what they think.

I have no problem moving to the new room; nor do I have any objection to re-treating this alternate room accordingly. I guess I'm just looking for input as to whether it would serve enough benefit to make it worthwhile...

Thoughts?

d/

from what i recall reading Donny, [="http://www.acoustic.ua/forms/rr.en.html"]sepmeyer ratios[/] don't have to be exact. it's better to get as close as possible but a little off here or there isn't a deal breaker.

What I wish you would do, from this point forward, is to keep all posts related to this topic in the same thread. You have said a lot of things over the past month and they are all over the forum.

It would be really,,,really helpful, trust me ;)

Maybe change the thread name to something more accommodating to your situation.

+1 on that, I am thinking of a graphic in Alton Everest's book where it showed the ratios, then the range of areas around that exact ratio that were considered fine. Everyone I've talked to just said that the ratios are a good guideline, but not an end all, be all. I'm far from an expert, but my thought would be when talking rooms of that size, the bigger the better, if for no other reason than a deeper bass response. I'd have to check, but I think it was in that same book, that it said to use the longest dimension, which would be diagonal, to figure out what the lowest frequency your room can contain is. I also might be imagining it in my feeble brain, I'm on two hours sleep after an 18 hr mix session that killed the mixers power supply, so I'm a bit hazy tonight, and probably should not be commenting at all.

You're absolutely right. My apologies. I'm going to limit this to one topic, one thread. Thanks, Space.

Room ratios have been around for decades and rooms in general have been designed to be pleasing visually and sonically by many builders/ architects. You only have to look around the building you are in right now to recognize this is not something new, it has been around you all your life you just were not aware of this.


The inclusion of room ratios for an acoustical environment is different in that the ratios used have been tested so that the builder has a better starting place than a typical room ratio that a typical builder might use.


Alton Everest ( Master handbook of Acoustics - 4th Edition) presents 3 of the most widely used ratios developed by L.W. Sepmeyer (1965) and M.M. Louden (1971)




Height Width Length

_______________________________ _________

Sepmeyer A. 1.00 1.14 1.39

B. 1.00 1.28 1.54

C. 1.00 1.60 2.33


Louden A 1.00 1.4 1.9

B 1.00 1.3 1.9

C 1.00 1.5 2.5


It must be noted that when these ratios were being tested a ten foot tall ceiling height was assumed. In some detail, we will find out why this was an important aspect to this particular testing procedure.


Based on Loudens first ratio “A”, 1.00, 1.4, 1.9 with a ten foot tall ceiling this would produce a room with the interior finished ceiling height of 10 feet with a interior finished width of 14 feet and a depth of 19 feet. This room will have a volume of 2,660 cubic feet. Plenty of height for the sound to expand and develop and exceeds the 1500 cubic feet room volume limit determined to be the least amount of volume a quality audio environment should have.


(C.L.S. Gilford, Affiliation: British Broadcasting Corporation,“The Acoustic Design of Talks Studios and Listening Rooms” circa 1979, maintained that a “small” room based on the research done would be a room with a volume of 1500 cubic feet. Further he states “It is shown that a distinctive characteristic is that, because their dimensions are comparable with the wavelength of low-frequency sound, the sound field is characterized by strong simple standing-wave patterns which cannot be eliminated without eliminating the reverberation itself. It is shown also that for the audible effects are confined to those associated with simple axial modes and that, by careful adjustment of dimensions, provision of diffusion and the proper distribution of absorbing material, the worst faults can be avoided. “)


An interesting thing happens when we look deeper into these ratios, when we look at the single components of the room and not the end result.


The speed of sound at sea-level is considered to be 1,130 feet per second and in order to get the fundamental frequency of the height or width or length we have to use the equation F=1,130/2xD.


The height of ten feet using the above equation will produce: 1,130/20=56.5Hz. This is important to know since 56.5 Hz relates to the note A1. It actually falls 1.5Hz past the frequency of 55Hz.


