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Anders Nilsson

Distorted sound from woofer, video clip attached. AR-3a improved

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Hi!

I am new on this forum and recently bought a very nice pair of AR-3A improved. I have limited experience and knowledge of speaker troubleshooting and would appreciate your help.

There is something wrong with one of the speakers as it sounds distorted already at a low volume and terribly distorted at higher volumes. I have attached a short video clip of the terrible distortion. Midrange and tweeter are disconnected in the video clip.

The crackling, distorted sound comes from the woofer as it remains when I connect the speaker in the subwoofer configuration (removing the tweeter jumper on the backside).

According to the seller, the speakers worked perfectly fine before they were shipped to me, but that is of course difficult to prove.

Where should I start the troubleshooting? What are the most likely causes to the distorted woofer sound?

To exclude a problem with the amp, I already reversed channels of the amp, and the distorted sound remains in the same speaker.

The amp is a NAD C320 BEE known to be very stable also at low impedances. 

Greetings from Sweden!

/Anders

 

20200725_153351.jpg

20200725_153332.jpg

20200725_153258.jpg

20200725_153206.jpg

20200724_184839.jpg

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If it doesn't rub when you do a manual push test, you can further isolate by swapping the woofers to see if the problem moves.  If it is the woofer and not in the wiring ,applying a signal directly to the woofer terminals would be my last choice after examining the cone and all of its attachment points.  You can Wait for RoyC to reply.  He probably already knows the answer from the sound in your video.

Adams

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1 hour ago, Anders Nilsson said:

Hi!

I am new on this forum and recently bought a very nice pair of AR-3A improved. I have limited experience and knowledge of speaker troubleshooting and would appreciate your help.

There is something wrong with one of the speakers as it sounds distorted already at a low volume and terribly distorted at higher volumes. I have attached a short video clip of the terrible distortion. Midrange and tweeter are disconnected in the video clip.

The crackling, distorted sound comes from the woofer as it remains when I connect the speaker in the subwoofer configuration (removing the tweeter jumper on the backside).

According to the seller, the speakers worked perfectly fine before they were shipped to me, but that is of course difficult to prove.

Where should I start the troubleshooting? What are the most likely causes to the distorted woofer sound?

To exclude a problem with the amp, I already reversed channels of the amp, and the distorted sound remains in the same speaker.

The amp is a NAD C320 BEE known to be very stable also at low impedances. 

Greetings from Sweden!

/Anders

 

20200725_153351.jpg

20200725_153332.jpg

20200725_153258.jpg

20200725_153206.jpg

20200724_184839.jpg

 

Could be a bad solder from the voice coil to the cone.

 I wasn’t able to open the video unfortunately.

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16 minutes ago, newandold said:

Could be a bad solder from the voice coil to the cone.

 

Thanks! I will check that. Do you mean the soldering in the terminal area like on the picture?

20200724_185211.jpg

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21 minutes ago, RickB said:

Wow could be, but check for voice coil rub and a loose spyder(spider).

Thanks! That was also my thinking, but I could not notice any voice coil rub or loose spyder upon inspection.

 

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1 hour ago, Anders Nilsson said:

Thanks! I will check that. Do you mean the soldering in the terminal area like on the picture?

20200724_185211.jpg

The terminal end is most common.

but for sure follow the lead continuity to the coil.

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I would now connect to the terminal and or the leads to the voice coil and test the woofer output. If it works ok then clean the terminals ,reconnect. If not then there is a wiring/ component problem.

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5 hours ago, Aadams said:

If it doesn't rub when you do a manual push test, you can further isolate by swapping the woofers to see if the problem moves.  If it is the woofer and not in the wiring ,applying a signal directly to the woofer terminals would be my last choice after examining the cone and all of its attachment points.  You can Wait for RoyC to reply.  He probably already knows the answer from the sound in your video.

Adams

I now resoldered the litz wire from the voice coil at the terminal area, and have also applied a music signal directly to the woofer, outside of the speaker cabinet. I think it is more difficult to judge the distortion when the woofer is outside the cabinet, but outside the cabinet and already at moderate volumes, the woofer starts to sound bad, almost like a cone breakup.

No visible problem with the spider and no voice coil rub.

Tomorrow I will try the woofer in the other speaker cabinet to see if there is a difference.

Could the problem be related to a bad crossover capacitor? 

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15 minutes ago, Anders Nilsson said:

I now resoldered the litz wire from the voice coil at the terminal area, and have also applied a music signal directly to the woofer, outside of the speaker cabinet. I think it is more difficult to judge the distortion when the woofer is outside the cabinet, but outside the cabinet and already at moderate volumes, the woofer starts to sound bad, almost like a cone breakup.

No visible problem with the spider and no voice coil rub.

Tomorrow I will try the woofer in the other speaker cabinet to see if there is a difference.

Could the problem be related to a bad crossover capacitor? 

Yes swapping the woofer is one of the best ways to be sure.

The woofer is very old and the trip may have been just enough to shake up a voice coil that was already on the way out.

