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RoyC

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  1. RoyC

    LST Tweeter Output

    That's a good point, Tom. I would add that using any replacement tweeter(s) of a different type in combination with original tweeters will significantly throw things off due to this arrangement. I don't recall hearing much of a difference, however, when all of the original tweeters were working properly with similar uninstalled output....or if all identical replacement tweeters were used. The tweeter arrangement consists of two parallel pairs of series-wired tweeters, filtered by a single (6uf) crossover cap. Roy
  2. RoyC

    LST Tweeter Output

    They are supposed to be the same. Due to the nature of their construction and age related degradation, however, the 8 old tweeters in a pair of LST's often vary significantly in output these days. In fact it is not unusual to find just 2 of these tweeters to vary in a pair of 3a's. Roy
  3. RoyC

    Another AR-3a restoration

    I'll go with bullets so you and the rest of the gang don't have to wade through a long narrative. -The only difference between the 4 and 8 ohm versions of the tweeter is the voice coil resistance. You can't tell by looking at them. The 8 ohm version is, of course, less sensitive. -The Midwest tweeter, like the HiVi tweeter, requires a parallel coil. The goal of these rebuilds is to eliminate the coil and to use the original crossover cap, though a modern tweeter/coil combo is likely to be the most consistent and long lived solution. -It is very likely you have not heard any of these tweeters in a "fresh state" in lots of years....don't know how many. As with the AR-3 drivers, the coating over the voice coil gap changed over time as well. It should be noted, however, that AR had the tweeter controls maxed for their listening vs live demonstrations. (I believe Tom T and/or Steve F mentioned there was some treble boost as well for those occasions.) -Output and overall response can be manipulated. The tweeters I sent to Kent were deliberately on the more reticent side of the replacement options. It is not just the sensitivity, however, that can be varied with the suspension foam. AR manipulated the physical and mechanical properties of drivers to dial in response characteristics...so crossover frequency can also be affected during the manufacturing and rebuild process. The cloth dome I'm using is lighter than the original paper dome, and its voice coil has a slightly higher dcr, so Chris and I are dealing with somewhat different issues to achieve similar results. Since we are not working with large volumes, we are both making an effort to match the response of tweeter pairs. (It is recommended to have tweeters rebuilt in pairs for obvious reasons.) Ideally these rebuilds will result in matched tweeters with characteristics as close as possible to AR's intentions. I have yet to hear a rebuild that was not a significant improvement over a typical original tweeter in its original state. -AR speakers of the era had inherently wide dispersion. The completely exposed tweeter dome and the tweeter's extremely high crossover frequency were its primary contribution to this attribute. For this reason AR "got away" with this tweeter's probable response variations. With two speakers playing under typical conditions, the vast majority of users were never going to hear any variations between a pair of these tweeters. Once again, I encourage the more technically inclined members to get an idea of what tones at 5000hz and above sound like...and to compare tweeters during restoration work. Frankly, as time went on, some of the back-wired versions of this tweeter I have seen should have been in that reject barrel. (Tom T has confirmed that quality control was not very good near the end of this tweeter's production.) Roy
  4. RoyC

