AR 3a Crossover - What difference would 180uf vs 150uf make?

[redpackman]

I'm in the process of restoring a nice pair of AR-3a's. This is the second set I've done and they're really turning out nice. I sent away for some new caps for the crossover. The crossover requires a 6 uf, 50 uf and 150 uf cap. The supplier sent all six and before I put them in I tested them with my run-of-the-mill cap tester. The 6 uf (poly film) and 50 uf caps were right on within around 2%, but the 150 electrolytics were both (one for each speaker) at around 179uf. I thought it was perhaps my cap tester so I took the 150's which were supposed to be within 5% tolerances to a nationally known speaker repair place with better equipment, and the 150 tested out at 171 uf.

I've let the supplier know,

But my question: what difference would that have made in the performance of the AR3a's. I am no AR/crossover guru, but I know some of you are. In the process I tested out the original Sprague can caps which have a good reputation for longevity and accuracy, and they were within about 2%, so I just left them in. The speakers sound fabulous!

But what would a 171-180 uf cap do in those speakers?

 

[WaynerN]

150uf is a very low XO point. The cross-over point is resistive dependant, so it's cross-over point would be different from 8 ohms to 4 ohms. (I'm assuming this is for the woofer), but never having seen an AR-3a XO, I'm not sure.

At any rate, its always nice to have them at least close to the same value, but the original caps probably were not 5%, more like 10% (or greater).

 

[F1nut]

The original caps from that time would have a tolerance of +/- 20%, so while 180uF is within that tolerance range it's at the maximum of the plus end. Since the new ones are supposed to be within 5% of 150uF you should return them.

 

[WaynerN]

I agree with F1nut, if they are out of spec (regardless of the circuit design), they should go back for a replacement. They probably should have found you some "matched" pairs.........

 

[StimpyWan]

I'm in the process of restoring a nice pair of AR-3a's. This is the second set I've done and they're really turning out nice. I sent away for some new caps for the crossover. The crossover requires a 6 uf, 50 uf and 150 uf cap. The supplier sent all six and before I put them in I tested them with my run-of-the-mill cap tester. The 6 uf (poly film) and 50 uf caps were right on within around 2%, but the 150 electrolytics were both (one for each speaker) at around 179uf. I thought it was perhaps my cap tester so I took the 150's which were supposed to be within 5% tolerances to a nationally known speaker repair place with better equipment, and the 150 tested out at 171 uf.

I've let the supplier know,

But my question: what difference would that have made in the performance of the AR3a's. I am no AR/crossover guru, but I know some of you are. In the process I tested out the original Sprague can caps which have a good reputation for longevity and accuracy, and they were within about 2%, so I just left them in. The speakers sound fabulous!

But what would a 171-180 uf cap do in those speakers?

Hey redpackman,

I have 2 Erse 150uF 100V NPE's. I had them for my AR90 recap, forgot about them, and ordered more caps. So, if you could use them, let me know? No charge. Just PM your address, if you'd like them? I'll ship 'em out Saturday. Hopefully, the bad caps aren't Erse too?

 

[Bob]

depends on that cap - used as a high pass or low pass?

higher values raise the f3 point, and more lower bass to the bass speaker, or less bass
to the treble speaker.

try it, break-it-in first, and listen to it with music you know, and then decide. the goal is
not to "replicate" the sound as it was before ( as it was designed in 19xx, as it sounded
in AR labs, fresh out of the box when new, etc) - its to get better sound by rolling back
age-related deterioriation, abuse from overdriving, mechanical damage from taking it
swimming, and horrors - being bounced around in the back of a pickup and being
waterboarded by beer hurlers.

go with better caps (by design, by value (not pricing), or by acclaim).

as far as 2% differences: 2 meters call it differently - which is correct or are both
within guard bands for margins and wrong, put in circuit, run for 4 months,
pull and measure - guarantee no longer 2 %. 3) in circuit, be able tell which
one is the out-of-tolerance one? I can't but assuming you can, then you
have a billion dollar IPO - HK is the parent company and would pay millions
for someone/something to help them voice their highend speaker brands
and want to save millions in testing,...

trust your ears and enjoy the music.

 

[redpackman]

Hey redpackman,

I have 2 Erse 150uF 100V NPE's. I had them for my AR90 recap, forgot about them, and ordered more caps. So, if you could use them, let me know? No charge. Just PM your address, if you'd like them? I'll ship 'em out Saturday. Hopefully, the bad caps aren't Erse too?

Thank you, Stimpy. I'm afraid they were Erse...and 6% tolerance, too. I contacted them about the first two and they sent me two others...same reading. At that point I doubted my cap tester so I took it in and had a professional test it...off by about 15%....171uf. I reinstalled the old Sprague, which were around 152 uf.

I think they had a bad batch. I let them know. I hope they do something about it.

 

[redpackman]

depends on that cap - used as a high pass or low pass?

higher values raise the f3 point, and more lower bass to the bass speaker, or less bass
to the treble speaker.

try it, break-it-in first, and listen to it with music you know, and then decide. the goal is
not to "replicate" the sound as it was before ( as it was designed in 19xx, as it sounded
in AR labs, fresh out of the box when new, etc) - its to get better sound by rolling back
age-related deterioriation, abuse from overdriving, mechanical damage from taking it
swimming, and horrors - being bounced around in the back of a pickup and being
waterboarded by beer hurlers.

go with better caps (by design, by value (not pricing), or by acclaim).

as far as 2% differences: 2 meters call it differently - which is correct or are both
within guard bands for margins and wrong, put in circuit, run for 4 months,
pull and measure - guarantee no longer 2 %. 3) in circuit, be able tell which
one is the out-of-tolerance one? I can't but assuming you can, then you
have a billion dollar IPO - HK is the parent company and would pay millions
for someone/something to help them voice their highend speaker brands
and want to save millions in testing,...

trust your ears and enjoy the music.

Thanks for the input. The bass sounded muddy with the 180 uf caps and much better with the old Sprague. Go figure.

 

[StimpyWan]

Thank you, Stimpy. I'm afraid they were Erse...and 6% tolerance, too. I contacted them about the first two and they sent me two others...same reading. At that point I doubted my cap tester so I took it in and had a professional test it...off by about 15%....171uf. I reinstalled the old Sprague, which were around 152 uf.

I think they had a bad batch. I let them know. I hope they do something about it.

That's not good. Oh well. I was hoping that I could help. There's always Bennic or Mundorf E-Cap NPE's. And I'm guess I'm glad that I didn't use the Erse caps now. I ended up using E-Caps on my AR90 bass shunt caps.

Good luck.