Absorption tweaks

I guess a few people are wondering why I'm asking the question. Is it enough to just be honest and say that I am always looking around for good and cheap absorption? I don't know for certain, but am guessing that many tweakers/tinkerers out there have found things that work extremely well but cost very little. Maybe some of you have gone to great lengths to analyze your rooms acoustically substituting one type of material for another. Maybe you cutup old sheets and glued them together and framed them. Maybe you did the same with tires you found at the dump because you like the smell. I can't possibly know what others are using unless I ask.

I've made my own panels and they're fine, but if I could be spending my time on something easier and cheaper I think asking a question like this is a good way to go. If you don't like it fine - just realize you can't speak for everyone.

 

Yep, that's a straight forward question. From a new member though, it's typically a request for advice.

To answer, I use GIK corner bass traps in two corners with a homemade GIK 244 bass trap in another corner. At first reflection points I use ATS Acoustic 4 inch thick panels and another, larger panel behind seating position.

That was how I did it in my old room. I recently moved into a 24x27x8 finished basement room and am still working on treating it. As the speakers are so much further from the walls, I'm not exactly sure wht needs done. Once I found a good spot for the speakers, treatment doesn't seem as critical as my old, smaller room. Any advice?

Here's a thread I started asking for advice. System is being relegated to the basement, I'm looking for wisdom Feel free to answer in either thread.

 

"My mantra - "Absorption is king". For reasons I won't go into, the industry would have you believe that diffusion is every bit as important when well placed throughout the listening space. This is an industry wide marketing point of confusion, since diffusion is what enables greater absorption of sound in general.

I'm the most die-hard tweaker I know, and have never heard any room as well damped as my own. That means "strategically damped" and not dead, but most importantly by no means lively which some would have you believe can be a good thing. What they usually mean is less lively than what it was prior to treatment. So ... better but a bad room is still a bad room.

For years I've driven around the country to at least 20 audiophiles homes, at least 10 well respected dealer's studios, several manufacturers. Attended four high-end shows. Very very rarely have I listened in a room that was treated correctly, meaning good amounts of *well-placed* absorption to go with that diffusion that people seem to be so willing to pay for. For those rooms that *were* well damped with properly setup speakers and equipment? Better sound than I hear in my own room, definitely. But it's not because of the electronics or the $$, and never because of the constant "know-it-all" hinting from gurus telling me what it is I'm hearing (when I'm actually hearing crap). A great room is a great room assuming it's large enough to enable/support the spatial cues which accompany a great many great recordings that INTEND to present perceptions of space/volume.

In short, less than 5% of all systems and rooms I've listened in/analyzed sound anywhere near as good as those in my own room. That's independent of equipment. Give me $15K and my own room, and I'll present you with sound that is as good or better than anything you've ever heard regardless of $$."

 

In case anyone is interested, this quote is pulled from the OP's profile.

 

Yes, sorry.. he is clearly the best person at making a room sound great, not sure I get the reason for the thread. Maybe I just don't like the presentation. Asking a vague question, then picking apart peoples answers, even if I agree with those criticisms, is troll-ish.

The OP seems to have a lot of knowledge on the subject. There are better ways to share it then picking apart peoples posts. Find one of the other 40+ threads on room treatments and share knowledge.

 

Of course you can't! Just kidding around! (which is why the smilie)

Of course I would like my audio room, to look pristine and my speakers to have only the finest furniture grade finishes.

But, since WAF is not a factor here, and SQ is, I have old speakers which are banged together out of sheets of plywood that has been painted gray, with black painted aluminum horns hanging off of the top. I have a huge boxy subwoofer that is covered with black carpet.

Maybe when retro industrial style comes into fashion, I will have some valuable fashion furnishings on my hands. Maybe?

I don't think that I will be holding by breath!

 

I just love it when people ask for advice, ignore and dismiss everything they don't like and proceed to answer all their own questions

 

No one knows how to make every room sound great - they can only experiment, test, gather all the data throwing a lot of it out as noise. A good amount of "noise" I've thrown out is the guru-know-it-all babbling about the wonders of expensive diffusion. I've never seen the need to spend so much money - fine if you do, but again ... you guys doing all your whining are doing it on your own behalf and not speaking for everyone.

You can certainly ignore the wording of my post if you like, and run with your own guesses as to what you think was my intent. But you're proving yourselves to be wrong about that. Maybe stop and relax a bit. Start over and stop trying to speak for everyone.

