chops Posted July 16, 2006 Share Posted July 16, 2006 Well this morning I finally opened up my Altec 902s to see what they had inside. The internals comprise of loading caps, push-terminal aluminum diaphragms and tangerine phase-plugs. Under closer inspection, the diaphragms are # 35480, which there has already been a thread about on the Altec User Board by our own sfogg. 902 #35480 diaphragms While apart, I cleaned out the magnetic gap with masking tape and cleaned the entire surface with a soft brush. As for the sound, I am still fighting with the top-end extension. No matter what I do, I cannot get these drivers to reach up to 20kHz. I've tried crossover points from 500Hz all the way up to 1kHz, all at -24dB per/oct via my Rane AC 22B and the top-end still doesn't improve. The ONLY thing between the Crown D-75A amp and the 902 driver is a 51uF Solen cap on the (+) terminal of the driver for protection. I keep reading about you guys saying that the 902 drivers with aluminum diaphragms have excellent extension up to 20kHz. If what you say is true, then how are you doing it? What am I doing differently? Even the old original alnico K-77 tweeters in my Cornwalls which are only rated to 13kHz produce more treble than these 902s do. I don't understand it. If anyone has any suggestions, please feel free to let me know. I know I can remove the loading caps and just add felt to the rear cover, but would that really do anything for the top-end? Anyway, here are a few pics (6 to be exact) of the findings this morning. Link to comment Share on other sites More sharing options...
sfogg Posted July 16, 2006 Share Posted July 16, 2006 http://forums.klipsch.com/forums/thread/607799.aspx Link to comment Share on other sites More sharing options...
chops Posted July 16, 2006 Author Share Posted July 16, 2006 http://forums.klipsch.com/forums/thread/607799.aspx Hi Shawn, Very interesting thread. I was kind of wondering if these diaphragms might be going, but I'll put in one CD and they sound fine, but put in another CD and they sound terrible. I just listened to Stereophile's Test CD3 and everything sounded just fine, however I have the treble tone control boosted +5dB. But the CD I played before that one just sounded awful. Even with the treble boosted, it still sounded real muddy. Yes, I know all recordings are different, but I have heard these two CDs plenty of times before and there was never this HUGE of a difference between them. That's what I don't get, that huge change in sound between recordings. None of the CDs I have have never tempted me to have to use tone controls. Everything always sounded either just right or a little hot. Now, most of these CDs sound either almost just right or down-right muddy, almost like they roll off at 10kHz or so. Hmm... Charles Link to comment Share on other sites More sharing options...
Guest " " Posted July 16, 2006 Share Posted July 16, 2006 chops revised. I found the altec 511/902 chart. See chart at lower right on page 2. The combination does have a roll off as you indicate. 909-8AData.pdf Link to comment Share on other sites More sharing options...
Duke Spinner Posted July 16, 2006 Share Posted July 16, 2006 you guy's are kiddin' me here ..Right ....??? YOU expect a single driver to go FLAT to 20,000 Hz...??????? Link to comment Share on other sites More sharing options...
3dzapper Posted July 16, 2006 Share Posted July 16, 2006 you guy's are kiddin' me here ..Right ....??? YOU expect a single driver to go FLAT to 20,000 Hz...??????? You almost had it Duke. YOU CAN expect an Altec driver to sound flat up to 20,000 Hertz. Just not in frequency response.[] Rick Link to comment Share on other sites More sharing options...
chops Posted July 16, 2006 Author Share Posted July 16, 2006 you guy's are kiddin' me here ..Right ....??? YOU expect a single driver to go FLAT to 20,000 Hz...??????? No I'm NOT kidding. Take a look at Figure 4 on that pdf file Fritz posted. No, it's not flat to 20kHz, but it's also those Pascalite diaphragms which were known to roll off sooner than the aluminum like mine, but it still makes it out to 20kHz eventually. Do I expect mine to make it out to 20kHz? No, but I expect it to make it further than the alnico K77s 13kHz or those Pascalite ones. And with the right recording, these 902 drivers sound just as open and extended as Bob's CT125s. Unfortunately, that's not the case most of the time. That's exactly why I keep saying that these drivers have the potential, I just have to figure out the proper tweak to get them there in my system. There are a bunch of others out there that own these 902s and claim that they have plenty of high freq energy, even too much sometimes. Link to comment Share on other sites More sharing options...
