RoyC

Carl, I've been reading Villchur's original patent document for some insights. The question of "how sealed" a cabinet needs to be is a good one, as "a small amount of air bleeding or air leakage is permitted" according to the document. It also states that "the enclosure is designed to provide an acoustic seal, that is, one which does not allow significant air leakage over a period corresponding to a half-cycle of the lowest frequency encountered". Nowhere in the document, however, does it suggest that the "acoustic seal" lowers fc, only that it provides "uniformity of frequency response at lower frequencies". According to Villchur the surround must "be substantially air-tight to confine the acoustical pressures produced by the diaphragm". The low fc of an acoustic suspension speaker is largely a function of an extremely compliant woofer suspension. It appears that the "elastic restoring force" of the trapped air inside the cabinet simply provides control, and prevents over-excursion. According to the document over 90% of the restoring force is provided by this cabinet pressure, and the rest by the woofer's mechanical suspension...so obviously the seal's integrity is very important to the scheme of things. Acoustic suspension speakers (like our old AR speakers) are more akin to aperiodic loading designs, which attempt to precisely regulate cabinet pressure through the restricted release of air pressure within the cabinet. A typical vented, or ported, speaker uses a much stiffer woofer suspension, and uses a cabinet hole to help produce low frequencies. It is difficult to compare a "leaky" acoustic suspension speaker to this design...apples and oranges, IMO. It is therefore probably prudent: 1) To make sure the old surround sealant has not stiffened to the point of compromising compliance. 2) That a satisfactory new sealant be sparingly applied to insure the integrity of the "acoustic seal". 3) Not to compromise compliance by glopping on too much sealant in an attempt to cover every tiny hole. Roy

Hi Guys, Thanks for the encouragement! There are those around me who would say you are simply enabling a madman. Carl, I agree that the fun part is sharing this stuff...and, as always, your input is very appreciated. I was about ready to bake a woofer in your honor, as your recipe sounded delicious :-)! Actually, I was using a hair dryer on the test subjects, and found fs goes down with heat, and increases a few hz in a cold room. The important thing is that the Permatex sealant's properties seem to remain consistent. As to the fc question...I have never noticed fc to decrease with sealed surrounds...only to increase with stiffer surrounds resulting from old or poor sealant. I believe the relatively airtight cabinet changes the character of the bass frequencies above resonance (making it sound less "flabby"), and offers protection from over-excursion. In fact, a cabinet that is "too sealed" can actually lose some of its bass appeal in my experience. As (I believe) Tom T. commented, we don't want it to act like a "barometer". Some versions of the 4x woofer, for example, really cannot be completely sealed due to porous dust caps and alnico magnet covers. Glopping too much stuff on the 4x surrounds will raise fs and fc, compromising bass response. Vern, Permatex was owned by Loctite from 1972 to 1999. The msds sheet for the high tack sealant can only be found on the Permatex website. Loctite made the stuff John mentioned above. With that said, our high tack sealant does have acetone and hexane in it, and should be applied in a well ventilated area (as with any material containing volatile organic chemicals). Roy

Hi Vern and John, Attached are some photos of the sealant John mentioned. It is "High Tack Gasket Sealant" made by Permatex (product # 80062 for a 4oz can or 80063 for a 15oz can). It is butyl rubber based, does not harden, and remains sticky, much like the original woofer surround sealants. John had luck thinning it with acetone, which makes it easier to apply, though it seems thin enough right out of the can for most applications. One thin coat does the trick. A 10" KLH woofer I recently treated had an fs of 34-35hz before and after treatment..virtually unchanged. Along the way I experimented with a number of the white surround "treatments". This group included the stuff sold by Simply Speakers, Orange County, M-Sound, and Global Adhesives (who labels it "white surround dampener"). These are all water soluble/PVA based, and as advertised, dry more flexibly than regular white glue. They are also advertised as being able to be used for a "wet look" on woofer cones. The problem with all of them is that they gradually stiffen. One 3a woofer I experimented on went from an fs of 16hz upon treatment to 32hz after one month! I experienced similar results with all brands on a variety of surrounds. As for Armorall, I have not found it to improve performance in any way. It certainly doesn't seal anything. Before applying the Permatex sealant, it is advisable to try to carefully remove the old sealant with alcohol and/or acetone if it has stiffened. Care must be taken not to un-glue the surround from the cone. Unfortunately I cannot recommend using the Permatex sealant on foam surrounds, as the solvents in it appeared to shrink or deform some of the surrounds I experimented with. Roy

It all makes sense... AR seems to have maintained (or possibly improved) the integrity of the AR-6 with the ceramic magnet woofer, and was able to simplify the crossover at the same time....and there are NO troublesome pots to deal with. I wonder where the "single coil/woofer capacitor" version RLowe discussed fits into the scheme of things? It is also a perfect example of how using different era drivers (or, especially, new "universal replacement" drivers) in our vintage speaker systems will likely result in disappointment. In fact, it is improbable to get anywhere near originally intended performance when using such replacements without crossover and/or stuffing changes. We now know where to go for used AR #4 and #12 coils :-). Great info, Klaus. I believe you are the forum's undisputed king of AR-6 land! Roy PS Do you have a suggestion for 8" replacement foam surrounds? The 10" JBL surround you recommended for 10" AR woofers is the best I have seen.

