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Post by zejamin on May 8, 2023 7:56:21 GMT
Hello all. I stumbled across Ethan’s website on a quest for better understanding of acoustic treatment and I just want to mention what a fantastic resource this is for us utter novices and to also give my sincere thanks to you guys who take time out of your day to provide such valuable information for no material compensation. It’s a truly incredible gift! So, I’m looking at treating one of two possible rooms that will end up being a workable control & mixing room. NOTE: Drawing is not to scale. Blue annotates walls and green annotates doors and windows Room A is currently my control and mix room. It is not well set up (sub-optimal monitor positioning, no treatment etc) and Room B is currently my bedroom. My main question is would it be significantly better to switch rooms and acoustically treat and mix in Room B rather than Room A? And where should I set up the speakers and listening position? I’m aware of the 38% rule and that I'll have to do some experimentation but unclear on which wall to face in an L-shaped room, especially when you have windows at likely 1st reflection points. It’d be more convenient to keep everything the way it is and not sleep and live in a tiny little bedroom, but at the same time it’s much more important to me to be able to produce great sounding music so if Room B is likely to be significantly better in that respect than Room A, I’m willing to do it. Living in NZ means options for acoustic treatment are a little different over here, not to mention a bit scarce. Rockwool and other products of equivalent qualities are pretty tough to get a hold of at a decent price and I’m working on a tight budget. So my other question is about options for acoustic treatment in floor to ceiling corners. I’ve managed to find some 4” thick rockwool (typical 600mmx1200mm 60kg/m3) on trademe (NZ version of eBay) for pretty cheap that I can turn into panels. But I believe Ethan has also recommended low density (approx 15kg/m3) fibreglass/glasswool insulation bales (I’ve found some with 1’ 3” diameter) stacked in the corners. Which would be the more effective option? Currently my thinking is to stack fibreglass bales (or rockwool panels) all up the floor to ceiling corners and lay as many bales as will fit down against the wall-to-wall corners on the floor. Also to put rockwool panels (with the rockwool wrapped in plastic on the panels that are not at 1st reflection points) on the walls, doors and ceilings with a 4” air gap so that they cover all 1st reflection points and wherever else I can fit them. Please let me know if you have any better suggestions or improvements. Thank you all for your time! |
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Post by rock on May 10, 2023 4:12:04 GMT
Welcome to the forum.
A larger room is generally better because A. The greater dimensions have lower frequency 1st room modes and B. The direct to reflective sound to the Listening Position will be greater, so for those reasons moving to the larger room will be an improvement.
I suggest the L.P. should face the 12'4"wall. Your dimensions indicate the front section (top of the drawing) is larger than the bottom so your speakers and L P will be in the front of the room. That's good. Don't worry that the back of the room is narrower but fully treat the 2' 11" section with absorption to compensate for the shorter front to back distance in that section. Treating the back of the room (the 9' 5" wall) is a good idea too.
You can stack bales but better, you'll get more volume and distribution from the same amount by using fiberglass uncompressed. "Fluffy" fiberglass absorbers should be 8" or thicker. Spacing absorbers up to equal the panel thickness from walls and ceilings increases low freq efficacy for both dense or lower density absorbers.
Yes, treat first reflection areas including the ceiling.
Using acoustic measurements can help you confirm your choices and help track your progress. REW is free software.
I think you're on the right track but just about everything in this post can be found in many other threads on this forum so if you search, you'll find many questions about rooms similar to yours but if you don't find what you're looking for, feel free to ask.
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Post by rock on May 10, 2023 12:51:03 GMT
Regarding placing bales VS purpose built basstraps: Even though I recommended building bass traps, it would be much easier and faster to just stack bales or rolls of insulation. If you're inclined to go the stacking route, I suggest you at least make and record acoustic measurements (with REW). This way you'll have data you can refer to in the event you want to make changes or improvements. Taking baseline measurements before treatment can be useful too. Once you get started treating your room, you're much less inclined to empty the room for baseline measurements, so do it first.
