Hi Eric, when I saw your sheet metal mode test, I recalled my research work some years ago. I did some research in the field of automotive acoustic at BMW on a sandwich material. I was working on a sandwich (a daming layer between 2 1mm sheet-metal plates). Compared to a plain sheet metal (1m x 1m) a structure with a damping layer attached reduces (in tests and calculations) the ERP (effective radiated power) @100Hz around 8db, the sandwich can do around 20db. This sandwich can be found in various BMW models. I think automotive acoustic is very similar to room acoustic. Many sources cause the car body vibrating. You want the inside quiet and with a homogeneous frequency response. There’re 3 effects which are used to control NVH: a) stiffness, b) damping, c) absorption. If you look at a car floor panel or firewall they all have ridges to increase stiffness. Then there’s a damping layer (Anti-drone coating) and the floor carpet works as a spring-mass-system plus absorption. The first eigenmode of a spring-mass-system is in general SQRT(stiffness/mass). And of course stiffness and mass are both functions of the length, width and thickness of the sheet-metal plate. With FEM you can easily calculate the eigenmodes. A single sheet-metal has a lot of different local modes, that’s why the “damping effect” works over a wide frequency range. I think it would be worth to do a test with some damping layer (Anti-drone coating) on the sheet-metal plates. You don’t need to cover the whole plate. Dial in a frequency and check where plate is resonating most than there attach the Anti-drone. This should help the sheet-metal "to eat" the vibration energy feed into. - ROCK-ON!
What a cliffhanger! Thanks for taking us all along on this journey. I've built my own studio and feel your pain through this entire video. Adjust, measure, adjust, measure. So much great info, thanks again!
I understand that open-celled foam is spec'd, but do you know if anyone has tested these with standard fiberglass insulation? Considering that bass passes right through 4"-6" of fiberglass with very little attenuation, how much air flow does the foam actually need? I'm sure open-cell was chosen for a reason; I'm just wondering how much less effective fiberglass may be and if it has any potential as an alternative to the open-celled foams.
Hey Eric! This series has been so fun to follow along with! We went through a similar process last summer with our demo/research room, and it is wonderful to see more people breaking down acoustics in a helpful and informative way! Thanks so much for sharing your knowledge and experience. We can't wait to see the next video!
Thanks so much Eric!! It is incredible how much value these videos are. You are and will truly make studio acoustic design work much much better for the work by doing this. Also, it is a cliff hanger. But we know, you’re gonna build the almighty tube traps to fix the low end! I’m pumped for that though haha
I can relate to the remark about embarking on some esoteric audio project and needing to explain what you're doing to random, blue collar folk working at some supplier. When I built my EMT140 plate reverb clone, I found a motorsports company who made race car bodies that could get me cold rolled sheet steel in the same dimensions and type that EMT used. They came through, but were totally flumoxed when they found out what I was doing.
Thank you for demystifying this crazy science Eric. So helpful, and I'm glad you binned the first video to make a super clear demo of your process with these panels.
Fantastic breakdown Eric! Thank you for being so thorough, especially measuring with and without the metal and the spacing! If you haven't done your second room yet I'd be curious to see how it the VPR performs with rockwool or some other standard porous absorber material.
Been waiting for this episode, in the proces of treating my room (Helmholtz and all) Really invaluable information for anyone who will be doing acoustic room treatment. Thanks so much Eric!!
Wow, that was some high quality content right there! Can’t wait to follow your journey working on your other room, with the cheaper material foam! Tonmeister from Copenhagen 🤠
Wow! Good on you, yuh nerd. ;) Chasing low end in a room is a super time consuming job, I've been there and continue to be there. Excited to see the tube trap adventure. Thanks for sharing this thorough journey into studio acoustics.
Eric: another great video, and really intriguing how these panels are working. And maybe you have some metal panels spare to make your own Plate Reverbs 🙂
Amazing video! Absolutely fascinating and so helpful. Thank you for bringing us along on this journey. I would be super curious to see a couple of measurements in the time domain (waterfall plot) in REW as well. Frequency response is great but sometimes doesn't tell the full story. The waterfall plot really shows the best of both worlds where you can see the frequency response and also see how long each frequency band is ringing for which can also really affect the punchiness of the bottom end. Thanks so much again Eric!!
I've always wondered how you built your tube traps as well? What material, where you ordered, how you made top/bottom caps, fully assembled them, and if you ever tested their impact on the room measurements. Thank you for the excellent videos!
Fascinating insight, Eric. Love it. Agree with you about there can be phase anomalies in the room but in your listening position it can flatten out. Thats how it feels in my room. How it sounds in the sweet spot translates into the real world well, bare in mind with a little bass bump. Also liking Grace's new single "Mother Road". That's how you deliver a vocal take. Would be good to hear a whole album of that style. Thought it might be you on Drums too. 🎶🎨
Great video Eric. Have you tried carbon pellet asorbers? Using carbon fishtank oxygenation pellets. They have a huge surface area because of all the pin holes for the bass to navigate and get lost in. Works great.