The 1972 Royal Opera version probably originally had alnico woofers, which would make them identical to my 1972 US version (including the thicker-trimmed cabinet style, as seen in your photo). All 5 of the 1972 US versions I have seen used white foam gaskets...no putty here either. It is obvious that the AR-6 was changed by 1975. It would be interesting to hear your impressions of the 1975 European version vs the earlier Royal Opera version, since you have both versions equipped with ceramic magnet woofers. If the crossover was later changed for that type of woofer, the 1975 cabinets with the later crossover, should sound "better". Given the radically different crossovers, there is no doubt they will sound different. I would also be interested in any measurements you take of the many #4 coils you have :-). Thanks again, Klaus! Roy

>You are right, they had multicoloured polyester stuffing and >the thin edges on the front, like the late European versions >of the classics (AR-5, AR-6 and the AR-3a Improved). The >woofers have the same part-number as the previous AR-6 >versions, these are made in week 47 of 1975. Your photo shows the later ceramic magnet woofer. I'm guessing that AR changed the original crossover for that woofer. Changes to the AR-2ax and 3a coincided with the introduction of ceramic magnet woofers as well, although the elimination of both inductor coils in the AR-6 design seems a bit drastic. I bet AR saved a few bucks with that move:-). Do the Royal Opera AR-6 woofers have alnico magnets? I've attached photos of a 1972 US AR-6, and it's alnico woofer. It would seem that the only difference between the Royal Opera AR-6 and the US version is the cabinet style. Other than cabinet style, maybe the AR-6 differences we are seeing are "earlier vs later", and not "US vs European"? My #4/#5 coils were probably a parts substitution issue or error that could easily have gone unnoticed for 35 years. Roy

>Just to complete the story, here is a couple of pictures of a >late European AR-6 cross-over, only a two position switch with >a resistor and a cap (6 myF) no coils. Only two terminals. Thanks Klaus... NO coils at all!? Wow, that is interesting! It seems that the European AR-6 is quite different from the US version, AND different than the Australian version Rlowe reported on. I also noticed some of the AR multi-colored polyester stuffing fibers in your cabinet. The US versions I have seen used fiberglass stuffing. It would seem that the drivers would also have to be different to work with such drastically different crossovers. In two of three US AR-6's I recently worked on, each had coils marked "#4" as shown in the schematics earlier in this thread. They were installed, however, with the # "4" facing down, and actually measured 1.20mh+/- (instead of .88mh). This means they were actually improperly labeled #5 AR coils. I wonder if this was known, and the coils installed upside down to hide the "4"? These were all original with absolutely no signs of previous tampering. There seems to be a number of varieties of AR-6 floating around out there. Roy

...correction...the AR-6 woofer magnet is closer to 6oz heavier than the 4x woofer. It is also about 1/4" deeper. The 1977 parts catalog still listed the AR-6 woofer separately (at $4 more than the 4x woofer), so they were probably never used interchangeably during the years the 4x and 6 were being manufactured. In the 1979 catalog the AR 8" woofer was listed as a "universal replacement" for those models. Roy

John, I've done some swapping of 4x and 6 woofers and found them to sound more alike than different. My observations are that the original AR-6 woofer has a slightly heavier magnet (about 3 oz), and somewhat more sensitivity. The 4x and 6 woofers were both used in cabinets of similar volume along with 11 to 12 ounces of the later type of fiberglass. The AR-4 woofers I have seen also had heavier magnets than that of the 4x. Anyway, I believe an AR-6 woofer would work fine in a later 4x cabinet. Regarding Rick's cloth surround AR-4 woofers, I agree that they should work very well in the 4x. If they are in as good shape as the photo indicates, they were a bargain! The cloth surround alnicos are still wonderful, reliable performers, and using them (thankfully) takes the foam replacement variables out of the equation. I also agree that matching the woofers is the most important consideration. Roy

Rick, Attached is a photo of an AR-6 8" woofer dated May 1972. Notice the deteriorating foam surround. It may be possible that some foam surround AR woofers found there way into later AR-4x's with higher serial numbers. Your numbers are among the highest I have seen. Roy

Rick, Changing the cap's original value and/or type is not going to bring the 4x any closer to the "open" character of the AR-3. Among other things, the dome drivers of the AR-3 provide greater dispersion. As John suggests, replacing the original cap with one of the same value is the first and most prudent thing to do. I also second John's comment regarding the pots. The original level control or an electrical equivalent is required to maintain the original AR sound. Roy

