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fedeleluigi

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  1. fedeleluigi

    The AR 12-inch Woofer "Collapsed-Spider" Syndrome

    Hi Tom, Unfortunately, nowdays it’s very hard to accurately reconstruct the history of all that AR did and made. Unfortunately, many witnesses are no longer available (or the available ones do not remember the events exactly) and many important historical documents are lost. As regards the introduction of the 12” ferrite woofer, the dates of some AR drawings (magnet, cone-skiver and the spider in my previous post) would suggest that its production probably started in 1969 (please, see the attached pictures with highlighted dates). Obviously, the dates of these drawings do not prove with absolute certainty that the production of the 12” ferrite woofer definitely started in 1969. If the L.C.C., Loudspeaker Components Corporation, Lancaster Wisconsin (mentioned in some AR drawings) and today’s Loudspeaker Components, L.L.C., Lancaster Wisconsin are the same company, there might be a chance that it can still have some important documents (receipts, part orders etc.) that could be very userful for trying to establish the exact production date for some of the drivers made by AR. Luigi this drawing is the 4th in "AR Drawings" this drawing is the 316th in "AR Drawings"
  2. fedeleluigi

    AR 2ax Advice Please

    Hi David, Examining the crossover photo you posted, the pots seem to have been bypassed (not in the correct way) by the previous owner. The photo is not so clear to see all the wirings precisely. When bypassing these 16 Ohm pots, the 16 Ohm resistance should be left in parallel with the respective driver (tweeter or midrange) otherwise the crossover network (in this case a 4 uF and 6 uF capacitor for the tweeter and midrange respectively) will be loaded by a different impedance and this will change the frequency cutoff and shift the crossover points in comparison with those of the original design. Obviosly, bypassing the pots (even if carried out in the correct way) does not allow to decrease and adjust the tweeter and midrange volume any longer and this could be a problem. Attached you can see the normal pot wiring, the early AR 2ax schematic and the correct and incorrect way of bypassing pots. Luigi
  3. fedeleluigi

    The AR 12-inch Woofer "Collapsed-Spider" Syndrome

    Differently from what is reported on some other pages of this forum (for example), the 200003 woofer spider has 7 corrugations (7 crests and 7 troughs ), not 6. Actually the 7th crest and the 7th trough seem to be a little smaller than the other ones and become almost "invisible" after the gluing between spider and cone. In other words the 7th spider groove hosts the paper cone as shown in the drawing I've made.
  4. fedeleluigi

    The AR 12-inch Woofer "Collapsed-Spider" Syndrome

    Hi Pete, There is a lot of information on AR Drawings about the spider of the 200003 ferrite woofer . Examining these documents carefully it comes to light that the first drawing of the AR 200003 spider dates back to 22 Jul 1969. So, most likely around this date the production of first 200003 ferrite woofer started. Revision B dates 1 Jul 1974 and apparently there was no change in spider manufacturing from 22 Jul 1969 to 1 Jul 1974 because Revision B only reports “drawing no. change" but a previous revision (O) dated 12 Sep 1972 reports "Revised Notes, DWG No. was X-3705" and something could have been changed on that occasion. Revision C (ISS. C) dates 5 Jul 1978 and apparently there is no variation about dimensions, material, treatment, supplier (LCC, Loudspeaker Components Corporation, Lancaster Wisconsin. I think that the same company is still operating nowdays and they could still have the original molds for the 200003 spider www.loudspeakercomponents.com ) in comparison with Rev. B. Differently from the previous drawing, on this last revision it is also reported something about the spider compliance (maybe there was some compliance variation in comparison with the previous spiders) but it's difficult to understand the standard used (where and how must the 50 grams be exactly employed? where do you have to measure the deflection?). You can find images of higher resolution on AR Drawings. The drawings are the 422th and the 423th but unfortunately there is no numeration. The last drawing is the 492th.
  5. fedeleluigi

