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About almikel

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  1. I wasn't - so thanks for the info @Al.M I've typically used my Sound Level Meter in C mode because I'm measuring the output of my stereo and want to know what's going on inside my room including the bass end. that's extreme - what was the expected benefit of the 2nd layer? additional isolation or additional compliance? Compliance I get. Mike
  2. especially with the master bedroom above the audio room! That won't work, because at that stage of construction you'll have so many flanking paths you'll have no way of determining if the block/concrete is providing sufficient isolation. My opinion is certainly not the "very minimal or nothing at all" - rather where a rigid wall is planned that provides good isolation, providing flanking paths are dealt with, a more compliant inner skin can assist in reducing "in room" bass issues when additional isolation isn't needed - potentially reducing the bass trapping required afterwards. I think this is a great idea - with the expense of a house build at stake, worth a few day trips on cheap flights interstate if you can find accommodating SNA members with "properly structurally isolated rooms that have been appropriately treated for bass"... I get this - but I've never experienced it - the quietest my completely leaky room gets to is about 30dB SPL C rated on my SPL meter (Brisbane suburbia close enough to the freeway to hear it on a quiet night). I need to take my SPL meter over to my mate's place with the multi layers of Fyrecheck/Greenglue in his studio - it would be way quieter than mine. There have been numerous threads here on SNA where people have been trying to treat rooms with rigid walls (block/brick) with significant low bass issues - difficult to solve without truly massive traps. In those cases I think sometimes the best option would be to bite the bullet and re-do the room with channel/clips/fluffy/gyprock to get some compliance/loss back into the room. As long as you're planning an inner skin of Gyprock decoupled from any rigid walls with insulation behind, whether multi-layered with Green/Quiet Glue or not, it will still be way more compliant than naked brick/block, and hence won't have the same low bass issues as naked brick/block. As others have said, go back and read all the articles at https://www.soundproofingcompany.com/soundproofing101/ Make sure you manage flanking paths - and focus on isolation to the master bedroom upstairs...one day it might be the boss cranking it, and you're trying to nurse a hangover and hoping for a sleep in...or simply the boss cranking it at 2am and you can't keep up!...this happens sometimes at my place - I'm very thankful of our tolerant neighbours...Plod has never showed up - if we ever do a reno, better isolation will be included! Totally unrelated to audio, but make sure anything underground has appropriate moisture control. cheers Mike PS: you're welcome to come and listen to my "lightly constructed/leaky room with lots of absorption" any time. IMHO my room has bass "reasonably" under control - sufficient that the bass sounds "dry" and typically gets turned up not down on the remote. Audio memory is cr@p, so you'll never be able to properly compare - but listening to different rooms is worthwhile.
  3. Thanks Tanya, that's a great link! cheers Mike
  4. almikel

    Catman's Analog Musings

    Hi Felix, I doubt the sonic differences defy measurement - the nature of a phono stage requires application of EQ based on the RIAA standard. The RIAA EQ standard is well defined, but each phono will have it's own implementation. The ear is quite sensitive to changes in EQ (ie frequency response), and the lower the "Q", the more sensitive the ear is to the change - which is counter intuitive. If you've matched EQ across phono stages and can still hear a difference then OK - but simply swapping phonos will typically subtly change EQ, so I'm not surprised you always hear a difference when you swap phonos, but is easily measurable. EQ match your phonos and IMO you wouldn't be able to tell the difference assuming they had decent SNR. cheers Mike
  5. almikel

