DrWho Posted May 16, 2007 Share Posted May 16, 2007 wow, I totally didn't see the second page in the thread... [:$] Quote Link to comment Share on other sites More sharing options...
djk Posted May 16, 2007 Share Posted May 16, 2007 "and you can also replace any passive radiator with a port. " Think so? Try it on an EV Interface A, a 12" PR with 400g added mass. When the box is small and/or the x-max is high, a port will not work. Quote Link to comment Share on other sites More sharing options...
seti Posted May 16, 2007 Share Posted May 16, 2007 A drone and passive radiator are the same thing. As far as function, passive radiators behave like ports. In fact, you can replace any port with a passive radiator and you can also replace any passive radiator with a port. They're all functionally the same. I think I was confused by placement and implamentation between the forte and jubilee..... I got it now. Quote Link to comment Share on other sites More sharing options...
DrWho Posted May 16, 2007 Share Posted May 16, 2007 When the box is small and/or the x-max is high, a port will not work.Smokestacks? [8-|] Quote Link to comment Share on other sites More sharing options...
WMcD Posted May 16, 2007 Share Posted May 16, 2007 I would be happy to send anyone interest the portion of the book on passives. PM me. I've been pretty free with posting material in the past. Now Amy has put up terms of use about copyrighted material. I don't want to get in trouble with her or the terms of use and I don't want Klipsch to get into trouble with anyone. I think what I've done in the past is fair use but why cause problems. The drone is not exactly like a port. The port has just a mass of trapped air. The drone has mass and usually much more than the slug of air in a port. Importantly, it has a sping in the form of suspension compliance. It is like another element in a filter. Gil Quote Link to comment Share on other sites More sharing options...
DrWho Posted May 16, 2007 Share Posted May 16, 2007 A port has a spring too...related to the compressibility of the air (which is mostly a function of the port tube geometry). Since the tuning point is also a function of the port tube geometry, the ratio between mass and compliance is always the same. With a port, you get to arbitrarily choose the compliance and mass - which allows you to adjust the Q of its behavior. Basically, you can make a port operate over a wider bandwidth, but it will be less efficient. Or you can make it operate over a narrower bandwidth and increase its efficiency. If you wanted, you could design a port such that it has the same mass and compliance as its ported counterpart and then the behavior of the two systems would be identical (at least in the ideal world). The biggest advantage to passive radiators is that they can take up less space. This becomes very important in situations where the alignment does not allow a port of proper size. You can achieve any tuning you want with a very small port, but then the air velocity in the port goes up. If you think about it, for a given SPL a fixed diameter driver needs to move a fixed distance...or even better, for a certain SPL a certain amount of air needs to be displaced. If your driver is large then it doesn't need to move very far to displace a lot of air. If it's small, it needs to move more. So with a port, the air inside the tube needs to move far enough to displace enough air for the given SPL. Eventually, the air in the port starts moving so fast that it can't go any faster. It's basically the same problem as bottoming out your driver - there is a max SPL it can reproduce. Everywhere inbetween there are losses due to the fact that at least some air needs to move, and there is always some resistance inside the tube. The air rushing back and forth also causes audible distortion (commonly referred to as port chuffing). As you make your port bigger, you reduce the velocity of the air and effectively reduce these distortions. Typically, you want the air velocity in your port to never exceed 20m/s at the peak output of the speaker, which is the point where chuffing becomes audible. However, port compression starts happening even as soon as 10m/s so really you'll want to keep it under 5m/s if you want to experience minimal losses. This is nearly impossible because then the port starts to get huge and the resonances start to move into the passband of the system - no now you've got new distortions to deal with. Passive radiators don't have any of these problems, but the downside is they're more expensive. I'm sure passive radiators have their own problems too, but I don't know what they are. I do know that they operate more linearly across every SPL - which I find ironic because so many people feel they need more power to drive speakers with passive radiators. I wonder if they aren't very responsive at low volumes...? Well...that's my take on it at least. It's what I teach at the subwoofer workshops the AES holds on campus so I hope I'm right! [] Quote Link to comment Share on other sites More sharing options...
Roc Rinaldi Posted May 17, 2007 Share Posted May 17, 2007 Passive Radiators for sale. http://cgi.ebay.com/KLIPSCH-ORIGINAL-FORTE-12-PASSIVE-RADIATORS-2_W0QQitemZ150123227767QQihZ005QQcategoryZ14993QQssPageNameZWDVWQQrdZ1QQcmdZViewItem Quote Link to comment Share on other sites More sharing options...
Negative9 Posted May 19, 2007 Share Posted May 19, 2007 Quote Link to comment Share on other sites More sharing options...
Klipsch Employees Trey Cannon Posted May 19, 2007 Klipsch Employees Share Posted May 19, 2007 Check with parts again, They may have the parts to build them and need a order to gen. the build request. Worth a try. Talk to Russ and tell him to check with me if he needs help. Russ is a good guy He will help if he can. Quote Link to comment Share on other sites More sharing options...
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