    Another AR-3a restoration

    Robert, I'm convinced this tweeter was a nightmare for AR to manufacture consistently. The suspension material's characteristics are affected by mixing ratio, amount applied, mixing temperature, and degree of migration into the voice coil gap as it expands. Other variables were the clear rubber coating applied over the voice coil gap, and the nature of the now-dried-out foam under the dome (my dome has a cloth roll over the gap in lieu of the coating). I have listened to and tested many hundreds of these tweeters over the years, and though they were all reticent in nature, the output differences have been all over the place. Ken Kantor also provided some data awhile back confirming the nature of these tweeters...so at this point I don't think its response is all age related. It also explains why some people prefer a smaller capacitor with the HiVi, and some don't, based on what they are used to or expect to hear. For this reason I'm back to recommending the use of the original capacitor value as a starting point with the HiVi tweeter. I believe the key to the successful use of the original tweeter was, in fact, the availability of level controls, along with a very high crossover frequency. (Listen to a 5000hz test tone sometime...not much to hear up there by itself.) I believe these were "variably reticent" tweeters to begin with, and there was a range of acceptability. In other words, the tolerances were not as tight as we might like to believe. Replacements such as the HiVi (with the requisite parallel coil) and Chris's rebuilds are actually on the "higher output" side of acceptability, imo, and the level controls are useful for these. My effort is simply to provide a less labor intensive repair of the original tweeter within the acceptable response range using the original cap value, without the need for a parallel coil. It is also a way to more easily re-purpose a tweeter body with a missing or badly damaged dome. Chris and I largely agree on the issues mentioned above, and will continue to compare notes. I'm certain his excellent rebuild, however, will remain the most authentic in terms of construction. Roy
  5. RoyC

    Another AR-3a restoration

    Ra.ra,...Do you own any of the AR models (3a/2ax/5) with the 3/4" black dome tweeter? These are unique animals, and the tweeter (crossed over at a very high 5000hz) is quite reticent by nature. AR's "normal" setting for these models was just off maximum, and I know of nobody who sets this tweeter below that point. The age degradation typical of this tweeter causes sensitivity and consistency issues, which has lead to confusion and some debate as to what the "proper" response should be. My repair is an attempt to consistently (that's the hard part) make it respond similarly to the original. The foam suspension material can be manipulated to result in very high to very low sensitivity, but its variable nature has led me to understand why the factory rejection rate was so high. Recently I had a long discussion with Chris (chris1this1) regarding the construction of this tweeter and was planning to discuss some of the considerations and concerns we both share in the repair of these tweeters. I just didn't want to hijack Kent's thread. Btw, very nice job, as always, Kent! Roy
  6. RoyC

    Crossover reccomendation

    Agreed...I've had the opportunity to try both the 12" AR and Large Advent woofer replacements. These are wholesaled by AB Tech (or CB Tech, or whatever its called these days) and retailed by Simply Speakers, "Vintage AR", and others. They are significantly less compliant. Their best attribute is they fit the cabinet holes. Roy
  7. RoyC

    Ar7 tweeter replacement

    I have (2) 038 tweeters available. Send me a PM if interested. Roy
  8. RoyC

    Inherited two AR3s. Need advice.

    I agree. John, Where are you located? Roy
  9. Hi Luigi, Thanks for posting the drawings. They are consistent with my experience. I have never seen an alnico magnet/cloth surround woofer in any AR-3 or 3a with date stamps showing manufacture dates after 1969. On the other hand, I have seen many of the notched ferrite magnet/foam surround woofers shown in the drawing in 3a's with manufacture dates from very early 1970 into 1972 (when the notches were removed). I have only seen a few post-1970 AR-3's, and they were also equipped with the notched magnet woofer...along with the AR-3a style mid. It makes sense to me that the ferrite magnet woofer would have been ready to go by 1970. This becomes important when replacing woofers in earlier AR-3a's originally equipped with the alnico magnet/cloth surround version. AR changed the woofer inductor coil in the crossover for the ferrite magnet/foam surround woofer from #7 (1.88mh) to #9 (2.85mh). When replacing woofers in earlier AR-3a cabinets it is therefore necessary to increase the woofer crossover inductor's value to 2.85mh when the replacement woofer is the later ferrite magnet version. This will have a much greater impact on achieving the correct sound than the usual, typically discussed repair items such as level control and capacitor types. Roy
  10. RoyC

    Another AR-3a restoration

    I have never seen an original AR-3a cabinet with a #7 (1.88mh) coil when originally equipped with the later foam surround, ferrite magnet woofer, nor have I ever seen one with a #9 (2.85mh) coil when originally equipped with a cloth surround/alnico woofer. The #9 coil was used to compensate for the woofer change. There are probably quite a few 3a's in use today with later replacement foam surround/ferrite magnet woofers and #7 crossover coils, which is not a good combination. On the other hand, the alnico/cloth surround woofer can be used satisfactorily with either coil due to its smoother response. A good rule of thumb is to replace the block caps, regardless of measurements. Roy
  11. RoyC

