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almikel

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About almikel

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  1. Agreed - and it's reduced the nulls above 100Hz also...as expected. ...trying to compare the waterfalls, people much smarter than I can do the overlay thing and even animate it - I only managed to scroll up and down many times to compare - looks like a great result, and remarkable for 2 bags of insulation in a corner. I'm not saying it's wrong, but IME I've never seen such a big change in a room by adding 2 bags of insulation in a corner... ...and I suspect after @acg did the measurements he was thinking, "can 2 bags of insulation really make that much difference?"...and ..."geez, maybe I don't need to bother with VPRs anymore?"... I'm sure @acg will do loads more tests/measurements to come up with a room treatment plan, which I'm hoping includes some VPR traps. My room treatment journey started with unopened bags of insulation stacked around the room. The "Midnight Foil" debacle coincided with us moving into a house with "Midnight Foil" installed and subsequently removed under the safety program, and the market for insulation plummeting. I joined SNA around the same time and learned the concept of "room treatment" and "bass trapping". We needed new insulation after the "Midnight Foil" was removed and I had an epiphany after finding cheap bags of fluffy fibreglass for $10 a bag on Ebay - get extra to treat the stereo room! I bought 50 bags - 10 for the ceiling and 40 for the room... ...OMFG what a difference those stacked up bags made to the room sound! The bass was so tight, I was completely addicted to room treatment! Fast forward several years and the outside yellow plastic binding on the bags was letting go - the bags still had a plastic inner bag containing the fiberglass batts, but the bags would explode out of the tubular wrapping which degraded under UV. I'd come into the stereo room and find more bags had "exploded"... ...I'd also made some room measurements by then, and all those bags of insulation didn't do much under 120Hz. Around that time I was doing a speaker upgrade, and decided to swap out the fibreglass for Poly sheets. I managed to sell the exploding bags of fibreglass to fund 4 bags of Acoustisorb 3, which I figured I could get home without realising how big they were... I had a cop pass me in the tunnel home - but he just cruised by... The best part of this story is that the room was naked of treatment after I'd sold the fibreglass, and the poly was stacked in the garage waiting for me to make "proper" traps... ...the wife cranked up the stereo in the "naked" room and said, "this won't do", so we dragged the bags of poly into the room - instant change to good "in room" bass. The room remains pretty similar to this The blue box on the left is the tapped horn sub that never got mounted outside the room. Based on my measurements, the poly treatment is not doing much under 100Hz, but with a few bands of EQ cut <100Hz plus a leaky room, the bass is amazing - the Acoustic Elegance TD18s are simply fantastic - so much mid-bass slam you can't help dialing up the bass on the remote...and with the PSE144's the room isn't "too dead" with so much absorption (IMHO) Mike
  2. You've got it right that's why absorption gets too big to work effectively below 125-150Hz. They're big at 150Hz and truly massive at 100Hz. I would never try to significantly impact an 80Hz issue with absorption - other more effective options are available like moving speakers/subs/LP, adding another sub, EQ etc Earthwool is fluffy insulation, so will work fine if you're happy with fiberglass - but forget it for issues < 125-150Hz, and you'll need big traps for it to be effective 125-150Hz. IME big/deep absorption traps clean up room sound very well 150Hz and above - but too much absorption can kill the treble in the room. Corner placement of absorption assists in not killing treble (treble gets to bounce around a few times before running into a corner), but to absorb bass, the corner traps need to be large, and have material positioned where velocity is high (ie gapped). IMHO anyone trying to treat a room should target the bass end first, and read Paul Spencer's Bass Integration Guide, part 1 here https://www.hifizine.com/2011/06/bass-integration-guide-part-1/ In my leaky room with lots of absorption (12 sheets of 2400x1200x75mm Acoustisorb3), the bass is "reasonably" controlled with a few bands of EQ cut <125Hz. The Acoustisorb isn't doing much under 125Hz even with 3 sheets thick and gapped. With my horns for the top end (PSE144), I don't find my room too dead, and the bass in my room is very good. Mike
  3. Interesting question... I'd never use expensive XHD on a boundary - I would always gap it (and place it where velocity was as close to maximum as possible = wavelength/4). I'd be happy using fluffy on the boundary as it's cheap, and know it's working anywhere velocity is >0 with an understanding that to work low it needs to be large/deep and way off a boundary (ie fluffy from front edge of trap back to boundary) - the same rule applies - it's most effective where velocity is highest = wavelength/4 . The term "superchunk" typically implies a corner placed absorption trap "straddling" the corner completely filling the triangular gap behind. I can't see any benefit in using expensive products like XHD to fill the triangular gap behind the straddling trap as the velocity is too low...but I'd think about filling it with fluffy, because it's cheap and the velocity >0... If you can afford to lose the space of big superchunks like 1200mm wide straddling corners floor to ceiling - I'd go fluffy - cheapest fluffy you can find. It will work wonders to clean up down to around 125Hz or so (and make a big difference to the "in room" sound) Absorption runs out of effectiveness at low frequencies, and in my "leaky" room, I've found EQ to be sufficient to manage issues below what my absorption can deal with to achieve good "in room" bass. "Rigid" rooms are much harder to manage low bass - other solutions may be required. cheers Mike