    AR3a woofer recone kit

    Hi Klaus, It's very important to preserve the woofer spiders. In order to disassemble the spider from the masonite ring I use an antifog nitro diluent as solvent. It is possible to use more powerful solvent to make faster the dismantling process but they could damage or alter the spider treatment changing its compliance. First it is necessary to gently remove the basket nets and unsolder the tinsel lead wires.Then I use a syringe to apply the solvent all around the glued spider-masonite ring. It's very important to apply it about every 2 minutes for about 30-60 minutes. This long time is necessary as the glue will soften very slowly. After 30-60 minuter you have to try to delicately separate the spider from the masonite ring beginning from the spider edge. You can use a needle (or somefthing similar). Be careful in order not to damage the spider. If the glue is still hard you just have to continue applying the solvent and wait until it softens Apply the nitro diluent where you can separate the spider from the masonite ring and keep on applying it all around the glued spider-masonite ring until you can separate them completely. After the separation you have to clean the spider and masonite ring from the glue remmants as soon as possible otherwise the glue remmants will harden again and it will be annoying to remove them later. Than you have to remove the paper former of the voice coil and the glue from the spider/cone. I's very easy to remove the paper former. As regards the epoxy glue I remove it by gently using a thin sand paper until the new voice coil fits the hole. If the new coice coil doesn't have the vent holes they must be created with a good punch pliers. Voice coil should have 55-58 turns per layer and DCR should be about 2.6 Ohm. Apart from the type of former material, the voice coils of AR-12in ferrite woofers were rather similar along all their lifespan. In the AR drawings you can find the aluminum voice coil (the drawing is the 299th and is dated 25 Jan 1980). If the original paper voice coils are not too damaged (you can see it only after carefully taking the woofer apart) and if you have good manual skills you could try to restore them but it's not an easy procedure. So be very careful when removing the voice coils from the magnet gap in order not to further damage them. Luigi
  6. fedeleluigi