    AR3a grills

    Larry/Vintage AR used to make replacement frames out of masonite, which is very hard to staple. He went through quite a few electric staple guns when he was using that stuff. Furthermore, the tips of the 1/4" staples would sometimes stick out on the other side. Last year I persuaded him to switch over to MDF which is a bit thicker, and much easier to staple. No glue is necessary, but a power stapler is still needed. I recommend painting the surface on the cloth side of the frame black (like the original). I purchase MDF at Home Depot. Rolls of 3/4" double-sided velcro can be purchased at some craft stores, Walmart, and Home Depot, with one side being the "hook" and the other the "loop". I cut strips to size, and attach it with 1/4" staples and a dab of Goop glue. Goop glue is actually strong enough to do the job without staples if it is not applied over another adhesive (and as mentioned above, the self-stick velcro is useless). This is the velcro I've been using: https://www.walmart.com/ip/VELCRO-R-Brand-ONE-WRAP-R-Roll-3-4-X12-Black/19535849 Roy
  12. RoyC

    AR 2ax Advice Please

    I have one...the trash bin. Corrosion and attempted cleaning have taken a severe toll. I also noticed a hole in the wiper tip in the photo, and it appears the resistor wire has been sanded or "Dremeled", which can change the resistance properties of the control. There is no value in retaining pots in this condition when reliable alternatives are available. Roy
  13. RoyC

    Crossover issues AR-2AX

    As ra.ra pointed out, you apparently incorrectly installed the larger cap (6uf) in the tweeter circuit and the smaller cap (4uf) in the mid circuit. There is nothing likely to be wrong with your new film capacitors. There could be issues, however, with what you did with them. If you did not use a parallel coil of some type with the Peerless tweeter (as you should have with the HiVi tweeter), there is much more current going through it. If so, your intended "upgrade" was most certainly a downgrade. There is also no reason to believe the Peerless tweeter would have represented any kind of improvement over a properly implemented HiVi tweeter. Buzzing is most often caused by a malfunctioning or over-driven driver. Roy
  14. RoyC

    Appreciation for Roy C!

    Thanks Chris, Speaking of trailblazing, you're the one rebuilding the AR tweeter I said could never be rebuilt! I'll be making a decision on the Peekskill meet by this weekend, as some previous travel plans may be changing. It would be fun to get together. I've actually got some interesting tweeter stuff to run by you.
  15. RoyC

    Appreciation for Roy C!

    Yikes, I walk away from the forum for a few hours and you all start talking behind my back! Hey, although I'm working on it, "I ain't dead yet". With the exception of my old friend Tom Tyson (who is all things AR, and should give paid AR tours of his basement), I've probably knocked around the technical particulars of AR speakers longer than most of you, but none of the regular contributors and friends posting in this thread can be accused of providing information any less freely than I do. I've learned more than you know from you guys. Furthermore, here is a story about a forum member who complimented me above for being "generous"...lakecat (Jeff) acquired a bunch of audio stuff at an estate sale a few years ago. Along with AR speakers, there was a piece of tube equipment he wasn't interested in, so he offered it to me for peanuts. When he told me what it was I suggested he should not do that. Within a couple of weeks a surprise $400 showed up in my Paypal account after he completed a sale of a Marantz collectible! So, back at ya regarding the generosity thing, Jeff! (Btw, Jeff is in Ohio, I'm in NY, and we have never met...though he still owes me a beer and a barbecued brisket meal). Seriously, other than to blush and say "thank you" I wasn't sure how to respond to this thread, but my appreciation for being a respected part of this gang, along with the friends I've found here, is easily equal to what you have posted above. Thanks again, Roy
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