Trdat
Junior Member
Posts: 78 
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Post by Trdat on Aug 31, 2016 7:34:38 GMT
We are told not to put a membrane or FRK on first reflection points, and I'm aware both GIK and Ethan are strong proponents of this theory. Now, I am aware many factors come into play especially quality of products and how your HI FI dedicated listening room is set up with other bass traps and other membranes on surface. But, if your aiming to keep your room as live as possible and considering that you will still be absorbing some highs at reflection points if FRK is facing out, how come putting FRK on say either roof or side first reflections is such a no go area? Arqen recommends a combinations of diffusers and I know FRK is not a high end diffusor and Ethan does mention switching between FRK surfaces and non FRK/membrane surfaces to keep a balance in the room. I can give more information on my set up if that helps. But I need to understand the harm in say having a your ceiling reflection points with 4 inch mineral wool batts with a thin paper over it to reflects the highs? I will have FRK on the broadband bass traps around the speakers at the front and will aim to put a wooden plate to help the scattering of highs on the the bass traps behind the speaker. Sorry to change the subject but in a somewhat connected thought, forums always go on about how reflecting highs will keep the room live what about some reflection of a bass guitar isn't that towards the lower end of the frequency scale, does reflecting those frequencies help at all, or is the goals to absorb as much as we can with reflecting highs on the bass traps that surround the speakers at the front and absorb with an even range at first reflection points?
Ultimately say your on a budget and your DIY your broadband basstraps with 703 FRK facing out 4 inch with a plate to help the scattering and then using mineral wool for ceiling and side reflection points aiming for 4 inch with the goal of keeping the room live, a combination of very acoustical, classical music to rock music where a slightly dead room might not have the best affect? Please correct me if i am wrong somewhere? I have scoured all forums but although there is a goal explained the reason behind it is never there.
PS. 16.5 feet by 9.5 feet with an average ceiling height. Just a 2 channel listening room.
Kindest Regards
Trdat
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Post by rock on Aug 31, 2016 12:13:31 GMT
I'm pretty sure Ethan mentioned the reason you need mid-high absorption (not reflection) is due to the slightly longer path the reflected sound makes causing phase cancelations that spectrally distort the sound you hear from your speakers. In other words, absorbing the early reflections, eliminates the phase cancellations and spectral distortion. The ultimate goal is to hear the direct path from your speakers.
Cheers,
Rock
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Trdat
Junior Member
Posts: 78
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Post by Trdat on Aug 31, 2016 13:53:46 GMT
Hello Rock,
Thanks so much a simple sentence and I've already got the picture I was looking for. I will keep first reflection for full absorption. Appreciate it! Ethan has explained it, it was more about knowing why you shouldn't use it rather than why full absorption so my misunderstanding.
So what is your opinion on using membrane plates like the one from GIK with the vertical slots the "wooden panel", on the DIY broadband bass traps on the front wall? I will use FRK facing out to increase bass absorption to keep it lively around the speakers. Im looking at simple DIY trap with just the wooden plate on top of the fiberglass and material..
Is it worth the effort considering my goals? Or shall i just use it for the two traps immediately behind(not exactly behind) the speakers that will be in the corners? Or perhaps none at all as the FRK facing out will do the job well enough?
Regards
Trdat
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Post by rock on Sept 1, 2016 12:26:50 GMT
I'm not familiar with the GIK products but I did take a quick look and if the "wooden panel" ones you mention are a combination absorber/diffusor, I don't think the corners are the best place for them. FRK (facing out) VS non FRK absorbers improve the low frequency absorption at the expense of less mid/high frequency absorption. That's why they are a good choice for corners since,1. that's where low frequencies tend to "pile up" or "focus" and 2. corners are usually not reflection points so mid/high absorption is not especially necessary there. One goal of LF absorbers (Bass Traps) is to reduce modal ringing which is "bass reverb" of sorts and is generally unwanted so I would not be concerned with absorbing too much bass. One goal is to achieve a relatively flat RT60. This room mode calculator amroc.andymel.eu/?l=13.5&w=10&h=7.5&ft=true&r60=0.6 will calculate an RT60 and other data. If you want to run acoustic tests, check out REW. Ethan has links somewhere, I think on the "read this first" post. I just plugged in your room dimensions ( assumed 8ft ceiling since you did not specify) and looks like (not surprisingly) you have several modes "piling up", if you built from ground up, you'd choose different dims but you'll work with what you've got. Just be aware, you'll need plenty of bass trapping to tame those modes. Cheers, Rock |
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Post by Ethan Winer on Sept 1, 2016 18:10:00 GMT
I've written about the importance of absorbing early reflections many times, but it's explained in depth in this most recent article on the subject: Early ReflectionsI also explain why "aiming to keep your room as live as possible" is not usually the best goal. At least for typical home-size rooms. What you really want is for the room to be neutral, so it contributes as little coloration as possible. --Ethan |
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Trdat
Junior Member
Posts: 78
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Post by Trdat on Sept 7, 2016 6:16:22 GMT
Thanks Ethan, I have read that article a number of times I will read it again from a new perspective.
