ra.ra
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Posts posted by ra.ra
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Regarding the AR-2x, it was available in at least two variations, with different tweeters, woofers and crossovers. If you use the AR-4x tweeter, your tweeter cap should be replaced with a 20uF. You'd probably need something similar if using the PRT tweeter. But if you use the original AR-4 tweeter (or AR-2ax mid), I think you can simply re-use the original AR-2 oil caps. These AR-4 (2ax) drivers are typically available at reasonable prices. With any of these replacements, the speakers could be used in vertical orientation.
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1 hour ago, KenB said:
I reassembled the units and they really sound lovely. However, I would like to replace the tweeters....
Hi Ken, welcome to the forum. I'm a bit confused by these statements - - - if they already sound lovely, why are you interested in modifying your AR-2's? If you want a historically accurate "upgrade", you might consider the original conversion promoted by AR, which would turn your AR-2's into AR-2x speakers. Replacing with a modern tweeter will most likely require unknown crossover modifications.
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One more pic here - - view looking at inside of front panel thru woofer hole. On left is phenolic ring tweeter and at right is the Danish midrange driver with its capacitor, which will be either 20uF or 33uF. Associated sand cast resistors are either attached to driver terminals or globbed onto cabinet panel.
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On 3/28/2020 at 8:52 PM, Mark T said:
I have a pair of DA D-4 speakers I bought new
in 1973.
Hi Mark, and welcome to the forum. It's always interesting to hear from someone who has held on to the same pair of speakers for nearly 50 years. Even after more than a year, I have not completed work on the four DA D-4's shown in this thread, but I'll attach a few pics which may be helpful for you.
You are correct to not attempt to remove the front grille cloth and underlying grille panel. The only exception might be to facilitate a driver replacement, and I don't even want to think about that procedure. Pertinent access can be accommodated after removing the rear switch panel and the woofer and its screen covering. See pics attached.
Even removing the woofer screen/grille is a bit of a challenge. First, you can see from the pic that the frame is constructed from four masonite (actually more like MDF) slats butt-jointed and stapled together, and this prevents the grille frame from remaining stiff and planar as you remove it. These are held in place with many small industrial headless nails, and the only way to remove grille is to be patient using correct tools to slowly and gently pry up the grille around its perimeter. Slightly painstaking, but I was able to remove all four with no damage to the black rear grilles.
Removing the switch plate is mostly straightforward, but after removing screws, you can see from pic that there was a material used (latex caulk?) to seal the metal plate to the wood cabinet, and it takes a thin slicing tool to break this seal. On the backside, you will find a jumble of components that make up the bulk of the crossover, but there will also be another capacitor and a couple resistors elsewhere inside the cabinets.
I've got some additional pics, but please ask questions as you go along. With one-owner speakers as you have, you may not have some of the problems that I've found - - - in my case, some of the switches and wire terminals have been damaged and will be getting replaced. The very helpful DA expert I've found goes by the name "stickman" on the Audiokarma forum.
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4 hours ago, Giorgio AR said:
.....it should be an M prefix........AR speakers were assembled in Italy
I'm sticking with my theory about the sloppy handwritten "H" indicating Holland, but if a plausible explanation for an "M" prefix turns up, it will be news to me. Additionally, I am not familiar with the notion of assembly taking place in Italy, so all of this could be very informative if it can be suitably documented. Your collection is indeed impressive.
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4 hours ago, Giorgio AR said:
....the third pair of AR7 ....... is a late model with vinyl coating ....... this one .....has consecutive numbers on the labels....
It is interesting to see the subtle changes throughout a product's years of production. Not only did the cabinet covering change from wood veneer to vinyl, but I notice a few other minor variations. Your third pair includes a rear-wired tweeter - - it is possible that the part number may have changed with this revision, but I believe it has the same diameter magnet structure as your front-wired versions, and neither tweeter utilized ferro-fluid. Also, I notice that your latest pair has that "Euro" speckled paint on the cabinet backside; and that the terminal panel with switch has been rotated 90°. In fact, I think your latest pair uses a different switch with plastic toggle. Consecutive serial numbers are mostly standard for AR-7's because they were shipped with two speakers in one box. You have a very fine collection.
4 hours ago, Lucky Pierre said:I listen to the combo daily in my kitchen.
Perfect little kitchen speaker - - often small enough to place on top of upper cabinets.
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1 hour ago, fallen_trumpet said:
I also tried Blue Bear soy based wood stripper (Paint & Urethane Stripper)....
I am unfamiliar with these stripper products, but it appears your early attempts are rather successful. There still seems to be no consensus about the precise type of wood finish originally used on the KLH Five, but I have read about agonizing attempts to strip these cabinets using other products. Perhaps your thread will open new doors for future restorers of this excellent speaker model. Please keep us informed.
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Hi Giorgio, that's a fine-looking quartet of AR-4x's you have. My response here will include a little bit of personal documentation along with some conjecture to try to assist with your mystery serial numbers.
