John Warren Posted June 30, 2008 Share Posted June 30, 2008 So what you are saying is that the only way you would know that is to look at a graph of impulse response? Because you can't hear it? Hmmmm. No, that is not what I am saying. The design choices that go into making a good tweeter will result in extending its bandwidth. The diaphragm has to be stiff and light, the coil has to be light, the flux density in the gap high, etc. When optimized the consequence is a tweeter with very wide bandwidth with bandwidth easily exceeding human hearing. SPLs an octave (or even two) above human hearing ends up being the consequence of trying to get the audible part of the spectrum right. Putting it another way, if you develop a tweeter that has fantastic transient behavior (relatively speaking) in the audible spectrum it will have output that exceeds human hearing. Look at Beryllium tweeters. Even the "cheap" ones ($100/ea) are -10dB at 30kHz! Quote Link to comment Share on other sites More sharing options...
jacksonbart Posted June 30, 2008 Share Posted June 30, 2008 So your saying a great painter paints outside the lines? Quote Link to comment Share on other sites More sharing options...
ZAKO Posted June 30, 2008 Share Posted June 30, 2008 Yes like Jackson Pollack Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted July 1, 2008 Share Posted July 1, 2008 John, The K77 doesn't have a particularly wide bandwidth or a super light diaphragm. Where does it fit in? Any redeeming qualities? (Cover your ears Darlin'.) Subjectively, for me the K77 sounds prettty natural and realistic, albeit I am not saying it is the best or anything. One of the worst tweeters I have ever heard was that old, ubiqitous soft dome tweeter that Polk used for so many years. I had a pair of Polk that used them back in the 80's and the tweeters sounded tizzy (sizzle?) and gave high pitched instruments remarkable infidelity. Maybe there was something wrong with mine, but man.... Andy Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 1, 2008 Share Posted July 1, 2008 Hello Andy- Listening to it at low to moderate listening levels I think it does an ok job. If you compare it to other tweeters you get an idea of what it can and can't do well. Not everyone does this however. Overall, I like it for reasons that may not be based entirely on engineering merit. jw Quote Link to comment Share on other sites More sharing options...
Don Richard Posted July 1, 2008 Share Posted July 1, 2008 The design choices that go into making a good tweeter will result in extending its bandwidth. The diaphragm has to be stiff and light, the coil has to be light, the flux density in the gap high, etc. When optimized the consequence is a tweeter with very wide bandwidth with bandwidth easily exceeding human hearing. SPLs an octave (or even two) above human hearing ends up being the consequence of trying to get the audible part of the spectrum right. The choices you mention will result in lower distortion and higher efficiency. These are easily audible, beneficial effects. Extending the response into the ultrasonic region is unnecessary to achieve those benefits. Ultrasonic performance on a tweeter is a marketing ploy designed to entice those who buy "per spec". Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 1, 2008 Share Posted July 1, 2008 you mention will result in lower distortion and higher efficiency. and wider bandwidth and concurrent *faster* impulse response. Extending the response into the ultrasonic region is unnecessary to achieve those benefits. Just how do you avoid extending a tweeter into the ultrasonic part of the spectrum if you want it flat to 20kHz? It will HAVE to be extended into the U/S regime. If you want -10dB at 20kHz, it will sound like a K77! And we know that's not considered "state of the art" by ANY stretch of ones imagination??? I'm smelling a SOCKPUPPET here????? DeanG, what do yo think?! (some edits here, I'm getting fustrated) Quote Link to comment Share on other sites More sharing options...
DrWho Posted July 1, 2008 Share Posted July 1, 2008 Hoffman's Iron Law shows that efficiency is inversely proportional to bandwidth... Quote Link to comment Share on other sites More sharing options...
DrWho Posted July 1, 2008 Share Posted July 1, 2008 How are 'you' definining transient response? It's not my definition. Transient response is the amplitude response of an impulse as a function of time. So why post the waterfall? becasue it's the amplitude response (SPL) of a cross-correlated MLS impulse in time domain. You missed my point. You're arguing that a higher frequency response tweeter is going to somehow show better behavior in its midband on the waterfall. But at the same time you're arguing that the frequency response and waterfalls are perfectly correlated. If the latter is true, then your waterfalls are showing you nothing that the frequency response isn't. You can't have it both ways. The main use I've seen for waterfalls has always been to highlight the ringing at certain frequencies. Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 1, 2008 Share Posted July 1, 2008 Hoffman's Iron Law shows that efficiency is inversely proportional to bandwidth... Agreed. I wasn't thinking about efficiency and bandwidth here (I'm getting a headache). Sirens have great efficiency, don't they! Quote Link to comment Share on other sites More sharing options...