    Learning about hifi

    there's also another thread dedicated to "Helpful Audio Technical Documents" here: Hours of reading and useful doco cheers Mike
  6. agreed - I've built many besser block walls, and always filled them with concrete and reo. Mostly for strength... ...there's that old bricky saying, "mortar is only there to keep bricks apart, its doesn't help much to stick them together". When building the retaining wall around the pool in our last house, we changed the plan, and had to take a course of besser blocks off (prior to core filling). One or two hits with the hand was enough to remove a block - mortar has no strength. Un-cored besser block stays where it is mostly through gravity - I don't consider it structurally strong, and any besser blocks in my world are always core filled with concrete and reo. The OP was always planning to de-couple the besser from the internal room structure based on his previous posts. The OP was also planning a whole lot more isolation between the inner room and the besser block - IMHO not required as long as the inner skin is de-coupled from the besser (and the besser is filled with concrete, making it a rigid structure). cheers Mike
  7. What are you trying to achieve? Your existing Gyprock ceiling will be helping to absorb bass already. 50mm of white Polymax XHD mounted on the existing ceiling will absorb first reflection higher frequencies nicely if you can get away with it. I wouldn't cut the existing ceiling. Mike
  8. Definitely not - it does a great job of not transmitting sound, but achieves that by reflecting the sound - as @davewantsmoore said, the more rigid the walls, the more low bass issues you'll have to deal with later inside the room. IMO your block/concrete walls will have sufficient isolation, and on those walls you need to build in some compliance. This can be achieved with your existing plans of an inner wall decoupled from the outer wall and insulation - but you don't need additional isolation (on those walls), and ordinary Gyprock provides compliance (ie will flex and absorb bass energy) - better than Fyrecheck/Soundcheck/double layers with greenglue etc. Absolutely use multiple layers of Gyprock/Fyrecheck/Soundcheck with Green Glue between for any walls/ceiling requiring additional isolation (especially the ceiling with the master bedroom above!!!). I helped a friend build a studio space, and isolation was a key requirement. We used 2 layers of Fyrecheck on each side of offset studs with Green Glue between (4 layers of Fyrecheck) + insulation on internal walls, and offset studs and 2 layers of Fyrecheck with Green Glue and insulation then the external weatherboards on the exterior walls. Ceiling had resilient clips and 2 layers of some sort of Gyprock/Fyrecheck and Green Glue and insulation. The timber floor was the weak point, and we ended up with flanking noise through that path, so isolation is OK, but could have been better... ...the point of this story is twofold: flanking noise is a key factor in every design this room with so many layers of dense Fyrecheck ended up as a reverberation chamber - significant bass trapping was required afterwards to manage the reflected sound. Likely not as much as block/concrete walls would have - Fyrecheck/Greenglue/Fyrecheck still has way more compliance/flex than block and concrete (which basically has no compliance, so all bass is reflected) IMHO if you've managed isolation with the "outer" walls, you want the "inner" walls to be as lossy as possible - without creating "flanking paths". Getting the bass right afterwards in a room with rigid walls is a significant challenge and consumes precious space. "Building in" some compliance/flex with the interior walls (ie "lossy") that have concrete/block as the outer wall will assist a lot when you're trying to get the "in room bass" right with treatment afterwards. I agree with @Peter the Greek that good isolation is a good thing - but as mentioned above - good isolation and good "in room" sound tend to work against each other - especially in the bass end. There's no point in building a room with fabulous isolation, but is so reflective inside that you can't manage the "in room" bass. You'll never bother the neighbours, but you won't be able to crank it either, as the boomy bass will drive you nuts - all of the band practise rooms our band uses being a great example - rigid walls, good sound isolation and terrible "in room" sound. cheers Mike
  9. These are decent sized traps...you've probably told me already, but what is the construction of the room? With those sorts of issues <100Hz, I'm guessing multiple brick/block walls, slab floor - ie rigid boundaries? An option that requires room construction and $ would be to install furring channel and ordinary gyprock with fluffy behind over the rigid walls. That would make the room "lossier" - the gyprock operates as a large membrane trap - no need for multiple layers of gyprock and Greenglue as you're not chasing isolation (the brick does that), and you want the gyprock to flex. Unfortunately the modelling tools don't cater for 1D BAD patterns, but I would do the same thing (use a 1D BAD pattern) - you can use the Porous Absorber Calculator to model a simple regular slat pattern - see how it models with your joist depth etc - the ceiling is a big surface, so I would expect a good result. Good process and lots of measurements, documenting the measurements along the way, from multiple mike positions with and without treatment. Leave the mike in exactly the same place for a measurement before and after treatment is placed. Turn off extraneous noise sources (pool pumps, washing machines, air conditioners) Re-do a measurement if a plane flies over Have the volume high enough to produce a good signal to noise ratio post graphs here for input focus on the RT60, Decay, Waterfall and the Spectrogram tabs in REW - and the Impulse graphs to identify specific reflections that could be causing SBIR beg for forgiveness from the family for the endless "Woop Woops" It's laborious, but over time you'll learn how to interpret the measurements. cheers Mike