I am in process of researching more about a DIY scatter plates. And now I am onto my rear wall and hoping this will be the last bit of my research before I either purchase or start my DIY projects.
My reflection points on the rear wall are a glass window and glass door and I was looking treating those points in general with thick absorption and possibly with a scatter plate.
I would like to treat the rear wall with what it takes and as diffusion is recommended on the rear wall I thought a combination of thick absorption with a scatter plate would be appropriate.
I am aware scatter plates or plates with slots in them are not recommended at first reflection points but my seating position is about 3.7 meters from rear wall which is not considered early reflection if I am not mistaken.
I am aware I can make the traps on stands which is an option but not an option I want to take unless needed.
I really want a lively room for my two channel listening and have taken your advice Ethan and will make my 6 inch ceiling cloud with no FRK(first layer 703 with second and third 2 inch layer mineral wool) with a 4 inch or so gap and side wall reflections again with no reflective material. But my bass traps will have FRK and some scatter plates on the front wall and rear wall.
So to understand better,
1. Can the scatter plate be used for rear wall reflection points?
2. More importantly If i decide to put the absorption/scatter plate on back wall but not at those reflection points, do they serve a purpose or do I have to resort to putting them on stands to place them at those rear wall reflection points for it do its job?
PS. I should have adequate bass trapping with FRK and scatter plates on rear and front wall corners, my concern is rear wall treatment and how to overcome my glass door and window in the back of room? And how much absorption do I need is two panels enough two large panels?
I am aware that treating rear wall is important hence I would like a 4 or 6 inch panel on rear wall to reduce those bass problems but you can see the issue I have, how would i best move forward?
Kindest Regards
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Post by Hexspa on Sept 8, 2016 0:56:53 GMT
trdat, hi I'm Michael. Please forgive my tone but I'm getting a confusion headache reading your post. Your room is small. I don't think you need scatter plates. I think you need to understand the basic fundamentals of treating a room and apply those first. Ethan's advice is obviously sound and readily available. I also have my thread and video series on selecting and setting up a listening room which incorporates much of the recently-discussed relevant info from this forum and other sources. It's especially geared toward people with no experience - i.e. a "quick-start" guide. I talk about windows, FRK vs. non-FRK and just about everything else you're asking. It's six short videos and I get right to the point. It is, of course, free and on YouTube (see link below). I've also made my PDF available to this forum for free as well. Please consider reading it - it's only 28 pages including several big pictures. Please review those resources and stick to 4" broadband absorption exclusively for now. A fundamental flaw in your understanding is about "liveness" of the room. First get your corners and RFZ treated with non-FRK 4" panels and then we can move on. This is my opinion based on my personal experience, observation and study. Good luck, -m the-audio-expert.freeforums.net/thread/150/set-listening-room |
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Post by rock on Sept 8, 2016 1:45:39 GMT
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Post by Hexspa on Sept 8, 2016 6:05:20 GMT
The room is about 1250ft3. Correct me if I'm wrong but I think liveness is his last concern.
The way I understand it is this: your low frequencies and RFZ need to be handled before your diffusors and "liveness" are considered.
If I understand his posts he hasn't put panel one in his room yet.
So why not move things in order? Get a bunch of panels, place them correctly.
He probably will need to cover every available surface to get his response decent. You saw the Hearing is Believing video - that room was probably similar dimensions and no surface was spared. Even the diffusion they used was really absorption too.