The original AR-4 used the letter prefix "F" in the serial number identification. Shortly thereafter, this model was revised to become the AR-4x - - with different woofer, tweeter, and crossover - - and adopted the letter prefix "FX" in the serial number ID. From my own collection, I can confirm these serial numbers for 4x speakers assembled in the USA:
- 1966: 38,000
- 1968: 160,000
- 1970: 320,000
- 1971: 380,000
I believe you are correct that the extra prefix letter in your serial numbers designates assembly outside the USA, and it is clear that your numbers and dates do not coincide with the USA serial numbers I have listed for general comparison. Clearly, the two European factories (England and Holland) used a numbering system completely removed from the USA production numbers, but I would not know if the two Euro sources shared and combined numbering or if they acted independent of each other.
My guess here: in your case, I believe the added prefix letter is not "M"; but instead is a crudely scripted "H" to designate the Amersfoort, Holland location. I suspect that new paper labels had not yet been created to show the European address printed on them - - but as your AR-7 speakers from Holland show in this attached thread, the Holland address was indeed included by 1973.
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I think there was more than one woofer used in the Rect-III, and the early ones had pleated paper surrounds, I think.
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Thanks for the pics. Did you ever find out from the previous owner what happened to original woofers? I'm just guessing, but it could be another sad case of tossing them once the original foam surrounds failed.
Attached are two interesting blurbs from October 1975 Hirsch-Houck Labs review from Stereo Review, as well as a frontal pic with original woofers. It's interesting to note that this is an acoustic suspension design, whereas most of the early Rect models were ported bass reflex designs. The notion of individually factory adjusting each of the pot controls to a fixed setting is mentioned in the review, and you can see the red tips (wax?) of the pots in your pics. Does that 7-inch octagonal Phillips driver have rubber surround?....and whizzer cone?
I have a few other Rect 5 documents if interested.
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4 hours ago, 300man said:
I can try to post pictures if there is any interest.
Welcome aboard, 300, and yes, we all like pics. Keep files in the 100KB range with a common file format (jpg) and you should be fine. This is a somewhat rare Rectilinear model, just after they abandoned their typical use of Roman numerals to identify their speaker line. This was during the company's fading days, but they still made a few excellent products (like yours). There was both a Rect-5 and a Rect-5a, and I believe all drivers were different from their earlier flagship speaker model, Rectilinear III (tall boys). Really a shame you are missing the original woofers.
If you have pics of the crossover, this might be of interest, too. I'd be curious to see the layout and cap values used for this configuration, but members here also might find it interesting to see that this model used the Aetna-Pollak pots found in so many early AR speakers.
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Hi blachool, and welcome to the forum. Welcome to fr3e, too! Aside from the usual woofer re-foam, the most typical component that gets restoration attention in 45 year-old speakers is the crossover capacitor. It may or may not require replacement, but it is a simple and inexpensive process that gives peace of mind for years to come. See attached link.
Cleaning the grille cloth can be a delicate operation, but many people have had varying degrees of success using various household cleaners, including upholstery cleaners or spot removers for carpets or simple soap/water solutions. I am fairly certain that your Advent cloth is a synthetic fiber, and you should try to keep the rigid grille frames as dry as possible.
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Thx for update on crossover components. I really like having the rotary control in the tweeter circuit, but I think it only showed up in the early issues of their popular speaker models. When you see the x-o replacement that Huw offers for sale, it is nothing more than some decent binding posts, a bit of wiring, and a new (rebranded) cap, all mounted to a small plastic panel.
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Thanks for the reply and the pics. The 17 is such a beautiful speaker: great proportions, real wood veneer. I do get confused about the various differences with these 8-inch AR drivers, but all of the ones I've used have been intended for small two-way speaker models.
I have a pair of AR-28b that use the 050 woofer and 034 tweeter, but my crossovers use a 5uF (50V Unicon) cap instead of the 6uF you mention. I found 5uF caps in the AR-18s and AR-18b as well.
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Congrats....AR-17's are a little bit on the rare side, and I've never seen a pair. What is the uF value of the cap in the 17, and how do you like the performance of that woofer? Which models used the 045 woofer?
Those look really great - - - nice work!
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Looking over previous posts, I realize I should've worded my comments differently - - - there was no intention to ruffle any feathers - - - my aim was not to tsk-tsk the OP, but to alert future users of the dangerous combination of unfused speakers at high volume levels with this type of program material. I still doubt that the amplifier was the problem here.
On a pair of Smaller Advents I restored last year, I removed the crossover panels to facilitate the installation of new caps and wiring. Like Guido has already noted, these 1/8" Masonite panels are typically installed with both glue and staples. After carefully removing all staples and cutting thru any exposed glue residue, I was able to easily push these free with a light tap-tap-tap from the backside using a block of wood to cover as much of panel area as possible. When re-installing, I used compressible foam strips for the air seal and small machine screws/washers for attachment.
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On 3/21/2020 at 5:48 AM, Guido57 said:
....replaced the crossover with the common EPI setup of a 10 uF capacitor parallel to the tweeter while adding a 1.5 ohm resister.