The width of 14 feet using the equation F=1,130/2xD (1,130/2x14(28)) = 40.36Hz which closely correlates to 41.20Hz or E1 on a midi keyboard.


The remaining length measurement 19 feet X 2 = 38 produces 1,130/38=29.74Hz, relates closely to 29.14 (A#0/Bb0)


Using the 8 foot ceiling height and Loudens first ratio produces a room 8 feet tall, 11 feet and a few inches wide and 15 feet and a few inches deep. That is about the size of a typical bedroom or the living room in some homes.


The consideration for having a balanced proportional room is valid and worth the effort to use in any sound related type room. A few things to consider along the way. The measurements that are obtained from the ratios define the interior side of the wall.


In order to use these measurements, you must determine how much and of what thickness your interior sheathing will be. This allows you to step out the placement of the sheetrock or MDF/OSB or whatever combination you may use, in order to establish were the actual framing will be placed on the floor of your build.




To that end, ratios are not scalable...they cannot be modified and expect the same results: [="http://www.acoustics.salford.ac.uk/acoustics_info/room_sizing/"]Room Sizing Tutorial | Acoustics, Audio and Video | University of Salford[/]

This is an awesome post, Space.

Things I found very helpful - and very interesting:

"Based on Loudens first ratio “A”, 1.00, 1.4, 1.9 with a ten foot tall ceiling this would produce a room with the interior finished ceiling height of 10 feet with a interior finished width of 14 feet and a depth of 19 feet. This room will have a volume of 2,660 cubic feet. Plenty of height for the sound to expand and develop and exceeds the 1500 cubic feet room volume limit determined to be the least amount of volume a quality audio environment should have."


"The consideration for having a balanced proportional room is valid and worth the effort to use in any sound related type room. A few things to consider along the way. The measurements that are obtained from the ratios define the interior side of the wall."

I'm going to attempt to merge all these different threads/subjects into one thread/topic.
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
Okay... so I've been researching poly-cylindrical diffusors...

Someone check me on this please:

From what I understand, diffusion itself does not lessen the energy of frequencies, but instead, actually creates more reflection(s)... but in doing so, it lessens the intensity of these frequencies.
The smaller, scattered frequencies will have random phase as a result of their individual and random "throw" around the room, and this can result in a smoother RT decay curve in the room.

So first of all, am I correct in the basic understanding of a diffuser's main purpose?

---------------------------------------------------
Here are some details about the room, should they be required:

Room Materials:


older type sheet rock on the walls and ceiling. The house was built in the 1940's. There is insulation in the walls, although not much. It appears to me to be the cheap blown-in style of material. Between the ceiling and the floor upstairs, there is OC R19. (I know this because I put it in myself).

The floor is hard wood - oak, stained and sealed.

There is one door, pretty sure it's pine, stained and sealed.

There are two windows - L 52" x W 32"; both are newer (within the last 4 years) double pane, energy efficient.

Room dimensions:


14' 6" L x 12' 3" W x 7' 11" H

Splay:


The walls on both the L and W dimensions vary from end to end by up to two inches.
The floor and the ceiling differ in height by 2 inches... but not on an end to end basis. The difference is in the middle of the room where either the floor has settled or the ceiling has sagged.

So the room is not exactly square.
------------------------------------------------------

The most obvious question is, do I need diffusion of any type at all?

If the answer to this is yes, or probably, then I'll continue...

Before I continue with my questions, I should tell you that I have been doing a lot of research on my own... I'm not trying to be lazy here. I have looked on the web to find the answers to these questions, but I've either not been able to find the answers, or I have run into contradictory information. It's also very possile that I'm not asking the correct questions... That being said...

If diffusion would be beneficial in my situation...

1. would I be better off using a poly-cylindrical form of diffusion as opposed to the "skyline" type that I have already built?