It "blossomed" with no assistance from me, Vern :-). The fiberglass was very compressed under the dome. Those tweeters also have very delicate aluminum voice coil leads that enter directly through the dome. It easily breaks off at that point. It was not repairable. >Yipes! Doesn't that mean there would be a deterioration in the >tweeter's performance? Sounds scary to me considering the >number of vintage 3/4 inch AR tweeters out there. That was my reaction as well, Carl. Between that and the possibility that the urethane foam/butyl rubber suspensions may be deteriorating after 35+ years, performance could very well be suffering these days. Roy

>Have you ever popped off a 1 3/8" dome to see what, if >anything, was underneath it. Yes, Vern...see attached photo. I originally posted the photo in the "Under The Old Dome" thread (just type "under" in an AR subject only search). Tom Tyson posted some very interesting information on this tweeter in that thread. >The 3/4" dome had a foam of some sort, I believe, to >lessen resonances. I have removed the domes from a number of the later, black 3/4" dome tweeters, and found crumbling deteriorated foam. Roy http://www.classicspeakerpages.net/dc/user_files/1974.jpg

>The AR 1 3/8" tweeter shared the same magnetic structure >as the 10" AR alnico aluminum framed woofers. >The difference between an AR-3 and AR-2 1 3/8" tweeter >was the AR-3 was 4 ohm and the AR-2 was 8 ohms. Vern, I believe the same orange dome, alnico tweeter was used for both. The dcr is low, below 2 ohms. I just double checked an early pair of 2ax's in the "restore" pile against an AR-3...same tweeter, same impedance. Roy

Pots don't get more fried than that! The 4uf cap was definitely a later addition, and was probably installed by the person who plopped in that small replacement tweeter. It was likely a futile effort, given the low crossover point of the original. To make your speakers whole again (along with new level controls) you will need the original cone tweeters. Carl, the dust cap measures 3/4", but the tweeter measures 2-1/2"...4 1/2" including the mounting flange. The 4x never used a dome type tweeter. The only cap required is the 20uf cap as shown in Carl's drawing, and in the attached schematic (courtesy of John O'Hanlon). Your speaker serial number indicates that it is an early 70's version with a #5 (1.187mh) woofer coil, as opposed to the earlier #4 (.88mh) shown in the schematic. Roy http://www.classicspeakerpages.net/dc/user_files/1787.jpg

Hi Kent, The AR-4x tweeter was always a 2-1/2" cone (see attached photo). It was crossed over at a rather low point, and the same as that used in the two-way AR-2x. Based on measuring a fair number of these tweeters, dcr appears to vary from 4.2 to 5.5 ohms, with the higher impedance showing up in post-1970 specimens. It would therefore also be prudent to acquire a matched pair if you choose used tweeters as replacements. It is very unlikely that there is a dome type drop-in replacement tweeter for the AR-4x. Roy

PM, It appears that the earlier version AR-2ax equipped with the cloth surround woofer contains 28+/-oz of rockwool, and the later version equipped with the foam surround woofer contains 18+/-oz of yellow shredded fiberglass. This is based on measurements I have taken of a number of AR-2ax specimens in the last two years. Of four early '70's AR-5's (same cabinet as 2ax with a slightly different foam surround woofer) I have weighed only yellow shredded fiberglass ranging from 20oz to 21oz. Roy

Here are some photos of the AR-6 crossover of the early 70's (serial# 25,500). The resistor wire measures just shy of 1 ohm. Roy http://www.classicspeakerpages.net/dc/user_files/1218.jpg http://www.classicspeakerpages.net/dc/user_files/1219.jpg

Pete, How about sending an old spider to a place like NuWay and having them replicate it? Roy

Thanks Tom...the last thing we need is a variable like that in the equation! Roy

Hey Pete, In the link you provided there is mention of a "problem" with "magnet half-life" in a speaker more than 20 years old. I wonder what that translates into relative to the parameters of our 25 to 40 year old AR woofers? We've been wrestling with "if and when" AR increased the magnet strength of the 12 incher. What if we are dealing with an overall net LOSS of magnet strength across the board? What are the likely symptoms of a "magnet half-life" issue? Would it affect alnico and ceramic magnets in the same way? Roy

Pete, My '71 woofers didn't have a model label/stamp on them, but they are usually referred to as 200003. Everything else about them appears identical to the other early 70's woofers, including type of spider, masonite ring and (subjective) performance. I have never seen a 70's version with a square magnet. I suspect that began in the early 80's from what we are observing. Roy

The Tonegen is the one marked "'94" in the photos above. "3013" was stamped on the '74 cone but no "F". None of the other cones were stamped at all. Roy

Hi Tom and Pete, The only magnet differences I've observed have been between a '71 version and all the rest. I've attached photos. The '78, '74, and '72 versions have the same dimension's as Pete's '78. The Tonegen's magnet actually has a smaller diameter by about half an inch than the others, with all other dimensions being the same. I believe it was Bret that noticed differences in the published BL specs in the 10pi. Pete, Millersound said that the '78 spiders were shot and replaced them. I didn't think to turn them upside down as you did. Maybe mine were the same as yours and I just thought they were "stiffer" because they were bottomed out..They did sag. Roy

Wow, that was fast! Thank You!! Roy