REW analysis help... uh, so now what do I do?

[darkbuddha]

So I downloaded REW for OSX and days later I've finally got my REW analysis results... I think... I'm pretty sure I did it right. I did an analysis of each speaker and all speakers combined (quad+sub), and I've read the primer and tips on using REW, and I sorta understand some things about the results, but I'm not quite sure what to do with it now. Help with interpretation and treatment advice would be greatly appreciated. Here are a couple results images:


SPL, 20-400Hz, no smoothing:




SPL, 400-10.5kHz, 1/6 octave smoothing:




Waterfall, 20-400Hz:




RT60:




Looks plenty horrible (just like it sounds), so the question is where is my time, effort, money, and aggravation best invested?


(Pics of treatment and REW analysis results are on page 2 of this thread.)

[Glenn Kuras]

Do you have any treatment in the room now? Have a diagram to post with your set up? It really comes down to setting up in the right location, bass trapping as many corners as possible and taking care of the early reflection points. You can then do things like tuned trapping and diffusion if need be.
How Bass Traps Work. Acoustic Panels and Bass Traps.
Monitor Positioning. Acoustic Panels and Bass Traps.
What Are Early Reflection Points. Acoustic Panels and Bass Traps.
GIK Acoustics: Room Setup

[darkbuddha]

Oops... got a bit ahead of myself, didn't I. I have another thread where I was trying to settle on a layout/setup for my space, which appears here: FNG needs a bit of direction and help . But to quickly answer your question, I have no treatment in the room right now. I do have a tentative (and intentionally basic) plan for treatment, but I'm thinking it will need some revision.

For the sake of convenience, here are some renderings and pics to help explain my current situation:

Renderings of current setup:





Renderings of proposed basic treatment plan:







Of course, I'm on a pretty serious budget (like so many of us), so I'm going to have to be selective about how and what I do. Any ideas would be greatly appreciated.

[kasmira]

It is kind of hard to determine exactly "where" you should place your treatment when you build it / buy it. The only thing that really makes sense is to get all of your traps together, and place them in spots where it makes sense in your room and test. Move them around...test, etc etc until you've found the best spots for them.

Generally speaking, the thicker the panel, the lower it will absorb. Also, generally speaking, the thicker the panel, the less dense of insulation you will want to use.

There are things like peaks on these graphs that make a lot of sense when you first see them. Obviously, bass is resonating at those frequencies at certain parts of your room, so by measuring, moving traps, measuring, etc back and fourth, you can find out kind of "where" these resonations are occurring. The easiest way to find some quick panel placement is have someone walk around with insulation or a trap, and you sit in the mix position. If it suddenly sounds "better" where you're at, place the trap wherever he/she is holding it. Experiment with how far away from the wall it should be. Does it sound better flush with the wall or 4" away from the wall?

However, things like nulls are a little harder to really understand from just a quick glance. However, its still pretty similar. Whats happening is sound is coming from your speakers, and bouncing off the walls at a different phase, which will cancel out certain frequencies. Putting a trap wherever the bass is reflecting to cause the phase issues will help to calm those nulls and smooth out the graph.

Your 80hz ring out looks like it might be a pain in the ass. However, if you do those big panels above your bookshelves, you could put insulation in that entire massive gap right there and that could righteously help your case.

Acoustics seems to be kind of a pain in the ass. Its funny because, from an outside perspective, it looks so easy - and seems easy enough to address problem frequencies, etc. But its SO CONDITIONAL, that if a bird takes a shit on the other side of your house, your next measurement will be different. But this is the fun in acoustics! You just have to go in it with the right mindset. An extra 3 traps might not even make your room sound any different to you...but measure it, and holy hell did it make a difference. Then the reverse could also happen to.. "Wow that made such a huge difference!!" then you look at the graphs..nothing, haha.

I'd suggest calling local suppliers to find good insulation prices, and just get some boxes of it, and try to build everything sooner than later. Its hard to keep building stuff every weekend just to have it sound a little better each time, you know?

Kind of went on tangents in my post, so, sorry for that. Just know that everything on these boards is conditional to certain situations, and only YOU or someone at your place will really be able to know whats going on. Hopefully others can give you a little more insight to what will be more practical for you to build, but no matter who says what, its going to need a lot of trapping, and I'd say that would be your first hurdle.

Good luck to you on your studio build.

