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About adam2434

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  1. Boston Acoustics A70 schematic

    Inductors and resistors generally do not go "bad" like electrolytic caps can over time. if the intention is a restoration, not sure I would mess with the inductors and resistors, as just the caps would need to be restored (replaced).
  2. Boston Acoustics A70 schematic

    Are you just looking to replace the capacitors? If so, you could just pull the crossover to verify the capacitor value. I believe there is just one capacitor in each crossover. The next question becomes electrolytic vs. film capacitor for the replacements. Film capacitors are larger, so do not always fit in the existing positions on the crossover.
  3. HD8 refoam

    Recapped the HD8’s last weekend. Used 4.7uF and 8.0uF Parts Express electrolytics. http:// http://www.parts-express.com/80uf-100v-electrolytic-non-polarized-crossover-capacitor--027-338?utm_source=google&utm_medium=cpc&utm_campaign=pla The original caps were 4.7uF and 8.2uF, but I figured the Parts Express 8.0uF with +/- 10% tolerance was close enough. Recapping these speakers was very easy. The drivers did not need to be disconnected and there was enough wire slack to allow the work to be done with the crossover resting on the back of the cabinet. I listened to them a little while after replacing the caps, and I can’t say that I noticed any differences in sound quality vs. the original caps. I honestly did not expect to hear a significant difference. I did this recap for “refresh” purposes and to increase my recapping experience. The new caps (black) are bit smaller than the old caps (red). Here are a couple crappy pics.
  4. HD8 refoam

    Does anyone have an idea whether the the 4.7uF and 8.2uF electrolytic caps are are tweeter or woofer circuits. I'm thinking of replacing the capacitors and I "think" I could fit a film cap in the 4.7uf spot, but would only do that if the 4.7uf is in the tweeter circuit. If the 4.7uf is in the woofer circuit, I'll just go with electrolytics for both.
  5. HD8 refoam

    Completed the HD8 refoam on Sat and listened to them a few times yesterday. They definitely have a bright tonal balance vs. the majority of other bookshelf speakers I own or have owned - including NHT SB2/SB3, Def Tech SM65, Elac B6, AR18s, JBL Studio 530, Polk S15, Sony Core, and a couple others I briefly tested. The only other model that I recall being as bright (and maybe a little brighter) is the Klipsch RB81 II that I owned for a while. This is the first Boston speaker I've owned. Are they generally on the bright side, or does it vary by series/generation?
  6. HD8 refoam

    I’ll keep updating this thread as a potential reference for folks doing future HD8 rehabs. I went with the Simply Speakers foams linked above. I was able to remove one dust cap without damaging it, but the other one tore. I ordered the replacement screen/fabric dust caps in the link below. They will be a hair bigger than the originals, assuming the stated dimensions are correct. http://www.ebay.com/itm/182236113612?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT The foams and dust caps, should arrive in the next few days, so I may get started over the weekend if time allows. The voice coil gap is tighter than the gap in the AR18s 8” woofers I refoamed a couple months ago. The plastic shims I used on the AR18s woofers were too thick, so I made some shims from some thick, shiny paper (cover from a calendar). The difference in voice coil gap on the same size woofer has me curious. I’m sure the gap is a design parameter, but I’m not sure what else it interacts with. For example, does a tighter gap for a given voice coil diameter and magnet size provide a more linear or more efficient response to the magnetic field? Regarding the crossover caps, the crossover has a 4.7uF and 8.2uF electrolytic. After I get the new foams installed and give them a listen, I may replace the caps with new electrolytics of the same values. I think film caps will be too large for the terminal cup.
  7. HD8 refoam

    Thanks, tvdantv. Simply Speakers does not recommend shimming the voice coil. I shimmed the voice coil on my only other refoam job, so not doing it makes me a little nervous about centering the cone on the voice coil. If I do shim the voice coil, not sure if the original screen dust caps can be removed without damage so that they can be reused. This kit includes shims and screen dust caps, but they indicate that the foams may need to be trimmed to fit inside the recess in the frame. http://www.ebay.com/itm/Boston-Acoustic-HD8-8-Woofer-Refoam-Kit-Speaker-Foam-w-Dust-Caps-/160391234508?hash=item25581003cc:m:mB80ruoxbDq48cr0JDaZpog
  8. HD8 refoam

    Have not ordered woofer surrounds yet, but pulled the woofers to start the prep work. Surprised at how small the magnet is for an 8" woofer. It's about the size of magnets I've seen on 4.5-5.5" midrange drivers. Heck, I've seen bigger magnets on a couple tweeters. Curious about the bass performance with such a small magnet, once new surrounds are installed...
  9. HD8 refoam

    Picked up a pair of HD8 and need to refoam them. Thinking of using these: http://www.ebay.com/itm/Boston-Acoustics-8-HD-8-HD8-HD-9-HD9-Woofer-Speaker-Foam-Repair-Kit-FSK-828-/130808153361?hash=item1e74c60511:m:mEtObaBkmlITsLwMj2o3Rrg or http://www.ebay.com/itm/Boston-Acoustics-A60-A70-HD8-HD9-A400-BEST-Filleted-Foam-Surround-Repair-Kit-/172368150863?hash=item2821f1414f:m:mCvcRpHM7zQBHFg-8SlIbPA Which would you choose? Or, is there a better option? My first refoam was on a pair of AR18s, and the resulting bass is pretty weak, so I am hoping to get the ideal foams for the HD8 to restore the bass to original performance. Thanks, Adam
  10. Rock Partners

