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speaker dave

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About speaker dave

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    Advanced Member
  • Birthday 03/23/1955

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    The Mountain
  • Interests
    Vintage audio, psychoacoustics, bicycling, shortwave radio, photography, record collecting (mostly classical piano).

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  1. I'm guessing the fan blade is tied to the core pole. We did a similar heatsink on a 10" woofer used in a couple of Snell models. It did lower the VC temp a little but we had to deal with air noise issues since you were essentially loosing the dustcap.
  2. Hi Dave,    I see you were last on this classic speaker pages on 21 Mar 2016,  I hope you are still a member? I was looking at the AR4X crossover design in thread number 5815 posted 2nd April 2010,   a couple of questions,  what is the crossover frequency that this design is expecting to apply to the standard AR4x woofer / tweeter?  Also, I have a couple of silk dome tweeters with FS:800HZ  impedance: 8 Ohm DCR:5.9ohm sensitivity: 90db power:50W frequency: 1K~~20KHZ recommend crossover point:>2.5 K       Would these work with that design and regular AR4X cloth woofers? What would have to be done to change the design to allow a crossover point of >2.5K. 




  3. As a young speaker engineer I wrote to many companies looking for work. Roy was the only one who took the time to write back and offer some personal advice and a friendly note.. A true gentleman. Rest in Peace Roy
  4. Hi Steve, Well, its not as simple as you say. First off there is always a compromise between axial response and spherically averaged response. The best axial performance will come from an LR approach. This always comes with a mild power hole, so that is a compromise. Subjective tests show (I believe) that power response holes are benign but it doesn't sound as if you would accept that. If you want your networks to add in quadrature then you can have flat power through the crossover but then you will have a rising lobe in the up or down direction. I don't know of any way to get dead flat
  5. If you can optimize both then you have covered all your bases, but, of course, sidestepped the issue of relative importance. That is the more interesting question: if one can be optimized to be ideal (direct field or reverberant field) and the other must be compromised, then which one should get more of the designer's attention? I always point people to Floyd Toole's original study of the 25 systems that listeners rank ordered and that he subsequently measured. From best to worst there is a clear correlation between the axial frequency response of the systems and their order of preference. L
  6. Really? You can hold a pillow in front of your face and not hear a difference in a distant speaker's sound? Far field or not, I have never been unaware of the direct field of the speaker. Are you really conducting this test or simply assuming an outcome based on your beliefs? A couple of my observations: If you go to the cinema and they play background music prior to the show, you can close your eyes and point to the sound sources hidden behind the screen (no need to close your eyes I guess). This is well beyond the critical distance and the direct field is still detected and given an imp
  7. I've already conceeded that Vilchur was the first to market an acoustic suspension system as we know it, the modern middle efficiency sealed bookshelf speaker. The question of invention though is really down to the patent office and the application dates. Even if Vilchur arrived at the notion independently to RCA (which happens frequently), RCA has the prior art and can claim the legitimate right of invention. It is also not like the case of Armstrong and DeForest, where DeForest stumbled across something and only Armstrong understood its worth. Olson and Preston talk of the benefit of very
  8. On the other hand I enjoy the odd "stupid pointless arguement". Regarding the invention of dome loudspeakers here are a couple of patents you should look up: 2237298 and 2442791 http://www.google.co...%20dome&f=false http://www.google.co...2442791&f=false Baumzweiger shows a dome radiator from 1941. By the way he talks about it as a microphone but in the preamble says that all are reversible transducers and equally valid as "receiving apparatus or transmitting apparatus". Baumzweiger later changed his name to Ben Bauer. Wente shows a nice dome radiator with an accordian shaped suspen
  9. Hi Carl, Thanks for the curves. Besides the diameter difference the HiVi unit has a short flare that will narrow its dispersion from what its size might suggest. (Although we should ponder why manufacturers would add flares that narrow directivity if wide dispersion is such a key parameter.) A better comparison might be the KEF T27. It is closer in diameter and has a flat mounting plate with no wave guide. (Not a perfect unit in other regards.) AR did have one advantage in that they tended (in the early days) to use domes with no surround and that would keep the effective diameter right t
  10. Oddly your arguement confirms my case: Electro Voice countersued and won based on the obvious prior art of the Olson/Preston patent (you really should read it). I agree that it was wise of Vilcher not to further pursue it. As to the tweeter patent, I don't see any mention of being a dome as a unique claim. It is a patent on a unique magnet structure and suspension. Apparently Vilchur didn't believe he had invented the dome radiator. Theory (see Beranek and Olson) says that dispersion is primarily determined by drive unit diameter. You can dabble with breakup modes and try and get a differe
  11. The AR 1 was certainly the first speaker in the modern mold. It was the first I know of that was designed, woofer and box together, to have flat response even at the expense of efficiency. In the end, adding mass until the response was flat, was the real invention. "Acoustic suspension" is more the marketing hook. Not sure about the first domes. University did some early dome tweeters. Bill Hecht claims to have invented the soft dome. Philips did mid domes in molded paper. There must have been plenty of designers that tried the back radiation of a compression driver with no phase plug.
  12. Although Edgar Villchur comercialized and popularized the Acoustic Suspension speaker he didn't really invent it and was predated by Olson and Preston of RCA. The RCA patent makes interesting reading. They discuss high compliance woofers, allowing the cabinet to provide most of the restoring force, and increasing linearity by relying on cabinet stiffness. Their interests were primarily in mass market radios but the example is acoustic suspension. http://www.freepaten...com/2490466.pdf I'm not sure that the AR domes have wider dispersion than any other manufacturers domes of the same diamete
  13. We've debated this over on DIY audio quite a bit. Cabinet wall damping is, of course, a very different thing than internal damping of the air cavity. One deals with resonances of the cabinet panels and the other with the internal standing waves related to dimensions. For cabinet damping and the origins of the BBC approach I refer people to a great paper by Harwood: http://www.bbc.co.uk...rts/1977-03.pdf He looks into typical cabinet materials and measures their stiffness and Q but the more interesting info is when he looks at typical cabinet construction and how the cabinet radiates at each p
  14. That looks like a very clean and professional repair ot me. I wouldn't worry about having a half roll where the previous surround was flat. Considering the alternative (dead speakers) it seems like a good choice. Clearly AR knew that the excursion required was nil and so gave it a flat surround, but foam surounds are fairly light and I'd bet the response is little changed. David S.
  15. As to the standard size, it is easy to cut down a carton, at least in length. I've cut boxes down in two dimensions, which is more work but doable. I'd add to the good comments above: fist bag the systems so that the packing has less chance to burnish the surface. Corner protection is the biggest issue and you can build up your own corner protection with multiple layers of corrugated and lots of tape. Styrofoam tends to fracture apart, but there is a polyfoam (?) that is a waxier material that is tougher and can be assembled with hot melt. I agree about not trusting a UPS store. Most of th
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