[cananball]

Originally Posted by darkbuddha

For the sake of convenience, here are some renderings and pics to help explain my current situation:

Way to whip out some diagrams!

[darkbuddha]

Thanks for the replies... and I like tangents, especially when they contribute to the whole point: understanding all this stuff.

I'm feeling the placements of treatments of my initial basic treatment plan (above) are probably sound, but the question is what kind of treatments I should do at each location. Some are a given, but I could really use some help stretching my budget of about $300. Here's what I'm currently planning on buying:

* 10 panels of 3"x24"x48" OC 70x (actually 1.5" OC rigid fiberglass duct board that I'll cut and bond together into 3" panels), $130.

* 12 panels of 3"x15.25"x48" Roxul Safe'n'Sound, $50

* 2 rolls of 9"x15"x300" R-30 pink fluffy stuff, $20 ($10 per roll).

* wood for frames, hardware, chicken wire, fabric, $100 (hopefully less!)


Things I'm doing for sure:

1. use the pink fluffy stuff to make an 18"x15"x96" bass trap column in the odd corner, and 12"x24"x30" blocks above the bookcases.

2. use 8 panels of Roxul s&s to make superchunk traps at the corners where the bookcases meet the walls in front of the desk.


This leaves me with 24' (288") of the 9"x15" pink fluffy stuff, four panels of 3"x15.25"x47" Roxul S&S, and the ten panels OC70x to cover first reflection points, a "cloud", and bass traps for the ceiling-wall corners, and anything else I can do.

What do you guys suggest? Regular broadband traps with the OC70x for the first reflection points, or panel traps to help catch more bass?? OC70x or Roxul S&S for the ceiling-wall traps? Roxul S&S or pink fluffy stuff for the "cloud"? Other suggestions?

Any feedback would be greatly appreciated.

[RJHollins]

what microphone did you use for the 'shoot' ?

[DanDan]

The Conclusion is the most important part of the Room Analysis Primer.

Software alone cannot evaluate a listening space. It does however bestow great certainty when making comparative choices. When treating a room there is simple clear advice on the usual websites as to where to put treatment and why. They all agree on the basics; Broadband or Bass Traps in the corners, a Ceiling Cloud, Side Reflection points. This is not voodoo and it doesn’t change from room to room. Treat the Room first, then use Software to make comparative choices such as best speaker position, best seating positions, best speaker eq settings, etc.

DD

[darkbuddha]

Originally Posted by RJHollins

what microphone did you use for the 'shoot' ?

Radio Shack digital SPL meter using the readily available REW calibration file, pointed at the ceiling, tested at 76dB.

Originally Posted by DanDan

The Conclusion is the most important part of the Room Analysis Primer.

DD

I did read that, and it reinforces my basic treatment approach, so I'll just go ahead with my plan:

3" OC70x for front & side early reflection points

3" OC70x for ceiling-wall corners

3" Roxul S&S for ceiling cloud

3" Roxul S&S for rear early reflection points

[DanDan]

Many of us have a minimum recommendation of 4 inches of fibre, plus a four inch airgap.

Three inches with a three inch airgap is not too bad.
However three inches without an airgap is poor value for money and effort.

DD

[darkbuddha]

Thanks for the reminder. The room is pretty tight, so I'll probably have to live with a 2"-3" gap in most locations unfortunately. Same for the ceiling cloud since there is a ceiling fan I have to clear. That said, I understand that with mineral wool that there is no benefit to having a gap and that filling any potential gap with more material is preferable. I might do a single 6" Roxul S&S panel in the rear... maybe.

I have to say that I really appreciate all the feedback I've gotten here. It becomes overwhelming after reading hundreds of threads over a few weeks and trying to keep it all straight in my head. I take notes, but there are enough variations that it gets confusing or mind-numbing. I often find that when it gets complicated and complex, the KISS approach is the way to go, which is where I'm at right now. I figure anything I do will likely be an immense improvement, so that's what I'm holding to.

[kasmira]

Originally Posted by darkbuddha

That said, I understand that with mineral wool that there is no benefit to having a gap and that filling any potential gap with more material is preferable.

Can anyone confirm this or link me to a thread about it? I have never heard this before (not that I disagree with you, I'm just not in the know), and considering I have mineral wool panels built, it would help me know my situation better.

