almikel Posted October 11, 2020 Share Posted October 11, 2020 11 hours ago, Stevan.B said: In terms of BAD panels, is there any advantage of using differing width slats to single width with random sequencing? easier with differing widths if you can get even multiples of your chosen base width. Otherwise I’d run a bead of sealant or contact adhesive where your BAD pattern says multiple slats together so they don’t rattle if you chose your base width as say 50mm, you could still easily end up with a sequence of 4 x 1’s In a row - so 200mm wide slat in that spot mike 11 hours ago, Stevan.B said: Link to comment Share on other sites More sharing options...
almikel Posted October 12, 2020 Share Posted October 12, 2020 (edited) 22 hours ago, Stevan.B said: FYI my room is not lightly constructed I think? It’s timber frame with sound check gypcock and sound screen insulation. I regard: double brick as "rigid" construction - or cored besser block etc - "in room" bass is a nightmare to manage...often the best approach is to build out with furring channel/whisper clips/insulation/gyprock to add bass absorbing "compliance to the room brick veneer with gyprock inner and batts in the walls as "in between" lightweight and rigid...the brick veneer outer wall is rigid, but the gyprock and insulation helps a lot to absorb lower frequencies external walls timber/blueboard, and gyprock internal walls with insulation between as "lightweight" - all the low bass leaks out - great for the "in room" bass, but not great for neighbours and other house occupants cheers Mike Edited October 12, 2020 by almikel Link to comment Share on other sites More sharing options...
almikel Posted October 12, 2020 Share Posted October 12, 2020 (edited) On 11/10/2020 at 8:45 PM, Stevan.B said: In terms of BAD panels, is there any advantage of using differing width slats to single width with random sequencing? apologies if this is sucking eggs... ...work out the width of the diffuser - say you want to cover that absorption panel on your back wall, and let's say it's 1200mm wide... Choose a "base width/standard width" of your slats/gaps - I've never been able to find good info on what the "best" width for the slats is...you don't get significant diffusion from 1D BAD slats - but my "thinking" is if the standard width is too narrow, bass will just go around it...but we're not trying to diffuse low frequencies with BAD panels, just reflect higher frequencies back into the room, so it likely doesn't matter much...widths of say 25mm/50mm/75mm/100mm would all work...maybe 100mm would work a bit lower, but you may have to sit further away...always compromises... ...look at what the standard widths of slats are... Let's say you choose 50mm wide slats as your base/standard width - across a 1200mm wide absorption panel that's 24 positions of slats or gaps in a 1D BAD pattern - not very wide - you could easily use the "coin toss" method to generate your random sequence...heads = a "1" or a slat, and tails = "0" or a gap... ...for a small panel I love the idea of doing your own "coin toss" method - which is truly random - rather than downloading an MLS pseudo random sequence from the interweb - your choice... ...with the coin toss method, I'd still likely do say 100 coin tosses, and choose any 24 wide run within the 100, just in case you tossed 10 heads or tails in a row somewhere in there So you now have a string of random 1s and 0s, 24 digits long eg "110100111010111100101101" Every 1 is a slat of your base/standard width, every 0 is a gap of your base/standard width. For multiples of 1s - you either adjoin multiple slats, and I would recommend using a bead of sealant/contact adhesive between them so they don't rattle, or use wider slats for multiples - in the example above using 50mm wide as your base slat, you need 50mm (a single 1), 100mm (2 x 1s in a row), 150mm (3 x 1s in a row) and 200mm (4 x 1s in a row) wide slats...but just join them as you need them. 0's are just gaps of base/standard width - 4 x 0's in a row is just a 200mm gap... I hope all that makes sense...PM me if I've confused you further cheers Mike Edited October 12, 2020 by almikel Link to comment Share on other sites More sharing options...
Stevan.B Posted October 12, 2020 Author Share Posted October 12, 2020 1 hour ago, almikel said: apologies if this is sucking eggs... ...work out the width of the diffuser - say you want to cover that absorption panel on your back wall, and let's say it's 1200mm wide... Mike Thats perfect actually, the rear absorber panel is 1800 wide, a 50mm slat would give us 38 positions. definitely easy enough to use a coin toss and see what comes up. i have access to table saws so ripping timber doesn't worry me, probably more piece of mind so they don't rattle Would you recommend removing the first reflection point absorbers or trying a BAD on them also? FYI i have 6 x 600x600 QRD's going on the ceiling mid ceiling between the MLP and speakers also, just working out the best way to hang it. Theres more than 2m between that spot and the listening position so should satisfy the 3x low wavelength rule (its 630hz on these panels ~60cm = 180cm at 3x). Link to comment Share on other sites More sharing options...
