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defektzero

AR-3a improved need "warm up" ?

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Hello,

my name is Henner, i live in Germany near Cologne and since a few days i´m a proud owner of a pair AR-3a improved.

It´s a version with the A.3 woofer, the A.12 mid-range, the A.19 tweeter and the bigger frame around the front panel. I did not open the box, but found the pix of the drivers at the restoring-guide in this forum.

The pre-owner refoamed the bassdrivers and left everthing else in original condition.

I like the sound of the speakers very much, but they need about an hour "warm up" evrey day I want to listen to them. In the beginning they sound a bit dull and colourless and later they play more airy and with better resolution.

What can be the reason for this? The 40 year old caps? or the suspension of the high and mid-range drivers?

I would be happy, if you could help me a bit...

 

With best regards

Henner

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Hello Henner, I' m Adriano and I 'm from Rome, Italy. AR 3a improved are from mid-seventies , and probably needs recapping . I have two pairs of AR 3 from esrly sixties and they sounds dull when I bought ' em in 2009 and 2013 . After a recapping my AR 3 becomes transparent, shiny, alive . Mit freundlichen Grussen , Adriano

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The AR 3 and 3A used potentiometers (level controls) mounted in the back of the cabinet.  If your speaker has them, it  may be the  cause of your problems. Over time, they oxidize and become intermittent.  Test them by rotating the controls while playing music with high frequency content. If problematic, you might replace them or clean them with a solvent.

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Welcome to CSP, Henner.

Not sure what might be responsible for the "warm-up" situation, but this first thread does mention that the 3a-Improved often used low quality caps in the crossover circuitry so, whether or not this has anything to do with the performance delay you are experiencing, you still may want to dig in and consider cap replacement. The second thread shows a crossover pic and schematic, also confirming that this model typically used switch controls, even though there appears to still be some disagreement about various versions of the 3a Improved. If you search through this site, you will find plenty of discussion about your speaker model, as exemplified in this third thread.   

 

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AR 3a improved used Sprague electrolytic capacitors, after 40 years they 're out of specific, that' s for sure. You could recap your speakers with better caps like german-made Mundorf , I use MKT polypropilene to recap my AR , now replaced by Mcap series , a bit expensive but it' s worth the try. 

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Hello,

 

first - thank you for your answers!

Regarding to your suggestions I will first take a look at the caps and change them. In the restoring-guide is mentioned to put resitors in series to the new caps to compensate the lower ESR of the modern parts. Do you have experience with this? I also plan to change the resistors in the signal path to MOX-resistors and I ask myself, if its not better to chose the right value of those parts to have not about 30 components in the x-over at the end. Did it anyone that way?

At least my ambition ist to serve the original charakter of the speaker, but I want the best possible performance too. How much might be the effect of aging to the high and mid-range drivers. And what I asked myself all the time: What are the three red spots around the tweeter for? The mid-range driver has a beading arround the dome but the tweeter is some kind of suspect to me :)

How does ist work?

 

Thanks for your warm welcome!

With best regards

 

Henner

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42 minutes ago, Sonnar said:

AR 3a improved used Sprague electrolytic capacitors, after 40 years they 're out of specific, that' s for sure. You could recap your speakers with better caps like german-made Mundorf , I use MKT polypropilene to recap my AR , now replaced by Mcap series , a bit expensive but it' s worth the try. 

Yes - but what values did you chose for the 6 µF cap? Mundorf does not sell those...

The improved version has just a switch on the back and I´m not able to regulate with potentiometers, if the sound doesen´t fit...

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In the MKP series , 2,7 and 3,3 in parallel. I use AR 3 and 3a with pots on the white dot , and I 'd prefer to set the switch on normal position. AR 3a's mids and tweeter are very strong loudspeakers, and only a distortion by a clipping solid state amp unable to drive low-z loads can destroy them. Could You post a picture of the tweeter with the three red spots around? If they 're around the little dome it's probably the original glueing of the dome. 

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17 hours ago, defektzero said:

 

Regarding to your suggestions I will first take a look at the caps and change them. In the restoring-guide is mentioned to put resitors in series to the new caps to compensate the lower ESR of the modern parts. Do you have experience with this?

Welcome to this friendly forum....

I do find a bit odd to pay premium for low ESR  film or foil cap and degrade performance (by adding series resistor) of this expensive component to meet higher ESR of bipolar cap. Why not use bipolar in the first place, as they will probably  will have longer useful life than AR3a Improved´s anyway?

