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briodo

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About briodo

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    Colorado Springs
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    Music, skiing, computers, and AR speakers

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  1. Agree with Aadams. Difficult to stop natural chemical reaction between metals over time. Encourage you to replace with new, whether they are pots or L-pads. And I have refurbished 3 early AR series pots, all worked perfectly for a year or two. I now just replace.
  2. Excellent write up on a topic that I view as one of the most challenging parts of speaker refurbishment. The AR9LS & LSi grill screens are the deepest I have seen from AR and present a formidable challenge to get a smooth, professional finish. Thanks for taking time to document the steps with clear photos. I need to do both my 9LSi and AR98LS, simply have never attempted due to experience with other grills that came out marginal despite being 1/4 the depth. There is hope!!
  3. I appreciate that feedback, and my comparison was on the upper range of the two speakers. I have not done an A/B with 9 & 9LSi. They are on different floors of my house and my wife drew the line on helping with speaker relocation other than out to the garage... I use the term listening to music VS the speaker with the 9. It simply disappears in ways the 9LSi does not. Both set ups have same amplifier, preamp, and source so I'm left wondering about what else I can tweak. Harry recommended resistor change and fiberglass type insulation for dampening, which I believe would help based on other sources confirming it works better than polyester fill. Then again, the 9 uses that white polyester fill. It may be I have to just start experimenting similar to what others have done. Thanks for letting me vent!
  4. That makes perfect sense, taming the wild beast so to speak. I have not done any scientific measurement of where the issue is from a frequency perspective, but it finally hit home while listening to the AR91's I refurbished next to the AR9LSi's. They sounded remarkably alike (no surprise) until particular female vocal came through at what appears to be around 2K on my graphic equalizer. The adjustments I made are close to what you've found, but the equalizer impacts both pairs of speakers. That's when it hit me about having a similar crossover design built into the AR9LSi, with both -3 and -6db down for all three upper drivers. Schematic review shows all three driver circuits are different enough to indicate this is not just a "get the same resistor network parts" from the AR9 and wire it all up (although I have been known to do that). Leading to my question if anyone has taken the time to do such a design?
  5. Great topic IMO. I own both and have a strong preference for the original 9, but wonder if it has more to do with crossover design than driver and orientation. The ARLSi upper MR is just too hot in current design. I've been messaging with Harry about his resistor change for that driver along with other enhancements and then realized the original AR9 crossover offers flexibility in adjusting drivers to the listener's taste. The AR9LSi requires external electronics to do the same. Has anyone taken to the time to design a AR9-like 3 switch resistor network for the AR9LSi? I can't find anything such an animal in the forum, but may not be searching correctly.
  6. Thanks Glenn, found the replacement parts using your parts list and have them on order. Will spend time figuring out alignment as they do not appear to require shims. Will invest some time learning technique. I did replace the red/black original caps with Dayton NPE last week and found a whole new speaker to listen to. Learning that craigslist purchases still require cracking the case open even thought someone replaced the foam surrounds. Just want to share my appreciation for the details on your rebuild. Provides all key points to restore a pair of AR12's to like new condition. The grill specs alone cover a whole list of systems from that era. Original foams from that era are hard to find, and your replacement design actually looks better than the foam, IMHO. Kudos to you
  7. My compliments to the author on this restoration. Great pictures and excellent details of how to bring back a truly rare classic. I have a pair of 12's I have done minor repairs on since they were purchased 5 years ago, a craigslist score for less than $100. The 10" had been refoamed but the caps were the red and black NPE that I replaced with Dayton NPE. I assumed the midrange was good since it does play but now looking at Glenn's close ups of the foam replacement makes me think mine have been "repaired" at some point with some coating due to the foam disintegration. I have a couple of pics attached and would appreciate feedback for those of you who have seen the correct foam material in place. The midrange drivers do not appear to have been touched, but the glossy surface tells me these are not foam surrounds at this point. See below. I tried to get different views on single driver, but the other looks identical. Do these appear correct?
  8. That is really good to know. I found a post from 2011 started by Carlspeak on capacitor values and will spend more time researching. I don't need to rush this repair and the sunk cost of the Dayton's are not going to force my decision if a better option is out there. It is clear the old ones have to go, just want to be good enough to represent the original design/sound knowing the surrounds will need to be redone in 20 years...
  9. Rethinking this comment, will remeasure tonight using 22 + 2.2 combo. Otherwise I'm deviating from specified parts and that is a slipper slope.
  10. You just need matching risers for your listening chair! ?
  11. Today was spent measuring the caps on all 6 crossover boards, qty 2 AR58S, and qty 4 AR91. I included the replacement Dayton NPE replacement caps in the measurement test as well. No surprises. Collins were way out, Unicom had good and bad, the TI's were 3 for 4 within tolerance. My baseline assumption of 5% tolerance is acceptable. I will be replacing all the caps on the AR91 crossovers due to age. However, my lesson on using Daytons (especially when doing series or parallel to reach target value) is to measure them before use. The 22uf I purchased all measured within tolerance without combining with the 2.2uf to reach the target 24uf goal for what I called C3. results attached for those who appreciate measurements. AR58S and AR91 Cap Value Measurements.pdf
  12. Thanks Stimpy, doing surrounds is my favorite part. I bought the 58S on Craigslist from a young Mom going through a divorce for $45 in 2012 or so. She told me her ex-husband worked in a car stereo store, which is likely source of whatever he used, which appears to be a passive radiator. I actually tore the paper cone trying to remove the hard plastic/rubber/epoxy he used, so Tom was spot on about them being beyond normal repair. I thought I got a heck of a deal, my wife looked at me in disbelief when I brought them home. Glad I'm not in this for the money. Crossovers are out and ready to work replacement caps for both pairs. Took a picture of the AR92 and AR58S crossover boards. BTW, I was pleased to see the 91 board connectors and switches fit the 58S back panel cutout. I will need to figure out how to save the SN label on both AR58S I tried a little heat and careful vacuum approach on the mid-range dome, no joy. It is really stuck. I've done several domes using that technique before, so something is different and appreciate some ideas on alternative methods. I don't mind a couple of dimples, but current dent is too much...
  13. Should show a pic of the AR91's as well. Still have the foam around the midrange and tweeter.
  14. I purchased the replacement capacitors for 2 pairs of 91's. I'm doing a two for one so to speak, having a pair of AR91's requiring woofer surrounds and recap. Cabinets are 9 out of 10. It's clear from others work in this area that NPE's from that era may need to be replaced, but mylar ones are likely to be good. I have a meter with capacitance reading, and will verify before replacing. Four woofers have been refoamed. I use shims after carefully cutting around the outside of dust cap leaving a small hinge so I can reglue. Aileen's tacky glue works perfectly for all aspects of the job. AND drys clear. The cut lines are barely noticeable. Also took a picture of the crossover board still inside one of the AR91's. It has the NPE's throughout. AR91 also has a brace from front to back placed between the woofer and midrange drivers, assuming to reduce cabinet flex from the woofer?? I'm thinking that may be an easy add to the AR58S. Any opinions on value of that brace? Going to work on the crossover board removal next.
  15. Looks like I have the correct crossover board base on resister/cap count. Thank you for this info!
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