almikel Posted October 14, 2020 Share Posted October 14, 2020 On 12/10/2020 at 10:03 PM, Stevan.B said: Would you recommend removing the first reflection point absorbers or trying a BAD on them also? I'd remove them...but I have speakers with a smooth "off axis" FR...so lateral 1st reflections are similar to the direct sound in my room. Easy to take them away and see what it sounds like...if your speakers are ragged "off axis" you could try more toe in, or add BAD slats in front of absorption at lateral 1st reflection points... On 12/10/2020 at 10:03 PM, Stevan.B said: FYI i have 6 x 600x600 QRD's going on the ceiling mid ceiling between the MLP and speakers also, just working out the best way to hang it. Theres more than 2m between that spot and the listening position so should satisfy the 3x low wavelength rule (its 630hz on these panels ~60cm = 180cm at 3x). You'll have an amazing room - very jealous Mike Link to comment Share on other sites More sharing options...
elmura Posted November 4, 2020 Share Posted November 4, 2020 (edited) My thinking would be to toe in the front speakers to point directly at your ears so you get more "air", and higher direct: reflected sound ratio. And if that's not enough, instead of slats on top of your sidewall absorbers, maybe a vinyl fabric like what's used for roller blinds. What do you think Mike? Edited November 4, 2020 by elmura Link to comment Share on other sites More sharing options...
almikel Posted November 6, 2020 Share Posted November 6, 2020 On 05/11/2020 at 8:16 AM, elmura said: My thinking would be to toe in the front speakers to point directly at your ears so you get more "air", and higher direct: reflected sound ratio. For speakers that have a poor "off axis" response I would recommend "toe in" such that the tweeters point directly at the listening position to get the smoothest response from the direct sound at the listening position. On 05/11/2020 at 8:16 AM, elmura said: And if that's not enough, instead of slats on top of your sidewall absorbers, maybe a vinyl fabric like what's used for roller blinds. What do you think Mike? I wouldn't recommend this. Vinyl over absorption can work to absorb problem "in room" bass frequencies with appropriately designed limp mass pressure traps - but limp mass pressure traps are not best deployed at lateral 1st reflection points - slats in a 1D BAD pattern (or 2D) over absorption at lateral 1st reflection points would be better. cheers Mike Link to comment Share on other sites More sharing options...
almikel Posted November 6, 2020 Share Posted November 6, 2020 On 05/11/2020 at 8:16 AM, elmura said: instead of slats on top of your sidewall absorbers, maybe a vinyl fabric I have a great interest in "limp mass" bass traps - if I was building dedicated bass traps for my room, "limp mass" traps is likely where I would start...but I've never built them... ...I have a very leaky room, where all the low bass leaks out, so I don't have low bass "room issues" that can't be managed by EQ... ...some points to note: "velocity" traps (eg absorption) operate "broadband", ie depending on depth/size will have reducing absorption at lower frequencies, but absorb all frequencies above "pressure" traps (eg helmholtz/membrane/limp mass/VPR) are all "narrow band" - and will have a specific band of frequencies that they soak up, and need to be "designed" to soak up the "problem" frequencies in the room (by "design" I mean calculated size/depth/area/position of the pressure traps) The standard lightweight construction of houses these days with Gyprock walls on studs is great for the "in room" sound, but not so great for other house occupants and neighbours The Gyprock walls operate as a "membrane trap", absorbing some bass, but lets the rest through...great for the "in room bass"...less "in room bass" bouncing around the room to manage, but less great for the household/neighbours that hear the bass that leaks out Good sound proofing/isolation will typically work against good "in room sound" Mike 1 Link to comment Share on other sites More sharing options...
elmura Posted November 7, 2020 Share Posted November 7, 2020 13 hours ago, almikel said: limp mass pressure traps are not best deployed at lateral 1st reflection points Maybe I wasn't clear. I wasn't referring to using the vinyl over the side wall absorbers for bass, but to help liven up his sound as he was complaining that the 1st reflection absorbers were killing the life of the sound. The vinyl will reflect higher frequencies whilst permitting bass & mid when placed over the absorbers. Link to comment Share on other sites More sharing options...
elmura Posted November 7, 2020 Share Posted November 7, 2020 I have a very sound proofed dedicated room with the bass problems you mentioned. Concrete slab, concrete core walls with polystyrene insulation (EPS block walls, glued plasterboard over (5-7mm cavity). The only escape for bass is through the door (which is hollow core), the single window at one end, and through the roof (timber truss, R4 fibreglass insulation, sarking, concrete tiles). I have problematic bass plus slap echo I need to treat. I've only used a SPL meter and test tones which is VERY tedious and old school (I've been doing audio for 18 years). I need to get a USB mic and learn REW to speed up the process and be more accurate. I will likely use a Helmholtz tuned resonator plus some strategically placed bass traps. My centre speaker (full sized, identical to mains) creates a lot of resonance down low (hollow sound). Not sure how to handle that coz I've placed the speaker close to the wall and all the power and cabling is there so can't easily place much treatment. Link to comment Share on other sites More sharing options...
