77Eric Posted August 3, 2023 Share Posted August 3, 2023 Hi, I've been searching for a pair of black RB-5's for a while now so when a pair showed up locally on CL I bought them, brought them home, hooked them up and was underwhelmed. It didn't take too long for me to realize that the tweeters (K-105-K) on both speakers didn't seem to be working right. I disconnected the biamping bars and the tweeters measured open (infinite resistance) and in a brief listening test made sound but akin to a little transistor radio. Pulled a tweeter on one speaker and it measured around 3.4 Ohms and hooking it up directly (no crossover) yielded reasonable sounds so I conclude the problem is not the tweeter. The next easy test was the 4 Ohm 10 Watt resistor on the crossover board. It measures 4 Ohms so that doesn't appear to be the problem. At this point I thought it best to ask for advice on my next moves. Am I missing something here? Any other tests I should do? Should I start looking for some replacement crossovers (116436)? Eric (longtime happy Cornwall II owner) 1 Quote Link to comment Share on other sites More sharing options...
wuzzzer Posted August 3, 2023 Share Posted August 3, 2023 Are you sure the jumpers are making full contact? What happens if you remove them and connect speaker wire only to the tweeter inputs? Quote Link to comment Share on other sites More sharing options...
billybob Posted August 3, 2023 Share Posted August 3, 2023 Welcome @77Eric...was looking at a pair in Daytona. sure wuz and crew can help. Quote Link to comment Share on other sites More sharing options...
amped Posted August 4, 2023 Share Posted August 4, 2023 If it’s sounding little like a transistor radio, should you be looking at the woofers? Does the source work normally with your cornwalls? 1 Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted August 4, 2023 Moderators Share Posted August 4, 2023 21 hours ago, 77Eric said: Am I missing something here? Any other tests I should do? Should I start looking for some replacement crossovers (116436)? Think there are a few things we can check before you are to that point. There are several things that are much more likely than two XOs needing replacement. what is the latest status. Travis Quote Link to comment Share on other sites More sharing options...
77Eric Posted August 4, 2023 Author Share Posted August 4, 2023 Hi all, Thanks for the responses and welcomes. I used to hang around here but I couldn't find my old account or maybe I was just a lurker so I'm limited to 1 post/day for now. I looked at it some more last night and I've come to the conclusion that there's nothing obviously wrong. I verified the jumpers are working correctly, and I guess the "transistor radio" effect when running the tweeter through the crossover (jumpers removed) is maybe OK since the crossover is at 1950Hz. The reason I went through this investigation was because of the rolled off treble which led me to check the tweeter resistance at the speaker inputs (jumpers removed). It was open and that threw me off. Looking at the crossover schematic, though, this is what one would expect (high pass filter won't pass DC). I will try running the speakers biwired so I can control the tweeter/woofer inputs independently and maybe try biamping as well. I'll report back... Eric 2 Quote Link to comment Share on other sites More sharing options...
77Eric Posted August 8, 2023 Author Share Posted August 8, 2023 Hi, I tried hooking up one of my RB-5's biwired and it sounded much better so that indicated to me that maybe the external jumpers aren't making good contact, or perhaps something else is amiss with the connectors. Since I just plan to use conventional wiring I went ahead and soldered in some internal jumpers using some thick copper wire I happened to have rather than trying to further debug the connectors. I put the speakers back in my system and have done a bit more listening and they certainly seem much improved. One theory I have is that perhaps these speakers sat in storage for a long time and the connectors got tarnished a bit or maybe the speakers just need to get broken in again? Also I believe there is a period of adaptation in terms of how I perceive the sound so perhaps just using them and tweaking my setup a bit will really get them all the way dialed in. They already are a big change for the better, though, so I'm looking forward to seeing how good I can make them sound. Eric 2 Quote Link to comment Share on other sites More sharing options...
Peter P. Posted August 8, 2023 Share Posted August 8, 2023 Thanks for the update. Another test you could have performed would have been to connect a voltmeter set to AC, across the tweeter connections. Play some music and ramp up the volume. Bonus if your voltmeter has a Max Hold feature. As the volume goes up, the voltage reading goes up. That should tell you whether the crossover is working. Crossovers don't usually blow. Your conclusions about the "transistor radio sound" were correct. I bought a used pair of two-way speakers and heard very little sound from the tweeters. I heard very little sound from the tweeters even after performing the paper towel tube test but an AC voltmeter test confirmed signal was reaching the speaker inputs. I replaced the tweeters for reasons other than my suspicions and of course, the sound remained the same. I concluded the 2500Hz crossover was just what the engineers designed, and the 8" woofers were doing most of the sound reproduction. 1 Quote Link to comment Share on other sites More sharing options...
77Eric Posted August 17, 2023 Author Share Posted August 17, 2023 (edited) Hi again... After listening to my RB-5's for a (short) while after my internal jumper fix I concluded that they still didn't even come close my expectations (based on internet talk along with my experience with my Cornwalls). I probably fooled myself in my previous tests, or maybe my fix helped a little but didn't really solve the problem. Back to the drawing board... The next thing I looked into was replacing the tweeters. Turns out replacement K-105-K Ti tweeter diaphragms are only $20 each so I ordered a couple from Analog Classics. Installing them is easy enough as there's no soldering, just simple nuts and bolts and crimp connectors. No need to even disconnect the speakers - just pull the tweeters out the fronts, replace the diaphragms, and put them back in. I measured the DC resistance of both sets of diaphragms and while the originals were 3.4 Ohms the replacements were about 5.8 Ohms. Initial listening tests were astounding! My speakers went from boring and lifeless to dynamic, musical and 3D! My toes were tapping! I'm not talking about a subtle change, either - this was a complete transformation. It's been a week or so of listening now and they still sound great! I finally am hearing what got these speakers their reputation. The obvious conclusion is that my original tweeters were not performing up to snuff (as I suspected from the get-go) but since the new ones look and measure differently I suppose it's possible that I just did a tweeter "upgrade". I don't really think that's the case, though, and I'd be interested to know if good original tweeters measure around 6 Ohms like the replacements did. Eric Edited August 17, 2023 by 77Eric Quote Link to comment Share on other sites More sharing options...
billybob Posted August 17, 2023 Share Posted August 17, 2023 Yes, you did the test so, your listening proved the results. Klipsch make several nice bookshelve speakers. Now you know why the RB-5s are sought out. Enjoy... Quote Link to comment Share on other sites More sharing options...
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