    Guys, I just refoamed AR18s woofers and removed the dustcaps completely, started with an Exacto knife, and peeled them away from the original adhesive with a tweezers. I did not have to cut them, and was able to reglue them intact. The dustcaps are rubber and did not permanently deform in the removal process. Not sure if the RP woofers would allow this, but just wanted to throw this out there. As an AR refoaming newbie, take this with a grain of salt.
  11. AR's Biggest Little Speaker? AR-18s

    I found the brochure (on this site) for the AR speakers series that included the 18s (the baby of the series). Great read - read it twice on business flights this week! Reading that brochure gave me the impression that AR speaker design was pretty advanced for that time. Looking at all the models in that series, it seems like the paper tweeter models might be the lower tier models in that series vs. the dome tweeter models. Is that correct, and were the dome tweeter models better performers across the series?
  12. AR's Biggest Little Speaker? AR-18s

    Both surrounds are holding fine after several hours of play at fairly loud volume. I do notice that the second woofer completed seems to have a stiffer suspension when I push on the cone. Not sure what’s causing that, but I do not hear a difference in the woofers. Overall, the 18s bass is lighter vs. the NHT SB3 (acoustic suspension bookshelf with 6.5” woofer) that I use in this room (large unfinished portion of basement). I have them on a shelf about head height when standing, with the back of the speakers around 5” from a sheetrock wall that separates the finished and unfinished parts of the basement. I think the bass will improve in a smaller room with the speakers near a wall, possibly with the woofers near the ceiling (I’m thinking mounted in the upper corners of a garage or rec room when my daughter has her own house). The bass they have is tight and detailed though. I think they would mate nicely with a musical, sealed sub to fill in the low end. In general, I am liking the tight bass that the acoustic suspension speakers I own have (18s, NHT SB3, and SB2). My floorstanders in other rooms are ported (Polk LS90 and Klipsch RF-7II), and I am now interested in trying out some acoustic suspension floorstanders, although options are limited vs. ported. Back to the 18s, I am pretty impressed with the way these little, entry-level, unassuming speakers sound. At a glance, they sound better than they should when you compare their dated paper woofer/tweeter and single cap crossover to current models with modern drivers and sophisticated crossovers. The 18s are an eye-opener for me. They make me wonder “how much has speaker design/performance really advanced in the last 35 years?”, given that this inexpensive speaker from 35 years ago sounds so good. I am a bit baffled, but you all are members of a vintage speaker forum, so you must have a reason to like these old speakers. I will keep an eye out for more of the model 18 variants. What are the larger models in this series? Did they make a larger bookshelf and floorstander in this series? OK, sorry, enough rambling...
  13. AR's Biggest Little Speaker? AR-18s

    Mine are not perfectly centered because I looked at the back side after the glue was set-up (a learning moment). I originally thought that using the surround outer edge to frame outer edge would be a good reference for centering, but learned that this does not result in perfect centering. My gut tells me that having the surround off-center a mm or 2 from the cone won't be a problem, as long as there is enough cone to surround bond area everywhere.
  14. AR's Biggest Little Speaker? AR-18s

    The PE instructions did say to apply glue to both surfaces and let the glue cure for 5 minutes before bonding. I followed those instructions, but bonding was still a challenge in some areas on the cone and frame, especially on the second woofer. Hopefully it will hold. I do honestly feel that I put a great deal of time and effort into this, so hopefully the bonds will hold. If they don't, it was still a good learning experience. Any thoughts on the other questions above?
  15. AR's Biggest Little Speaker? AR-18s

    The other 18s refoam and recap is done. Will test tomorrow afternoon after the glue cures around 24 hours. For some reason, the second woofer did not go as smoothly - the foam did not want to adhere to the cone and frame, and took constant work and attention to get it to adhere. Hopefully it holds. I will give them a rigorous test over the next few days. If the foams do not hold, I will probably just part-out the tweeters. My intent is to give these speakers to my daughter to use as garage or rec room speakers when she get a place of her own in a couple years. I showed them to her and she was very appreciative and thought the retro look was cool. Both woofer frames have some rippling (see pic). I have never seen this before. I wonder if this is just an artifact of a crude manufacturing process, or if the ripples are there by design for some reason I don't understand? I also attached a pic of the Dayton cap, which I soldered in place and hit with a got glue gun to secure to the board. Based on the appearance of the woofer and some research on earlier models, seems like these drivers date back to the early 70's, although the speakers were made in 82-83. Is this typical for AR? Here are some learnings and observations from this project, my first refoam: 1) The cone and frame clean-up prep is time-consuming, but straight-forward. 2) I'm glad I decided to shim the voice coil gap. It added a step, but it was no big deal to remove and reattach the dust cap, and it provided some peace of mind. 3) Centering the surround by eye to the frame does not necessarily center the cone on the surround. This was apparent when viewing the back side of the cone. If I decide to refoam again, I will adjust foam placement based on viewing the back side of the cone. Does this sound right? Thanks for all of the input. Adam