giovanni56
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Posts posted by giovanni56
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On 5/9/2024 at 9:56 AM, Andre_Db66 said:
Spero che tu abbia ricevuto questi altoparlanti gratuitamente considerando l'ampio olio di gomito che hai investito... 😁
Lavoro meraviglioso, davvero ammirevole. Amo le persone che si impegnano a sistemare le cose, buttate via dagli altri come spazzatura (ndr).
Splendido lavoro, divertitevi
Thank you very much for your appreciation, it was a long and hard work.
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13 hours ago, bjmsam said:
Oh! Che trasformazione. Un viaggio epico sicuramente. Congratulazioni!
Come avete riparato la muffa sui coni del woofer?
With an anti-mold, purchased at OBI.
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5 hours ago, AR surround said:
Restauro assolutamente stupendo, Giovanni! Ti lodo per la pazienza, lo sforzo e la perseveranza.
Thank you very much, too good and very kind
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I apologize for the photos that are not in chronological order
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A long and complicated restoration, dented and scarred furniture, broken edges, non-original refracted wood frames, punctured canvases, missing metal profiles on the four crossover side supports, out-of-specification crossover components, woofers full of mold inside and outside the cones, some broken and stripped binding posts, two inductors not secured to the backing plate, poorly mounted level selectors in one case, case support sockets not original and to be rebuilt, blocked midrange to be overhauled, missing internal absorber to be integrated, misplaced inside the cases, one failed tweeter. It was a long and laborious job, for example, the metal profiles of the side panels of the woofers I rebuilt by hand by cutting and shaping one piece at a time, then fitted them to each other manually with a file and finally glued them to the edges of the port panel, despite everything, I am completely satisfied with the aesthetic and functional result. They are two very good speakers.
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20 hours ago, fedeleluigi said:
Hello Giovanni,
I agree with you. In the old thread I linked some posts before I wrote: "Anyway, the minimum of 4.8 Ohm at 80 Hz seems 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."
Unfortunately Renato Giussani, the engineer who probably carried out the measurement for the Italian magazine, died a few years ago and therefore no one will be able to clarify the apparent inconsistency.
I knew Renato personally, and during a chat in which we talked among other things about the hectic times of Hi-Fi in those years, he told me that it was not uncommon that some tests might contain errors due to the hurry to compose the pieces in time for the specialized magazines, then later corrections of the errors were published, in this specific case I do not remember corrections published in later issues, however, I agree with you that in that frequency range the impedance curve must be similar to that of the Ar3a Improved, because the differences on the crossover are minimal, although the latter in the low pass of the woofer has a lower inductance value than that of the Ar11, but a larger capacitor although it is damped by an R of 1.5ohm.
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Ar6 small speakers with big sound.
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2 hours ago, lance G said:
Many thanks to you Giovanni,
Attached picture is of one of my original crossovers before recapping all EXCEPT for the 2500 uF. Apparently mine are Callins as yours were, so seems like it's time to change them out !
Your information is really useful to me as I was given the impression, including from the forum, that it was acceptable to leave the 2500uF cap's in place as they are considered to be "historically robust".
I first measured them and then replaced them; if in the measurement I had found values, at least on two instruments in the tolerance range of the component, I would not have changed them; by the way, such high capacitance values are difficult to measure correctly. Even the 470 uF Callins was totally "off."
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On 5/3/2024 at 13:36, tourmax said:
Recentemente ho avuto un set di AR4x che ha fatto saltare i tweeter. Misurano come un circuito aperto.
Quindi ora devo sostituire quei tweeter se voglio che questo particolare set di AR4x canti di nuovo. Trovare qualcosa in AR da queste parti è difficile quanto trovare una pepita d'oro da 2 libbre e probabilmente ci vorrà un po' di tempo prima che ne trovi altre 2 su eBay o simili.
Le nuove sostituzioni di stile sono un'opzione, ma ho tempo di aspettare che vengano visualizzati gli originali. Ho appena messo in servizio un secondo set di AR4x (che erano in attesa di restauro).