What about that other guy on here with the garage? Remember how much treatment he had in there? No diffusion or concern for liveness.
Point is, let's focus on the meat and potatoes before messing with the parsley.
-m
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Trdat
Junior Member
Posts: 78
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Post by Trdat on Sept 8, 2016 8:59:59 GMT
Micheal,
I understand your frustration, apologies.
I will do everything in one go so hence trying to understand everything. Will be DIYing everything over two days. You are correct no panels yet except a superchunk bass trap on top middle ceiling.
I have RFZ covered I am doing the following.
4inch no FRK on side walls, ill be covering a large space cause I don't sit in one spot and like to move around. So 2 or 3 panels, material is cheap where I am.
(This will help cover more available space in the room which is what your recommending)
6inch no FRK on ceiling with a 4 inch gap or slightly more again 2 or 3 panels above. You mention 4 inch another confusion? I have read thicker is better?
I should have enough bass trapping(i probably need more) with either 4 or 6 inch (going to try for 6 inch) straddling the wall on the front and the height will be mostly covered and and on rear it will be only one panel towards the top of the wall. I do have a large superchunk bass trap in the middle of the front wall ceiling.
I will have FRK or at the very least keen on the idea with my bass trapping. But its interesting to say I don't need scatter plate or plates with slots on corner bass trapping? This is where I am confused as you also mention no FRK on corner traps as well. And are you recommending no scatter plates or FRK for my small room?
And if so then I suppose the same goes for absorption on back wall no FRK or Scatter plates? Where would you recommend scatter plates if any at all?
PS. Will watch your vids!
Kindest Regards
Trdat
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Post by rock on Sept 8, 2016 12:46:14 GMT
The reason I mention RT60 is because it relates to the overall coverage of panels in given room. Some will be bass traps and some will be for RFZ. If you plug in the dims and select "EBU listening room"(if you click on the link there, you can read the PDF) the calculator gives you and RT60 of 0.2 sec that will be achieved with a particular amount of coverage. In this case between 311 and 253 sq ft. Note that there are both the Sabine and Eyring calculations are used but they are not that far apart, the point is, the more absorption, the lower(shorter) the RT60. That's the "liveness".
I agree that the bass and RFZ panels are of primary importance but for comprehensive plan, it's not wrong to estimate the total coverage for a target RT60 as well. So...
If you cover all 12 corners with 2'x4' panels you'll cover about 280 sq ft. Your RFZ panels, maybe 2 on each side and 2 on the ceiling that's another 48 sq ft = 328 sq ft.
OK, you're pretty much in the ball park as far the calculator goes. Now you have an idea and if you think you want a little more liveness, you can start off with less panels at the expense of either bass trapping (room mode reduction) or RFZ so it's up to you. I would consider measuring at various stages to see what's going on with modes, response and RT60.
I don't know what a "scatter plate" is but it sounds like you're talking about "diffusors". The distance between the listening position and the back wall is far enough to use diffusors there. They won't increase the "liveness" but they will smooth it so if you have enough absorption, why not?
Cheers,
Rock
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Post by Hexspa on Sept 9, 2016 4:08:44 GMT
Rock, thanks for that clarification regarding that function of the calculator. Indeed it's useful to get a ballpark figure for square footage of coverage needed to achieve a particular target.
I've been using a different metric standard but I guess one is as good as any. As you may know I've used 20dB decay above 40Hz within 150ms for this room. I'll have to read up on EBU; sounds legit. (For my room's dimensions, 600ms is the calc's RT60 target which is close to double what I'm currently achieving.)
Anyway, all that calculation and stuff just gets us back to "treat your corners and RFZ then measure to see where you're at."
Regarding the scatter plate, take a look at it on the GIK website. I'm quite certain it's not a diffusor at all. At the present time it seems like a relatively inexpensive acoustic product sold without much concern for it's usefulness in an otherwise untreated room. In other words, someone might say, "Hey, I got $50 to spend on treatment - lemme get this." *facepalm*
This is really a perfect example of why I'm starting an acoustics company. It's the old Dylan axiom: there's too much confusion, I can't get no relief.
The only reason I'm here is because I managed to make it simple for myself. Not to knock standards and Sabines but they just seem to make you walk around the block to get to your back door. Why go through all the trouble when you can just walk down your own hall?
