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almikel

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About almikel

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  1. good points (a) Looks have never been my strong point for treatment (b) they are narrow band devices - so they need to work where you have issues
  2. old thread - I don't think there are any decent design criteria for BAD panels... Take the lower diffusion point - if it starts where wavelength = unit width, for 1kHz that's 344mm wide - that's bollocks - I've never seen any BAD panels with that wide a single unit. The depth of absorber is likely valid - BAD panels work via reflection and absorption, and if the absorption isn't working then the diffusion will be compromised, so for diffusion down to say 1kHz, a depth of ~100mm is likely required. Beyond that, choose a slat width that's convenient (anything between 10mm and 100mm), and use a BAD sequence for layout (from the web, or flip a coin many times - head=slat, tails=gap). Mike
  3. The ceiling is such a good place for treatment - out of the way, and a large area. It would be a good reason for buying another tool. Ignoring the cost of the tool , the material shouldn't be "too" expensive if you can DIY it. With a slat profile like that, you could ignore using a BAD pattern, and just have regular gaps... ...or just go back to plain profile slats for those sections - a 1D pattern will get some diffusion, but just a regular pattern will still get useful scattering (I'd go the 1D pattern, as there's marginal additional work required). Another of Svenr's useful threads - this one for modular 1D BAD diffusers - he's using them on walls, but no different to ceilings. cheers Mike
  4. It would be a good reason for buying another tool. Keep in mind you said earlier you didn't want to lose the head height... ...but if you were prepared to lose the head height, then a combination of limp mass (for bass trapping) and those amazing slats PtG posted for diffusion and broadband trapping would create a spectacular ceiling. Good work - yes that's correct, but limp mass will inherently have a lower Q (less sharp) than hardboard, and IMO anything that broadens the "narrowband-ness" of pressure traps is a good thing - so filling with absorption is good. mike
  5. Now those as slats would be way cool
  6. loads of fun mucking with the multi-layer part of the calculator http://www.acousticmodelling.com/multi.php modelling some limp mass traps. based on a previous post by @svenr I just used his figure of 1.8kg/m2 for the mass of ordinary flooring vinyl (if building a trap you'd obviously want to check this). I couldn't find Svenr's build thread, but he mentioned his vinyl membrane trap in another thread here (scroll down a few posts for simulation graphs of the limp mass traps): Here's the model of the bass performance for a 200mm deep (estimation of your rafters) limp mass trap using 1 and 2 layers of flooring vinyl with 200mm of fluffy above (fluffy Gas Flow Resistivity estimated at 5000 thingies) As with any pressure trap they are quite "narrowband". If you want to experiment with different parameters, once you hit "Calculate" it takes you to the "Results" tab, just hit the "Calculator" tab to re-enter different parameters (hitting the back button means you need to enter everything again). Using expensive Polymax XHD for the damping above the vinyl in this scenario reduces performance. Another tick for Svenr. You could place several of these on your ceiling with a mix of 1 layer and 2 layers of vinyl and achieve good "bass" trapping - possibly enough not to need additional corner traps. I have the same ceiling as you do - just lower - if I stand on my toes my head brushes the bottom of my rafters (no pogo dancing for me in my room!). The cost of Mass Loaded Vinyl (MLV) has always put me off, but I might try some of these in the parts of the room I don't stand using off cuts of flooring vinyl and a bag of poly fluffy. Hats off (again) to @svenr for showing ways of using "non acoustic" products for room treatment. Mike
  7. Hi PtG, I've never mucked with the multi layer aspect of this tool - even has limp mass - thanks heaps! What absorber type were you using in the example above? 27000 is very high - must be 96kg/m3 or something? What I found interesting when I plugged some numbers in is that the slats improve the bass performance over no slats, rather than just reflecting higher frequencies - prob not surprising when I think about it, as the solid (slat) part would operate as a membrane once you got enough coverage say >50% (ie more slats than gaps). Good to know the multi layer capability is there - hours of tinkering - thanks again. cheers Mike
  8. yes they look very cool - if you could source the perforated masks, the rest would be very easy to DIY. Making the mask yourself is a lot more work - drilling all those holes - even if you just copy the mask, blow it up on a printer and use it as a template. What kind of effect can one expect from such a ceiling trap? The 1/4 wavelength rule suggest it is not going to be very effective below 200Hz. PtG's idea still has merit. Don't take "too" much notice of the 1/4 wavelength criteria (it's certainly not a "rule"). 1/4 wavelength is just where air velocity is maximum - trapping still occurs wherever the velocity is >0. Bass traps are also about size, and the models ( eg this one http://www.acousticmodelling.com/porous.php ) only cater for depth and air gap. Another member here discussed the "grazing" benefit of large traps, that the models don't show, resulting in the measured performance of a room with this sort of trap being better in the low end than the models predict. If you did cover the ceiling in slats with absorption above, I'd be confident the performance of the absorption would work much lower than 200Hz. As I suggested above, an alternative to the slats/absorption approach on the ceiling would be a "limp mass" membrane trap (or multiple limp mass traps so the whole ceiling wasn't covered). IMO this would achieve better low frequency performance, but not as good broadband performance as slats/absorption. I'll have to go searching, but @svenr posted a thread for low cost treatment, and a component of that treatment was a limp mass membrane trap across a large part of the ceiling - my recollection is that he didn't require any additional "bass" traps beyond the ceiling limp mass trap for modal control. Svenr used ordinary flooring vinyl as the "membrane" with fluffy above, but "Mass Loaded Vinyl" (MLV) is a more typical product used - and can be sourced from the same insulation providers that sell Ultratel etc (but MLV is much more expensive than flooring vinyl). A good thread that includes design parameters for limp mass traps here: https://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/743040-tims-limp-mass-bass-absorbers.html In your case you could just consider the depth parameter set at the depth of your rafters - and ignore Tim's advice about size - use the channels between your rafters and make them as long as you choose, but leave some ceiling space free since you're worried about losing the ceiling height . The cavity behind the limp mass needs to be sealed for them to work though - you'd need "noggings" at each end of every trap. well it's meant to be random, hence why flipping a coin works for a 1D BAD slat pattern. You "could" create a 2D BAD sequence just by laying another layer of slats over the top of the 1D slats at 90 degrees. This will then diffuse in 2 planes (hence their name 1D and 2D - similar to QRD diffusers - a 1D QRD looks like a cutlery drawer with different depths in each longitudinal "slot", and only diffuses in 1 plane. A 2D QRD "Skyline" diffuser looks like buildings (skyscrapers) all at different heights - these diffuse in 2 directions. @hochopeper did the maths to generate an "original" 2D BAD sequence based on Cox and D'Antonio's work. RPG (Cox and D'Antonio) introduce symmetry in their 2D pattern for looks, but still maintain sufficient "randomness" for diffusion. Yes they do - peaks and troughs exist based on the room response and sound waves bouncing off boundaries and combining - where the waves are in phase, they add, when they're out of phase, they cancel (drop a pebble into a fish tank and watch how the ripples bounce of the boundaries and re-combine after a few seconds). Pull energy out (via traps) and peaks and troughs are reduced. cheers Mike
  9. Slats are (usually) timber strips with gaps in between and absorption behind. The hard surfaces reflect energy helping to stop the room getting too dead. You get scattering if the pattern (gap and slat) is regular. If the gap/slat pattern is random you get diffusion - this is a 1D Binary Amplitude Diffuser (BAD) panel - invented by the gurus of diffusion - Cox and D'Antonio. I've never found good sources on where diffusion starts/stops with 1D BAD panels. They don't generate as much diffusion as say QRDs, but because they don't, their sitting distance restrictions aren't as strict as with QRDs. I tried to pull a little bit of information together in this thread - not necessarily all technically correct The BAD sequence needs to be random to generate diffusion. Flipping a coin works, head=slat, tail=gap, or use a random sequence like this one https://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/395773-diy-binary-amplitude-diffuser-anyone.html 1D BAD as slats on a wall 2D BAD panel cheers Mike
  10. What makes a good soundstage for speakers?