Kimmo

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On 4.5.2016 at 11:29 PM, Sonnar said:

If they 're around the little dome it's probably the original glueing of the dome. 

Yes, that´s what I mean. I´ve never seen a construction like this.

I ordered Mundorf MCap series for the x-over and I´m curious for the results.

 

Adriano, you were thinking about using a Lab.Gruppen amplifier in another thread - do you have experiences with that brand meanwhile?

Some people in Germany use the IP 450, wich has no fan for cooling, for HiFi/HighEnd applications - but i was not able to listen to one yet...

And i´m wondering no one uses a Bose 1800/1801 with the 3a´s?

 

Henner

 

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I've use the Bose 1801 power amp with a pair of AR-3as (and also AR-LSTs), and this is an outstanding amplifier.  Probably hard to find one in proper-working condition now, but it is a superb amplifier.  It is a low-distortion, "brute-force" design that is largely bullet-proof driving low-efficiency, low-Z loudspeakers such as the AR-3a.

--Tom Tyson

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I agree, Bose 1801 was an outstanding performer, but It's a 40 years old amp, and it needs an expensive rebuilt. I use a cheap QSC pro amp ( ISA 280 ) to drive my AR and I'm totally satisfied, but I'm planning to buy a LabGruppen because it' s considered the hi-end of the pro amps: I 've heard an fp2600 driving B&W 801 first series, loud and clean and smooth , excellent powerful bass. Another top-ranking hi-end pro amp is the German-made CAMCO , but it' s very expensive ( see Camco Vortex 6 ). In my experience , these amps are excellent in sound, very clean, very reliable, powerful, dynamic, transparent and easily drives difficult , low-z loads . I haven't problems with my QSC cooling fan, very quiet, inaudible. 

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This is a brute-force amp, by a modern design , and it has more power than You really need . However , a powerful amp used with discernment is less dangerous than a bad low-powered solid state amp in saturation ( clipping ). 

image.png

image.png

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On 10 maggio 2016 at 3:47 AM, tysontom said:

I've use the Bose 1801 power amp with a pair of AR-3as (and also AR-LSTs), and this is an outstanding amplifier.  Probably hard to find one in proper-working condition now, but it is a superb amplifier.  It is a low-distortion, "brute-force" design that is largely bullet-proof driving low-efficiency, low-Z loudspeakers such as the AR-3a.

--Tom Tyson

Hello Tom,

Could you please tell us wich are the best sounding amplifiers driving AR 3a, LST and 10 Pi you have listened to?

Thank you

Luigi 

 

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Today the last parts for restoring the x-over have arrived, but i will need a few days for doing this. If I find polyester as damping material in the cabinet, like I expect after reading about the improved version - will it be better to use fiber-glass instead?

...And I´m interested in a discussion about amps, too. I know, only a test will show, what fits best to me, but some ideas especially for affordable solutions would be helpful.

 

Henner

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Hello Henner, I think it' s better to leave original damping materials inside the cabinets. My AR speakers are very old and filled with original yellow rock-wool,, I removed it when I worked on the crossovers, then I repositioned accurately in its place. About pro amps, You could try every pro amp simply renting it for some days at a professional music store for musicians and djs, or just invest some little money for a very powerful and cheap Behringer, many hi-fi lovers use their class-D amps, but I prefer a classic AB just like QSC ISA 280 or 450. Greetings, Adriano

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34 minutes ago, Sonnar said:

Hello Henner, I think it' s better to leave original damping materials inside the cabinets. My AR speakers are very old and filled with original yellow rock-wool,, I removed it when I worked on the crossovers, then I repositioned accurately in its place.

The yellow stuff should be fiber-glass, rockwool is more grey/brown/green and polyester will never have the same grade of damping as fiber-glass. I asked this question, because fiber-glass or rockwool is used in the 3a cabinets with the same driver as mine. Maybe they wanted more an improvement in profit by using polyester? I will test it and write something about...

It´s a good idea, to rent a pro amp in a music store for testing - never thought about that. The amplifiers, that i liked very much, were mostly class a designs. But my travel through HiFi-philosophies took me to high effieciency fullrange-speakers in the last years and i sold the "big" amps i had. There is only a 20 W classe a Hiraga left here, i use together with a Meaxas Charisma pre. Those two components are a perfect match on a pretty high level, but better to use wth high effiency speakers. I paid 700 € for them together and now I´m looking for a best buy with more power.

I also owned a Chinese Jungson JA 88 D, wich was really excellent and a real bolide with 30 kg and enough power.  A friend (DIY amp builder) told me, that the design was "somehow similar" to an early Threshold amp, he knew. Unfortunately I can not find one again :(

Mmmh - I think, I will look arround, If some music store next to me has an IP 450  for rent and test it...

