A JBL white paper and a bunch of questions about what’s possible

[captainbeefheart]

7 hours ago, DirtyErnie said:

So, if you can electrically bias your electrolytic caps to avoid their hysteresis, you should also be able to magnetically bias your iron-core inductors to avoid their hysteresis, right? This might only work with I-core inductors, where you can stick a magnet on the end...

 

The mechanism of the two are different. Electrolytic capacitors need a charge to build the oxide layer on the anode which is the basis for the argument of keeping them biased. The claim is when crossing the 0 point the dielectric absorption causes nonlinearities so keeping a charge on the anode and the oxide layer formed while the AC signal rides on top of the DC bias is supposed to solve this problem. Ever discharge an electrolytic capacitor and then remove the shorting wire? The voltage starts to increase again without an external charge. The lesson here is don't worry about DC bias as long as you don't use aluminum electrolytic capacitors.

 

Magnetic Hysteresis is a different mechanism. It's the lag of flux density behind the magnetic field intensity. Commonly shown in B-H curve graph where 'B' is the flux density and 'H' is the magnetic field intensity. What you are proposing is like them using a larger core or higher permeability material during construction.

 

 

[Chief bonehead]

On 2/4/2022 at 11:02 AM, MMurg said:

 

Klipsch has been doing this one for ages.  It's why Klipsch internally uses the term "balancing network" instead of crossover network.  It both divides the signal per driver and eq's the driver's response if needed.

Yes. Klipsch has been doing this for quite some time. 

[jwgorman]

18 hours ago, Chief bonehead said:

Yes. Klipsch has been doing this for quite some time. 

I need to keep up. I still look at Fortes as new fangled. Looks like JBL does use a selector that allows switching in various cap values. 

 

[KT88]

For a technically interested layman who likes to be impressed (I don't anymore), this white paper is a great marketing tool. Most of it you understand if you are a layman, e.g. gold-plated connections, great magnets, patent pending horns, great thick baffles. This includes, for example, this section, which is supposed to impress and to ne understood but has no place in a real white paper:

 

They are optimized for each transducer and associated frequency range and separated within the enclosure to minimize any potential cross talk. Each crossover board has been designed for maximum headroom and to operate in an extremely linear behavior. All of the electrical components are of the highest quality and lowest internal loss. The inductors used are air core so as to not introduce nonlinear hysteresis effects. Capacitors are constructed using polypropylene foil, which is known for having minimal distortion caused by dielectric absorption non-linearities. All resistors carrying applied audio are selected for their superior sonic characteristics and are of wire-wound construction…

 

It is mainly this "nasty" mixture of pseudoscience and not stopping benefit praise.

But this marketing "white paper" must contain also elements of which is calculated with the author that one does not understand them but will be impressed as an interested layman. E.g. the section: 

 

The networks also employ DC voltage bias to operate the capacitors effectively in a Class A mode. DC Bias for the 4367 Studio Monitor is accomplished using a diode charging circuit internal to the crossover network and driven by the applied signal, so no additional external power is needed for this feature.
The biasing of the capacitors is done through a diode that creates DC voltage from the input signal, and a large value resistor to isolate the diode from the input and limit the current drawn. This keeps the charging circuitry from affecting the audio signal in any way.
 

The trick is that glossy brochures do not always achieve the best effect. Of course, you also need them for a 360 degree marketing concept. It is especially the manipulation that can be achieved when a pseudo-scientific report is written. The goal is to create magic.

This is exactly how I understand this JBL "white paper". A little understanding, a little not understanding so that the competence of the manufacturer JBL is proven and...finally buy. Then you have an expensive speaker and you "know" that other people have put a lot of expertise into it.

[KT88]

Another point. The small handcraft shop that magnetized my K77 Alnico used to be an official JBL and EV base service. Because they are very good but too small they have been deprived of this status. They told me that the quality of the current JBL speakers is staggering and shocking in comparison with a golden past.