  10. your definition of "nearly the same" is different to mine...which is somewhat funny as I've said the same thing numerous times and Dave has pointed out my "nearly the same" wasn't so near agreed - it's a long time since I costed XHD - a quick googleweb search for fluffy shows $54 for a bag of 6 Greenstuff R2.5 1160mm x 580mm x 90mm batts For a "superchunk" style trap of fluffy that would be 5 bags (with some crush) for a 1160mm wide x 580mm deep - floor to ceiling trap (batts simply stacked flat floor to ceiling) - $270 per trap... ...more expensive than I expected... Assuming stacked in a corner (no straddling), the length mode will "see" 1160mm deep and 580mm wide and vice versa for the width mode (opposite if you change the orientation of the trap) - "similar" performance in each direction...and as expected with absorption, effectiveness dropping with frequency. ...difficult to compare with XHD straddling a corner, as the modelling tools don't cater for straddling, but let's just run with a 1200mm wide sheet of 100mm XHD straddling the corner with 600mm deep air gap to the corner and assume an "effective" air gap depth of 300mm (50% of the 600mm depth to the corner) Even if we say the "effective" depth of the air gap of the straddled XHD is 500mm we get Large fluffy traps seem to "out perform" denser materials for bass trapping using absorption. Unfortunately the effectiveness of absorption reduces at lower freq. Truly massive absorption is required to get to 100Hz - pressure traps and/or EQ is required <100Hz Mike
  11. Heating in winter sorted[emoji106]
  12. Are there any pressure traps you would recommend? I recall one of @svenr's posts where he had tamed a difficult room with limp mass covering the entire ceiling (using ordinary flooring vinyl) and fluffy behind/above. That's a big trap and I'm not surprised it worked...proper "bass" trapping always seems to come back to large traps regardless of type. Also interesting when using the modelling tools is that when modelling "thick" traps (say 300mm and thicker), fluffy insulation seems best when the same real estate is consumed. 300mm of fluffy vs 300mm Polymax XHD no air gap You only see benefit with the Polymax below 60Hz, with fluffy much better above that Gapping any absorption improves its low down performance, but keeping real estate the same, here's 400mm fluffy (no gap) and 300mm Polymax with 100mm air gap - fluffy is still a clear winner Fluffy is still a clear winner. You can easily consume hours mucking with the tools and different materials and air gaps... It was one of @svenr's posts and mucking with the modelling tools that made me re-think what treatment products I would use if starting from scratch and targeting bass in a dedicated room - lots of fluffy, measure, use EQ, measure, consider pressure traps <100Hz, measure...etc - but you need lots of fluffy. ...I don't regret buying my sheets of Acoustisorb3 - naked room vs 4 bags of Acoustisorb3 - instant "night and day" change to the "in room" sound... ...my room had 42 bags of fibreglass stacked around the room, and sounded great - which I sold to fund the Acoustisorb3. The room was naked for a time, and the room was horrible to listen to. After the Acoustisorb arrived I was planning to build some "proper" traps and had it stacked in the garage, leaving the stereo room "naked" of treatment. My wife suggested we drag the bags of Acoustisorb into the room as she couldn't listen to the naked room anymore... ...5 minutes later the room sounded good again after simply bringing lots of absorption into the room...it's not too different now, years later...no science applied. Fortunately lightly constructed rooms don't have low bass issues. A few bands of EQ <100Hz works wonders, and the Acoustisorb does the rest. cheers Mike
  13. be cautious with EQ - especially boost, but also cut - EQ can easily make the FR worse elsewhere. Apply treatment first, and only use broad EQ cut after. If EQ cut is applied to "minimum phase" room issues it will fix both the FR and the associated resonant decay tail - after applying EQ, if the FR was fixed, but the decay tails weren't, I'd remove that band of EQ. Yes it does - which works with EQ when the resonance is "minimum phase" - you want to reduce the energy the sub is producing in this region. Then stop worrying so much about a flat LFE response - back off your EQ cut! Sure continue with treatment design for a flat FR in the low end - this will always lead to a better "in room" bass response, but dialing back your EQ cut will immediately bring back some bass - who cares if the FR is a bit lumpy if it sounds better? I've dialed in EQ cut in my (leaky) room for issues <100Hz and added a room curve to boost lower frequencies for taste...but I also have EQ shelving filter control on my remote, and I dial the bass and treble up and down as needed depending on the track and my mood...being a bass nut in a room where the bass is reasonably under control (helped by a leaky room), the bass gets dialed up on the remote often. cheers Mike
  14. All traps (pressure and velocity/absorption) work by absorbing acoustic energy, and in their band of operation, don't discriminate between "excess" energy (say from a resonance) and any other energy/sound wave hitting the trap. The reason they work on resonances is because the resonance is bouncing around the room and keeps (hopefully) hitting and going through the trap, absorbing the "excess" energy and damping the resonance. The frequencies that aren't resonating are not bouncing around the room as much, so don't pass through the traps as many times - but energy is still absorbed within the trap's band of operation. The only difference between pressure and velocity/absorption traps is their band of operation, pressure traps being narrowband and velocity being broadband down to their cutoff frequency - think of velocity traps as a low pass filter, and pressure traps as a notch filter traps don't know whether there's a problem or not, they just absorb energy in their band of operation - the poor design of using thin foam (absorption) in many band practise rooms I've been in being a perfect example. Rigid walls reflecting all the bass and chopped out treble absorbed by the foam. cheers Mike
  15. By all means have a crack, but I've never seen any design tools for variable depth pressure traps (ie straddling a corner) and to work best, pressure traps need to be on the boundary in the high pressure zone, the opposite of absorption traps which work better when gapped. An idea I've had for ages, but never built, is a corner trap incorporating 2 pressure traps + absorption, placing each element where it works best. Diagram below My plan was to use Limp Mass for the pressure traps, but Helmholtz would also work. For limp mass I'd keep the fluffy off the limp mass membrane (inside the pressure traps and in the void. Why do you want to affect decay and not SPL? You have a peak at 100Hz with a long decay tail, which is typical of room resonant behaviour - the peak and the decay tail are related, and get fixed at the same time with (appropriate) treatment. Mike