2. if I can - or should - consider using poly diffusion in my room, does anyone know where I could find the formula needed to calculate the size and/or amount of the poly cylindrical diffusion that I need... width, depth, curve, etc.

3. can I make a diffuser of this type that serves 2 separate purposes - those being diffusion and absorption?

For example, along the wall behind me, where the wall meets the ceiling, could I run a 12' length of poly diffusion along this section, but in doing so, also add absorption material inside the diffuser?

If this is possible - because I'm dealing with a half cylinder shape - I would think that something like Roxul would be better to use, than trying to fit and meld rigid glass with the shape... (and also allowing myself enough room for a 2" air gap between the insulation and the wall).

Would any of this serve a purpose that would be worthwhile? Or am I into a more esoteric type of treatment which leans towards diminishing return?

Any info would be greatly appreciated ;)

d/

.

Poly cylindrical diffusers aren't really that complicated. They are the poor mans solution to diffusion, and there is no formula per say, but it is nessesary to put some fluffy insulation behind them to dampen any resonances if you are sealing off the tops and bottoms. If you have the time and patience to build skyline diffusers they do a much better job at actual diffusion, rather than just scattering the reflections. I guess you could calculate the resonance of the diffuser if it is sealed, and tune it to trap a specific frequency as well. They do not have to be one half of a circle, they can be bent into a gentle arc as well. It it not recommended the two be placed side by side without any gap as they create a focusing parabolic effect. If you need to place them side by side some absorption between.

I'm not aware of any sort of calculations or formulas for diffusion, as there are for like absorbstion coefficients. I think it gets pretty complicated pretty fast, and I've never seen anything like that in any of the books I've read. Although I do believe there are requirements for the volume (physical room volume) for you to actually achieve a "truly" diffuse environment/diffusion. You really should check your local library d, and see if they have the master handbook of acoustics, by f Alton Everest. That's where I got it, and had it for a few years lol. It covers a lot of the stuff you've been investigating lately, and you don't need a PhD to understand it.

I'd really be more concerned about bass trapping, than management of the mids highs. What you have built already for diffusors is probably gonna be just fine, considering the size of the room.

There will be some absorption with the type of polys I have seen. The thin 1/8th plywood will allow bass to penetrate and be absorbed somewhat by the fluffy fibreglass,as well a consuming some energy while entering and exiting the diffuser.Mids and highs will bounce off, but who knows what the cut off frequency will be, and phase relationships at the the cross over point will have changed, due to the exiting waves starting at zero, and the reflected waves keeping the same relationship with themselves.
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
My original intent in asking about poly cylindrical diffusion, was to treat the areas where the wall corners meet the ceiling - which is a corner in itself.

Through my recent research, I don't believe that my room is big enough to take advantage of the potential benefits of diffusion.. In fact, it falls far below the minimums that I have researched.

As of this writing, and from what I learned thus far, I think that I should stick with absorption as the main element of treatment - broadband and corner bass trap treatments.

Although, I'm perfectly happy to be told that my theory is flawed and that I'm wrong. ;)

I am picking up Rod's book this week, and Andre has been kind enough to send me some info that I plan on beginning to study this weekend.

Sooner or later, I'm gonna start to grasp this.
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
Update:

One of the benefits I've noticed as a result of my recent treatment is with tracking. I recorded a friend's vocal in my mix space last week, I had him stand near the center of the room, distance to mic was around 5-6 inches, with a broadband cloud directly above him, broadband panels on either side of him (wall mounted), hardwood flooring. The track came out sounding very nice; smooth, warm, with a nice edgy presence - but it was good edgy presence... the pleasing kind without harsh/peaky transients. It didn't sound "dead"- it sounded real. Nice detail, air and silk. It was a very "listenable" track.

Of course, this is a testament to his voice and his mic technique as well, he's a veteran, so he knows how to "work" the mic.