Originally Posted by darkbuddha

I might do a single 6" Roxul S&S panel in the rear... maybe.

I would suggest it. I have two 6" deep panels in my room currently, and even though its the only thing I got so far - it makes a pretty nice difference.

You could also just do a full soffit design in that weird corner in the back (where it looks like you drew in a soffit trap in your drawing)

Originally Posted by darkbuddha

I have to say that I really appreciate all the feedback I've gotten here. It becomes overwhelming after reading hundreds of threads over a few weeks and trying to keep it all straight in my head. I take notes, but there are enough variations that it gets confusing or mind-numbing. I often find that when it gets complicated and complex, the KISS approach is the way to go, which is where I'm at right now. I figure anything I do will likely be an immense improvement, so that's what I'm holding to.

Definitely true man. I'm grateful to have found a place like this where professionals will help you out - its very relieving to know if you need help, you can get it. If I ever built a ground-up studio, I would definitely be calling one of the members on this board for a design, if not just for the amount of work & time that they put in to helping completely random people.

Get building ASAP! Like you said - you will have plenty of different cofigurations to try out once you get them built..so we know what the first step is now

You might want to take a little more money into account for your materials. Something at some point will probably end up costing you more than you thought. Fabric can be pretty expensive, for example.

[darkbuddha]

Originally Posted by kasmira

Can anyone confirm this or link me to a thread about it? I have never heard this before (not that I disagree with you, I'm just not in the know), and considering I have mineral wool panels built, it would help me know my situation better.

See, this is the problem with getting in too deep too quickly and then starting making generalizations rather than being specific. Just do a quick search on "roxul airgap" and you'll find the kind of threads where I read about using an airgap with mineral wool. My mistake is that I generalized it, when in fact, it really only applies to less dense material, like the Roxul S&S I'd be using (i.e. under 3 lbs. pcf). Denser stuff (Roxul Rockboard 60 or 80) would still benefit from an airgap.

My new question is whether it's beneficial to layer different density materials, and if to use an airgap or not. Might post a new thread...

[DanDan]

I could imagine that layered densities would be ideal. One could start at the air boundary with a very light density, gradually increasing with depth.
However who has access to various layers like that and how would you install them?
Some have suggested a rigid panel on the outside, i.e. a corner straddling trap, with light fill behind.
Again I can imagine that a light fill is better than no fill, but I haven't seen tests. A semi rigid panel does begin to have slight membrane action. Drum head action Glenn and I would call this. Without tests we don't know if the light fill will inhibit this or help it. Similarly if we submerge a dense panel hoping for a little VPR action, the result is unknown.

If I were to place a bit right now, I would say fill.

I have not seen anything to suggest that an airgap has less or no effect with light density fibre. Do you have evidence of this darkbuddha?

DD

[darkbuddha]

Originally Posted by DanDan

I have not seen anything to suggest that an airgap has less or no effect with light density fibre. Do you have evidence of this darkbuddha?

DD

I do not... I'm just going off some of what I've read (and possibly misunderstood) in a few of the hundreds of threads I've looked at here and a couple other places. Threads like this: Roxul SoundNSafe 3" or 6" for basstrap and broadband

As I said, I probably generalized this concept too much and too quickly. I think the thing to do is to simply test with and without a gap, and test different layering of materials (i.e. OC70x over Roxul S&S and vice versa) and see if/how it benefits me. Luckily, testing is cheap with REW.

[DanDan]

There is plenty of testing out there with and without different distances from the wall. http://www.bobgolds.com/AbsorptionCoefficients.htm
You would need a large sample to see the effect in REW, I expect.
You could also try to predict performance using a calculator.
However prediction may become quite uncertain at the outer reaches of the range of densities/Gas Flow Resistivities.
Porous Absorber Calculator

DD

[darkbuddha]

Actually, I don't see anywhere on http://www.bobgolds.com/AbsorptionCoefficients.htm that specifies whether any of the products other than the OC70x stuff was tested with or without an air gap. Does anybody know?

There does seem to be a general consensus that having an air gap behind an absorber increases their effectiveness in lower frequency ranges, which may be good for my needs. What I've gotten from all of this research and discussion is that there are lots of possible trap designs and enough variability that any guesstimation of a treatment design is only a basic guide. For my purposes and concerns (i.e. treating my room), it seems easy enough to test with and without, layered and not layered, etc. to see if the results improve my room in a way that it needs.