  4. it's fluffy insulation - enough of it will work well - but you know that You may be correct - but with fluffy I don't think it matters whether it's 4000 or 7000...in the scheme of things it's all about @davewantsmoore - I cherry picked your post and left out GFR because IMHO in the lower realms of GFR (ie fluffy insulation), it's only size that matters...get enough fibres in the way and it doesn't matter so much that a particular product's GFR isn't available - ie IMHO one fluffy product will work similarly to any other fluffy product - assuming a decent "volume and area" of a trap...and of course placing it where velocity traps work (where velocity >0) cheers Mike
  5. I'm not sure how well that would work for absorption trapping - a bit unpredictable regarding gas flow resistivity etc. @ShikiS - your plan of 200mm deep and 500mm airgap will have a noticeable impact deployed in the 4 vertical room corners if wide and tall enough. Mid bass will be cleaned up substantially. How low they absorb depends on size and air gap. 600mm wide (straddling) is the absolute minimum width you should consider to get much absorption <200Hz. 1200mm wide (straddling) is better to absorb down to 150Hz or so. Any issues <100Hz, absorption just gets too big - IME EQ works well here. cheers Mike
  6. agreed - poly is a PITA to cut
  7. That's a tough gig for absorption - it needs to be truly massive to work that low...if you have EQ capability, a few bands of EQ can work wonders <125Hz in lightly constructed rooms where no significant bass remains in the room (because it goes through the walls). Mike
  8. @Peter the Greek had a fabric he recommended for covering fibreglass - or swap the Ultratel for poly. Poly works nearly as well as fibreglass, so if you're sensitive to fibreglass, I'd get rid of it and replace with poly. cheers Mike
  9. ...just change the file extension to .jpg or .pdf ... @Marc will never know ...but seriously, no recording is going to do this system justice! Having followed this thread for many years I'm hoping @acg will have a GTG or 2 or 3 when completed - Brisbane is just down the road, and I'd love to hear it in the flesh (following on with the Pink Floyd references)... ...getting very close on a very long journey - fantastic work! cheers, Mike
  10. Structural Insulated Panels?
  11. what does SIP stand for? I was looking at similar products to replace the roof of our kitchen and back deck, which are a skillion roof off the main house structure - fantastic (heat) insulation with amazing spanning ability due to the structural strength of the outer skins bonded to the insulation - the insulation operates the same as the web in an "I" beam, and the thicker the insulation, the more it can span...if we ever reno our current house (typical QLDer that we'd like to build under), I'd be looking at this product for the lower story walls. I've never considered their soundproofing qualities - but I'm interested in why they would work for heat insulation, but not sound isolation? Usually the properties of a material that are good for heat insulation are also good for sound - a generalisation typically used for insulation products like batts, not an integrated roof/wall product like you linked to... ...is it the direct coupling between inner skin/insulation/outer skin that degrades sound proofing performance, or not enough mass or the system doesn't manage flanking paths well or something else?... It's not unlike the design of a VPR bass trap, with a metal plate bonded to insulation, with modes excited in the metal plate damped by the insulation...of course sound isolation is very different to "in room" treatment, and the design criteria of VPRs is very specific - it just struck me as similar in concept, and given bass traps need to be big, a room constructed using this type of product provides a large surface area to work, and wouldn't absorb treble... ...really just spitballing here, as I've only considered these type of products for roofs, not walls, and never thought about their acoustic properties... cheers Mike
  12. Dave is looking for a starting baseline - he’s not confident in any previous measurements. Put the sub in a convenient spot and the mike at the LP - remeasure and post Mike
  13. Full respect to Earl G...but... Lol mine is smaller than PK’s, and we make do with what we have. As much as I’d like a bigger room, the bass is pretty good in my “too small” room. Mike
  14. even more so with your comment below whichever way it's routed that's a (edit) direct flanking path - sound can travel both ways through the vac piping system.
  15. let's assume the sub/s used produce a flat response anechoically - this is expected and desirable. You're correct that it's the room that screws things up. Consider a single sub, and the differences at the listening position for frequency response/decay etc when changing the position of this single sub around the room. It's easy to see that different EQ would need to be applied to produce a flat FR at the listening position depending on the sub position in the room. Extend this thinking to a 2nd identical sub in a different position in the room - likely it will require different EQ (and delay) to produce a flat response at the listening position because of the room. As above, start with a single sub to get that right first. Once that is sorted, tools like Multi Sub Optimizer can assist in tweaking EQ and delay on multiple subs. Mike
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