John Warren Posted June 17, 2006 Share Posted June 17, 2006 Maron- hello! Note that I had to correct a couple of the constant terms. The fonts I used didn't show as intended in the second relationship. jw Quote Link to comment Share on other sites More sharing options...
John Warren Posted June 17, 2006 Share Posted June 17, 2006 Sometimes I think the problem lies with the words that are used in trying to describe the things that are happening. Take, "moving air" for example. At 100dB/30Hz, there is enough air coming off the face of a woofer that you can feel it. 10dB more and my wife could probably use it as a blow dryer. A tweeter at 100dB/15kHz doesn't appear to be moving much of anything -- especially a K-77.. OTOH, it makes sense that if they are both generating the same SPL -- they must be doing the same of something between me and drivers so my ears can perceive equal loudness. You are correct, that "something" is developing a pressure at your eardrum. All the eardrum experiences is a pressure that causes it to move. What we ignored is directionality. Tweeters "beam", woofer don't. Stand 90° off axis and most tweeters are -10dB down. So much for the constant volume velocity. Quote Link to comment Share on other sites More sharing options...
djk Posted June 17, 2006 Share Posted June 17, 2006 "Which you can't do since the larger mouth also has a larger mass of air it has to 'move.' F = MA" It's the mass of the moving assembly that causes the problem, not the air per se. "Larger mouth horns tend to have less HF response then smaller horns because of the additional air mass is mass rolling off the drivers HF response. " See above. The air trapped between the diaphragm and the phase plug causes a 6dB/oct low pass effect. The design of the phase plug deals with this. "Funny how tweeters use such itty bitty horns then...." Size is determined by directivity control. If they don't need to go low, they can be small. They can be very large and still go high. The baffle opening for the Heresy K700 horn has about the same area as the mouth of the JBL 2404 tweeter, a bit over 26 square inches. I would not ask a K700 to go to 20Khz, nor a 2404 to go to 700hz. Quote Link to comment Share on other sites More sharing options...
Q-Man Posted June 18, 2006 Share Posted June 18, 2006 I don't think that the new Altec 390 is a 300 Hz driver. I was told that the 390 is a 290 without the 2" snout. The 390 is more of a pancake version, and the crossover frequency should be 500 Hz and above. I hope that I'm worng, because if the 390 is anything like the 290 it will make a sweat midrange driver for you to use. A few years ago when I was talking to Bill at Great Plains Audio, he kept telling me that he was going to produce the 290 again. I would call him every few months and bug him about them. I had to find my six 290's on ebay and a couple at Jammin Jersey. Then I bought some new diaphragms from Bill. JW, I'm fine. I think the bigest reason that I havn't been around so much is that I'm finaly satisfied with the way my system sounds. I havn't had the urge to tweak anything. It's been four years now that I've been wanting a new theater room. I finally decided to build a new house and go for it. That is why I need two more networks from you. I am going to use seven Klipschorns and four LaScalas. Drop me an email sometime and let me know how you are. Q. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted June 19, 2006 Share Posted June 19, 2006 I am going to use seven Klipschorns and four LaScalas. Good Lord! That's a Klipsch Heritage dealership, not a home threatre! Q-man, keep us informed on your progress. Your posts are always appreciated. DM Quote Link to comment Share on other sites More sharing options...
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