[DanDan]

From bobgolds.com
RW5 300mm gap 1.25" (30mm)100kg/m3 0.40 0.75 0.90 0.80 0.90 0.85
RW6 300mm gap 2" (50mm) 140kg/m3 0.65 0.55 0.75 0.85 0.75 0.85

DD

[darkbuddha]

Originally Posted by DanDan

From bobgolds.com
RW5 300mm gap 1.25" (30mm)100kg/m3 0.40 0.75 0.90 0.80 0.90 0.85
RW6 300mm gap 2" (50mm) 140kg/m3 0.65 0.55 0.75 0.85 0.75 0.85

DD

Thanks! I sit corrected... I totally missed those. Any ideas on the depth of the gap? It should be about the same as the thickness of the material, correct? Whatever it was, that gap provide a seriously nice improvement in performance (at least according to the numbers).

[Adhoc]

Originally Posted by darkbuddha

Actually, I don't see anywhere on http://www.bobgolds.com/AbsorptionCoefficients.htm that specifies whether any of the products other than the OC70x stuff was tested with or without an air gap. Does anybody know?

There does seem to be a general consensus that having an air gap behind an absorber increases their effectiveness in lower frequency ranges, which may be good for my needs. What I've gotten from all of this research and discussion is that there are lots of possible trap designs and enough variability that any guesstimation of a treatment design is only a basic guide. For my purposes and concerns (i.e. treating my room), it seems easy enough to test with and without, layered and not layered, etc. to see if the results improve my room in a way that it needs.

Check out enclosed excelfile. There are lots of measurements for various absorber material with a distance to a wall behind. Go to "Selection Table" => Column AQ Legend-Character of absorbtion, filter out type of absorber => Column AS Material Criteria, filter out 1 = mineral fiber => Column J Distance, filter out cells showing a value.

[DanDan]

There is plenty of proper stuff about the gap on the Q4Avare thread.
1:1 to 5:1 are common enough. A typical suspended ceiling is even greater.
DD

[darkbuddha]

I have read some of the q4avare thread, but it's a bit overwhelming. In any case, I read that and then I read this:

Originally Posted by avare

Lots of misconceptions going on there.

1. 4" is THE MINIMUM for absorbers doing anything resembling full range and first reflection control.

2. 6" is great to use for all.

3. With SafenSound there is no advantage to having a gap at 6". Fill the space.

With the price of Safe N Sound compared to 703, it is cheap to do it right!

Andre

and this:

Originally Posted by avare

No gap with Safe N Sound is better.

The question is why does Andre say this given his posts regarding the benefits of gaps in the q4avare thread. Maybe I should ask him?

[DanDan]

Context buddha. The overall depth stays the same. A full unterrupted depth of fibre is best, but half plus gap is only a little less effective. So 8 inches of 703 is a bit better than 4 inches with a four inch gap. If the cost of the material is high, which it typically is with the rigid boards, then an airgap is really a free lunch. You get very nearly the performance of twice the depth of fibre, by simply leaving a space behind it.
With SnS being so cheap, and the full fill performing slightly better there is no practical need for a gap and certainly no benefit.

DD

[avare]

Originally Posted by darkbuddha

I have read some of the q4avare thread, but it's a bit overwhelming. In any case, I read that and then I read this:



and this:




The question is why does Andre say this given his posts regarding the benefits of gaps in the q4avare thread. Maybe I should ask him?

The materials I specifically refered to have different gas flow resistances. 4" of 703 has approximately over twice the airflow resistance of Safe n Sound. Put in some practical design application of total absorber cost and Safe n Sound at 8" is less than half the cost of 4" of 703. You can spend over twice as much for the same acoustic performance.

Please note, when writing things, I try to include significant factors. I wrote 703 and Safe n Sound at specific depths. NOT fiberglass and mineral wool. It is difficult to respond when clear directions are given and they are abused and taken totally out of context.

Adnre

[darkbuddha]

Originally Posted by avare

The materials I specifically refered to have different gas flow resistances. 4" of 703 has approximately over twice the airflow resistance of Safe n Sound. Put in some practical design application of total absorber cost and Safe n Sound at 8" is less than half the cost of 4" of 703. You can spend over twice as much for the same acoustic performance.

