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About fedeleluigi

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  1. Restoration stopped at woofer

    Check both the voice coil and the tinsels (braid wires) by an Ohm meter. Old tinsels could be broken and measure open whereas the voice coil is OK. Luigi
  2. Where to find 10" Bass Drivers for AR9LS

    As you can see here (http://www.classicspeakerpages.net/library/acoustic_research/special_sections/additional_ar_documents/ar_parts_list_price_sheet_n/ar_parts_list_price_sheet_n_3.html) the AR 200033 woofer and later the Tonegen 1210033-0 woofer (used from about 1985 and later on) was used in AR 92 (and 925), 9LS and 9LSI, 30b, 28bx, 28bxi and AR Sub Woofer. Hope this can help you to find the correct woofers for your 9LS. Luigi
  3. Picked up some more AR speakers

    David, I'm sorry for the the snow storm and power outage. Hope they are "pessimistic" and you can have power again in a short while. Luigi
  4. Picked up some more AR speakers

    A parallel R and C circuit in series with a loudspeaker load can also be used with pro amps in order to protect them from very inductive loads. As an example, you can look at this link:https://adn.harmanpro.com/site_elements/resources/1010_1425481978/Macro-Tech-Series-600-1200-2400-Reference-Manual-130252_original.pdfthat's the Crown Macro-Tech amplifier manual. Please look at fig 3.14 at page 17. Even though the Macro-Tech amplifier were very stable amps into reactive loads, they can have problems with very inductive loads such as those caused by the presence of an autotransformer. Anyway, although the RC circuit shown in the fig. 3.14 will probably not give a flat frequency responce in the lowest frequencies (especially with a low impedance loudspeakers ) it will effectively protect the amp from most of dangerous inductive loads.
  5. Picked up some more AR speakers

    It is lowering the cap resistance. Just like when you put (2) 10 ohm resistors in parallel you get 5 ohms and when you put (2) 10 ohm resistors in series you get 20 ohms. The 2500 uF cap and the 10 Ohm resistor carry out a protective role against the inductive load caused by the presence of an autotransformer in the 10 Pi crossover network. Moreover, the 10 Ohm resistor, the 2500 uF cap and the autotransformer inductance constitute a special type of RCL network with a specific Resonance Frequency and Q factor. The resistor is important to determing both the Q factor and the Resonance Frequency of this particular type of RLC circuit. The Q factor can greatly affect the speaker bass response. You can examine the mathematics at the attached links (exersice 8 with solution). Pay attention that Q Factor, Resonance Frequency and Voltage drop through the capacitor also depend on R (R2 in the example) value. Unfortunately it is in Italian. Excercise n.8: https://it.m.wikibooks.org/wiki/Esercizi_di_fisica_con_soluzioni/Correnti_alternate solution https://it.m.wikibooks.org/wiki/Esercizi_di_fisica_con_soluzioni/Correnti_alternate#8._Circuito_risonante_con_2_R_2 Also In English you can observe how the R affects the Resonance Frequency of this type of RLC circuit at fig.5 of this link: https://en.wikipedia.org/wiki/RLC_circuit Luigi
  6. Picked up some more AR speakers

    Thanks David, I do hope some member of this forum that has an AR 10 Pi MKII or 11 MKII manufactured in the USA can share that information (type of polyester and weigh measured with a good scale). Thank you
  7. Picked up some more AR speakers

    David, In a previous post of mine I asked you to describe the type and weigh of polyester present in your 10 Pis. That was because in the two European AR factories were used different types of polyester wadding during AR 10 Pi and AR 11 MKII lifespan. If I have time to disassemble some AR 10 Pi to show it I'll take some pictures and post them. The weigh of the poliester wadding changes according to the type of polyester used. By the photo you posted I can recognize the type of poliester wadding used in your AR 10 Pi. The AR engineering file states that were used 10 oz of that type of polyester. Anyway, I've found in AR 10 Pi and 11 MKII an average of about 250g (8.82 oz, that is -12% compared to 10 oz) ) with this type of white polyester . As I'm interested in knowing the polyester weigh of the AR 10 Pi and 11 MKII manufactured in the US, could you please weigh it in both speakers? Thank you PS I post the engineering file (sheet 2) of the AR 10 MKII. It dates 18 Apr 1977, and the revision of cabinet wadding dates 9 Nov 1977. The AR 11 MKII engineering file show the same dates of revisions to new design (18 Apr 1977) and change of wadding ( item 11, 9 Nov 1977) and the same engineer (?) signatures. Can anyone recognize the signatures in these files? I do hope Tom Tyson and Steve F can recognize them. Thank you
  8. Picked up some more AR speakers

    Could you better describe the stuffing ( better if you post some pictures of it) and exactly weigh it? Both these factors are very important for woofer damping. Luigi
  9. AR9ls crossover slopes

