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fedeleluigi

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  1. fedeleluigi

    AR 11" woofer driver refoam (AR9)

    Pete what's exactly the problem with the woofer match?
  2. 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
  3. fedeleluigi

    Need help for AR-12 refurbish

    Keno, you could use not original tweeters but you have to adapt the driver flange to the cabinet hole and modify the crossover network. If you want to do a good job you should use a speaker simulation software and in the end carry out some measurements. Imho, If you don't want to do all this and wish to keep the AR 12 originality as far as possible, today the best option is to use the replacement tweeters supplied by Midwest Speaker Repair. The 8 Ohm version is the correct one for the AR 12. It's a drop in replacement tweeter and If you use the 8 Ohm version you do not have to modify anything. Some members of this forum have already used these replacement tweeters (the 4 Ohm version) for some restoration of 4 Ohm AR speakers. Luigi - https://www.midwestspeakerrepair.com/shop/home-audio/mw-audio-mt-4121-75-inch-dome-tweeter/ - https://www.ebay.com/itm/AR-Acoustic-Research-Replacement-8-ohm-Tweeter-for-AR-2ax-AR5-LST-2-MT-4121-8/162689351715?hash=item25e10a8023:g:k~kAAOSwc8lZzEo4
  4. fedeleluigi

    Old AR speaker measurements!

    You can see AR-3a, 3a improved, Pi/One, LST, MST measurements on Library Additions and Corrections
  5. Risposta in frequenza in camera anecoica = Anechoic Response. It shows some irregularities especially at about 2500, 6000, 14000 Hz because of the destructive interferences at the microphone position caused by the use of 4 tweeters. See also the polar responses. Risposta in camera d'ascolto rilevata con "rumore rosa" attraverso filtri a terzi d'ottava = Room Response measured with pink noise through 1/3 Octave filters. Diagrammi polari = Polar Responses (note that they are not so regular. Unfortunately 4 tweeters cause a lot of constructive and destructive interferences. In other words, waves with the same frequency emitted by different drivers combine and add together or cancel depending on their phase at the point where they combine). Curva d'impedenza = Impedance Risposta ai transitori = Tone Bursts DISTORSIONE ARMONICA= ARMONIC DISTORTION at 90 and 95 dB (actually only at 500 Hz the II and III armonic distortion are measured at 90 and 95 dB. At the other frequencies the real SPL depends on the frequency response of each loudspeaker); the tables show the III and II armonic distortion for all the loudspeakers tested in that issue of the magazine. Numbers out of parenthesis are III armonic distortion. Numbers in parenthesis are II armonic distortion. Vin= Voltage employed to obtain 90 and 95 dB at 500 Hz
  6. No anechoic response measurement was reported. Risposta in camera d'ascolto rilevata con "rumore rosa" attraverso filtri a terzi d'ottava = Room Response measured with pink noise through 1/3 Octave filters (switch position: 2) Diagrammi polari = Polar Responses (note that they are not so regular as 3a's. Unfortunately 4 tweeters and 4 midranges cause a lot of constructive and destructive interferences. In other words, waves with the same frequency emitted by different drivers combine and add together or cancel depending on their phase at the point where they combine). Curva d'impedenza = Impedance at different switch position (2 and 6) Risposta ai transitori = Tone Bursts
  7. Risposta in frequenza in camera anecoica = Anechoic Response Risposta in camera d'ascolto rilevata con "rumore rosa" attraverso filtri a terzi d'ottava = Room Response measured with pink noise through 1/3 Octave filters Diagrammi polari = Polar Responses Curva d'impedenza = Impedance Risposta ai transitori = Tone Bursts DISTORSIONE ARMONICA= ARMONIC DISTORTION at 90 and 95 dB (actually only at 500 Hz the II and III armonic distortion are measured at 90 and 95 dB. At the other frequencies the real SPL depends on the frequency response of each loudspeaker); the tables show the III and II armonic distortion for all the loudspeakers tested in that issue of the magazine. Numbers out of parenthesis are III armonic distortion. Numbers in parenthesis are II armonic distortion. Vin= Voltage employed to obtain 90 and 95 dB at 500 Hz
  8. Risposta in frequenza in camera anecoica = Anechoic Response Risposta in camera d'ascolto rilevata con "rumore rosa" attraverso filtri a terzi d'ottava = Room Response measured with pink noise through 1/3 Octave filters Diagrammi polari = Polar Responses Curva d'impedenza = Impedance Risposta ai transitori = Tone Bursts Distorsione = Distortion DISTORSIONE ARMONICA= ARMONIC DISTORTION at 90 and 95 dB (actually only at 500 Hz the II and III armonic distortion are measured at 90 and 95 dB. At the other frequencies the real SPL depends on the frequency response of each loudspeaker); the tables show the III and II armonic distortion for all the loudspeakers tested in that issue of the magazine. Numbers out of parenthesis are III armonic distortion. Numbers in parenthesis are II armonic distortion. Vin= Voltage employed to obtain 90 and 95 dB at 500 Hz
  9. Risposta in frequenza in camera anecoica = Anechoic Response Risposta in camera d'ascolto rilevata con "rumore rosa" attraverso filtri a terzi d'ottava = Room Response measured with pink noise through 1/3 Octave filters Diagrammi polari = Polar Responses Curva d'impedenza = Impedance Risposta ai transitori = Tone Bursts
  10. fedeleluigi