Fortunately if that’s the case a woofer for that system can still be had. The seller may also work with you to some extent on some credit. I was once faced with a situation like that and the seller gave me some credit towards the repair.

 

Bill

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17 minutes ago, Anders Nilsson said:

Could the problem be related to a bad crossover capacitor? 

It is unlikely, especially with the big caps being Spragues.  If you are hearing distortion with the woofer out of the cabinet there is probably no need to switch the woofers but it would offer confirmation.   Have you checked the attachment of spacer ring on the metal frame?

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3 minutes ago, newandold said:

Fortunately if that’s the case a woofer for that system can still be had.

Where do I find a replacement woofer, in case it has gone bad? Is it possible to find an exact match?

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The outer edge of the new surround is glued to the Masonite spacer ring. The woofer in the photos shows a ring later woofers don’t have the ring. 

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4 minutes ago, Anders Nilsson said:

Where do I find a replacement woofer, in case it has gone bad? Is it possible to find an exact match?

I’ve been collecting original spares on EBay for years....but you have to be very careful with whom you’re dealing.

That being said, and especially that it’s a 3A, it would be best to have that original rebuilt.

 I have used Bill Legall’s Millersound in Landsdale PA and also Simply Speakers in FL.

Surely there are a few guys here with some suggestions of their own 

Bill

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2 minutes ago, Aadams said:

The outer edge of the new surround is glued to the Masonite spacer ring. The woofer in the photos shows a ring later woofers don’t have the ring. 

Alright, I see! The masonite ring seems firmly attached. Cabinet seems airtight when pushing the cone of the woofer. Relaxation time of the cone is long!

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29 minutes ago, newandold said:

I’ve been collecting original spares on EBay for years....but you have to be very careful with whom you’re dealing.

That being said, and especially that it’s a 3A, it would be best to have that original rebuilt.

 I have used Bill Legall’s Millersound in Landsdale PA and also Simply Speakers in FL.

Surely there are a few guys here with some suggestions of their own 

Bill

Thanks Bill! 

In Sweden where I live, I know of a well reputed speaker service company. I will contact them if needed.

I agree it would be best to have the original rebuilt.

https://www.hogtalarservice.se/

 

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16 minutes ago, Anders Nilsson said:

Thanks Bill! 

In Sweden where I live, I know of a well reputed speaker service company. I will contact them if needed.

I agree it would be best to have the original rebuilt.

https://www.hogtalarservice.se/

 

The website looks great....looks like you’ve got your place....From the posts on this I’ve read to date, it appears you’re going to need them.

Bill

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Anders,

"...and recently bought a very nice pair of AR-3A improved."

Your speakers are not AR-3a Improved. They are the European AR-3a, which had the same cabinet.

Roy

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Anders,

Here is a thread about a woofer like yours.  It is worth reading for the information about properly repairing these old woofers.

 

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19 hours ago, RoyC said:

Anders,

"...and recently bought a very nice pair of AR-3A improved."

Your speakers are not AR-3a Improved. They are the European AR-3a, which had the same cabinet.

Roy

Thanks Roy, That is valuable information to me. The badges are marked AR-3a improved, and they were advertised that way.

My guess is the speakers are built in 1975 in England. Is it possible to tell the manufacturing year from the serial number 03060?

/Anders

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23 hours ago, newandold said:

Yes swapping the woofer is one of the best ways to be sure.

I swapped the woofers and distortion remains in the same woofer. No longer any doubt there is a problem with that woofer.

The return speed is faster (but still acceptably slow) of the bad sounding woofer, compared to the good one when depressing the cone. I have made sure the periphery of the woofer is airtight.
Attached video is well describing the distorted sound. It´s like the cone is not stiff enough and start to resonate at certain frequencies.

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@Anders Nilsson I do think that the paper collar of the voice coil is damaged or even totally cracked and this generally causes that kind of problems you are hearing. Unfortunately the collar damage is a problem of the 12" ferrite woofer produced before about 1977. Then AR switched to aluminum for the voice coil formers and it is much more stronger than paper. On page 5 (fig. 2.4 and 2.5) of "Restoring the AR-3a" you can see the characteristic final crack of the paper voice coil collar.

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19 hours ago, Anders Nilsson said:

Thanks Roy, That is valuable information to me. The badges are marked AR-3a improved, and they were advertised that way.

My guess is the speakers are built in 1975 in England. Is it possible to tell the manufacturing year from the serial number 03060?

/Anders

The grilles are interchangeable. It would have been easy enough to replace the badges along the way. What is printed on the tags on the back of the cabinets? Whatever the case may be, they are clearly original 3a's in every way. The Improved has a different crossover and a switch.

I don't have a number, but there were far fewer European 3a's manufactured than the US version. Your 3a's were manufactured in 1972 or 73 based on the appearance of the drivers, the woofer issue (most likely a damaged voice coil as seen in the link Aadams posted) and a few others I have experience with. I believe the highest serial number I have seen was around 13,000, and that pair was manufactured in 1973 based on the drivers' date stamps.

Roy

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