 

Henner

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I have found over the years that my system sounds better when it has been on for a while. I've tried this out by powering on, sitting down, and listening immediately. As time passes, it does sound better.

Also, I have powered up the system, left the room for an hour or so with the same results upon my return.

 Same thing when evaluating equipment for a possible purchase at a seller's house or just listening at a friend's home.

Audio is extremely complex with an incredible number of variables. Trust "your" ears.

Please use a mask when handling that rock-wool. Nasty stuff. I usually get rid of it but that requires some figuring of what to replace it with and how much. I have tested this by replacing only one speaker's rock-wool (or fiberglass). Couldn't hear the difference and usually forgot into which speaker I placed the new stuffing. 

 

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A full-range speaker has too many limitations to me. Perhaps the best one point source I 've ever heard was the Altec 604 8G , very expensive , and it needs a very large cabinet , 9 cu. In. . A good loudspeaker, in a class by itself, but not an accurate speaker for acoustic instruments in my opinion, as every high efficiency loudspeaker . I use a 20 watt per channel old tube amp to drive my Altec/JBL horn loaded system ( a very high efficiency system but not accurate  but AR speakers are a very difficult load , and they have very low sensitivity, so I 've had many powerful amps , but no one was able to drive correctly AR 3 / 3a with the exception of the excellent Crown PSA-2 : now the modern QSC offers the same ability to drive difficult loads with a smoother and more clean sound . To me, AR are the most accurate and neutral speakers ever built for the reproduction of classical / acoustic instruments, and the low-end has no competitors. You only have to find an excellent, powerful, very stable solid state amp. Mach 's gut , Adriano

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On 5/10/2016 at 3:38 AM, Sonnar said:

I agree, Bose 1801 was an outstanding performer, but It's a 40 years old amp, and it needs an expensive rebuilt. I use a cheap QSC pro amp ( ISA 280 ) to drive my AR and I'm totally satisfied, but I'm planning to buy a LabGruppen because it' s considered the hi-end of the pro amps: I 've heard an fp2600 driving B&W 801 first series, loud and clean and smooth , excellent powerful bass. Another top-ranking hi-end pro amp is the German-made CAMCO , but it' s very expensive ( see Camco Vortex 6 ). In my experience , these amps are excellent in sound, very clean, very reliable, powerful, dynamic, transparent and easily drives difficult , low-z loads . I haven't problems with my QSC cooling fan, very quiet, inaudible. 

I also use QSC and Crown pro amps now simply because of their excellent stability, low distortion and reliability.  You just don't need to worry about problems with these amps, and they can easily drive any loudspeaker load without issues.

 

--Tom Tyson

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On 5/12/2016 at 11:58 AM, fedeleluigi said:

Hello Tom,

Could you please tell us wich are the best sounding amplifiers driving AR 3a, LST and 10 Pi you have listened to?

Thank you

Luigi 

 

Hello Luigi,

There are many very fine amplifiers capable of driving these three AR speakers, but they all share in common relatively high power, great stability into capacitive-reactive loads and stability into very low impedances.  These are common to all of the amps capable of driving these speakers, and I doubt that anyone could ever detect differences between them with a proper double-blind listening test.  That said, I can tell you the amplifiers I have used over the years with my AR-LSTs, AR-3as, AR-10s and AR9 speakers (and other speakers).  I have used a McIntosh MC2500, Threshold s/500, Crown Studio Reference I, and more recently a QSC PLX-3602 (still in use).  Each of these amps performed well with these speakers without any issues whatsoever, and I don't think I could ever have detected any differences between them. 

So, to answer your question, there is probably no "best" amplifier for driving these speakers; only those amps that are stable and powerful should be used, and there is no real sonic differences among them. 

McIntosh_2500_(01b).jpg

1.  McIntosh MC2500 amplifier (500/500).  The McIntosh amplifier is built very much like a Hewlett-Packard instrument, lots of cast-aluminum, stainless-steel hardward, military-grade gold-plated printed circuit boards and so forth.  Built to last.  It will produce full output power into 1, 2, 4, 8, 16 ohms without any problems.

McIntosh_2500_Test_(05A).jpg

2.  This shows the power output of the MC2500 (720 watts/channel continuous until the 20A circuit breaker tripped at the McIntosh Clinic).