    the 57 is a truly great speaker - possibly better than the 63 - in their sweet spot, just sublime. Unfortunately move left or right 500mm and the image collapses to one side, and they won't cop SPL. I have ultimate respect for Peter Walker, his speakers and amps, but 57's wouldn't survive in my setup when the volume is elevated - unfortunately.... ....but in my setup I can move way off axis and the image never collapses to one side - all the electros I've listened to (Quad 57's, 63's, Martin Logans) all suffer from the image collapsing once you get off centre. Fine if you're listening alone in the sweet spot - with 2 people on a couch each person hears 1 speaker - this is not ideal. Mike
  11. A rug in front of the speakers, and anything you choose to put under it, will only have an effect at high frequencies (say 5kHz and above). What are you trying to achieve? IME some focus on treatment below 500Hz is beneficial in all rooms, and rugs (and anything underneath), won't help in this area...WAF is always a challenge. cheers Mike
  12. nothing would pretty much get you going - start with that. cheers Mike
  13. you've done a great job placing that centre speaker in the right spot - well done! is there any perceived EQ in-balance with the mains? i wouldn't think there would be?? great project and outcome - enjoy the results! cheers Mike
  14. What makes a good soundstage for speakers?

    likely the best sound stage I've ever heard was a set of Quad ESL 63's (a bipolar design), where the singer presented centrally just in front of the speakers, and the rest of the band was just behind the speakers. I've never been able to replicate this sort of accuracy of soundstage with my speakers in my room (horn top end crossed at 350Hz to box mid bass). Who knows whether it's the open baffle design, Electrostatics, the "horn" sound of my speakers, or my room? If you liked the sound of the Maggies - just stay with it! Mike
  15. What makes a good soundstage for speakers?

    I'm sure they would sound great, but wow, that rear tweeter would just complicate room placement and treatment. Traditional box speakers struggle with soundstage and imaging usually because because of less than ideal crossover design and inherent challenges in maintaining consistent coverage pattern (directivity) when crossing from 1 driver to another - a rear facing tweeter won't change this. Mike
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