fedeleluigi
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Posts posted by fedeleluigi
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@lARrybody the DC resistance you measured (3.9 Ohm) is not correct for the 200003 woofer (it should be about 2.6 Ohm +/- 10%). If your digital multimeter is accurate the tinsel wires could have some problem or the voice coil could have been replaced with a not appropriate one.
The woofer basket looks like a 1975 one therefore if the the woofers are the stock ones the original tweeters were replaced with later versions since the tweter domes/suspensions were yellow until the first months of 1976 and later black. In any case there was no foam on the tweeter flange for the AR-10 Pi MKI. The original tweeter used in the AR-10 Pi MKI and AR-11 MKI are shown in the file "Restoring the AR-3a" (Fig. A.21 and A.22).
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15 hours ago, BjarneAndersen said:
Many thanks for your reply, I will now try to make some new coils after the drawing.
You can find a higher definition drawing in the library (AR drawings). The drawing is the 241th and is named "no image".
Luigi
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Hi Scoup,
Thank you for answering my questions.
I think that It's rather difficult to make accurate comparisons among speakers, especially if they are old, because there are many variables that can "distort" the perceived results. That's why I asked you some questions in my previous post. For example, in vintage speakers capacitors are often out of specs randomly. Different types and brands of caps may rapresent other unpredictable variables. Beyond capacitors, the drivers can also age differently depending on many factors. In other words, with aging, even speakers of the same model often sound differently from each other.
Similar speakers like AR9 LS and AR9 LSI should be placed in an identical position if you want to make a correct comparison because speaker placement does affect the sound a lot. So, in this regard, I think you should have swapped the speakers position to get more objective results during your comparison.
Different model of speakers often require different placements and/or amplifiers to get the best they can give.
The SPL at the listeng point should be as similar as possible for all the speakers under test.
Obviously our subjectivity is another variable but it's very difficult to eliminate it without resorting to a double blind experiment.
Luigi
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Hello Bjarne,
Unfortunately the coil is out of focus. It seems that you made only one layer winding covering all the former. If so, this is not correct. 1) the winding must be a two layer winding and 2) the former must not be covered completely.
In the AR Library I've found the tweeter voice coil drawing of the "Lamba driver" used in the AR 9 LS, 98 LS and 78 LS. It is the 241th drawing.
As regards wire, even though the drawing reports: "2 wire: 22 to 24 turns of N° 38 AWG (a diameter of about 0.1 mm) copper……….. in two layers, 11 to 12 turns per layer", actually I have usually found an inner layer of 14 turns and an outer layer of 11 turns.
Hope you removed the tweeter diaphragm only mechanically since solvents usually change tweeter suspension stiffness permanentely and consequentely the tweeter FS and Thiele-Small parameters.
Luigi
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6 hours ago, Scoup said:
Listening to the LS vs the LSI, I preferred the LSI.
Hello Scoup,
Did the LS and LSI have new crossover capacitors?
If both of them had, did their crossovers use the same type and brand of capacitors?
Did you test each of their driver before comparing the loudspeakers?
During the comparison test, were the LS and LSI alternately placed in the same room position?
Thank you for any clarification about your comparison test.
Luigi
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On 4/27/2019 at 6:58 PM, tysontom said:
This early 1969-1970 ferrite woofer (Roy and I can't determine precisely when the new ferrite woofer appeared in the AR-3a)
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"
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On 5/9/2019 at 2:32 PM, David Cutter said:
No visible signs of previous repairs.
I just squirted cleaner in the holes in the pots and turned them for a while. They rotate more smoothly now. I know a proper cleaning will require removing and opening them up.
On 5/9/2019 at 3:16 PM, David Cutter said:
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
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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.
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On 4/26/2019 at 7:47 AM, Pete B said:
Thanks for the info Tom, do you know any more details about how spiders are made?
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 in comparison with Rev. B. As regards supplier, it was LCC (Loudspeaker Components Corporation, Lancaster Wisconsin). I think that the same company is still operating nowdays and they could still have the original molds/dies for the 200003 spider www.loudspeakercomponents.com .
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? How/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.
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On 4/6/2019 at 6:16 AM, KlausDK said:
Has anybody tried, or do you think it would be possible to dissasemble the woofer, remove the old former/coil from the cone and attach a new former/coil from the above set to the old cone?
Hi Klaus,
It's very important to preserve the woofer spiders. In order to disassemble the spider from the masonite ring I use an anti-fog nitro thinner 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 remnants as soon as possible otherwise they 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 voice 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
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On 9/16/2018 at 8:30 PM, Keno said:
How about replacement tweeters for these model?
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/
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On 6/26/2018 at 12:34 PM, larrybody said:
I wonder why the 6th 20 ohm resister is not listed?
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
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@seventy1 Thank you seventy1, but the picture you post is not visible.
Luigi
Edit: Ok, now it's visible,
Thank you
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12 hours ago, DavidR said:
Will be back once power is restored. Could be days they say
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
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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.pdf
that'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. -
15 hours ago, DavidR said:On 3/3/2018 at 7:39 PM, DavidR said:
> Also, what is the 10 ohm resistor doing to the xover circuit where they put it across (parallel) the cap leads of the 2500uF cap?
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
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
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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
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On 2/6/2018 at 8:34 PM, DavidR said:On 2/2/2018 at 4:40 AM, DavidR said:
My AR10pi speakers are the MkII version. They have polyfiber and not fiberglass stuffing. Could this be original?
I still need to peek at the crossovers and see what's in there for caps. Hoping for Sprauges but I've seen pics with Callins caps in some.
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 signatures of the same engineer (probably Tim Holl).
Thank you
This is an European AR-10 Pi MKII showing a soft multi-coloured polyester stuffing but other type of stuffing were used as well. The white polyester was only used at the end of production. Obviously, the stuffing weight changed depending on the different materials.
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On 2/2/2018 at 4:40 AM, DavidR said:
My AR10pi speakers are the MkII version. They have polyfiber and not fiberglass stuffing. Could this be original?
Could you better describe the stuffing ( better if you would post some pictures of it) and exactly weigh it? Both these factors are very important for woofer damping.
Luigi
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I forgot 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
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9 hours ago, DavidR said:
tweeters do not stand out well.
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
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On 1/28/2018 at 8:26 PM, ar_pro said:
I've never personally been able to hear any difference between the Tonegen and the standard 200003-1 driver in this circumstance.
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 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
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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
AR3a originals?
in Acoustic Research
Posted
@cbolen Yes, all the drivers are original. The woofers are very rare. If the woofer spiders and voice coils are ok, you only need to refoam them. Since this type of woofer is rare, could you please post clear photos of all the dates printed both on the ferrites and the bottom plates ? Thank you.