Quindi immagino di non avere molto da perdere per cercare di smontarli. Non possiamo renderli più “morti” di quanto non siano già. Diventeranno più forti dopo l'operazione o moriranno sul tavolo operatorio. Non c'è molto da perdere, a parte un po' del mio tempo.
Vanno alla scrivania.La prima cosa è sollevare il bordo incollato. Ma devo essere molto gentile per non distruggere quei coni e i loro dintorni integrati.
Circa 2 ore di lavoro delicato con una lama da hobby fine e sottile e tamponando l'IPA con un bastoncino di cotone hanno sollevato il bordo.Parliamo di lentezza e snervante! Frazione di un pollice alla volta!
Ma ora il limite è stato sollevato. È interessante notare che non si tratta di uno spazio aperto dietro il cono del tweeter ma di un materiale isolante fibroso.
Immagino che AR pensasse di aver bisogno di un maggiore controllo sul movimento del cono rispetto a un semplice dorso chiuso. Ad essere onesti, questi sono i primi tweeter che abbia mai aperto, quindi potrebbe essere una pratica comune.
Non c'è alcun "filo orpello" come vedresti sugli altoparlanti più grandi, quindi immagino che esca lateralmente attraverso il centro dei terminali. Sembra avere senso dato che la parte centrale delle morsettiere è saldata nei "fori" centrali e non c'è altra prova dei fili su nessun'altra parte.In realtà ho provato a rifluire la saldatura nel caso in cui si tratti di un giunto di saldatura freddo che causa una perdita di continuità, ma niente da dire. Rimangono completamente aperti. Sembra sempre più che la bobina sia in cortocircuito internamente. Forse dovrò provare a riavvolgerlo e vedere cosa ottengo. A volte ricostruisco i motori riavvolgendo la bobina, quindi non è una cosa nuova per me. Sarà semplicemente un filo molto più sottile. O forse non sarà "fattibile". Almeno lo scoprirò in un modo o nell'altro.....
Ed è lì che li ho lasciati per la giornata. Ho i nervi a pezzi per aver sollevato il primo giro. Domani vedrò di rimuovere quella saldatura e se riesco a estrarre i coni/bobine.
Questo non è un posto dove essere "affrettati". Queste parti sono piccole, poco pratiche, vecchie e si rompono facilmente.
E i miei nervi hanno davvero bisogno di una pausa in questo momento...
"I have actually tried reflowing the solder in case it is a cold solder joint causing a loss of continuity, but nothing to say. They remain completely open. It looks more and more like the coil is shorted internally"
If you measure open circuit it means that the coil is not shorted but is interrupted, at open circuit the ohm meter indicates nothing while at short circuit depending on the scale set in the meter some value should be read.
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On 4/30/2024 at 8:01 PM, fedeleluigi said:
You may note the minimum impedance value on the plot of the Italian magazine is about 2.8 Ohm between 6000 and 7000 Hz while your plot shows about 1.8 Ohm in the same frequency range.
Yes, I had checked the graph in the magazine which has an impedance trend in that frequency range higher than 1ohm, as I noticed the minimum of 4.8ohm between 60 and 100Hz which I never measured in the three pairs I had available, I always measured minimums between 3 and 3.6ohm, in the graphs I posted the value is 3.2ohm. The first time years ago that I noticed that difference taken by doubt, I checked the speaker components, and everything was okay. Such a difference cannot be justified, unless, someone has let's say, "softened" that graph or made an unintentional mistake; you may have noticed that the impedance values on the vertical axis of that graph are reported manually, in my opinion whoever did it, probably entered the impedance values on the vertical axis by shifting a few positions. I can assure you that the measurements I reported are scrupulously correct.
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5 hours ago, lance G said:
Hi Giovanni.
E' molto contrario a te non tornare su questo argomento? 🙂 .
Io (e probabilmente altri?) Sarei molto interessato a quanto erano distanti le big cap?
Inoltre, di quale marca (marca) erano?
Grazie in anticipo, Lance.
Callins, they were out of specification, measured on three LCRs gave values from 4800uF to 5200uF, to be thrown in the puddle.