Duke Spinner Posted July 16, 2006 Share Posted July 16, 2006 if the diaphram has any amount of "work hardening/".....i.e, the aluminum ones .. they roll off at 12 - 14,000 hz Link to comment Share on other sites More sharing options...
chops Posted July 16, 2006 Author Share Posted July 16, 2006 if the diaphram has any amount of "work hardening/".....i.e, the aluminum ones .. they roll off at 12 - 14,000 hz IF "work hardening" was the issue, then you would lose low end extension due to the lack of movement and probably gain a little extra output on the top end. The last time I checked, tweeters moved less than midranges and midranges moved less than woofers. But yet, the less they move, the higher in freq they play. Hmm... Link to comment Share on other sites More sharing options...
sfogg Posted July 16, 2006 Share Posted July 16, 2006 "then you would lose low end extension due to the lack of movement and probably gain a little extra output on the top end. " Did you read the thread I linked to above? Shawn Link to comment Share on other sites More sharing options...
chops Posted July 16, 2006 Author Share Posted July 16, 2006 "then you would lose low end extension due to the lack of movement and probably gain a little extra output on the top end. " Did you read the thread I linked to above? Shawn Yes I did... twice! Nowhere on that thread did it mention anything about work hardening or lack of driver movement. Nor did it mention anything about what exactly was wrong with the old drivers. The big question in that thread seemed to be why there was a spike after 20kHz and what was the cause of it, something that both new and OLD drivers produced. Link to comment Share on other sites More sharing options...
Duke Spinner Posted July 16, 2006 Share Posted July 16, 2006 http://forums.klipsch.com/forums/thread/607799.aspx ya know what I can't stand ,Shawn ....??? when people read a post, and then ask the same dumb question over again just a few posts down .... don't you hate that too ...???.....[].....[].......[].......[].........[] Link to comment Share on other sites More sharing options...
chops Posted July 16, 2006 Author Share Posted July 16, 2006 http://forums.klipsch.com/forums/thread/607799.aspx ya know what I can't stand ,Shawn ....??? when people read a post, and then ask the same dumb question over again just a few posts down .... don't you hate that too ...???.....[].....[].......[].......[].........[] Why? What "same dumb question" did you ask again? LOL As far as I know, I didn't ask any same question twice. Look again. [^o)] I'm just trying to figure out why you always have to come onto every thread I start and take a dump on it. Why do you do that? Are you trying to make me blow up in public and get banned from the forum or something? Do you get some kind of "rise" out of bothering me for no earthly reason? I asked a ("a" - as in singular) question, you gave an answer, I replied back to your answer, now you're starting cr@p with me. I just don't get it. [:|] Link to comment Share on other sites More sharing options...
sfogg Posted July 16, 2006 Share Posted July 16, 2006 That whole thread is exactly about the difference between a work hardened diaphragm and a new good diaphragm.... Shawn Link to comment Share on other sites More sharing options...
Duke Spinner Posted July 16, 2006 Share Posted July 16, 2006 when people read a post, and then ask the same dumb question over again just a few posts down .... why, Chopsy.... I just copied that almost verbatim from a previous thread of YOURS.........[] yer daddy needs give you a spankin'......[] Link to comment Share on other sites More sharing options...
chops Posted July 16, 2006 Author Share Posted July 16, 2006 That whole thread is exactly about the difference between a work hardened diaphragm and a new good diaphragm.... Shawn Nowhere in that thread did it mention the words "work hardened". How was I supposed to know that's what you were getting at? Link to comment Share on other sites More sharing options...
chops Posted July 16, 2006 Author Share Posted July 16, 2006 when people read a post, and then ask the same dumb question over again just a few posts down .... why, Chopsy.... I just copied that almost verbatim from a previous thread of YOURS.........[] yer daddy needs give you a spankin'......[] Read my post above! And STOP screwing with my name! Link to comment Share on other sites More sharing options...
Duke Spinner Posted July 17, 2006 Share Posted July 17, 2006 [] Link to comment Share on other sites More sharing options...
djk Posted July 17, 2006 Share Posted July 17, 2006 When you bend a coat-hanger back and forth many times it will feel funny, get stiff and then break. Same thing happens with aluminum diaphragms. When they get stiff and hard, the micro detail at high frequency will not move the diaphragm. No movement, no sound. Even with a new diaphragm the driver can sound dull in a large room. The energy delivered to the throat begins to roll-off at 3.3Khz, even in a TAD with a Be diaphragm. The directivity of the horn narrowing will make it measure flat on axis, but the total energy going into the room is still rolling off above 3.3Khz. This is why people add tweeters to Altec and TAD that measure flat to 20Khz already. Link to comment Share on other sites More sharing options...
chops Posted July 17, 2006 Author Share Posted July 17, 2006 [] Once an idiot, always an idiot. Link to comment Share on other sites More sharing options...
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