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Post by zejamin on May 11, 2023 9:16:14 GMT
That’s really helpful advice, thanks Rock. I’m going to go to the bass trap route and build panels. I’ve got REW downloaded and have a pretty good idea of how to use it after trawling through this forum. Before I commit to pulling up carpet though I just want to check that it’s definitely better to have a reflective floor in small rooms such as mine once they’re decently treated. And also if it’s better to modify the air gap between panels to avoid repeated nulls and peaks? For example this comparison between a 100mm thick absorber with a 100mm air gap and a 50mm air gap.  The cancellation of the nulls and peaks created by the air gap are probably not worth the loss of absorption at low frequencies but thought it was an interesting idea if that ever became an issue. www.youtube.com/watch?v=IFNaBc4PUNI&ab_channel=AcousticsInsiderThere's an interesting point about 9 mins in. What do you guys think? Are we less concerned with freq response in small rooms as measured on SPL graphs and more so with decay time as observed on waterfall graphs? |
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Post by Hexspa on May 11, 2023 19:56:51 GMT
Let me give it to you easy:
Larger room, forget 38%; go with 20, 32, or 45% - your choice (20% north side big room is probably best), use 6" rigid on ceiling, 12" safe n sound on side walls at 24"-thick front-and-rear walls. Treat windows like normal boundaries. Corners are just the convergence of surfaces and consequently 1/4 wavelengths. Other than that, they're not important (for speakers it's the same but for pressure instead of velocity which gives "room gain" but that's a different story).
That's how I have my room set up now and it's great. I was thinking about posting measurements but I want to get the extra 24" front-to-back dimension treated. I'm meeting or exceeding my targets 20dB decay within 150ms above 63Hz and energy time curve down at least 10dB within 40ms. Actually, I only have one remaining resonance at 60Hz which I'm assuming is front-to-back (easy to check but I just haven't) that exceeds that just by 3dB or so. With the 2' fluffy soffits, I'm sure that'll go away.
Keep it simple, you don't have to reinvent the wheel. I have 8 [edit: 12] 6" 4x2' panels [8 are cloud, 4 are rear], 12 12"-thick 15"x48" safe n sound side panels, nine 31.5"x48" fluffy superchunks (diagonal soffits) in the corners. If you do that, you'll get the result - guaranteed. Anything less and you're going to compromise. Actually, you get a little wiggle room but not too much. Like I said, try to do what I'm doing and you'll be happy.
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Post by rock on May 13, 2023 20:36:30 GMT
About carpet, F. Alton Everest has pointed out the argument against carpet in that it's limited to HF and that then the ceiling absorption should complement the carpet's absorption. The simpler solution is to use total wide-band absorption for the entire ceiling and no absorption on the floor; i.e. no carpet. I believe Ethan has suggested using area or throw rugs where and when required or desired etc.
Your question about f response VS decay time: Good point! As far as f response, you're not going to get it flat I'll quote Ethan from another thread:
"All rooms have peaks and nulls. The best you can do is aim to make them as small as possible using bass traps and by varying your speaker placement and listening position. If you can get the span between the highest peak and deepest null to within a 10 dB window, you're doing very well!"
Controlling decay time is a big one and it will only get better (less) with more absorption.
I like Hexspa's advice above: Keep it simple! (but having some idea of what and why you're doing it is not bad either;)
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Post by Hexspa on May 14, 2023 20:40:59 GMT
SPL is overrated! Focus on decay and minimizing reflections if you want accuracy. Minimize nulls through placement and then peaks through EQ.
