Chris, what model DQ20's do you have, the 20 or the 20i??According to the WIKI the 20 i's have the 8517 variant which did have?ferrofluid in it and they are quite old and probably?very thick.
You wrote 8513 variant, it also has ferrofluid. ?The paragraph below?indicates the 8512 is the closest match though I can not confirm this myself. It looks like the 8511, 12 and 13 are all closely related. The 11 does not have ferro and the 13 has?thin diffusion?absorber. The 11 is 1dB more?efficient but has the most ragged?response. A simple?resistor?change could fix this.
I do not see any?tweet listed for the 20's. Can you read the?model number on your existing?tweeters to confirm?
"My 4 year old son recently blew up one of my DQ-20i tweeters and I had to replace them. The originals were Scan-Speak Type D2008 Code 8517. The drop in replacement which is available at Madisound and elsewhere is the Scan-Speak type D2008 Code 8512. Since there is a difference in codes I called Scan Speak in Denmark and spoke to an engineer there. He could not find any info/records on the 8517, but assured me that the D2008 would be a sonic match. "
In general unless you want to measure and/ or mess around with this a lot I would suggest staying with this Scan series is your best bet. While it is highly likely different tweeters will sound different I suggest they may not actually sound better.?
To optimize any other tweeter requires measurement tools and the knowledge to use them correctly. The H tweeters are smoother and likely would sound better if you know how to integrate them BUT they measure tweet sensitivity differently than Scan does. Scan and most others use 2.83 volts drive level measured at 1 M and H uses 1 watt which is NOT the same unless the tweeter is exactly 8 ohms, which few are. So at the very least some attenuation adjustments would likely be advisable. While this can be done by trained ears it is difficult for the average listener.?
Still, if you are up to it you don't have much to lose by trying to remove the ferrofluid and carefully clean out the gap. Unless you listen at high volumes I personally would not replace it with fresh unless you can find out what it originally used and can obtain it. There are multiple viscosities of fluid available and they do affect the response and the sound. Removing fresh ferro will increase the efficiency of the tweeter about 1dB. If the FF is old and thick the change will be much larger.
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Be careful to correctly align the voicecoil when you reassemble. On tweeters I always use impedance curves and/or pure sine waves to tweak the final alignment, by moving the coil relative to the magnet, to minimize distortion. Very occasionally the best results are obtained by using thin brass shims to change the voice coil angle. As you know this is delicate work and very small movements have big effects. This is necessary unless the tweeter has very tight tolerance alignment pins. I use REW and sometimes ARTA as a signal source and an inexpensive set of calibrated measurement mics like the UMIK1 for all of my speaker work.
Fuse and connector oxidization are real issues and cause a lot of problems. In areas of high pollution and humidity even gold develops crud on that impairs current flow. Cheap connectors are really bad in this respect. Because of this I recommend plugging and unplugging every accessible connector in your system and, when possible, rotating them back and forth at least yearly. Cleaning them with products like the CAIG chemical series also help.
I would not mess with caps or resistors at this time but do double check all your solder joints under strong light and a good magnifier. The joints should look very shiny and smooth. If not, reheat them and let them cool until they do look shiny. Solder joints can degrade with time.?
I this the schematic you are using?
Charlie Conger