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On 12/3/2024 at 20:26, RoyC said:
Prima di tutto stiamo parlando di impressioni soggettive su un tweeter sostitutivo 4x basate sul feedback degli utenti, non sulla vostra opinione sul tweeter AR originale. Va notato che il tweeter sostitutivo di tipo PRT non ha la stessa struttura del tweeter 4x originale... che ha una sospensione più conforme. Il sostituto del PRT non è altrettanto efficace nelle frequenze medie, principalmente a causa delle differenze di escursione. Nonostante ciò, moltissimi utenti ne sono soddisfatti. È la differenza tra questo tweeter e il tweeter AR-4x originale in discussione, non eventuali difetti (o "distorsione") associati all'uso complessivo di questo tipo di tweeter.
In secondo luogo, la tua congettura sul motivo per cui AR ha utilizzato i tweeter a cupola non è accurata. Non è raro che i produttori di altoparlanti utilizzino con successo tweeter a cono in progetti a 2 vie. AR ha utilizzato tweeter a cupola per le frequenze più alte nei modelli a 3 vie per migliorare la dispersione e la gestione della potenza, non perché i loro driver a cono fossero distorti. I tweeter a cupola venivano utilizzati solo nei modelli più robusti a 3 vie, mai nei modelli a 2 vie. Il tweeter a cono utilizzato nei modelli a 2 vie come AR-6, 7, 8 e 18 è ancora molto apprezzato.
Ovviamente qualsiasi driver utilizzato al di fuori dei parametri di progettazione può "distorcere". Alla fine probabilmente stiamo parlando della stessa cosa. Abbiamo solo una diversa definizione di "distorsione".
Very good explanation, thank you
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26 minutes ago, giovanni56 said:
With the calculator, the results are obtained by applying formulas that are applied for resistive loads while the loudspeakers behave as reactive loads as a function of frequency, moreover, many other parameters are needed for a proper implementation of a crossover, for example:
the measurement of the impedance and T&S parameters of the transducers, the frequency response of the transducers, the nominal diameter of the transducers, the measurement of the distance of the emission centers between the speakers, the measurement of the offsets of the emission centers of the speakers, the resistance value R of the inductances that will be used in the crossover, the altitude and distance of the measurement microphone from the emission center usually of the midrange for a three-way speaker, etc. etc, finally, good simulation software and a measurement system in a reverberant or otherwise anechoic environment (near-field measurements). I see it difficult to make a good crossover with a simple calculator or table, also because you could get a potentially critical load, getting a very low impedance with deadly phase rotations, for the amplifier to which you connect the system.Forgot:
Many listening checks of the system for possible corrections and finally validation of the reproduction system made. -
On 4/29/2024 at 4:13 PM, Andre_Db66 said:
Ho usato una calcolatrice fai da te, non le tabelle. Forse dovrei sperimentare di più con il valore dell'induttore. L'ho alzato al massimo perché sentivo ancora così tanto il passa alto che ovviamente è cessato quando ho implementato un condensatore. Tutti i materiali utilizzati erano in giro, quindi non ho speso soldi perché non è la soluzione definitiva. La mancanza di tempo ha impedito ulteriori modifiche. Presto ascolterò e giocherò di più.
Secondo la tabella i 17 mH potrebbero essere sufficienti purché includa un limite...
With the calculator, the results are obtained by applying the formulas that apply for resistive loads while the loudspeakers behave as reactive loads as a function of frequency; in addition, many other parameters are required for proper implementation of a crossover, e.g:
the measurement of the impedance and T&S parameters of the transducers, the frequency response of the transducers, the nominal diameter of the transducers, the measurement of the distance of the emission centers between the speakers, the measurement of the offsets of the emission centers of the speakers, the resistance value R of the inductances that will be used in the crossover, the altitude and distance of the measurement microphone from the emission center usually of the midrange speaker for a three-way speaker, etc. etc. finally, good simulation software and a measurement system in a reverberant or anechoic environment (near-field measurement) to verify the frequency response on axis, at 30° and 45°. I see it difficult to make a good crossover with a simple calculator or table, partly because you could get a potentially critical load, getting a very low impedance with deadly phase rotations, for the amplifier to which you connect the system. -
1 hour ago, fedeleluigi said:
@giovanni56 Hello Giovanni,
Thank you for the clarifications.
