JefDC Posted October 2, 2018 Share Posted October 2, 2018 I had a pair of Qb's in 1979 and Qjr's later. The tweeter can be removed from the front, if he is broken look carefully to the foil inside, you will see an etched coil on the foil. If the coil is burned out you can disassemble the tweeter and repair the coil with a soldering iron. I remember doing that once, re-assembling the tweeter was quitte difficult because of the strong magnets. The (foam) surrounds of the woofer of the Qjr were indeed decomposed about 15 years later Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted October 7, 2018 Moderators Share Posted October 7, 2018 I learned a lot from this thread Quote Link to comment Share on other sites More sharing options...
Schu Posted October 8, 2018 Share Posted October 8, 2018 On 8/10/2018 at 9:49 AM, Deang said: Ya, me too, but it took ten years to convince people that new capacitors make a difference - I don't think this crowd is quite ready for the resistor thing yet. Why not... Quote Link to comment Share on other sites More sharing options...
codewritinfool Posted October 8, 2018 Share Posted October 8, 2018 On 8/10/2018 at 6:47 AM, wvu80 said: Loctite PL Premium Polyurethane Construction Adhesive This is great stuff. It expands. Be careful not to use too much. If you do, let it completely dry and then use a knife or chisel. Resist the urge to try to clean it up while it is wet. 1 Quote Link to comment Share on other sites More sharing options...
parlophone1 Posted October 8, 2018 Author Share Posted October 8, 2018 I finally found the time to take out the tweeters from the speaker boxes. Unhooked the wires an measured both drivers with ohm meter. One driver measures 3,8 ohms and the other 3,3 ohms. The later always had a bit more his when turntable preamp was on. This one also has a wire clips a bit more loose than the other driver. These measurements are in line with some comments on other forums indicating that drivers should be OK. Regardless of this I will try to find new fuses for the tweeters as this could be the next possible cause for tweeter performing badly. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted October 8, 2018 Share Posted October 8, 2018 31 minutes ago, parlophone1 said: I will try to find new fuses for the tweeters as this could be the next possible cause for tweeter performing badly. The only way a fuse will affect tweeter performance is if there is excessive resistance (from corrosion or bad connections) through the fuse holder. Quote Link to comment Share on other sites More sharing options...
parlophone1 Posted October 9, 2018 Author Share Posted October 9, 2018 That is also my opinion. I could have tried to clean up the fuse contacts and see if there would be any change. I don't know if it would be possible for me to find the AGC 1 1/4 fuses (metal thread in glass). However, I will follow the advice of the owners of the speakers and install 0,75A - 1A fuse instead of 1,25 as specified by Infinity. The originals seem to cause too many burn out tweeters. Quote Link to comment Share on other sites More sharing options...
Panelhead Posted October 9, 2018 Share Posted October 9, 2018 On 10/2/2018 at 11:28 AM, Deang said: Tweeters are sometimes damaged, and the listener is unaware. It's territory that comes with aged induced hearing loss, etc. I bought a nice pair of used speakers. Met half way on the interstate. Owner said he was selling because they were “rolled off” on top. When I hooked up no highs. Both Dynaudio D-28 tweeters were dead. The crossovers were first order so the mids ran a little higher than normal. Found a NIB pair and they sang like birds again. I do not know how long the previous owner listened with no tweeters. Suspect an oscillating amp killed them. Those D-28 tweeters could handle some power, even with first order crossovers at 4K. Quote Link to comment Share on other sites More sharing options...
Deang Posted October 9, 2018 Share Posted October 9, 2018 Most tweeters are fried by low power amps. The hearing starts to go, and the person has to keep turning it up to get the same effect. It doesn't take much in the way of clipping to take out a tweeter -- especially the vintage ones. Quote Link to comment Share on other sites More sharing options...
parlophone1 Posted October 10, 2018 Author Share Posted October 10, 2018 I hear you. Could be my hearing, not excluding that yet. But another pair of ears familiar with how the speakers sounded confirmed what I hear now. Until running some additional targeted tests (which I am unaware of except the one ChrisA mentioned above) I tend to believe its not the tweeters. I will investigate further. I had the speakers hooked up to a new push-pull tube amp rated 2x100W for a couple of years now. This should by any standards be enough. Additionally, I never play loud. My volume knob never passed 12 o'clock position, most of the time being at 8-9 o'clock position. They worked fairly good all that time, certainly better than after I messed with crossover. Yesterday I cleaned the fuse contacts with isopropyl alcohol and replaced 1,25A fuses with new 0,5A fuses. My ears say nothing much changed. However, lower rated fuses should be safer for tweeters. So, without further testing I tend to blame myself and my work on crossovers. Quote Link to comment Share on other sites More sharing options...
Marvel Posted October 10, 2018 Share Posted October 10, 2018 Have you been using the same amplifier all this time? What amplifier is it that you are using? Quote Link to comment Share on other sites More sharing options...
parlophone1 Posted October 11, 2018 Author Share Posted October 11, 2018 Yes, the amplifier is in the system from the day of purchase. It was made by a company Sound Carrier, KT88. Quote Link to comment Share on other sites More sharing options...
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