I'm asking what materials people use, not what you think they should use. I'm asking where people put these materials, not where you think they should place them. Many people are able to answer this question by thinking for themselves. No need for know-it-all bullying to tell people how to answer or think. It's not needed and not at all related to the post.

 

@Slimwhitt - you're copying my profile here because ... ? why not start a thread on the subject instead of posting it here. is the point to whine about it just to whine, or ... why are you even here if you're more concerned about bashing people than discussing audio and bettering your audio experience as well as others? if you want to know something or question something or better yet DISPROVE something start a thread or conversation. how does your posting of my profile info further this post or people's knowledge of the topic?

 

Threads like this one make me glad that my speakers are in effect in the middle of a large and asymmetric open space. The back wall is at least 3 meters away and covered with bookshelves.

 

@schmo "I just love it when people ask for advice, ignore and dismiss everything they don't like and proceed to answer all their own questions"

Where did I do that? I think this is exactly what YOU are doing. Please cite a single example where I have done what you state I have done.

 

@Claude I've noticed that a great number of listeners have had great results with bookshelves holding books or LPs or whatever fills them up without reflecting sound. I might try to go that way along one or two of my walls one day.

 

Time for a few of us to calm down. Pour another glass of wine and zen out to your fav; album

 

Regarding GIKs products - I think they're excellent. I have two bass traps and would like to add more - the homemade GIK 244 used by @timind could be a great idea. It gets expensive though. All the info posted in this thread regarding fiberglass is excellent as well. Not ignoring it. In fact I'd be most interested in knowing where to find the cheapest fiberglass for projects similar to @schmo's. He mentions "Safe n Sound insulation (like $70),". I'll probably get a bunch unless others here know of something similar at a cheaper price.

 

I'm sorry, I just found it irritating. It would be like a car mechanic not identifying himself as such, asking what kind of oil everyone uses in their car, and then schooling a bunch of amateurs for trying to give helpful replies. Maybe I misread the tone of the replies and honestly, I apologize if that's the case.

The safe n sound is a rockwool product, fluffy and crumbly. It was the cheapest and most recommended product I could find locally for the task. Btw, if you want to reply with the @ symbol, you have to use the username, not the name underneath. So it would be @DyersEve726 and I'd get a notification that you mentioned me in a comment.

No hard feelings bud

 

Yeah, I can be irritating but I'd rather not be. I'm not often, but at the first scent of know-it-all-ness or censorship ... yep, I can be sensitive. I can do better. Please note that I wasn't the one posting my profile info here, and didn't foist any of that on anyone. I obviously don't know much about anyone on this forum, and didn't realize there might be some need to tone down the profile. I'm certainly not trolling (never have) and in no way selling anything. Even if I had something to sell I don't have time for that, and according to many I've come across in the high-end industry I think I'd go nuts trying to compete with others for a variety of reasons.

Still, if I could I'd go straight to a database that stores thousands of entries about absorption materials and tweaks and prices and results. Without access to this I *have* spent a lot of time reading about absorption, but I still don't have a great idea for what people are actually doing and what they feel has been successful.

 

Thanks @timind for pointing out the OP's information. It does raise questions about why he would post such a broad question other to build a trap.

To @hazyj No one can debate your experiences. If they work for you. Great.


From Don Davis' Sound System Engineering chapter on small room acoustics.
"TEF has clearly shown us that the reflection free zone is easy. The tough part is obtaining the optimum diffusion from the live end. In fact, the difference in quality of control rooms is the difference in diffusion present at the mixer's ears. The more diffuse and mixed the total sound field at the mixer's ears, the better the quality of the sound."
TEF is the measurement of Time, Energy, and Frequency, which is the measurement of diffusion over time in a room. Note, I do not ascribe to live end dead end.

In a nutshell, a good sounding room will be infinitely diffuse (over all frequencies) and seasoned with absorption to a taste that matches the listener's desired level of decay.

Everyone should agree that you can't diffuse large bass waves in a small room. There isn't enough room. Instead we trap them. Above bass, diffusion can be more effective. The decay of the mid-range and higher frequencies are taken care of with the bass trapping. Hence my comment that you want to treat the bass first because the rest of the frequencies are a free lunch.

After that, if you want faster decay on the mid-range and higher. Feel free to add more narrow band absorption. That is your prerogative, and part of my comment about setting the room to match the listener's desired level of decay. Some people will like a more lively room, others a more dead sounding room. It's your choice.