If you are interested in a comparison, in the link below I posted the impedance plots of AR-11 MKI, AR-10 Pi MKI and AR-10 MKII measured by some Italian magazines in the 70's.
Unfortunately, they do not say how the switches were set during the impedance measurement of AR-11.
You're welcome Luigi.
Looking at the impedance curves, I think the Ar11 MKI was with the switches set to 0db, as well as on the Ar10p but with the woofer control on 4p¬. -
16 hours ago, fedeleluigi said:
Hello Giovanni,
Your 200003 woofers show a very high FS, about 50% more than the typical (16 Hz) measure of the made in US woofers: Did you use a very stiff surround to refoam them?
The values of 24.2 Hz and 23.6 Hz that your last two plots show are more typical for Tonegen woofers.
I'll appreciate any clarification.
Luigi
Ciao Luigi, the two woofers are Ar200003 that had the spider sagging, most likely the high Fs is not due to the foams I use, but to the treatment I did to regenerate them, the measurements were taken without any "break-in" after the refoam and the "respider," in similar cases after a good "break-in" the Fs averaged 19Hz.
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On 4/9/2024 at 11:54 PM, ReliaBill Engineer said:
La rete passa basso del primo ordine da 6 dB/ottava è piuttosto “lunga” nella sua attenuazione. Dovresti usare un filtro del 2° ordine per ottenere una pendenza più ripida di 12 dB/ottava.
Ecco un altro grafico che mostra i valori del condensatore e dell'induttore per ottenere un'attenuazione di 12 dB/ottava. Induttore in serie, condensatore in parallelo ai terminali del woofer. La parte superiore della tabella mostra il cablaggio per il woofer passa basso.
Those tables give capacitance and inductance values that are derived as if the drivers were pure resistors, in reality the drivers have a resistive and reactive component that varies (by a lot, especially at the Fs of the component), depending on the frequency, so they give a very rough indication with respect to the correct values for making a proper crossover.
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The measurements were taken with the midrange and tweeter switches at - 0db both and - 3db on the midrange and 0db on the tweeter, respectively. In my opinion the Ar11s are for certain amplifiers difficult to drive especially with the midrange and tweeter level controls at 0db, however, the frequencies of a music program between 1.8kHz and 20kHz, where the impedance decreases dramatically, have an average low energy content
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Measurements before recap show a minimum impedance of 2.79 ohms at 57Hz, after recap of 3.25 ohms between 50 and 65Hz. The capacitors were all out of specification, especially those in the 2500uF impedance compensation cell on the woofers.
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If it is helpful, I have weighed some mobile crews (cone+spider+coil and cone+spider+coil+foam), and the weights averaged 68 g without the foam and 80 g. However, when the whole moving assembly is installed, the foam and spider, in my opinion, add less mass than their weight, because the part of the two that is attached to the basket is not influential on the value of the total weight, to hazard a guess, perhaps the installed cone including the spider the coil and foam, will have a moving mass of about 72/74 grams, however, in T&S measurements, the Mms takes higher values, above 100gr, because of the contribution of the radiation impedance of the air mass that must move the cone and the mechanical impedance of the suspension (spider + foam).
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In Italy, photos of a pair of Ar6s with narrow front edges and labels indicating production made in the USA have been published. This is the first time I've seen an Ar6 with US-made narrow front edges, I have a doubt that the labels have been reprinted and are not original, I think actually those Ar6s were made in EU. Can anyone in the group clarify for me? Ar6 with the thin edge were also built in the US?
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11 hours ago, AR55 said:
AR non ha introdotto i tweeter raffreddati con ferrofluido fino al '77-78', quando ha introdotto il migliorato AR11.
Hi AR55, but these 20001311 are following 77/78
Ar9 Restoration
in Acoustic Research
Posted
"Was it worth it?" of course it was worth it, especially for the owner of the speakers who had never heard his Ar9s the way he hears them now that they are as good as new. They are speakers that installed properly in a proper room and with level amplification, express a sound of excellent quality.