    AR3a Original Owner

    @AR3a MD Welcome to this forum! There is a very good and useful manual about the AR-3a restoration. On page 13 you can find how to restore the original pots or replace them with L-Pads. Personally, I do prefere to restore old pots or use voltage dividers than to use L-Pads especially for midranges. http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/restoring_the_ar-3a_full_pd.pdf
  11. fedeleluigi

    AR-11 Crossover Frequency Response Simulation

    Pete, I can't understand why you put the ESR values before and not after the capacitors (40 uF for the AR 11 and 50 uF for the 3a). Anyway, as regard the 3a, shouldn't the 0.5 Ohm resistor be situated between the 50 uF cap and the inductors? thank you for any clarification. Luigi
  12. fedeleluigi

    AR Tweeter replica/replacement

    Open the AR 10 PI "door". You should very gently detach the three black "cups" ( 5, 27 on the drawing). They are glued to wood so use a cutter blade to very delicately detach them. Be careful not to deform the black cups! Under the three cups there are three nuts (4 on the drawing) and you have to unscrew them and then the PCB can be removed. Anyway if the rivets are not oxidated, I would not remove the PCB from the cabinet. I would only detach the faston terminals one by one to clean them. Without removing the switch board you have to use a mirror or take a photo to see if the PCB rivets are oxidated or not. Obviously, also some other AR such as AR9 may have the same sort of PCB oxidation problems or some old solder joint issue. Should you decide to remove the switch PCB remember to resolder all the old solder joints present on the PCB itself.
  13. fedeleluigi

    AR Tweeter replica/replacement

    I forgot in my previous posts to suggest that you clean from oxidation the numerous electrical connectors (faston terminal) present on the switch PCB in the AR 10 PI. The faston terminal oxidation could be a cause for detail loss. Before detaching the numerous faston terminal from the switch PCB, take carefully note of their wire colour and precise position on the PCB otherwise it will be impossible to reconnect them in the right position. Probably, to be on the safe side, it's better to clean one by one. In the last picture, the oxidation present at the rivets of the faston terminals is also a certain cause of signal (and detail) loss. You should check out this possible problem as well.
  14. fedeleluigi

    AR-12 crossover

    The 20 Ohm resistor in the schematic is a misprint. Actually It is 2.0 Ohm and not 20 Ohm. You can see it from the AR 12 crossover picture. That's why the 20 Ohm resistor is not listed. In other words in the crossover network there are two 2.0 Ohm resistors and no 20 Ohm resistor is present. Luigi
  15. fedeleluigi

    AR-11 Crossover Frequency Response Simulation

    Thank you for the clarification, Pete
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