I am afraid this episode of the blog is going to be a frightful mess. No, not that scary little Marantz again (ahh, just you wait...), rather this will be whatever is hanging around, fit to be thrown into the stew pot. If I was half as good a writer as Mike is a cook, this would be a savory treat like his cioppino of a few Saturdays ago, but I fear I will fall short.
First up is an addendum to this ESR meter post. Those of you who have used a DMM to check the viability of a speaker in the box know (or should) that this is a very crude measure of health. Those caps in the crossover block the dc of the meter so all you get is the resistance of the woofer. Useful, but is there something better? Well, glad you asked, because the handy dandy ESR is that something better.
I recently found a salvageable pair of JBL 4410's at a local thrift. (Yes, the thrift gods were smiling on me that day. Perhaps I should sacrifice a Yorx boom box in their honor?) The DMM told me the woofers were there, 6.2 ohms each. Mike pulled out the ESR meter and, interestingly, one measured 9.1 ohms and the other 7.2 ohms. Hmm. Different from before and different from each other. What was up?
The ESR meter is evidently able view the entire network of crossover, pots and drivers and arrive at a more complete picture of the health of the speaker. The 4410 has a very sweet pair of mid and tweeter pots that we had verified were set the same before and after, but in general pots are a prime source of sonic grunge. The JBL pots are beefy works of art complete with holes in front large enough to squirt with Caig's Deoxit. The pots were doused generously, wiped 30 times and reassembled. On retest they both tested at 9.1. We were both perplexed that the higher number was the healthier one and can only surmise that we were now seeing more of the system.
Next up is the general issue of questions left in comments. (Yeah, I get comments. Sometimes. I swear.) Blogger lets me know they are there via email, but I am sometimes miss them in the blizzard. But the biggest problem is they do not have an address for a response. So, you will need to explicitly leave an email for me to respond. I'll try my best.
Questions left on older posts are an interesting variation of the problem. If I post a comment in response I am never sure the ask'er will even return to read it. Some time ago Kenny left a question on the Dual/Philips amp write up: he has an identical unit that makes a rushing, hissing sound when it warms up. What causes that? Good question, one worth a blog of its own. I talked to Mike about this and hope to write it up this weekend. Mike doesn't like to divulge the secrets of the Krell, but I caught him in a moment of weakness.
Now for something with a picture. Among my several obsessions is vintage CD players. Here is a quite lovely Rotel RCD 955AX. Orion's Blue Book says it was $450 in 1992:
Note the soon to be cioppino ingredients in the background. Sometimes you have to compete with dinner for a bench at Austin Stereo Service.
Here it is with its top off and Imogen Heap locked and loaded. Lots of air off to the right, but the smallish main board has some very nice bits as you can see below.
Lots of film caps, brown and blue, make the walk from left to right past the Philips chips set. The black electrolytics at the right are Black Gates, tasty, like Mike's fish stew.
That's it for now. Next up: the sounds of failure.