I stopped by the Strauss booth at NAMM last month and saw those whoppers you have at your place. They're even bigger than I imagined. Hard to tell how they sounded in that environment but they looked impressive, as did the smaller NF-3's.
That speaker wall interaction is SBIR. my understanding is that the primary/most effective way to eliminate this is to flush mount the speakers, or to move them either right next to the wall which would move the SBIR frequency down below the speaker’s frequency response, or to move them well away from the wall which would bring the frequency up to an easily treatable point. In my control room, I have the speakers right against the treatment on the front wall to reduce this down to a reasonable frequency. If you mess with your speaker distance you will see this change dramatically.
@@bulletproofzest as close as possible (hopefully) moves it up to where the speaker is more directional (and/or easier to absorb)...moving it away works if you can get it below sub crossover point...1/4 wavelenghts
@@simccaffrey thanks yeah I realized I may have them backwards. it’s been about two years since I’ve been knee deep in my control room build. Managed to get +/- 5 db all the way throughout which is pretty amazing in a control room as small as mine, and fine tuned the rest of the way with room correction software. I had a consultant design my room and since completion I’ve been busy enough with studio work that I haven’t had time to finish the final trimwork details 😂. But paying a consultant for the design was gold. Room was great from the first time I fired up my speakers and cut my mix time in half. Side note, I actually did some fixtures very similar to Eric’s with galvanized steel, and while they were easily the most difficult fixtures of the build, at least at first, the construction was much easier than it looks like Eric’s are. Mine are mdf boxes which go the full length from floor to ceiling, these are sealed air tight with caulk, then inside the box I cut furring strips which serve as a frame for the insulation and set the gap between the membrane and the insulation. Over the top of this is REALLY tight fabric which prevents the insulation from touching the membrane, then the membrane is fixed to the panel using roofing rubber gaskets which maintain the air tightness of the fixture and allow the membrane free movement. A thin frame over the top of this sets the gap between the front of the membrane and the fixture in front of it. Mine are tuned to the third harmonic of the lowest frequency my room can accurately support. There is also about 24” of broadband trapping with a combination of free faced insulation and limp bag insulation in front of these fixtures. Worked a treat.
Very interesting endeavor Eric. Have you considered using "active" bass traps, like the PSI Audio AVAA C20 or C124? Another approach would be multiple subs adjusted to create a more spatially even sound field. I work in acoustics, and I have my doubts that you'll ever reduce modes sufficiently with only passive absorbers, unfortunately.
I love this video and Eric so much, but I think there are some things he may have missed (or I missed them)! I see a lot of laser focus on that ~120Hz null on the FR graph, which seems to be how he is basing the efficacy of his VPR panels that are supposed to be tuned to 60Hz. What I don't see, however, is little to any positive effect happening on the RT20 graph at 60Hz(at least until he makes the foam touch the sheet metal)! I'm no expert like Eric is consulting, but it seems that while all of these panels are indeed resonating at 60Hz, their resonance is not being impeded in any way because they are not sealed enclosures (the energy can always escape through the sides rather than being attenuated by the gas flow resistivity of the foam panels). Thus he is only creating a more complex resonance at 60Hz in his room, which may be giving him the sporadic benefits an octave higher where Eric is looking based on where he places the RTA mic in the room. He built a room with three pairs of parallel surfaces and is leaving many "holes" in the treatment that will allow for sound energy to do bounce uninhibited against said untreated parallel walls. I too like to voice my mixing spaces with more low end, but an RT60 that is essentially 1.5s long at 60Hz is going to really hurt his reliance on his monitoring and perception of his mixes, regardless if he fixed the FR graph. Nothing but love and respect here for the brilliant engineering mind of Eric! I'm excited to see what solution he came up with in the next vid!
For the diyers on a budget here, you can get 3x4 sheets of galvanized) steel (which is what it looked like you have) at Home Depot for about $25 to $30 at 26gauge and 30gauge, drill some holes in em, and build your panels.
Great info! These sheets work sort of like a drumskin right, thicker is a higher pitch, and higher tension as well. Reminds me of plate reverb tuning as well. Tip: in the youtube studio editor you can edit your video, I suggest editing out from 1 hour 23 minutes to the end ;-)
Been anxious for this video man. Thanks! I wonder how much the plates will move after each begin to resonate over time. You may reference this in the video (I'm 1/3rd through haha).
Thank you Eric for this series you are putting together. It's Informative and entertaining! I love it! Here is one question that came to mind. Was a soffit mounted speaker setup ever an option for you, since one of the main cancellations that might occur are due to reflections on the wall behind the speaker? And why didn’t you go this path? Thank you!! :)
Hey Eric! Hopefully you see this. For your next WTF, I’d like to hear more about prepping for hard hitting drummers (Grohl, TBS, etc). I have a heavy hitter and on a bell brass snare. I love his playing and I love the single ply head sound and all of its overtones. I’m curious how you prep for heads denting, lug locking, hardware moving, sticks breaking etc etc. currently I just stock up and try to monitor tuning as best I can. Thanks so much.
