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About svenr

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  1. Thanks VanArn - to keep things affordable I need to stick to a standard transformer - perhaps single secondary without centre tap and 120V or so voltage. Where could I find something along those lines? The usual electronics providers do not stock high voltage transformers anymore.
  2. Hi, I'm hoping someone can point me to a transformer with the following specs: Primary 240VDC, Secondary #1 100V-0-100V @ 100 mA, Secondary #2 15V @ 250 mA
  3. Make a sketch please - it is not quite clear what you are planning.
  4. Foam tape is the easiest. Check intertechnik.de .Any sort of putty / sealant is a pain in the ass if you need to remove the driver.
  5. I used Allboard Distributors for many "square cut" projects. Their stock prices and cut costs are very good and the accuracy (especially with many identical sized panels) excellent. Overall dimensions were around +/- 0.5mm. They also offer CNC services - need to contact them to discuss. Edit: Whenever I tried a local cabinet maker joint I always got the same BS - extremely high price, not interested, too busy, too small a job. [/rant_off]
  6. @Willco - where did you get that sketch from - it's hilarious.
  7. For simple calculations use this website: http://www.acousticmodelling.com/multi.php The point of the 300+100 example was solely to demonstrate the difference in absorption between expensive and cheap material. You wouldn't use that at the reflection points, but I use systems up to 1m thick in control room designs (mainly ceilings). @Pieface - the peakiness is due to interaction between air gap size, absorber thickness and flow resistivity. You can improve that by adding a thin layer of denser material to the back - but the differences are of no relevance. You are right about the low frequency difference - not significant. But note the difference in the 300+100 system - the cheap mid density stuff strongly outperforms the expensive high density stuff (as you expect but often forget). The flow resistivity data has to be requested from the manufacturer if you cannot find it (they will tell you a story how the heat bonding of the fibers forms a denser layer on the outside which has a bit of an effect on the absorption behaviour - but they will provide you an average value nonetheless). But look for other datasheets of similar material and do a sensitivity check on this - you'll find that it is not that important what the actual value is. The R rating is a function of the thickness, obviously. The material is the same. @Peter the Greek - use the calculator to model such systems. For plastic films, use the limp mass membrane option plus the surface mass (easy to calculate once you know the density of PE). Try 1.8 kg/m2 (el-cheapo linoleum from your local flooring mob) and see what you can do with that. Normal quality building materials (sealants, putty, etc) are perfectly alright.
  8. I just saw advertisement for expensive "acoustic" putty and sealant, claiming to be "designed to perform better than traditional approaches". What does this do? Be more air tight than a conventional gap seal? The "treat the room" mantra is certainly a thing in the market now. We should have a forum dedicated to audiophile putty, sealant, gyprock and polyester wool.
  9. @Darren69 - $2k for ceiling treatment is a lot of money. See the below for an example of a ceiling absorber using standard polyester wool. Making a 2sqm absorber costs in the order of $ 50 - the most expensive is the fabric cover. http://www.stereo.net.au/forums/topic/117267-absorber-material-is-expensive-better/
  10. I see a lot of people spending lots of money on "acoustic" absorber material. I get PMs asking where certain expensive stuff can be bought in small quantities. The message is this: it's only the flow resistivity that matters - nothing else. Cheap products with flow resistivity in the 5,000 Pa.s/m2 range even perform much better than expensive high density products with flow resistivity in the 12,000+ Pa.s/m2 range. Below are two examples - a typical ceiling absorber and a broadband wall absorber. I use two products - Polymax XHD and Greenstuf. The price difference can be checked on Google. Have a look at the performance difference and then let me know whether the higher cost for the high density material is warranted.
  11. I was making a practical joke. In fact, I'd buy cheap (and perfectly well working) polyester wool and standard gyprock, make fancy labels and packaging, add 600% to my cost and re-sell it to you after generously giving you a 10% discount. That's what manufacturers and retailers do. if you are still interested, let me know.
  12. I can sell them to you - just tell me how much you need! I can probably give you 30% off if you order enough!
  13. Recent example here - when designing large broadband absorbers you'll need a lot of absorber volume. Many people gravitate towards expensive "acoustics" products such as the very expensive Polymax XHD. But turns out, its high flow resistivity makes it actually less effective in absorbing low mids than any of the standard polyester wool product available for a fraction of the price. One cannot stress this point enough - acoustic properties are determined by basic physical properties of a material: flow resistivity, density, Young's modulus and Poisson's ratio. That's it. There are no additional properties that would make AcoustiSorb Xtra a better absorber or SoundProof AcouPanel a better choice for a wall.
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