The comment about pillows, curtains, egg crates, rugs, etc. stands. They are narrow band absorbers that will not affect the bass or create diffusion. What they would accomplish would also be accomplished by treating the bass.

For some more information about absorption coefficients of different products see Bob Gold's list.


For effective affordable trapping, nothing is cheaper than fluffy fiberglass. Build yourself a false corner as deep as you want or can. Fill it with fluffy fiberglass. I wouldn't go more than 2lbs per cubic foot, less as it gets thicker. Mine is over three foot wide across the front and is stuffed about 1lbs per cubic foot. After installing I have measured reduced ringing down to 20hz in my room. I doubt I put more than $200 into it, floor to ceiling using fabric from Guilford of Maine that matches the purchased stuff from GIK.
Because these are big, it is often recommended to add something reflective to the face to save some high frequency energy from disappearing.

 

I found this page incredibly helpful when choosing materials. Gives all kinds of actual scientific measurements for different products in varying thicknesses. It can help you even target specific frequency ranges.

https://www.bobgolds.com/AbsorptionCoefficients.htm

EDIT: Woops, just realized the person above me just posted this exact link. My bad! Obviously I'm not the only one that considers it to be super informative!

 

@Kyhl Good info, much or even most I think I agree with. But I think this concept of optimal diffusion needs to be delineated some. For instance *why* is diffusion across the entire range so important and what makes optimal diffusion optimal? It's a complicated question, but I think the answers I've come across always leave out an important point. Diffusion becomes effective not only when it results in mixing the "total sound field at the ears", but also largely because it increases the exposure of the mixed sound to attenuation mechanisms in the listening space. Even the sound of a loud hand clap in a terrible room eventually dies out completely. Where does that energy go? It needs to be absorbed to go away. So if adding "optimal diffusion" makes it go away faster it's mostly because the mixture is now much more readily absorbed by whatever does the absorption in the room.

One way to go is to spend a ton of $$ placing diffusion all about the room to get to some optimal point. This works, not only because diffusion is added but all that material doing the diffusion is also absorbing. By the same token, if absorption is well placed it's not only absorbing energy. It is also diffusing it. I've had a lot of success using cheaper absorption placed well throughout my room because it does both absorb and diffuse. And since a good amount of furniture and other structures in the room are doing a good job of diffusing the sound, I've had success with going more in the direction of well placed absorption. However, I don't know enough about the materials that others use including the price or effort they put in to those. I'm also not so sure of myself to think I know everything about where to place absorption. For instance, I've had great results in my room placing absorption directly behind panels if there's a wall there. Maybe others are getting the same results as I am by placing absorption somewhere else for panels close to walls. I can't possibly know unless I ask, and then it's hard to know how effective others' advice might be unless I try it out myself.

 

great link. wish there was an Amazon link to each of these materials

thanks guys.

 

Like absorption, diffusion is used to control reflections.
Instead of absorbing, a diffuser will scatter the sound throughout the room. The point of controlling reflections is to remove distracting reflections from the room boundaries and the comb filtering that occurs with those interactions.

One way to control the reflections is to absorb them. Another way is to scatter them about the room. They both can accomplish the same result of removing problem reflections however absorption will reduce the volume of the sound wave quicker than what we consider natural. Where diffusion will allow the natural decay of the sound wave over time while also keeping the waves from collecting in space and time where they create comb filtering.
I found the video on this page helpful in visualizing the differences. They didn't to an absorption option but I imagine it would look like the untreated version but where the balls do not bounce back as high.


Within that, some might prefer a faster decay, others may like a slower decay. A slower decay would equate to a more lively room. These decay rates by frequency can be measured. I haven't gotten much into working with the decay rates in my room because I have so many bass issues that I know the decay rates of the mid and high frequencies are already on the fast side after dealing with so many bass issues.

 

Ok so we have established that the OP has some knowledge on the subject of room treatment and was not so much asking for advice (a quite reasonable assumption) as asking for other people's opinions. In that spirit I offer mine.

I use GIK products - twenty-one soffit bass traps and ten other panels (no diffusors! I tried some but in my sized room - 386cm x 420cm x 240cm high - they caused more harm then good). I've bought these over a few years until I'm now where I want to be. I've done this from my own experience, help from GIK, and copious threads on line.

I live in a flat (apartment) and it is not practical for me to make my own absorbers.

Here are some images:



Positioning of speakers and chair using 'The Thirds' principle.

