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RTally

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  1. I have refoamed many speakers and have never had a problem using Aleene's glue between the foam and the metal basket. As noted above, ensure the basket surface is clean.
  2. Seems like everyone else has covered the rest, but I want to caution you about using wire wool (Steel wool in the United States). If the wire wool is magnetic, you must remove all the drivers from the baffle before using the wire wool. During use, wire wool leaves fines, which are very small metal pieces. The fines will be attracted to the magnets in the drivers. If the drivers are still installed, the fines will be attracted to the front of the drivers. You do not want this to happen. Also, many woodworkers do not like using wire wool because the fines also get caught in the wood grain if not careful. Instead of wire wool, I suggest using a solvent to remove the grime and old finish. Then use a fine grit sandpaper to touch up the surface. I like to use 180 or 220 wet-dry sandpaper with a sanding block. You can then use oil or other finish that you prefer.
  3. That is a loaded question. At the risk of starting a controversy over caps, . . . Electrolytic caps are inherently noisier than film caps, but it is questionable if it is audible. The way the electrolyte reacts inside the cap is the source of the noise, as compared to the solid material of other caps. Film caps will last longer than my lifetime. Electrolytic caps have a limited life, typically 15 to 20 years, maybe 25 for modern ones. Film caps cost more than electrolytics when looking at economical options. Electrically, electrolytic caps better match the original caps in the speaker if those caps were electrolytic. Film caps will have a lower equivalent series resistance (ESR), which will result in a slightly brighter sound. Many add a 1/2 ohm or so resister in series to accommodate the reduced ESR. For me, I use electrolytic caps when recapping inexpensive speakers that I do not plan on keeping. For the better speakers that I plan on keeping around, I use film caps all around, even in the woofer circuit. My brand of choice is Audyn Q4. If I ever get really expensive speakers (valued at over $1000), I will likely use better quality caps. I do not like spending more on caps than the speaker is worth. I also recap one speaker at a time and A/B test to ensure it is worth it. Usually it is.
  4. Generally, it is not worth the effort to measure caps except for personal gratification. Since you have to remove them from the crossover to test, you might just as well install new caps and be assured of a future, long service life for your speakers. When testing, you need to measure both capacitance value and effective series resistance (ESR). Many times a cap will be within spec for capacitance value but the ESR has increased as the electrolyte has dried over the years. The increased ESR contributes to attenuated mids and highs. As JKent mentioned above, those black caps with red ends are notorious for failing. They have a reputation for failing catastrophically, as in exploding. Regardless of how they test, I would immediately toss them and replace with film caps.
  5. Seriously, if what I wrote above does not mean anything to you, I suggest you replace the tweeter with an exact replacement. It is not enough that that a tweeter physically fits into the hole in the baffle. The replacement tweeter must match the original tweeter electrically. Indiscriminately replacing drivers in speakers will most likely result in less than desirable results.
  6. The back of my KLH Six is labeled 8 ohms. I assume that means the tweeter has nominal rating of 8 ohms. If you replace an 8 ohm tweeter with a 4 ohm tweeter the crossover frequency will double for a first order filter such as used in the Six. If you do not change the cap values, you will end up with a hole in the frequency response between the woofer crossover frequency and the new tweeter crossover frequency. That is, the woofer will roll off at its original 1500 Hz crossover frequency and the tweeter will pick up at 3000 Hz, twice the woofer's crossover frequency. When replacing drivers, if an original, OEM driver is not used, the replacement driver should match the original TS parameters as closely as possible. If you do not want to rework the crossover, you need to at least match the driver impedance at the crossover frequency.
  7. The thicker conductor is the tinsel and connects the woofer terminal to the rivet that is supposed to be in the cone. Tinsel is very flexible and is typically a braided conductor with many very thin strands. The thin wire from the rivet extends to the voice coil (VC) and is the lead from the VC. The VC lead should be attached to the cone between the VC and the rivet (that is the purpose of the thin black line of stuff on the backside of the cone).
  8. I don't understand the resistance to using the proven doping compound made by RoyC. It is not expensive. It works very well. And it is readily available. Using grease to seal a surround sounds like a bad idea to me. Grease, even thick viscous grease, will not stay on the surrounds when the woofers are played loudly. The rapid, back and forth movement of the cone edge will through the grease off the surround. I cannot imagine the mess that grease would make, both inside and outside the cabinet. And if anyone ever wanted to seal the surrounds correctly, that grease would not be fun to remove. Either use the correct stuff or leave them as they are. If you do not want to improve them, leave them be.
  9. If I were to buy a replacement woofer from someone else, I would want assurance that either the surrounds are as original (never been redoped) or that only the good stuff was used (RoyC's or vintage-ar). Too many people have used Permatex, PVA glue, and other crap to seal the surrounds. If the wrong stuff has been used, the woofer will have a higher Fs, changing the way it sounds. You cannot tell by color. As others have noted, the original woofers sometimes had black surrounds. My pair of 20's have black surrounds and they were original.
  10. RTally

    12.5 question

    KLH cloth surrounds are generally either brown/tan or black. I believe that the black surrounds were that way from the factory and just had carbon black added to the doping material. RoyC's goop will work on either type. I know 'cuz my KLJ Sixes have brown surrounds and my Twenties have black surrounds.
  11. Every woofer I have refoamed (dozens) have sounded better after several hours of use. My experience is that foams loosen up and go deeper with use.
  12. When doing the push test, after you push in, hold that position for at least 10 seconds so that the air pressure stabilizes. Then quickly release the cone to see how long it takes to return to resting position. One second or longer to return is good. Less than 1/2 second indicates air leakage, either through the surround or elsewhere.
  13. I am firmly in the camp of using a tone to magnetically center the voice coil. The advantage is you do not have to mess with the dust cap - no cutting out the dust cap, no gluing it back in. For the tone method, use a tone generator (I have an app on my phone) and play a 30 to 40 Hz Hz tone through the driver. Play the tone only loud enough that you can feel the cone move. I glue the inside of the surround to the cone and let it dry. Then I attach the leads from my stereo to the driver and get ready to play the tone. I glue the outer edge of the surround to the basket and then play the tone as I press the surround edge in place. Using Aleene's glue, I have a couple minutes to mess around with the cone and surround to ensure all is well. Before the glue sets, I turn off the tone and then play with the cone. Push it in evenly and see if you can hear or feel any scratching. Press on each side and see what you notice. I do this so that I can learn what happens when the cone is not centered. I then play the tone again to ensure the VC is centered while going around the edge of the surround to ensure it is seated and the glue is starting to cure. When I am satisfied, I turn off the tone and let the glue cure. Sometimes I clamp the surround to the basket to hold it in place. Other times I just keep pressing around the surround until the glue dries. Aleene's sets up in about 5 minutes. After the glue is cured, press the cone evenly around the VC to ensure there is no rubbing. I've done dozens this way and have never had a problem. You are done.
  14. Do the push test. Push in the woofer, hold for several seconds, and then quickly release. See how long it takes the cone to return to its normal position. Generally, anything over about 1/2 second is fine, with the better sealed speakers taking more than a second to return. If the cone pops back too quickly, you have a leak somewhere, either the surround or elsewhere.
  15. I have two pair of Dynaco A25 speakers. Three of the four speakers have the port on top. I have seen references to this version being called A25X, not to be confused with the A25XL.
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