Type AL Crossover (La Scala) Capacitor replacement?

[glens]

I don't "follow" JBL's doings, and within the past year just caught wind of the bias thing.  The little bit of research I did made it seem like it's primarily, if not solely, for the Japan market.  And I understand those folks can be what amounts to the capstone of the audiophile "fluff" pyramid.  So there's that...

 

Also within that time I first learned of bypassing caps in a high-level crossover.  In all my years of intermittently messing with this stuff it never occurred to me that anybody would even consider doing that.  The signal that gets through a tiny-value cap at those impedance levels doesn't even begin to become meaningful until several times the upper frequency even a newborn human could possibly discern.  Which is why I especially got a kick out of BEC's "offer" because he obviously understands that too.

 

I don't care or mind if anybody wants to pursue such things as these two, I merely feel a duty to be a voice of reason once in a while when I see them being mentioned.

 

 

[tigerwoodKhorns]

3 hours ago, PrestonTom said:

 

 

Regarding the issue of biasing, JBL has a long history of this. These are no-nonsense engineers that probably do not engage in fluff. 

 

I was going to mention this.  Gregg Timbers is the go to on this.  I researched this recently.  He eventually went with charged coupled which he questioned at first, then used in the Everest and recommends for the 250. 

[PrestonTom]

" .....

I don't care or mind if anybody wants to pursue such things as these two, I merely feel a duty to be a voice of reason once in a while when I see them being mentioned.

...."

You might want to be careful about thinking that you are the only "voice of reason". There are others also

[glens]

Haha!  Thanks.  I'd not intended to imply I felt alone in that respect.

[glens]

2 hours ago, tigerwoodKhorns said:

6 hours ago, PrestonTom said:

Regarding the issue of biasing, JBL has a long history of this. These are no-nonsense engineers that probably do not engage in fluff. 

 

I was going to mention this.  Gregg Timbers is the go to on this.  I researched this recently.  He eventually went with charged coupled which he questioned at first, then used in the Everest ...

 

I saw that, too.  I still don't "get" it.

 

Whatever "crossover" anomalies (reversal lag in electron flow?) might show up in a capacitor being chosen as appropriate for the task at hand would seem at first blush to actually still be present, perhaps even to a greater extent, in the presence of bias.  Sans bias there (as envisioned) would be merely a window of dead time before current begins to flow in the opposite direction.  That being with a quiescent period of electron flow through the dielectric.  If there were supposedly a period of hysteresis where the electrons continued flowing in one direction, on momentum, after the push ceased at / during the direction change, causing (even further?) delay getting started the other direction, then why wouldn't that condition be worsened against a bias (and sped up with it the other way)?  If the anomaly were problematic without a bias present, wouldn't it at least have symmetry?  And with a bias, an asymmetry?  Is an asymmetrical "crossover distortion" less objectionable than one symmetrical?

[Dave A]

5 hours ago, glens said:

 

I saw that, too.  I still don't "get" it.

 

Whatever "crossover" anomalies (reversal lag in electron flow?) might show up in a capacitor being chosen as appropriate for the task at hand would seem at first blush to actually still be present, perhaps even to a greater extent, in the presence of bias.  Sans bias there (as envisioned) would be merely a window of dead time before current begins to flow in the opposite direction.  That being with a quiescent period of electron flow through the dielectric.  If there were supposedly a period of hysteresis where the electrons continued flowing in one direction, on momentum, after the push ceased at / during the direction change, causing (even further?) delay getting started the other direction, then why wouldn't that condition be worsened against a bias (and sped up with it the other way)?  If the anomaly were problematic without a bias present, wouldn't it at least have symmetry?  And with a bias, an asymmetry?  Is an asymmetrical "crossover distortion" less objectionable than one symmetrical?

I suggest a cable, capacitor and finally crossover cooker for you Glenn. Your rational approach to this whole thing is tawdry.

[mustang_flht]

Hi,

In addition to the good reviews already given.

You have an Australian friend who built filters from La Scala, he may have some good advice:

 

 

[Deang]

Sent to me in an email a long time ago: 

 

"The idea behind battery bias is to use high-K capacitors like electrolytics and, with bias, achieve film type responses.  DA trends with K-value."

 

He saw that I was doing it with metallized films, and thought I was wasting my time. I stopped doing it, even though I had a few (including myself) that said, well, a number of nice things about the sound.

 

 

[JohnA]

4 hours ago, Deang said:

Sent to me in an email a long time ago: 

 

"The idea behind battery bias is to use high-K capacitors like electrolytics and, with bias, achieve film type responses.  DA trends with K-value."

 

He saw that I was doing it with metallized films, and thought I was wasting my time. I stopped doing it, even though I had a few (including myself) that said, well, a number of nice things about the sound.

 

 

 

I don't understand it and I'm skeptical.  Since there is an ocean of B.S. and fraud in Audio, it is easy to dismiss the unusual.  Adding a DC bias to a cap has been used often enough to make me wonder, though. 

 

[innerwestsoul]

Hi all,

 

Back on script... @Wirrunna came over to my place yesterday and left me with enough caps to implement stage 0.5 of the plan - Re-cap one of the ALs and bring it back up to spec.

 

I've just done the deed - Improvement in that side is dramatic - on George Duke - Brazilian Love Affair (Columbia 1992 Digital Remaster), the title track is a very dynamic, fast percussion-driven jazz fusion (dare I say) masterpiece with heavy bass guitar courtesy of Byron Miller. And it's absolutely popping for me right now. I listen to a lot of music with this sort of space and bounce (being more of a jazz / funk / disco kind of guy than a rock-lover) and the separation and detail I'm hearing today is truly magical.

 

** Not that I ever actually had a "problem" of any sort with the original ALs - I'm just seeing what more I can squeeze out of these speakers and from step 0.5 it seems like - quite a lot more.

 

Next step - Procure a few more parts, and re-cap the other side.

After that - We're plotting how to build an ES network using some great ideas that John has accumulated over the years. I'm also considering getting some new tweeters to mount externally in physical alignment with the squawker driver but that's one for another thread.

 

Cheers

 

IWS

 

PS - Holy Hell - Track 8 "Up from the Sea it Arose and Ate Rio in One Swift Bite" - Here's a youtube link to help persuade you to look out for this CD next time you're in the local thrift store