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AR3a woofer recone kit


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I've used the kit and found the voice coil to be about right but the cone is too light with the resultant Fs being significantly higher than spec.

I think Roy C. will attest to this as well.

I was able to resolve the Fs issue with a different (more compliant) spider. The kit's surround, which is is the preferred version, is neatly pre-attached to the cone...so all good there. The voice coil has about 1/2 ohm greater dcr and slightly higher inductance...not too bad. Unfortunately, the cone itself is less than half the weight, and much stiffer than the original cone. For folks debating differences in such things as capacitors, level controls, and amps, the resulting response difference between the re-coned woofer and any version of the original woofer is much more significant than these concerns. Otoh, for those who simply want to get their speakers working it is really the only option next to finding a decent original woofer.

It should be noted that the kit will only fit the foam surround version of the AR 12 inch woofer basket, not the cloth surround version.

Roy

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I have not seen recently similar cone material that was used for original AR foam surround woofers... it feels like mixture of asphalt or bitumen and pulp?

Is it possible to increase weight of replacement cone with weight around VC opening or doping back side of cone with PVA and something with a bit more weight. This may work with AR3a and AR9 if additional weight does not decrease efficiency too much. As HF response would be wild quess, this may not be OK with AR3 . Refoaming good original woofer would be best option anyway... but every day less original ones do exist.

Debating differences in such things as capacitors, level controls, and amps is nuisance compared to performance of old drive units, like Roy says. Drive units in vintage gear are old and most likely do not meet original specs too often. I was a bit irritated when I received second set of AR2ax mids in last December. Even the resonance problem of first pair was cured... this pair was not perfect either. But... using some other drive unit feels like cheating.

Best Regards

Kimmo

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  • 3 years later...

I have a friend, who has blown both woofers in his 10Pi playing some digital music, both coils were pushed out of the magnetic gap, and didn't manage to get back in, so the formers/coils were/are riding on the magnetic pole, with the former completely crushed around the vent holes and deformed.

The cone, however, seemes to me OK. 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?

BRgds Klaus

Spole2.jpg

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1 hour ago, KlausDK said:

The cone, however, seemes to me OK. 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?

BRgds Klaus

 

Hi Klaus,

I have managed to save the original cone a number of times, but the adhesive holding the old voice coil in place is very tough to deal with. If that area becomes too damaged as a result of separating the old voice coil from the cone, it is very difficult to center and install the new voice coil.

Roy

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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

 

 

 

 

dismantled_12in_woofers1.jpg

disassembled_12in_alu_woofer.jpg

cleaned_spider_cone_hole1.jpg

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10 hours ago, fedeleluigi said:

If the new coice 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).

Thanks Roy and Luigi, Luigi, where do you get new voicecoils from? As you can see from the picture, the paperformer in my friends speakers ar completely damagaed/separated.

BRgds Klaus

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  • 1 year later...
On 4/6/2019 at 12:36 PM, fedeleluigi said:

anti-fog nitro thinner

Hi to all, in particular Luigi, I have found the same problem but this woofer has been already repeired (probably not perfectly, and this could have been the reason of the fault).

Adcvices? How can I detach the spider and or the ring from the magnet?

Do you know where to find the voice coil if to be changed? And adviced to restore it with the right positions and cetrered ... Do you have spare parts?

Thank you very much!

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