I maintain: corners, RFZ, measure and evaluate.
Either way, thanks again Rock for that pro tip. I appreciate it.
And, trdat, go with cheap - it's what I did.
-m
PS - If you really *MUST* use FRK then just install your panels without any fabric covering or FRK initially. Then, after you have a sense of what raw treatment can do, you can take the next step and optimize your panels with the use of FRK.
PPS - RE: 4 vs 6" - Actually, using rigid panels you can go up to 8" thickness! The only downsides are cost, weight and volume (how much physical space they take up). Above 8" you'll want to move to fluffy. Air gap still applies where 3x the thickness is maximum recommended. As always, I'm deliberately trying to limit your options so you can just start moving in the right direction without getting confused by too much information. This isn't out of underestimation of your intellectual capacity but more of a remembrance of my own mental proneness to overwhelm.
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Post by rock on Sept 9, 2016 15:17:46 GMT
Hi -m,
Fair enough. Right, all the calculation does get us back to treating the corners and RFZ. That was exactly my point.
Since Trdat was concerned with liveness, I wanted to point out to him that it was a "thing" (RT60) and in fact it does exist (and is measurable) whether or not we want to deal with it. I also agree it's better to have a deader small room than a live small room but that there are suggestions "out there" of just how much is OK since as you know, making a room truly anechoic is not always either practical, possible or possibly even desirable.
Cheers,
Rock
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Post by Hexspa on Sept 10, 2016 7:32:22 GMT
Hi -m, Fair enough. Right, all the calculation does get us back to treating the corners and RFZ. That was exactly my point. Since Trdat was concerned with liveness, I wanted to point out to him that it was a "thing" (RT60) and in fact it does exist (and is measurable) whether or not we want to deal with it. I also agree it's better to have a deader small room than a live small room but that there are suggestions "out there" of just how much is OK since as you know, making a room truly anechoic is not always either practical, possible or possibly even desirable. Cheers, Rock True |
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Trdat
Junior Member
Posts: 78
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Post by Trdat on Sept 12, 2016 12:46:42 GMT
Thanks guys, I didnt know that calculator existed and Hexpa I understand that there is different ballpark that we can use to achieve a similar understanding of how to achieve a certain amount of liveliness but I will use this as at the moment I understand it. And thanks I have read your PDF great info although the sound testing part I will need a month to concentrate and understand it properly.
In summarizing all the information I have come across I going to take hexpa's advice and bass trapp then RFZ and go from there.
Why? Cause Rock you mention EBU listening and Arqen mentions using .4 or .5 seconds to achieve liveliness although he does mention a small room needs be covered between 30 to 40% covered to come close to a neutral sound for small rooms. And I think it was you Rock who also mentions to cover close to 50%. Then Ethan and Rock also mention to forget about the goal of liveliness and aim for a neutral sound in a small room.
So to aim for a neutral sound i need over 20 panels(I will use calculator to recheck my calculations) For a live room I need 12-15. My panels are 1 meter by 60 cm and are 2 inch thick but I will be going 6 inch on my ceiling RFZ Zone.
So I have purchased approx 6 packets of 8 mineral wool batts and start with wall to ceiling bass traps time 4 panels(6 nch), ceiling RFZ times 4 panels(6inch)and side wall(4inch) RFZ which will get me to about 14 panels without treating rear wall and rear side wall and unfortunately rear bass trapping.
I am presuming my next packet of mineral wool will be used for back wall bass trapping which will ultimately get me closer to 20 panels much closer to a neutral sound which is what i have been advised on. My goal is a large RFZ zone with 3 panels on side wall and 4 panels on ceiling, now if you think I am going over board with panels or RFZ zone I can take a panel out from each side and use it for bass trapping. But its seems accroding to the various information that even up to 20 or more panels will get me to neutral sound which should technically be my goal?
But my understanding has improved overall, I was fixated over the whole liveliness understanding. And that is purely because my first installment of acoustic material made from recycled cotton a massive superchunk bass trap(reflects high frequncy) and two 4 inch panels that i put around the front wall of the speakers rendered the sound of the live bouzikia from my sound system very dead. Now whether that was a figure I mean sound of my imagination or I genuinely felt the deadness I cant say. So hence my justification for my liveliness paranoia.
Kindest Regards
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