You may be able to 3D print washers to an accurate spec to match your requirements. I’d be concerned about spray glues for attaching panels, they always let go over time.
The melamine foam was used originally because of the way people glue the metal to it. If you're building these without it touching then there's no reason you need to use that specific foam. No reason any other material with a similar GFR wouldn't have a similar effect.
I'm glad to hear that the screwdriver fits in the headphone jack. I had been wondering about if for a while, myself. Thanks for all the info, Eric. Really appreciate it. Means the world. Have you seen or tried the active bass traps from PSI audio? The are kinda like a reverse subwoofer and affect the impedance of the air around them. Just wondering your thoughts on this.
This is really interesting. I am wondering if you had any issues with the sheet metal ringing. In essence, it looks like you are creating a sort of plate reverb. I will be really interested in seeing a waterfall graph measurement that shows decay times for these lower frequencies. Again, thank you for taking such a deep dive and explaining these concepts so well. Brett
Have you compared the Renz's panel to your DIY panel? I wonder if the panel can vibrate freely even though there are studs inserted through them. I thought that the metal plate should not be restricted in any way, hence the option chosen by Renz of just using glue.
Can you say R A B B I T H O L E? I basically moved my monitors around and varied the angle and width. I placed 24"x48" - 6.5" bass traps in the corners behind and also experimented with my subs placement. My 120hz dip flattened out tremendously. Also my console contributed a lot to the FBR nulls... Experimenting with placement helped me more than anything.
Would it not be easier to house the foam and the sheet in a frame? The metal could hang from the frame and you could have wooden rails to stop the foam moving?
Watched this episode again after my personal hype died down. Looking forward to the next video. To play the devil's advocate, when you look at the original introduction of one VPR panel versus covering the room with them, is there really much difference on the graphs? It looks fairly similar to me. I really want to try this VPR approach but now you have spent some time with it, do you think it's actually worth it? It seems to be very specific about certain frequencies and not remotely like an open window according to graph. Ie nothing like what you see with broadband absorption which is very smooth until it reaches a low point where it stops absorbing.
Hi Eric, did you measure the room like this: all cloud absorbers installed but without the metal plates VS: all cloud absorbers installed with the metal plates in place as should be? That would be sooo interesting!!! Greetings from germany! ;-)
Thank you very much once again for sharing such details. I would love to know how these panels/approach affects the time domain apart from the frequency response. If you could share such measurements, it would be amazing.
Panel test at 25:00. Will it do anything in the room, meaning he has it LOUD with the woofer 3" from the panel. Certainly at 85 db in a room nothing will vibrate at 70 hz?
Such an insightful episode! Overall, puzzled by why when you had freeform construction you went with a rectangular room and then tried to fix everything from there? Why not use that opportunity to construct walls out of parallel, vary the ceiling a bit? Seems like that would have been a pretty easy lift with the overall project.
Amazing!!! What type of steel? Cold rolled? Stainless? Also wonder if polyester insulation like poly Max would work instead of foam. Harder to work with but for a sandwiched together version without the gap it could be the go.
Really valuable tests Eric! Question: Have you ever considered soffit mounted speakers? If so why did you chose to free-standing? I think it would have saved you a bunch of trouble with that SBIR trough at 120 Hz
Hey Eric can you make some impulse response with the studio you have kinda like Celestion digital has there own impulse response and also there now new dsr I think it would be cool because you’ve worked with slash that would be cool to have like a slash impulse response or better a dynamic speaker response we could buy from you would you ever consider doing it ??
So much interesting information. Are the VPR panels' back foam touching the wall or do you leave a gap? What would happen if you leave larger gaps to the wall? As the general principle (?) with ceiling absorbers.
Potentially a detail no one cares about BUT, looking at the screw test but, did you drywall the studio THEN put plywood on top? I’ve always heard the convention is to do it the other way.
You mention testing smaller sheets, but didn't mention the dimensions of them. Did this testing go any further than what you showed? It seems like you stuck with the 48"x36" -- was that because you had already ordered and done most of the testing on these, or were the smaller sheets significantly less effective?
2:19:30 But Eric, you must realise that melamine foam and rockwool/miner wool aren't equivalent? At 4 inches, foam is already declining in absorptive power from 10khz, 4" of mineral wool will only start declining around 400hz.
Just a quick question on the foam, what is the fire rating? Being in the building trades and having a home studio and also having built a couple rooms out myself. I have always gone with rock wool with guilfords of Maine fabric because while it has its limits for absorbing frequencies it’s amazingly fire proof. Our fire codes in Massachusetts are pretty strict. Thanks for sharing Eric :)