sfogg Posted July 1, 2008 Share Posted July 1, 2008 "Just how do you avoid extending a tweeter into the ultrasonic part of the spectrum if you want it flat to 20kHz?It will HAVE to be extended into the U/S regime." Sure, but have some amount of output there is not at all the same thing as claiming an octave (or two) above human hearing. A JBL2404 is rated to 19kHz (+/-3bD). Its -10dB point is 21.5kHz... in other words it is dropping fast and certainly doesn't have an octave or two more bandwidth above human hearing. Shawn Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 1, 2008 Share Posted July 1, 2008 "Just how do you avoid extending a tweeter into the ultrasonic part of the spectrum if you want it flat to 20kHz? It will HAVE to be extended into the U/S regime." Sure, but have some amount of output there is not at all the same thing as claiming an octave (or two) above human hearing. A JBL2404 is rated to 19kHz (+/-3bD). Its -10dB point is 21.5kHz... in other words it is dropping fast and certainly doesn't have an octave or two more bandwidth above human hearing. Shawn Shawn, True for the 2404H (ring radiator, horn loaded) but not so for most Be domes. Take a look at the Fostex T250D on Madisound website (-10dB at 50kHz) or TBang Be on Partexpress (-10dB @30kHz). jw Quote Link to comment Share on other sites More sharing options...
sfogg Posted July 1, 2008 Share Posted July 1, 2008 John, "True for the 2404H (ring radiator, horn loaded) but not so for most Be domes. " Which simply shows that it isn't a hard and fast rule. Besides, neither of the examples you gave have usable output two octaves above human hearing either. The Tang Band doesn't make it one octave above and the Fostex is down around 8dB at 20kHz (around -6dB at 19kHz). The Fostex goes ultimately higher then the JBL but the JBL is flater in the range of human hearing. And one would still need a waterfall plot to see if they have any resonances and such in them. There have been numerous 1" metal dome tweeters that had resonances for example. That a driver may or may not have a wide bandwidth doesn't really have any bearing on if it will resonate or not. It could resonate in its bandwidth, it could have resonances outside of its usable bandwidth. Shawn Quote Link to comment Share on other sites More sharing options...
Don Richard Posted July 1, 2008 Share Posted July 1, 2008 Just how do you avoid extending a tweeter into the ultrasonic part of the spectrum if you want it flat to 20kHz? Design it to do that or purchase such a unit that meets those specs. Quote Link to comment Share on other sites More sharing options...
Deang Posted July 1, 2008 Share Posted July 1, 2008 I'm smelling a SOCKPUPPET here????? DeanG, what do yo think?! Yeah, I'm pretty sure Don, Who, and Fogg are all Roy. I hope you're not asking me what I think about the tweeter thing because I listen to a 2" compression driver and I don't even remember what real highs sound like anymore. Hey, it's just one thing less in the sound to worry about. Quote Link to comment Share on other sites More sharing options...
Jeff Matthews Posted July 1, 2008 Share Posted July 1, 2008 you mention will result in lower distortion and higher efficiency. and wider bandwidth and concurrent *faster* impulse response. Extending the response into the ultrasonic region is unnecessary to achieve those benefits. Just how do you avoid extending a tweeter into the ultrasonic part of the spectrum if you want it flat to 20kHz? It will HAVE to be extended into the U/S regime. If you want -10dB at 20kHz, it will sound like a K77! I thought the original question was "How important is the U/S regime?" The argument above says it is important because it provides a greater response within the audible range. This may be splitting hairs, but I think that is the same as saying a greater response in the audible range is important, and inaudible reproduction is a by-product that is unimportant in and of itself. Quote Link to comment Share on other sites More sharing options...
Deang Posted July 1, 2008 Share Posted July 1, 2008 No, it's the other way around. Quote Link to comment Share on other sites More sharing options...
Jeff Matthews Posted July 1, 2008 Share Posted July 1, 2008 No, it's the other way around. Okay, I see your point. You argue the two are inseparable. So, in that case, you can't say U/S response is unimportant. So, it all becomes a test in logic and semantics. Still, the end result is not "Oh, goodie! My speaker can play things I can't hear." It's more like, "Because my speaker can play things I can't hear, it provides better quality for things I can hear." Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 1, 2008 Share Posted July 1, 2008 Shawn- But the 2404H is horn loaded(?). I would excpet the gains in sensitivity come at the expense of the drivers inherent upper bandwidth capability. Look at the JBL 2402 (bullet), same motor/diaphragm but with a 5dB/W/m increase in sensitivity at the expense of bandwidth (3-15kHz +/-3 dB). The nude 2404H might give you -10dB at 30kHz but with a sensitivity of 90dB/W/m in the range where it counts. Regarding the two examples, I was careful not to say *useful* regarding output when discussing frequencies above 20kHz. I looked at the graphs, found the -10dB points and called that an upper limit. That said, doesn't the Tang Bang plot out to 100kHz? jw Quote Link to comment Share on other sites More sharing options...
Don Richard Posted July 1, 2008 Share Posted July 1, 2008 Yeah, I'm pretty sure Don, Who, and Fogg are all Roy. If I'm a sockpuppet for Roy, do I get the employee discount?[] Quote Link to comment Share on other sites More sharing options...
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