    Refoam AR-9 woofer

    Mez, That's Ok if the woofer is the replacement part manufactured by Tonegen ( part# 1210003-XX). If the woofer is the original AR woofer (part # 200003), the outer edge of the foam is normally glued to a masonite ring that is glued to the metal frame. If someone erroneously removed the masonite ring you should restore it. Luigi
  7. You're welcome, Your measurements are very interesting! Please consider that 20 oz of fibergass could overdamp the late 200003 woofer generation (that is what I do hear with my ears but I never carried out measurements). To the best of my knowledge, AR 11 and 10 Pi MKII did only use 10 oz of "white" polyester in USA. The same type of white polyester was also used for the AR9 and (later) the AR9ls series. In Europe different types (with different densities and consequently different masses) of polyester were used for the AR 11 and 10 Pi MKII and only the late production in 1979 used the "white" polyester (about 9 oz). I've read the AR 11 MKI review again but, unfortunately, they do not say how the switches were set during the impedance measurement. The frequency response shows 3 curves (0, -3, -6 dB). Since only the midrange and tweeter can be attenuated, the 3 curves are exactly the same up to about 500 Hz. So the minimum (4.8 Ohm) at 80 Hz is not affected by the midrange and tweeter switch position. The minimum around 3 Ohm at 6000-7000 Hz may suggest that the switches were set for the maximum output (0 db attenuation) and furthermore the worst condition is what generally matters most. Anyway, the minimum of 4.8 Ohm at 80 Hz would seem a little high in comparision with that of the AR 3a improved that had the same 200003 woofer generation used for the AR 11 MKI and a rather similar woofer low-pass crossover network. As regards the AR-10 Pi impedance measurements (both MKI and MKII), they say that the switches were set for the maximum output (4Pi, 0dB, 0dB for woofer, midrange and tweeter respectively). Examining the AR 10 Pi crossover network, when the woofer environmental control switch is set to obtain the maximum output (4Pi), the inductance in series with woofer is 4.73 mH (1.88 mH + 2.85 mH), the capacity in parallel is 100 uF and thanks to the autoransformer, the output voltage that supplies the woofer is higher than the input one. Because of the autotransformer the impedance varies according to switch positions: the review says that when the woofer switch is set on 2Pi and Pi the minimum impedance is 7.5 and 13.6 Ohm respectively (around 100 Hz) .
  8. From the AR drawings: AR 11 MKI : 20 oz fiberglass AR 11 MKII: 10 oz (white) polyester wadding . Several types (and weights to always obtain the optimal damping) of polyester stuffing were used in the European factories for the MKII versions. As regards the white one (used only in the very late production), I've generally found a single sheet of about 250g (8.82 oz). The 10 Pi MKII of the test (Fc: 40.5 Hz) had the multi-coloured poliester (in my experience i found about 450g =15.87 oz when this type of stuffing was used). In another magazine that also tested the 10 Pi MKII, the Fc was 42.8 Hz and the woofer Fs 16.9 Hz . The suffing was multi-coloured polyester too. As said in my previous post, unfortunately, I don't have any impedance graph (and Fc) for the AR 11 MKII but I think that its Fc is similar to that of the AR 10 MKII.
  9. From what I've read in your first post your AR-11's are MKII. I coudn't found an impedance sweep for the AR-11 MKII but I've found one for both the AR-11 MKI and the 10 Pi MKI . I've also found some measurements for the AR-10 Pi MKII that essentially differs from the 11 MKII for the use of an autotransformer in the crossover network whereas the cabinet volume and drivers are the same (AR-11 MKI schematic, AR-11 MKII schematic, AR 10 Pi MKI and MKII schematic) . The FC is 40.5 Hz for the AR-10 Pi MKII (besides the impedance sweep, see also the red highlighted text) and seems to be around 36-37 Hz and 38 Hz for the 10 Pi MKI and AR-11 MKI respectively. Hope these graphs can be useful to you.
  10. Examining the AR drawings in the library, the mass without foam measured by @aquila2010 for the 200003 woofer moving mass should probably be correct ( around 70 g). The drawing #002 is dated 8 Jan 1984 and reports a mass of 41 +/-3g for the cone/surround assembly. The drawing #004 (it seems to be dated 7/1/69 ) should show the first ferrite cone/surround assembly and its mass is exactly the same as before. In other words the mass of the cone/surround assembly should have not changed during the 200003-(0/1) woofer lifespan. The drawing #299 (12-in W // 200003 // voice coil // 25-Jan-80 // 13-Feb_81) refers to the aluminum voice coil and reports a mass of 24g +/- 15% (from 20.4 g to 27.6 g) . I coudn't find the spider and dust cap masses on their respective drawings. Therefore, without spider and dust cup, the mass of cone/surround/voice-coil assembly is about 41g+24g = 65 g (anyway it could ranges from 58.4g to 71.6g taking into account the maximum variations admitted in the AR drawings) for the aluminum-voice-coil woofer. Realistically the spider and dust cup and glue could have a total mass of around 5-10 g, so the "about 70 g" without foam reported by Aquila2010 is likely correct and probably applies to the aluminum-voice-coil woofer as well. Anyhow I've several 200003 woofers disassembled but haven't a very accurate scale at the moment. If I can somehow get one I'll report all their moving masses.
  11. fedeleluigi

    AR-11 MK1. Identification and rebuild.

    This tweeter is original (MKI) . This is a replecement tweeter probably made by Tonegen / Foster. Very likely it is more sensitive/efficient in comparison to the original tweeter.
  12. fedeleluigi

    AR-11 MK1. Identification and rebuild.

    Here is an interesting thread about the masonite ring. Unfortunately I do think that you have to made it by yourself or with someone's help
  13. fedeleluigi

    AR-11 MK1. Identification and rebuild.

    JimEG, Unfortunately someone refoaming this woofer erroneously removed the "masonite" ring. You can see it on the other woofer: it is glued to the basket and the outer edge of the foam is glued to it . The masonite ring should be restored.
  14. fedeleluigi

    AR 11" woofer driver refoam (AR9)

    Pete what's exactly the problem with the woofer match?
  15. fedeleluigi

    AR 11" woofer driver refoam (AR9)

    No they haven't. As regards the 12" foam/ceramic woofers made from about 1970 to around 1977 I have always and only found paper formers, at least so far. So the AR 11/10pi MKI woofers have paper formers, the AR 11/10pi MKII and the following 12" woofers used in the 9 and 9LS series have aluminum formers. Luigi
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