Please note, when writing things, I try to include significant factors. I wrote 703 and Safe n Sound at specific depths. NOT fiberglass and mineral wool. It is difficult to respond when clear directions are given and they are abused and taken totally out of context.

Adnre

Thank you for responding. I can only read what is written, and without the benefit of your expertise, sometimes what is written is not so obvious or clear. In or out of context, certainly I did not recognize that in your statements regarding no gap with SAS were based on a comparison to 703 in terms of gas flow resistance, since in that thread there is no mention that comparison. The only comparison between 703 and SAS is on the basis of cost, which I clearly misread as conciliatory.

I certainly didn't mean to abuse your comments (in or out of context) other than to attempt to reconcile the seemingly conflicting information that I find confusing. Again, I can only read what is written and cannot divine that which I do not know. I research, I read, I wonder, I question, others kindly respond (like yourself), and I learn. I will continue to do exactly that in an effort glean every bit of knowledge, wisdom, and insight I can get.

Unabashedly,

Wyatt

[avare]

Originally Posted by darkbuddha

Thank you for responding. I can only read what is written, and without the benefit of your expertise, sometimes what is written is not so obvious or clear. In or out of context, certainly I did not recognize that in your statements regarding no gap with SAS were based on a comparison to 703 in terms of gas flow resistance, since in that thread there is no mention that comparison. The only comparison between 703 and SAS is on the basis of cost, which I clearly misread as conciliatory.

I certainly didn't mean to abuse your comments (in or out of context) other than to attempt to reconcile the seemingly conflicting information that I find confusing. Again, I can only read what is written and cannot divine that which I do not know. I research, I read, I wonder, I question, others kindly respond (like yourself), and I learn. I will continue to do exactly that in an effort glean every bit of knowledge, wisdom, and insight I can get.

Unabashedly,

Wyatt

You are welcome. The perceived conflict was from reading what was not in the message. If it was intuitive, it would not be acoustics, and aspirin would not have been invented.

Gas flow resistance is the great elephant in the room when it comes to porous absorbers amongst people learning studio acoustics. It is the predominant factor in determining the absorption of a porous material, and one of the first physical attributes introduced in physics related courses on acoustics, yet it is almost never mentioned in the personal recording studio design world. Gearslutz is typical of this.

Flowing gaseously,
Andre

[darkbuddha]

Originally Posted by darkbuddha

Things I'm doing for sure:

1. use the pink fluffy stuff to make an 18"x15"x96" bass trap column in the odd corner, and 12"x24"x30" blocks above the bookcases.

Finished these last night... no testing yet, but immediately apparent is more flutter/slapback in the room. Very annoying. Need to get side panels up ASAP.

[ritelec]

Originally Posted by darkbuddha

Some are a given, but I could really use some help stretching my budget of about $300. Here's what I'm currently planning on buying:

* 10 panels of 3"x24"x48" OC 70x (actually 1.5" OC rigid fiberglass duct board that I'll cut and bond together into 3" panels), $130.

* 12 panels of 3"x15.25"x48" Roxul Safe'n'Sound, $50

* 2 rolls of 9"x15"x300" R-30 pink fluffy stuff, $20 ($10 per roll).

* wood for frames, hardware, chicken wire, fabric, $100 (hopefully less!)

wishful thinking..................


Go gettum darkbuddha !!!

[darkbuddha]

Originally Posted by ritelec

wishful thinking..................


Go gettum darkbuddha !!!

Yeah, the budget is a bit broken already... I'm in for $100 in wood, hardware, plastic mesh, fabric, and pink fluffy stuff, and I'll probably need at least another $60 in fabric and wood to do the side panels and bass traps. The good news is that I found a different place with good prices for OC703 and other insulation which should save me $50 on materials, but we'll see. What is clear so far is that DIY is still cheaper than buying pre-built and namebranded stuff. Besides, you can't buy pride.

[darkbuddha]

Picked up insulation from IDI today...

1pkg of 16 sheets of 1.5"x24"x48" OC703 = $90.88 ($.71/sqft)
2pkg of 8 sheets of 3"x24"x48" Thermafiber SAFB = $47.36 ($.37/sqft)
Total with 7% tax = $147.91

Not bad methinks. That saves me over $30 off my original estimate for insulation and I'll have more insulation than I probably need. I suppose I could resell some of the extra SAFB and recoup some more, which just might offset the overage that I've put out on supplies so far. We'll see I guess.