Soffit Traps in all wall-ceiling and all wall-wall corners; four Monster Panels on each of the back and front walls;
one 242 panel beside each speaker to prevent side wall reflections. No ceiling absorption - I don't need it - and carpet on the floor.

Use of a digital equaliser to tidy up.

The result may be too 'dry' for some - typical decay times of 120ms for most frequencies - but I like it!

 

My first thought as well, except it's full-on troll behavior.

Had the question been more straightforward and honest ("Where can I get great cheap materials to build panels?"), things would have played out differently. The irony is the OP states he dislikes know-it-alls, yet portrays himself as one. The whole thing just reeks, IMHO.

 

I beieve people are being a bit too hard on the OP. He in my opinion after a bit realized he may have come on a bit strong based on a post heading that might not have met the approved expectation of some and tried to explain his intent, reassure he wasn't trolling and explain in a more clear fashion what he intent was, so lets move on.

I also like the OP am always curious as to how people have treated their rooms, what they learned from the experience and were they able to incorporate any unusual materials or existing furnishings in a way that they believe actually helped as opposed to hindered.

I believe room treatment is the number one thing to do after purchasing your initial set up and before starting on the upgrade path because you just might be replacing a good sounding piece of equipment in an attempt for better sound when actually the room was preventing the piece from shining.

My room makes use of manufactured sound absorption, homemade diffussion and placement of existing pieces of furnishing in ways that might use them to help benefit the sound. The room is small, 12 foot by 15 foot by 8.5 foot, so as many mentioned controlling the bass was the first concern. GIK triangular bass traps placed in the front two corners and two 6 inch thick GIK flat wall panels place on the back walls as close to the corners as possible. My first reflection points were the second issue I was going to try to address however once I pulled my speakers out into the room close to the thirds principle I had a pair of windows on one side and a five foot wide pocket door on the other. This made hanging panels on the wall impossible. The pocket doors are an interesting treatment, I can keep them fully open or adjust the opening width from fully open to fully closed. The doors are of a panel design and solid wood so the actually have some built in diffussion. Typically I keep them fully or half open. This stops first reflection and also I believe allows the bass wave to expand out into the next room benefitting the bass sound. The other side which is two windows totalling a 5 foot width, matching the pocket doors, are dressed with wood interior shutters with adjustable viens and draps. The draps are pulled back and on moderate temperature days I can open the windows to match the open pocket doors and address first reflection this way and increase the volume of my room. On cooler or warm days the windows are shut and I can adjust the shutter viens to allow the music to flow through and maybe diffuse along with trapping early reflection sound waves. Not as effective as the pocket doors but seems to work nicely. Directly behind me I have a framed fabric batik painting which I have stuff the back with fiberglass insulation. This absorbs the higher frequency sound waves from bouncing back to my ears. My sofa is pulled a few feet off the back wall so my head is a little over 3 feet from the back wall. I have CD racks set on the side walls that extend from the rear corners to slightly ahead of my listening position. I deliberately keep random spaces between some CDs and do not push all of them all the way in varing the surface texture this was intentional and I believe does create some beneficial difflection. The floor has a wool area rug that pretty much goes wall to wall but has a hard wood floor border of about 30 inches. The last two treatments I have incorporated are two home made diffusion panels that I have placed on the front wall between the bass traps. I went on line and found a plan for this. If I recall correctly it was designed to diffuse in the 750Hz range, I could be wrong about this but it was the recommended pattern to use for the midrange frequencies. The trough widths and depths were computer generated for the frequency range picked. They are about 6 foot tall and 36 inches wide each. The last item is a ceiling fan mounted in the middle of the room just in front of the speakers. The large fan paddles break the plain of the ceiling up. Not a big effect but I am sure it has some effect, how could it not.

To answer the OPs question, yes I believe treating the room is critical and can be done creatively with store bought, home made and adhoc ways. I will also say other than the diffuser panels no calculations or programs were used to treat my room, just my ears and experimenting. It took a few years to come to the place that I think works really well and this has been reinforced by opinions of fellow audiophiles who have come to my room to listen to my system, everyone is very impressed with the sound. It is not over damped or under. I can clap my hands anywhere in the room and there is no echo. As you walk into my room you can immediately sense an atmospheric change or it feels that way to your ears. I credit the excellant sound both to the equipment that took a lifetime to put together along with the room and its treatments.

 

@mds, do you have a pic of your diffusion panels? Link to plans? Or can I pm you for a copy?

I agree with your first paragraph concerning the OP's intent.