Deang Posted December 14, 2006 Share Posted December 14, 2006 So, how long do these things last before performance is degraded. We'll assume the driver hasn't been abused. Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted December 14, 2006 Share Posted December 14, 2006 hmmmnnnn... does the phenolic dry/ harden, due to age..?? we all now know aluminum diaphrams work harden, and loose excursion .... Quote Link to comment Share on other sites More sharing options...
JJkizak Posted December 14, 2006 Share Posted December 14, 2006 Wonder if they ever tried titanium or beryllium, they are real "springy"? JJK Quote Link to comment Share on other sites More sharing options...
JohnA Posted December 14, 2006 Share Posted December 14, 2006 Ti is common for diaphragms, but it doesn't perform well below 1000 to 1500 Hz. I think yhere is a HI-END japanese manufacturer that uses Be for some of it's diaphragms. I've no idea what they may sound like as the price is so many orders of magnitude beyond what I can afford. Quote Link to comment Share on other sites More sharing options...
CaptnBob Posted December 14, 2006 Share Posted December 14, 2006 The life span is indefinite - I've got some in K-77/T-35s that must be 45 years old that sound indistinguishable from new diaphrams mounted on old magnets. Somewhere in the "Dope From Hope" PWK talks about titanium diaphrams. As I recall, he said they tended to shatter when overdriven. Quote Link to comment Share on other sites More sharing options...
DrWho Posted December 14, 2006 Share Posted December 14, 2006 2 weeks. Anyone got a pair needing replacement? [6][] Quote Link to comment Share on other sites More sharing options...
TBrennan Posted December 14, 2006 Share Posted December 14, 2006 Bob---That was Be PWK was talking about. The very finest compression driver I've heard, a JBL, uses Be. Quote Link to comment Share on other sites More sharing options...
DrewBolce Posted December 14, 2006 Share Posted December 14, 2006 I have replace the phenolic diaphragms on my khorns, both the mid and tweets. Both were worn out. As a disclaimer they have lead a hard life. I have abused them with many different amps in various stages of disrepair. They were about 25 years old. The sound improvement was dramatic. There was some whiting at the accordion edges, along with some phenolic dust. I believe the Koss KG75 (much appreciated $20.00 ear clips) headphones are Titanium. They have excellent bass. I wonder if Ti can be made to work for a low power application like a headphone but is no good for a compression driver. Quote Link to comment Share on other sites More sharing options...
BEC Posted December 14, 2006 Share Posted December 14, 2006 I think there is something to aging on phenolic diaphragms but I am not sure of the mechanism of aging. I have found in replacing K-55V diaphragms, a total of 4 that had low output below 1 khz. I don't know how often that happens. In all those cases, the low end came back after replacing the diaphragm. I have seen lots of K-77 pairs that had one with lower output than the other. When the diaphragms were replaced in both, output became very nearly equal. Below is a picture of an old (left) and a new (right) K-77 diaphragm. I know that they get darker with age and am wondering if the darker coloring indicates added mass. Bob Crites Quote Link to comment Share on other sites More sharing options...
TBrennan Posted December 14, 2006 Share Posted December 14, 2006 That's interesting Bob, the things seem to change color as they age just like American Bridge fiberglass (MSA) hardhats. Those hats start out the same color as the new diaphragm and get darker as they age until they look just like your old diaphragm. AND they also get brittle and go out of date, the hats are only good for four years, after that they can crack like an eggshell. The hat pictured went out of date in 1982. Makes one wonder....... Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted December 14, 2006 Share Posted December 14, 2006 hmmmnnnn... does the phenolic dry/ harden, due to age..?? we all now know aluminum diaphrams work harden, and loose excursion .... Duke, What are the symptoms as the diaphragm is "starting" to go bad. Is it an overall loss of output, a loss at the highest frequencies, distortion? You have probably heard them in the various stages of decay. -Tom Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted December 14, 2006 Share Posted December 14, 2006 Tom ... we discussed in a previous thread, that aluminum Dai's work harden, from age/ abuse... they loose the lower end since that requires more excursion Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted December 14, 2006 Share Posted December 14, 2006 I replaced some 808 diaphrams .... they were in some Valencia's that had seen some Hard use...Disco ..?? lotta difference xover was at 800 Hz .. the increased output there was Very noticable Quote Link to comment Share on other sites More sharing options...
Audio Flynn Posted December 14, 2006 Share Posted December 14, 2006 From a generic plastics non audio sense... -phenolic is very rigid -phenolic is very dimensionally stable over a broad temperature range -phenolic is brittle; I expect it to be more brittle over time great question I suppose if no cracks can be seen under 10X or a little higher magnification they should be OK. I am per plexed; I will ask around work... Quote Link to comment Share on other sites More sharing options...
Deang Posted December 15, 2006 Author Share Posted December 15, 2006 I asked the question because I really dig the sound coming out of my JBL 2470's. As most of you know, a pair of replacement diaphragms for those are about $500. I'm trying to decide if it's worth ponying up the dough to have a spare set. I also worry about a time where you plain just can't get them anymore -- and you have to run the phenolics to get a good 450Hz out of them. I'd put the money towards new drivers if there was something, but there ain't. Quote Link to comment Share on other sites More sharing options...
JohnA Posted December 15, 2006 Share Posted December 15, 2006 Dean, Why don't you ring up JBL and ask. Quote Link to comment Share on other sites More sharing options...
DrWho Posted December 15, 2006 Share Posted December 15, 2006 I vote you enjoy them until they break...by then, I should have designed some awesome drivers for you to try out and tell me they suck until you finish modding them *crosses fingers* [] Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted December 15, 2006 Share Posted December 15, 2006 Aaaaaahhh ... now we are down to tha meat of the issue at hand .. Dean is worried about his 30 y/o phenolic dia's.. no doubt thier brown as dog poo and twice as dry .... hey, at least you can fit some aluminum ones in there, if yer short of fund's ...[] Quote Link to comment Share on other sites More sharing options...
ben. Posted December 15, 2006 Share Posted December 15, 2006 Nice new sig, Dean. Well, I think the fact that these things are essentially sealed in a compression driver or in a box their entire life, they are under less environmental stress. I'm thinking of the UV that hard hat saw in its day. It's reasonable to assume that they get progressively brittle, but it might not be so bad that their durability or lack thereof makes them unuseful. I remember from my brief stint in mountain biking that Al has a finite lifespan when mechanical stress. A few years of good performance from an Aluminum bike could be all you'd get. Quote Link to comment Share on other sites More sharing options...
Deang Posted December 15, 2006 Author Share Posted December 15, 2006 I don't think aluminum will get it Duke -- won't go low enough. Quote Link to comment Share on other sites More sharing options...
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