    Without measurements or simulations (in the latter case you also need Thiele ans Small parameters, etc. ) by examining a crossover network you can only say the electrical crossover slopes. On the contrary, what really matters for the sound and to obtain a "flat" frequency response in the crossover region, are the acoustic slopes of each driver response in the crossover region itself (i.e. where the drivers are crossed over). The crossover region is the common region in a louspeaker frequency response in which two (or more) drivers simoultaneously sound. In this region the driver emissions overlap and add together. Obviously also the relationship between the acoustic phases of drivers is of fundamental importance to get a flat frequency response in the crossover region. Moreover, other parameters should be also considered such as the Q-factor and the type of filters (Butterworth, Bessel, Linkwitz-Riley etc.). As regards the acoustic slopes, they depend on the interaction between the elecrical slope of the crossover network and the natural frequency response of the driver. In other words: Acoustic Slope = Filter + Driver Natural Response For instance, in the AR 18 S and 38 S manual, you can read in the specifications (read at "crossover network"): "Highrange has a first order electrical network plus mechanical slope to give a total of 18 dB/octave". http://www.classicspeakerpages.net/library/acoustic_research/post-classic_series_1981-19/post-classic_series_manuals/ar18s_-_ar58s_manual/ar18s_-_ar58s_manual_pg6.html This means that in the AR 18 S and 38 S, the electric slope of the tweeter crossover network is only 6dB/octave (only a cap in series with tweeter) but it adds together with the natural frequency response of the tweeter providing a final acoustic slope of 18dB/octave in the tweeter frequency response at the crossover region. The "mecanical slope" of the 18 S / 38 S tweeter depends on its natural frequency response. So, simplifying a little, what really matters in order to get a "flat" frequency response in the crossover region are the drivers acoustic slopes and phases in the crossover region itself. Said that, as regards AR9 LS electrical crossover slopes, they are: Woofer low pass: 18dB/octave Lower midrange high-pass: 12dB/octave Lower midrange low-pass: 12 dB/octave Upper midrange high-pass: 12dB/octave Upper midrange low-pass: 12dB/octave Tweeter high-pass: 18dB/octave The Ar9 LSI schematic shows some variations. I do think they were made because the new Tonegen units had some little differences compared with the previous drivers. One of these schematic variations concerned the electrical crossover slope in the tweeter crossover network. It was changed into a 12dB/octave high pass filter. Luigi AR9LS Improved crossover schematic
  10. Picked up some more AR speakers

    I forget to say that the switches terminals shoud also be carefully cleaned to remove oxidation. Pay close attention to how the switches are wired and double check them using the schematics. AR 10 PI switch wiring connections are rather complex! The capacitors are about 40 years old. So they shoud be checked too. You have to desolder at least one of their terminals and measure them by a good capacitance meter. Luigi
  11. Picked up some more AR speakers

    Here the original crossover schematics. Richard Lowe did an excellent work with the last update (AR10pi-CircuitNotes Version 1.1 Sep2014). By using these schematics you can check everything is wired correctly (also the switches). Luigi
  12. Picked up some more AR speakers

    Probably it could depends on your listening enviorement, amplifier, loudspeaker position or personal taste. Anyway, the 200003-1 part number you mentioned was usually used for the square magnet 12" woofer introduced with the LS series (9LS, 98LS, 78LS a and also used in the AR 58S) at the end of 1981 or beginning of 1982 and manufactured until nearly all 1984. In 1985, the LSI series used Tonegen drivers. The 200003 woofer used for AR11 MKII and 10 Pi MKII, AR 9, AR 91 and 915 had the classical round magnet, aluminun voice coil former, a paper cone and a spider sligtly different from the previous 200003 and was produced from about 77/78 until just the introduction of the square magnet 12" woofer. Many years ago Kan Kantor's assistant Ruchi Goel (last post of this page) measured various AR 12" woofers and the Tonegen showed measurements rather different. Unfortunately those measurements are lost (their links do not work any longer since many years)! As said in my previous post the Tonegen woofer is definitely the best drop in replacement part for the originals AR 12" woofer. But I do think that If you want to get the best possible in terms of balance and naturalness of sound, the original woofers, manufactured in the same period as loudspakers, perform better. Untill now I haven't spent much time to try to optimize the Tonegen woofer sound by modifying crossover and/or cabinet stuffing. I think that some very good improvements could be reached. Anyhow if you are happy with the Tonegen woofer sound, don't pay too much attention to my considerations and subjective opinions. Luigi
  13. Picked up some more AR speakers

    Using a digital multimeter you can't actually measure a loudspeaker impedance. Anyway using it as you did I can read only about 10 Ohm regardless the switch positions. You actually measure only the 10 Ohm resistor in series with the autotransformer. You should check every driver has a correct DCR and is correctly wired. Woofer: red wire must be connected to positive and black wire to negative Mid: orange wire must be connected to positive and brown to negative Tweeter: yellow wire must be connected to positive and blue to negative. Driver terminals (especially tweeter's) must be cleaned well. Please, post some pictures of all the drivers. Luigi
  14. Picked up some more AR speakers

    How did you exactly get these readings? What instrument did you use to measure the loudspeker impedance? Anyway: with Woofer in Pi, Mid in -6 dB and Tw in -6 dB you'll have a 16 ohm loudspeaker ( an easier load but with the smallest loudspeaker sensitivity); With Woofer in 2 Pi, Mid in -3 dB and Tw in -3 dB you'll have a 8 Ohm loudspeaker; With Woofer in 4 Pi, Mid in 0 dB and Tw in 0 dB you' ll have a 4 Ohm loudspeaker (a more difficult load but with the greatest loudspeaker sensitivity). In my experience, using a tube amp you have to practically try both the amplifier different outputs and the different positions of loudspeaker switches to find out the best sonic match. Luigi
  15. Picked up some more AR speakers

    Congratulations David. By the pics you posted they would seem to have all Tonegen woofers. Although they certainly are the best "not" original AR woofer replacement, I do prefer the 200003 woofers made in US in the same period (about 1978 to 1982) of AR 10 PI mkII and AR9. In my experience, although all original AR 12" woofer (# 200003) are considered interchangeable, every AR loudspeaker has a more balanced and natural sound with the drivers manufactured and used in the same period. At least in my listening enviorement. Luigi