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Post by zejamin on May 15, 2023 9:49:05 GMT
Fantastic tips, thanks guys. Goodbye carpet! Would be cool to see where you're at with your room Hexspa. Going back to your advice about treating windows as normal boundaries added with the reality that the west window is probably going to be a first reflection point: What's the best way to treat it or rig a panel over it. On that note, what's the best way to mount panels in general with a big air gap? I've been playing around the porous absorber calculator on acousticmodelling.com and it seems that there's basically no difference in the effectiveness in absorption between panels 8" and 12" thick (Though without the air gap there's a bit more of a difference). Would anybody be able to help me understand why?   Also, when playing around with the gas flow resistivity (which apparently has a rough linear relationship with density) it seems that while density does matter, it would appear that you can get more bang for your buck by choosing a lower density material such as 30kg/m3 (approx. 10,000 Pa.s/m2) over higher density material like 60kg/m3 (approx. 20,000 Pa.s/m2)  If you’re concerned about the slight loss of absorption of the low lows (<100Hz) then increasing the thickness of the lower density material to 150% would still be cheaper than material 2x as dense and will absorb better at all frequencies.  If you’re concerned about the loss of space by using thicker panels, then decreasing the air gap by 50% would still yield roughly the same level of absorption up to 100Hz then performance significantly increases above 100Hz  NOTE: All examples use 100mm as a starting point for the panel thickness and air gap. Also, rigid backing as mentioned under Global Parameters does not mean rigid fibreglass. It means the wall of a room. I just want to make clear I’m not stating any of this as fact. This is just where I’ve gotten to in my research and what the modelling of these graphs suggests. It’s probable I’ve either missed or not taken an important factor into account. Thanks again for your responses, they're incredibly informative |
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Post by rock on May 19, 2023 13:52:27 GMT
I don't know if this is the "Best Way" but using "L" brackets mounted to the wall will work. This example will get you a 4" gap. For a 2' x 4' by 4" thick, use 2 of these 8" brackets on the bottom. 2 more on the top can help support the weight. If you design your panel frames so you can slide the top brackets between the bottom the the frame and above the absorber material. You can hide the brackets by attaching the wall side so it's behind the panel. www.menards.com/main/hardware/utility-hardware/corner-flat-braces/national-hardware-reg-zinc-corner-brace/n220-178/p-1444448903811-c-9700.htmYou can only go so far with this method and it obviously depends on the size of bracket you can find. For really big/deep panels, it might be better to make them free standing on the floor. BTW, Did you see Jesco's email where he has photos of a couple of professional studios under construction? ALL surfaces are 100% covered with absorption (how thick??? IDK) but the point, virtually complete absorption. After that, the "finishing" interior is either wood slats and acoustically transparent fabric etc. to give some "life" back to the design. He didn't go into design details but I think the point was that we amateurs don't have the luxury or resources to build from scratch and that we have go jump through all kinds of hoops to try to turn a "regular" room into a studio. |
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Post by Hexspa on May 19, 2023 21:43:39 GMT
Zejamin, by all means explore the calculator. I've already done that work and came up with the ideal thicknesses per absorber type: 24" for fluffy, 12" for safe n sound, 6" for rigid - each with a 1x air gap. The reason 8" vs 12" safe n sound-equivalent shows little difference is due to a few things: your air gap is not 1:1 in both examples, you haven't selected random incidence (which you get when gapping a panel in a room), it's absorbing more from 20-40Hz which is a significant difference. For absorption coefficients, anything above 0.15 is significant and that just about meets that difference. The final reason, which doesn't apply here, is that beyond a certain thickness (per material, technically its gas flow resistivity), you end up with too great of a resistance and the panel becomes increasingly reflective. Essentially, you begin to put solid walls up. Here are the pre-eq response images of my room. I didn't take a sweep after EQ because I'm using Equalizer APO and I'm not sure whether the filters are going to affect the sweep and I didn't want to deal with it at the moment. Bass peaks are easily tamable with EQ and, subjectively, they're having their effect. The reason I boosted my subwoofer, which is causing that 20dB bass boost, is because I planned to EQ later and I wanted maximum level at the lowest frequency possible. In any case, impulse response envelope and decay are where the real battle happens so just imagine a semi-Harman bass-boost on the bottom instead of the gigantic bass peak. This is a non-smoothed response with both speakers and sub playing so, really, the SPL is very good. Impulse envelope should be around -10dB within 40ms ( Mellor) or -15dB within 20ms ( Winer), my decay target is -20dB above 63Hz within 150ms ( Spencer). Decay plot values are 140 and 160ms. For the heck of it, I'll post the predicted EQ curve too which is applied to an average of several measurements in about a 1' radius of my main listening position. The three nulls from 125-310Hz are probably from the desk. I will be adding 24"-thick fluffy soffits to the front and rear walls to tame the 60Hz resonance. Let me note that the speakers here are two Yamaha HS50 and the HS8s sub (the older one with a thru out). You can see from the EQ image that a few dB is shaved off at a higher frequency. This should be fine because the directivity of these speakers is pretty smooth which is what you look for when applying EQ to mains. Please see the Audio Science Review Spinorama-based review.     Attachments:
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Post by Hexspa on May 19, 2023 22:42:32 GMT
Here's a shot from the rear right. From the left, you can see four 6" rigid panels which absorb a mini hall wall that borders the kitchen. Past those, you can see the rear corner of a 31.5" fluffy super chunk. These are doubled up to make 24" soffits. Continuing around, I'm actually missing about 24" worth of recording zone right now but past that you can see the 15"-wide, 12"-thick safe-n-sound panels made from vinyl drywall bead. If I was to do it again, I might use metal since the vinyl is a little wobbly. Continuing clockwise, there's a super chunk in the front left corner of the room gapped about 2'. Behind that is my subwoofer. The front wall is totally untreated and the right wall is a mirror of the left sans the rear panels. Let's not forget the cloud which I significantly enlarged from my last space. Instead of one 2x4' 4" cloud and then two more of those above my recording zone, we've done the entire studio area with 6" rigid, about 64ft2. Seeing others' results, I noticed that often those with the biggest clouds got the best results and I can confirm it's very helpful. There are about 6" gaps between the rigid panels due to us needing to mount them on joists instead of drywall due to weight. This is true for the recording zone and the RFZ monitoring zone. Since my speakers are less than 1m distance, I haven't noticed any negative effect on stereo imaging and the measured response of each is not drastically different. To reiterate, the listening position is about 45% the width and not centered. Subjectively, and backed by measurements, the bass is nice and solid here. Actually, the response is a little better about 1 foot behind my MLP but I'll just use that as an excuse to stretch my legs  . I have a very thin carpet but that's mainly to damp my footsteps and other mechanical noise so my neighbors don't hear me as much. Probably doesn't really help but I like to pretend it does.  |
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Post by zejamin on May 29, 2023 7:40:23 GMT
Thanks for the idea rock, I'll keep thinking of ways to mount my panels when they're finished. Ideally I'll be spacing them 8" off the walls.
Also good point about the pro studio builds. I guess there really is no such thing as too much low frequency absorption.
Cool to see your room and progress Hexspa! Glad to see this stuff does make a real difference.
It's interesting that even a smaller desk can reintroduce nulls like those in your post-treatment graph, guess I'll have to swap out the big desk.
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Post by Hexspa on May 30, 2023 12:15:51 GMT
Thanks for the idea rock, I'll keep thinking of ways to mount my panels when they're finished. Ideally I'll be spacing them 8" off the walls. Also good point about the pro studio builds. I guess there really is no such thing as too much low frequency absorption. Cool to see your room and progress Hexspa! Glad to see this stuff does make a real difference. It's interesting that even a smaller desk can reintroduce nulls like those in your post-treatment graph, guess I'll have to swap out the big desk. Yes, I think it's a few things including the multi-tiered desk. It has the speaker riser that goes all the way across the front and doubles as a dual 19" rack so that's two levels plus I have a 27" monitor (though angled) and an 88-key midi controller between that and a QWERTY keyboard. Those nulls represent quarter wavelengths of under 2' so what else could it be? I'd love to remake this desk out of acoustically transparent material but, with all this other crap I don't know how much it would matter. I think in theory it should be fine to broadly boost the 2-300Hz range then raze off a few peaks, especially since my reference level is just 63dB but I'm going to change monitors at some point. If you look at the FR of these speakers, they're very boosted above 1kHz and that makes the lower midrange look scooped. I'm not trying to blame my gear but in this case it matters as far as I know; you mostly only want to EQ below the transition frequency and 300Hz is pushing it. Either way, if you look at the note-to-frequency values it's only like four notes that are sucked out (two per null) so I'm not that worried. But, yeah, nothing is ever perfect but we make the most of what we have. Sometimes that's resorting to headphones. EDIT: thinking about those lower midrange nulls, I may have left my stool next to the mic stand. My reasoning was probably "this is where it's going to be anyway" but once I wrap this room up, I'll have to remember to measure with and without. |
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. I have a very thin carpet but that's mainly to damp my footsteps and other mechanical noise so my neighbors don't hear me as much. Probably doesn't really help but I like to pretend it does.