McIntosh_2500_(04a).jpg

3. Heavy construction and auto-transformers used in the MC2500.  There was no transformer-output phase shift or other issues sometimes reported in the audio press, as these were special "bifilar-wound" (very closely spaced windings) transformers patented by McIntosh years ago.  These transformers were 100% linear within all audio frequencies, but the transformers added hugely to the cost and weight (130 lbs).

s500_002.jpg

4. Threshold Stasis S/500 Stereo Amplifier (250/250).  This amplifier is unconditionally stable into any load of any impedance.  It also has gold-plated, military-grade epoxy circuit boards and very high-quality components.  Threshold is gone now, but it was one of Nelson Pass' better efforts over time.  This particular S/500 picture was courtesy of the internet.

1-025-025506-Crown-Macro-Reference_1.jpg

5. Crown Studio Reference I, a powerhouse amplifier drawing a lot of line current.

Studio-Reference-NEMA_TT30 Powercord_002.jpg

6. Crown Studio Reference I 30-Amp TT30 NEMA power cord, requiring a special 30-amp receptacle or 220 wiring.

PLX3602_front_right_hi.jpg

7. QSC PLX-3602 Class-H 3600 watt pro amplifier currently in use.

--Tom Tyson

 

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On 19 maggio 2016 at 7:16 PM, tysontom said:

Hello Luigi,

There are many very fine amplifiers capable of driving these three AR speakers, but they all share in common relatively high power, great stability into capacitive-reactive loads and stability into very low impedances.  These are common to all of the amps capable of driving these speakers, and I doubt that anyone could ever detect differences between them with a proper double-blind listening test.  That said, I can tell you the amplifiers I have used over the years with my AR-LSTs, AR-3as, AR-10s and AR9 speakers (and other speakers).  I have used a McIntosh MC2500, Threshold s/500, Crown Studio Reference I, and more recently a QSC PLX-3602 (still in use).  Each of these amps performed well with these speakers without any issues whatsoever, and I don't think I could ever have detected any differences between them. 

So, to answer your question, there is probably no "best" amplifier for driving these speakers; only those amps that are stable and powerful should be used, and there is no real sonic differences among them. 

McIntosh_2500_(01b).jpg

1.  McIntosh MC2500 amplifier (500/500).  The McIntosh amplifier is built very much like a Hewlett-Packard instrument, lots of cast-aluminum, stainless-steel hardward, military-grade gold-plated printed circuit boards and so forth.  Built to last.  It will produce full output power into 1, 2, 4, 8, 16 ohms without any problems.

McIntosh_2500_Test_(05A).jpg

2.  This shows the power output of the MC2500 (720 watts/channel continuous until the 20A circuit breaker tripped at the McIntosh Clinic).

McIntosh_2500_(04a).jpg

3. Heavy construction and auto-transformers used in the MC2500.  There was no transformer-output phase shift or other issues sometimes reported in the audio press, as these were special "bifilar-wound" (very closely spaced windings) transformers patented by McIntosh years ago.  These transformers were 100% linear within all audio frequencies, but the transformers added hugely to the cost and weight (130 lbs).

s500_002.jpg

4. Threshold Stasis S/500 Stereo Amplifier (250/250).  This amplifier is unconditionally stable into any load of any impedance.  It also has gold-plated, military-grade epoxy circuit boards and very high-quality components.  Threshold is gone now, but it was one of Nelson Pass' better efforts over time.  This particular S/500 picture was courtesy of the internet.

1-025-025506-Crown-Macro-Reference_1.jpg

5. Crown Studio Reference I, a powerhouse amplifier drawing a lot of line current.

Studio-Reference-NEMA_TT30 Powercord_002.jpg

6. Crown Studio Reference I 30-Amp TT30 NEMA power cord, requiring a special 30-amp receptacle or 220 wiring.

PLX3602_front_right_hi.jpg

7. QSC PLX-3602 Class-H 3600 watt pro amplifier currently in use.

--Tom Tyson

 

Hello Tom,

Thank you very much for answering.
You are very experienced so every information you give us about AR loudspeakers is always very useful  to every reader in this forum. I have noticed you have used and still use very powerful amps.  Do you think the more power the better for sound quality even for normal sound pressure levels?
 Although it is a controversial issue,  I have generally noticed the more power the better with transistor amps (using the same type of circuit). On the contrary, imho,  push-pull tube amps (about 40-80 watts) using a single pair of tubes per channel (6550, kt 88 etc), sound generally better than more powerful amps using parallel pairs of push-pull tubes and the same kind of circuit.
What is  your experience and opinion about this question?
 
Thanks again
 
Luigi

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