Upgrading the JBL-S26 Crossover (long) (1 Viewer)

[Lee Bailey]

So then Dean, no matter if I'm using the right mH inductor, it has to also be the same DCR as the one that I'm replacing? Does a digital MM suffice in measuring the DCR of the inductor? That LC meter at Parts Express looks good, but for only occasional use, it would not be a smart purchase for me. I sent a note off to Polk, to see if they'll help me out with the crossover specs.

One more question. Should I include a Zobel network? There currently is not one on the speakers at this time.

 

[Lee Bailey]

I did some more digging around for that Diaural Capacitorless Crossover design. If you want to see what the schematics look like, you can go here: European Patents ,search on patent US6115475, and it will open a page with an option to view the drawings. Looks like the magic to it is knowing what size resistors and inductors to use. Something for the truly D.I.Y. person to play with.

 

[Brett DiMichele]

Dean,

I agree with everything you said with one exception. I
don't see how lowering the DC Resistance can be detrimental
to the sound quality? The crossover frequency and slope is
not changing at all so the drivers will still blend.

Northcreek seems to think the lowest possible DCR the better?


Hit us with all you know about DCR because that's the only
thing that has kept me from ordering the Alpha Foil or the
perfect lay 14 awg's.

 

[Chris Tsutsui]

For what it's worth, I am using inductors that have 0.41 DCR instead of a 0.38 DCR inductor. They are both copper foil 16 gauge with the exact same inductance.

I save $10+ total with the new Jantzen ones.

I figured the .03 DCR difference won't make a difference. And I prefer inductors made in Denmark.. like my women. heh jk

 

[Brett DiMichele]

I like mine from Sveeden, Ya....

 

[dean_g]

Northcreek is right -- the lower the DCR the better. Remember though, Northcreek is thinking in terms of building their kits, not 'upgrading' OEM crossovers. Their designs and associated crossovers factor in the lower DCR's -- which impacts the resistance of the circuit as a whole. Now, when you upgrade a OEM crossover with inductors owning lower DCR's, you are effectively changing the resistance of the whole circuit. So now, you get to start playing with the resistor values to get the voicing back in line. This is like opening Pandora's box because to do this kind of thing you have to have a VERY good understanding of how crossovers work. Not only that, but the relational aspects as well (inductance and DCR of the drivers in question -- as well as box design and port relationships).

You might think, "What's the big deal -- if I lower my DCR on my inductor, I'll just raise a resistor value before or after." Uh, it don't really work that way, and it can really get complicated.

DCR

It is much better, and so much easier just to keep it simple. Replace the inductor for the bass with a 14 AWG Solen, and leave the rest alone. If they are iron core, they can be replaced with air core as long as you keep the DCR as close as possible. Replace the mediocre caps in the tweeter/midrange circuit with decent polypropylenes or film and foil (if you can afford them) -- and pull the resistors in favor of some non-inductive types. Improve the sound, without altering the voicing -- where much work was done to capture.

You might be surprised at the improvement of the bass by changing out that one coil.

 

[Brett DiMichele]

Dean,

Thanks for the info. The way Northcreek makes it sound you
can gain better sound in anything by using the lower DCR
inductors or at least that was what I walked away from it
with. Ohh well...

I am not changing the woofer inductors I am eliminating the
woofer inductor all together. My woofers will be connected
directly via the binding posts to my external amp which has
it's own variable XO. I am getting rid of the woofer section
of the OEM XO completely.

That leaves me with 2 small guage inductors one on the
tweeter and one on the midranges that I wanted to change
out for the larger 14 awg (the stock ones look to be 22 or
so awg) but I guess I am F'd here...

 

[Chris Tsutsui]

We need an inductor expert on the forum, where we just post a picture of the inductor and he replys with the inductance, the DCR, and then sends an mp3 file of the "VOICING". heh

 

[Lee Bailey]

Well, it took me a while, due to being out of town, but I was able to get the specs from Polk for my speakers. I made new crossovers for my R40's. The schematics I got showed that the tweeter was no longer using the 1st order crossover, it now had a 2nd order version. So I ordered the parts and got them completed during the weekend. This is what it looked like after construction, and before installation. The smaller board behind it is the terminal cup with the original crossover board attached to it. I went from the iron core inductor to a Perfect lay version, with Solen Poly caps, and Mills resistors. Sounds even smoother than before.



My thanks to the original post for getting me started on this trek.

 

[Michael R Price]

A question to the experts: I recently found that my speakers have a 1.1mH, 16 awg inductor in series with the two paralleled 8 ohm woofers, and a 7.5 ohm resistor in parallel with the woofers. My questions are: why the heck did they put in an inductor with such high resistance, and why is there such a low value resistor directly across the woofer terminals? (And is it worthwhile to change this setup at all short of going active?)