RoyC

I agree 100% with everything Kent has advised. Crusty corrosion on pots' wiping surfaces always has pits under it. There is no rational argument relating to sound to retain them in pitted condition no matter how shiny you can make them. Toss them or sell them to someone who just has to have original AR shafts sticking out the back of the cabinet. Btw, referring to an earlier post in this thread, the pot's center disk cannot be rotated. It is solidly riveted in place and not worth the effort. Roy

David, The caps are not Sprague, but I have never known them to damage an amp. The DCR of the AR 12 inch woofer is 2.6 ohms. Roy

David, Polyfiber was used as the cabinet damping material in later AR-11's and 10pi's. I believe it was 11 or 12 ounces. Roy

Hi David, Yes, they were the same drivers used by the AR-11 and the last version of the AR-3a. The 2nd iteration of the AR-11 and 10pi had essentially the same midrange, but the metal screen was silver colored and the fiberglass pad was pink (A.14 on page 30 of the 3a restoration guide in the Library). AR did not begin using Tonegen drivers until well into the 80's. Roy

Kent, Perhaps it was an oversight...John never questioned the 25 ohm resistor/L-pad combo, and, in fact, verified it before we wrote the guide. Page 15 of the 3a restoration guide was written by him with my input. (Btw, it is easy to verify with a simple ohmmeter.) In my opinion, the only valid reason not to use the resistor is when trying to eek out a bit more output from an old 3a style 3/4" dome tweeter. John was dismayed when he discovered the AB Tech "AR" level control replacements were, in fact, ordinary 8 ohm L-pads. It was the primary motivation to come up with a way to bring the influence of the L-pad closer to that of the original pot. Roy

Tim, The L-pad and AR pot are both variable attenuators, but are different animals. The "8 ohm" designation of the L-pad has a different meaning than the "15 ohm" designation of the AR potentiometer. The "8 ohm" L-pad, in fact, presents a higher total parallel resistance to the circuit then the 15 ohm pot. For every position of the L-pad, the parallel resistance is higher than that of the pot in relation to the series resistance. The L-pad's "8 ohm" designation means it is designed to provide attenuation in such a way as to keep an 8 ohm driver as close to 8 ohms as possible at each setting. The pot's "15 ohm" designation is simply the total of the series and parallel resistance at each setting. For example, when the 15 ohm pot is set so the series resistance is 3 ohms, the parallel resistance is 12 ohms. When the 8 ohm L-pad is set to 3 ohms in series, its total parallel resistance is near 30 ohms. This is why we recommend using a 25 ohm parallel resistor when using an L-pad...to reduce the (parallel) resistance, and therefore shunt more current past the driver to emulate the characteristics of the AR pot. (Placing resistors in parallel reduces the total resistance.) The bottom line is there is no practical reason not use an L-pad, especially when replacing crusty, corroded pots. (For the record, this is not an "evolving thing". It is why we included it in the 3a restoration guide. I think Kent was referring to the tweaking of the HiVi tweeter/capacitor combo.) The pot shown in your photo would be sent to the trash bin in my shop, though I would save the shaft, spring clip, and (possibly) the wiper for the parts bin. I only retain and clean pots with tarnish, not crusty corrosion. There are always pits under the corrosion, which translates into dropouts and questionable future reliability. Roy

The wire on the pot is a jumper between 1 and "B", which is a quick fix for a corroded, non-functional pot. It by-passes the series leg, maintaining the parallel resistance of the pot in the circuit. It is not original, so someone had opened the cabinets once before. It is the best way to by-pass a pot. Try the new L-pads as is. If the tweeters' output seems too strong in the midrange, solder a 25 ohm resistor across their terminals. This will make the L-pads' effect similar to that of the pots at typically used settings. Roy

I have had a few of these apart over the years, Pete. The magnet is not vented. In fact there is a wooden dome glued to the pole piece under the fabric dome, leaving only a very small space behind it. Roy

I don't know precisely when AR transitioned back to metal voice coil formers, but it is logical to assume the 10 inch woofer vc was changed over about the same time as the 12 inch woofer. I believe the earliest such 12 inch woofer I've seen had an early 1977 date stamp. As a point of interest, the earlier type of 10 and 12 inch AR woofers with cloth surrounds had metal voice coil formers. When AR went to foam surround woofers, around 1970, the vc former was changed to paper until the mid to late 70's period under discussion. I've often thought that AR's move to the foam surround type of woofer was more motivated by cost savings than performance improvements. Roy

Fortunately we know the coil and cap values AR used with their later tweeters in various models, which can serve as starting points. For example, the AR-3a Limited crossover used the AR-11/9 type of tweeter with a 4uf cap and .16mh coil, along with 8 ohm L-pads. That is a valid starting point, beyond which (motivation and resource dependent) tweaking and response measurements could be conducted. Keep in mind, knowledge of how crossover components affect response is extremely helpful and saves lots of time. Roy