I needed to use very little EQ - besides my go-to HPF - which I pretty much assign to everything, the frequencies of which varies from track to track - it required just a bit of attenuation around his personal sibilant range
(-3db @ 4.7k ). I also used some smooth, gentle compression, ( Eventide Ultrachannel, 3:1, -10db, 20ms attack, 150 ms release, little-to-no makeup gain) but beyond that, I really didn't need to do anything else to it. Besides the obvious benefits regarding mixing, I can only assume that the treatment I've installed in the room has also resulted in a nicer room for tracking - at least for vocals, anyway.

We tried two mics on his voice, an AKG 414EB and a Neumann U89. While very similar, the 89 worked better for him on this particular track (with my own voice I prefer the 414EB) although that could certainly change as range and song styles do.

I'm working on a rough mix now and will post samples in the next few days.
 

DonnyThompson

Well-Known Member
Joined
Nov 25, 2012
Location
Akron/Cleveland, OH
06/22/2014 Update:

Some observations regarding the recent treatment:

Translation

A vast improvement on the translation of my mixes to playback systems outside my mixing space. Much more accuracy. ( Of course, the downside to being this accurate is that bad mixes are clearly obvious as well.) ;)

Imaging

I'm hearing far more detail in mixes, both L to R and in Depth as well. This detail became most apparent after installing the cloud above my mix position.

Tone

I find myself having to use far less corrective EQ to accomplish what I want to hear. Let me rephrase that... I'm finding that when I adjust EQ, it appears to be far more effective with much smaller increments than the amounts I used to have to use to achieve the same result(s) - which I've since found out were inaccurate results.

Diffusion


I've yet to install any, as of this writing. Space has suggested reading material for me, and Andre was incredibly generous and sent me study material. I've decided that I'm not going to add any diffusion until I study more on the subject.

Absorption vs Reflective

As of this writing, the ratios of absorption to reflective surface(s) are about even to each other. I didn't really plan it that way, but so far this is the way it has worked out. While I have broadband and bass treatment, I also have hardwood flooring and untreated areas of walls and ceilings.

Recording

While my intention was to create an environment that was more accurate for mixing, I've had the chance since to record several vocal tracks, and the results are incredible. The vocals aren't hyped in any way, there's nothing there that jumps out to the untrained ear, but what I'm hearing is a much greater sense of "natural" tone, and the vocal tracks are much easier to sculpt, and require far less tonal sculpting.
I thought at first that perhaps it might be a kind of "placebo effect" - a power of suggestion - assuming that these tracks would automatically sound better because of the treatment - but it really is there.
It's not my imagination.
I've gone back and listened to vocal tracks I recorded in the past and there's a substantial difference to the way they sound. The older tracks sound "hollow" in comparison.
I need to mention that I listened to these vocal tracks outside of my mix space... I took a collection of old and new vocal tracks and played them back in my car, and the newer tracks sound far more natural compared to the older ones that were recorded before I treated the room.

Further Treatment

I'm not really sure at this point. I'm going to cease any further treatment until I have put some time into studying. For all I know, I may have too much treatment in place... I'm not saying I do, I'm saying that at this juncture, I don't know. Andre has sent me some priceless study materials, and until I dig into this material, I'm putting a temporary hold on any further steps. I want to know that any further treatment I add is genuinely needed, and I want to know the whys and the hows before I just blindly throw up more OC, Roxul, or Diffusion. There's no point in adding anything further until I know why I should be adding it.

Special Thanks


I've got a long way to go and much to learn, and I don't know if I'm done with my project yet; time and lots of studying will tell.
I'd like to thank everyone who took interest in my project... but especially to Space and Andre, Your advice and assistance was priceless. Sincere thanks to both of you for taking the time to help.
You directed me down the right paths and helped me to find many of the answers on my own, and this was important.
We can all be told what to do, step by step... but ...it's a lazy approach, and one in which we don't retain knowledge. Discovering and learning things on our own is the only way to truly retain the knowledge.
Thank you both for giving me the road maps from which I could do this correctly. :)

d./
 
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