Hi Guido - - - my comments are based on limited experience with the EPI-100, which uses the same drivers and crossover configuration as the 110 model. I want to mention that the cap in this circuit is in series with the tweeter (not parallel), and also ask where you've seen this notion of a 1.5 ohm resistor.
Pic attached shows original EPI-100 crossover, which appears to have wiring connections very much like the one shown in your pic. (Pay no attention to the 8uF cap value rather than the typical 10uF - - this remains a mystery that has not been solved.) I know the wiring does not look exactly like the schematic, but I'm accepting it as accurate since the speakers sound so wonderful. And just like yours, my pot controls are 25-ohm, 5-watt.
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On 3/21/2020 at 6:30 PM, bmz said:
....a recap of my ar-4x using mundorfs m supreme. Their closest value is 22uf 250v.
The 4x speaker will typically show noticeable improvement after a re-cap, particularly if the original caps were the large wax block type, but the replacement caps need not be anything too exotic. One thing to be aware of with the 4x is that it uses a cap value (20uF) which is abnormally large for a tweeter circuit. The Daytons that Larry mentioned will work fine. Mundorf makes a wide variety of excellent and suitable capacitors in many price ranges, but it is unclear which model of Mundorf cap you are considering.
The Mundorf MCap Classic has a white body and is available at 250V and 400V for a 22uF cap value, with the 250V version having 29x44 mm dimensions. Many restorers like these for crossovers, even if they are slightly more costly than more common brands of poly caps. The Mundorf MCap Supreme Classic has a black body, but I think is only available at 600V for 22uF cap value. This cap is very large with dimensions of 50x106 mm (2" dia by 4" length) and will be rather expensive.
If you do proceed with this re-cap project, do not forget to inspect and diagnose the tweeter pot controls - - these will certainly require careful maintenance or full replacement if you wish to get the most out of your restored classic speakers. During this process, take a few moments to closely inspect the drivers, too.
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1 hour ago, real1shepherd said:
I used to use fast blow fuses on the speaker wires....
My first thought reading the original post was curiosity about whether external fuses had been in use. Without them, driving (four) vintage loudspeakers from a single source of amplification while blasting techno music for a youth dance sounds to me like a recipe for disaster.
1 hour ago, real1shepherd said:...but bringing in the big DJ amp was my mistake.
I am unable to comment on the suitability of this particular amp for this application, but I think the mistake was not providing fuses in the first place and unrestrained use of the volume control. Playing techno and house music with significant dynamic peaks at high decibel levels can be dangerous for aged speakers not intended to handle such material. I have owned audio gear for near 50 years and have never blown a speaker driver due to abusive behavior, but then I've never had much interest in trying to recreate stadium sound levels from equipment intended for home use.
The Advents are probably worth restoring, and the tweeters are not all that hard to find for replacement. During this process, you'd be well-advised to inspect all internal components and refresh noticeably aged or damaged parts. And don't forget to install some external fuse blocks on backside with appropriate fuses.
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Hey Don, those 2a's look pretty nice, but I would suspect they need a full disassembly and careful rebuild with all components checked out and confirmed. After you've given them a test drive, let us know what you're observing regarding functionality of drivers, etc.
Nice to see the original grille cloth and badges - - with slow and careful attention, you might be able to get those grilles looking real good, despite the one small tear that might be re-stitched. From the rear close-up, those pots appear very crunchy - - you may want to give them a little spray of electronic cleaner/lube before you even try to give them a rotation.
Am not certain, but I think you may have birch cabinets that have a light brown or honey stain by previous owner? Just a guess, but it does not look enough like cherry or walnut.
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3 hours ago, Lazer said:
I’m in the process of a reform on the VIFAs in my Snell Eiii and will hand lay the wood glue (per AN suggestion) with a pinstriping brush
Hi Lazer and welcome aboard. I am not familiar with this woofer, so you may wish to post some pics for better description. If you'll note in Carl's original post, he mentions a non-hardening polymer, so I would think wood glue (which hardens) is among the last substances you'd want to apply over a foam surround. The substance shown on the AR woofer in the second post was very soft and pliable after 30+ years, and it felt very much like cured rubber cement.
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Excellent post, nice speaker, all original components. The pics show everything a potential buyer might need to know. Best 'o' luck.
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13 hours ago, MGM Audio said:
Glue (which kind ? ) or glue and staple ?
You might want to post a pic or two to show your specific situation - - some of the European products have minor differences from the U.S. versions with the same model number. The AR-18s (not AR-18) from the U.S. employs a very thin stretchy brown fabric over a molded plastic grille frame - - definitely no staples involved. Attached pic shows Euro version of AR-18s.
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Kent's advice is spot-on. The Seventeen is a more serious product and among the favorite models of many KLH devotees. The Thirty-two is a wonderful small bookshelf speaker that I like a lot but does not garner much attention amidst the panoply of speaker models coming out of that factory. Attached is my experience with the Thirty-two.
AR2 Tweeter
in Acoustic Research
Posted
Yes, see the fine print on AR's literature attached in earlier post.