Agreed, Jeff. Subsequent to my 2012 post I found SpeakerWorks.com to have a good AR-12 replacement, as well as other hard to find items...excellent retailer. http://www.speakerworks.com/speaker_repair_kits_s/65.htm Roy

rl1856, This new tweeter is for all practical purposes an AR-11 tweeter, which is not, and never was, an electrical "drop-in" replacement for an AR-3a style tweeter. AR modified the crossover by the addition of a small series capacitor when the AR-11 tweeter was used as a replacement for the earlier tweeter, and changed the crossover when it was used as the AR-3a Limited tweeter. My point above is that I presently find it too expensive to experiment with when there are already satisfactory solutions for the AR-3a type of tweeter. If anyone here has the $150 for a pair to experiment with for this purpose, I'm sure we would all be interested in the results. My educated guess is it will probably need a parallel coil of around .1mh to work in a similar fashion to the earlier tweeters in models like the 3a, etc. On the other hand, I played around with it enough to believe it is an excellent candidate as a drop-in replacement for any model originally equipped with the AR-11 or AR-9 type of tweeter. Jeff, I meant "roll off" in the other direction, as this tweeter and the AR-11 tweeter have much more midrange response than the 3a type tweeter. The solution for the AR-11 tweeter, as implemented in the AR-11 speaker, is a .1 parallel coil in the crossover. It is also the purpose of the .05 coil for the HiVi tweeter when used in the AR-3a. Roy

Agreed, Kent...That was largely Larry's perspective. My perspective is that it is too expensive to experiment with for use in early speakers when Chris' rebuilds and much less costly HiVi tweeters are available. On the other hand, I'm convinced there has never been a better post-AR general replacement tweeter for models from the AR-11 onward. For these models the MW tweeter may be as close to a "drop-in" replacement as we are ever likely to see. Roy

No...the tweeter is back in Larry's shop. The off-axis numbers are primarily a function of dome construction and position. I'm willing to bet the off-axis response is at least as good as the AR-11 tweeter, as these tweeters are virtually identical. In fact, the AR-9 tweeter dome is identical as well, with the exception of its (deliberately) recessed position to minimize off-axis response. (One reason the HiVi tweeter does fairly well as an early AR tweeter replacement is its semi-exposed dome.) I'm sure there are differences, but of all concerns regarding the integration of the MW tweeter, off-axis response will easily be the least critical. After discussing the tweeter with Larry today he said he will continue to sell only the HiVi tweeter as a replacement for early AR models, and he seems to have a large inventory of original AR-11 and AR-9 tweeters for later models. We agreed the greatest drawback to the MW tweeter at this point is cost. Roy

The photo is of one cabinet (serial number C19973) of a pair of 3's I acquired from an estate. The speakers were in their original AR shipping boxes which are labeled as "teak". The solid wood front trim pieces do look like oak. Roy

ra.ra and ar_pro, I completely agree with your comments, guys...though I'm personally curious as to what the leads look like under the covering. My motto seems to have evolved into "if it ain't broke, break it". Aadams, As mentioned above, I have no measurements. It is best to think of it as an AR-11 tweeter, which is more than adequate for the AR-3a...but like the AR-11, AR-9 series, HiVi, and any other tweeter of modern construction, the MW tweeter's response will require a crossover modification to properly integrate with early models (3, 3a, 5, 2a/2ax, LST, and LST-2). No tweeter of modern construction has the natural roll off characteristics of the early AR dome tweeters. Compared to the others, the MW tweeter's primary positive attributes are likely to be its appearance, ease of installation, and as a good general replacement for later models. Roy