almikel Posted November 8, 2020 Share Posted November 8, 2020 On 07/11/2020 at 10:30 AM, elmura said: Maybe I wasn't clear. I wasn't referring to using the vinyl over the side wall absorbers for bass, but to help liven up his sound as he was complaining that the 1st reflection absorbers were killing the life of the sound. The vinyl will reflect higher frequencies whilst permitting bass & mid when placed over the absorbers. fair enough, and easier than slats - but the vinyl may reflect all the frequencies the panel was absorbing - negating the effect of the panel. Slats in a 1D BAD pattern over the absorption would keep treble in the room and would provide some diffusion. On 07/11/2020 at 10:51 AM, elmura said: I have a very sound proofed dedicated room with the bass problems you mentioned. Concrete slab, concrete core walls with polystyrene insulation (EPS block walls, glued plasterboard over (5-7mm cavity). tricky room On 07/11/2020 at 10:51 AM, elmura said: The only escape for bass is through the.... roof (timber truss, R4 fibreglass insulation, sarking, concrete tiles). a bit painful to do (I dislike climbing in roof spaces more than working under the dashes of cars), but it would be interesting for you to try more fluffy insulation in the roof cavity - it would assist room bass issues if the concrete tiles are reflecting bass back into the room (the tiles may be letting a lot of bass out). A member here on SNA that I have great respect for ( @svenr), who unfortunately I haven't seen post in a long time, had some great results in very difficult rooms (essentially concrete bunkers) cheaply using cheap flooring vinyl across the entire ceiling with fluffy insulation above - a very large limp mass pressure trap...taming the room bass completely. I'm not suggesting you do this...but it's an example that managing low bass in difficult/rigid rooms requires large and specialist traps. On 07/11/2020 at 10:51 AM, elmura said: I need to get a USB mic and learn REW to speed up the process and be more accurate. agreed - and as I'm sure you already understand, it's the interpretation of your REW measurements that's the key part of the REW learning curve... ...taking measurements is the easy part - the much harder part is interpreting the results and implementing treatment that has the expected effect on subsequent measurements... On 07/11/2020 at 10:51 AM, elmura said: My centre speaker (full sized, identical to mains) creates a lot of resonance down low (hollow sound). Not sure how to handle that coz I've placed the speaker close to the wall and all the power and cabling is there so can't easily place much treatment. Rigid rooms and low bass resonances are tricky to manage - have you tried EQ cut on the resonances? With REW you'll be able to identify the room resonance peaks, and REW can also identify if the peaks are "minimum phase". If the room peaks are "minimum phase" then EQ cut will assist greatly in fixing the amplitude and the time domain response of those peaks. On 07/11/2020 at 10:51 AM, elmura said: I will likely use a Helmholtz tuned resonator very keen to see your results and/or happy to participate in your design/testing process. I would suggest: go big - really big if the room bass issues you're targeting are <100Hz. A small Helmholtz resonator tuned to suck out say 80Hz won't change the room response much if it can't suck out enough of the 80Hz resonance as with all pressure traps (excluding perhaps VPR traps), they're narrow band devices, so you may need multiple Helmholtz devices if you have more than 1 problem bass issue in your room prototype/measure/tweak - almost guaranteed your 1st prototype Helmholtz trap won't measure/have the room effect you expected. Build them with tuning in mind There are 2 types of Helmholtz resonators I've seen around the interweb: panel type with lots of holes in the front panel - where the combined volume of the holes in the front panel interact with the volume in the sealed cavity behind like this: tuned volume type - which work the same to a vented/bass reflex speaker, just opposite - soaking up bass in the room at the resonant frequency The principles/science is identical across either type Only IMHO, type 2 would be easier to prototype, at least in the opening area/length of the neck, unless you can prototype new front panels for type 1 quickly (hole volume/depth). Effort for prototyping the rear cavity volume and damping applied within the cavity would be the same across either. Which type are you planning to try? The science behind Helmholtz resonators is very solid - every bass reflex/ported speaker, every 2 stroke motor exhaust, every tuned length intake manifold works on the same principle. Getting Helmholtz resonators to work to soak up bass resonances in your room can absolutely work, but will require plenty of prototyping/measurements/tweaking...and similar to the prototyping/measurements/tweaking required of any specialist bass treatment...size is the key for any bass treatment - go huge from the start...much easier to see/hear a difference from measurements...then go bigger to get the changes/effect you want through further testing/measurements...if you went huge enough at the start well done!!! @elmura - best wishes for your journey - as I mentioned above, I'm happy to contribute where I can add value. cheers Mike 1 Link to comment Share on other sites More sharing options...
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