I finally had a chance to examine the new AR replacement tweeter sold by Midwest Speaker Repair. Larry/Vintage AR provided the Midwest tweeter and an original (black dome) AR-11 tweeter, and I had an AR-9 tweeter on hand for comparison. The construction of the new tweeter is very impressive, and at least as good as the original AR tweeters. The integrated faceplate/magnet cup is the same as the AR tweeters, but it is made of aluminum vs the plastic of the originals. A convenient feature vs either original tweeter are the recessed, gold plated terminals, making it a simple drop-in fit for any AR dome tweeter cabinet hole from the AR-3 (see photo below) through the AR-9x series into the 80's. The new tweeter is otherwise physically identical to the black dome AR-11/10pi/12 tweeter. Other observations: -DCR of the two AR tweeters measured 3.3 ohms vs 3.7 ohms for the Midwest tweeter. (The MW tweeter is also available in an 8 ohm version.) -The cloth domes of all three tweeters appear to be identical, including the dome shaped piece of hard material just underneath each dome (based on past dissections, this material is wood in the AR tweeters). The AR 9 series tweeter dome is recessed in the faceplate, but is otherwise identical. -All tweeters weigh 1.5 lbs+/-. Magnet size is identical. -No measurement equipment was used, but the new tweeter subjectively has very similar tonal qualities to that of both original tweeters. It is, however, slightly more sensitive. -I quickly dropped the tweeter into an AR-3a and believe a larger parallel coil than the .05mh coil used with the HiVi tweeter will be needed to properly integrate it...but it sounds very promising. One downside is the front covering of the new tweeter would have to be cut to access the leads for front-wiring. -It may serve as a very easy tweeter replacement for the AR-11, 10pi, 12 (8 ohm version), and AR-9x series models with no crossover adjustments (for most people) when satisfactory originals are not available. -The Midwest tweeter is head and shoulders above any AR 3/4" general replacement tweeter I have seen since the very early 90's when AB Tech ran out of Tonegen-made replacements, and in my opinion, it is worthy of experimentation in many models. Between the HiVi Q1R, Chris' (chris1this1) early tweeter restorations, and the Midwest tweeters, we have never had better options for as many AR models. Attached are photos of the new tweeter next to an AR-11 tweeter, as well as one showing its perfect fit in an AR-3 cabinet hole. Roy

Lou, They do fit the vast majority of AR cabinets (including all AR-5's and most 2ax's) equipped with 10 inch woofers. They don't fit the early cabinets (AR-2/2a and early 2ax) originally equipped with cloth surround or very early foam surround 10 inch woofers. The use of an additional 1mh of inductance (around 3mh total) to the 2ax woofer coil brings it in line with the original sound. Fc is actually quite good. Still, I recommend the original woofers whenever possible. Roy

Harry, It may be a couple of weeks before I will get to see the one purchased by Larry/Vintage AR. Roy

I agree with Geoff and Kent. You already have the best woofers for the AR-5. The "Vintage AR" woofers are not in the same league, and would require a crossover change to be somewhat like the original. Roy

Larry Lagace ("Vintage AR") told me he intends to order one, and has invited me to assist in comparing it to the various original and replacement AR tweeters in his inventory. He also recently acquired some NOS AR-11/10pi tweeters, and has a number of Chris' 3a tweeter rebuilds, which will make it even more interesting. Roy

Hey Frank...Deep breaths, brother...in...out...Put on some music, have a nice beverage. Let's see if we can begin to sort this out. I have some preliminary thoughts: -It looks great. I particularly like the recessed terminals and the fully exposed 3/4" dome. It appears as if it will be a perfect fit in the existing AR cabinet hole. -The listed specs and construction tell us it is a "modern" tweeter, much closer to the AR-11/10pi tweeter than the 3a type of tweeter. This means it would still require a crossover modification just like all the other tweeters in Frank's inventory to work properly with the older AR models (including the LST). Models after the 3a, beginning with the AR-11, already have this modification in the form of a parallel inductor in the crossover. -Replacing front-wired tweeters would likely take some work. If the magnet is the same size as the original tweeter, front-wired installations may need to be changed to back-wiring. (The HiVi tweeter is easy to front-wire due to extra space around the magnet, through which the leads can be passed.) -At $80 including shipping, they are considerably more expensive than the $20 HiVi tweeter. -Chris's rebuilds are much closer in spec to the original 3a type tweeter, do not require a crossover modification for use in the 3a or LST, and are about the same price. -I would not at all be concerned about it being manufactured in China. Vintage AR has sold hundreds of Chinese manufactured HiVi tweeters and L-pads, and has never run across a defective one. ALL of the AB Tech replacement parts in the last 2 decades of business were manufactured in China. There are very few parts not manufactured in Asia these days. Many of them, like the HiVi products (Swan) are designed here in the US or Europe. I'll order one to play with, primarily to find out how close it is to the AR-11 tweeter and to verify how well it fits the cabinet hole. The Simply Speakers tweeter is a left over from AB Tech. Recessed dome, over-priced, and nothing special... Roy

Ra.ra, only those who have read lots of audio forum fluff, and have calibrated hearing, can hear those Solen/Dayton differences...and as a bonus they don't require any actual technical knowledge about electronics. I have read your posts, AR surround, and don't at all mind riling you up. To quote Paul Simon..."a man hears what he wants to hear and disregards the rest". Roy

Hey Jeff, I've successfully used heavy duty spray adhesive. Just spray the frame, and carefully place the material over it...then trim if necessary. I leave enough material over the edge to tuck it in the cabinet molding groove without folding it over the edge of the frame. I've attached a couple of photos. Roy

Last week I had an opportunity to test one of Chris's completely rebuilt AR-3a tweeters in Larry/Vintage AR's shop, and it is excellent. In my opinion, he has pretty much nailed it. Voice coil measurements and suspension materials are virtually identical to the original tweeters...and he does a great job of re-forming the original paper dome. Roy