Coils

[bigredplane]

I see we had a big discussion on capacitors that informed me a lot. How about coils and the differences in them? As you may know, I'm just getting started in re-doing the crossovers in a pair of L96's. Any suggestions in this area would be appreciated. I have one question: Should I replace the L-pads with resistors once I find the level I want? Scott

[pelly3s]

i wouldnt replace the L-pads because if you switch rooms with them then you wont be able to adjust them for the room. HAND WIND YOUR OWN COILS lol sorry I had to say it. I've done that all too many times. Honestly I dont know the difference in them too much. maybe someone else can help on that question

[Ian Mackenzie]

You are better to get speciliast advice here, do a search first and dig up what you can find like a schematic. Then Pm Giskard and ask consisely what information you are looking for if you still need help.

Just quickly the crossovers for these systems were customised by JBL and the coils have particular electrical characteristics such as inductance and dc resistance. If you attempt to replace these parts its important to try and get an exact match otherwise the voicing (Balance) may change due to subtle variations on the response of the system and you don't want to do that.

To be honest, unless the coils are damaged, I would leave then alone and focus on the fixed resisters, the capacitors, new pads if required and perhaps better wiring. But be careful not to get confused with driver polarity.

Hope this helps.....Parts Express is a good one stop shop for all these parts.

Ian

[johnaec]

One thing I've always been curious about - schematics always only show the inductance of the coils, but not the DCR. What's the significance of this?

John

[4313B]

Figure 0.4 mH to 0.6 mH for the majority of JBL coils.

[Robh3606]

Giskard is that for DCR or Inductance?? .4-.6 ohms??


With the pots you can really dial things in. The only issue I have had is the pots can get noisy with age. You could make step attenuators with fixed values. If you go the attenuator route you could get sealed switches that would be more immune to oxidation but you had better get the values right. Ian gave you good advice on the inductors there is not too much that can go wrong with them.

Rob:)

[4313B]

Sorry Rob! I obviously can't talk on the phone with Don, download porn, play Call of Duty: United Offensive online with 31 other guys and effectively answer forum posts at the same time. :banghead:

Figure 0.4 ohms to 0.6 ohms for the majority of JBL coils.

Oh, and the L96/L112/L150A has the ubiquitous 3.5 mH air core across the LE5. That one is special and has a DCR of ~ 7.5 ohms.

[Robh3606]

Sorry Rob! I obviously can't talk on the phone with Don, download porn, play Call of Duty: United Offensive online with 31 other guys and effectively answer forum posts at the same time. http://audioheritage.csdco.com/vbulletin/images/smilies/banghead.gif

So a slow Friday??

Rob:D

[4313B]

You got it! :p

(BTW, haven't we gone over the L96 fixed resistor thingie already?)

[4313B]

I have one question: Should I replace the L-pads with resistors once I find the level I want?I posted a chart showing values for fixed resistor pads somewhere on the forum. Back when the Ti Series first came out I had a talk with their designer and asked what happened to the L-Pads. The response was something to the effect that L-Pads were "out" and fixed pads were "in", and I don't mean fashion-wise. Well we all know that now but like their convenience (kind of like popping in a CD instead of going through the vinyl care ritual). I'd personally build fix resistor sets in the spirit of the Ti Series. Two or three position switches. Make it fairly easy to change the resistors out if you want.


i wouldnt replace the L-pads because if you switch rooms with them then you wont be able to adjust them for the room.Yeah, I can understand that too. They are convenient. Whatever you guys want to do. I'd at least upgrade from the light weight 10285's to the heavier duty 58450's.

[bigredplane]

Sorry Rob! I obviously can't talk on the phone with Don, download porn, play Call of Duty: United Offensive online with 31 other guys and effectively answer forum posts at the same time. :banghead:

Figure 0.4 ohms to 0.6 ohms for the majority of JBL coils.

Oh, and the L96/L112/L150A has the ubiquitous 3.5 mH air core across the LE5. That one is special and has a DCR of ~ 7.5 ohms.

So is the 3.5 air coil across the LE5-12 the only one I need to worry about the most in not changing it do to the DCR of 7.5 ohm. What about a bigger awg coil on the low pass.

PS Did I miss something here? What does downloading porn have to with the sound of coils. What times the show start?

Scott

[Ian Mackenzie]

Here's a great link that kinda melds theory and reality.

There's another link to a coil simulator if you have the time to wind your own.
An LCR meter (about 35 bucks) is not a bad idea but these sims a fairy accurate.

http://www.colomar.com/Shavano/inductor_info.html
Air Core Inductor specs for 3.500 mH

By the look of it you'd need very fine 30 gauge wire or so for 7.5 ohms dcr

Unfortunately the tables aren't support in the forum posts so just plug and play.

Ian

[4313B]

So is the 3.5 air coil across the LE5-12 the only one I need to worry about the most in not changing it do to the DCR of 7.5 ohm. What about a bigger awg coil on the low pass.Changing the DCR of the parallel coils will change the knee of the curve, keep them as close to stock as possible. Minimize the DCR of the large series coil in the LF section. The 3.5 mH coil across the LE5 can have a lower DCR than 7.5 ohms, just put a proper resistor value in series with it. So, if you wind a 3.5 mH coil and it comes up with 0.7 ohms of DCR put a 6.8 ohm resistor in series with it.

[bigredplane]

Changing the DCR of the parallel coils will change the knee of the curve, keep them as close to stock as possible. Minimize the DCR of the large series coil in the LF section. The 3.5 mH coil across the LE5 can have a lower DCR than 7.5 ohms, just put a proper resistor value in series with it. So, if you wind a 3.5 mH coil and it comes up with 0.7 ohms of DCR put a 6.8 ohm resistor in series with it.

So lower the DCR in the LF section is really only thing I can can do to in upgrading the coils?

Thanks Scott

[4313B]

Pretty much yeah. The stock air cores really aren't bad at all.

[bigredplane]

Pretty much yeah. The stock air cores really aren't bad at all.

Don't some coils just sound better then others? I think I will replace the L-Pads with resistors and make them easy to change. What caps would you use in that speaker. I will be driving then with a Cary V12r tube amp at 50 watts per.

[4313B]

Some coils are supposed to sound better than others.

I think the latest on that can be found here - http://audioheritage.org/vbulletin/showthread.php?t=1388
B&KMan had a line or two about coils.

For caps I would charge couple either Solens (recommendation from G.T. at JBL) or Daytons bypassed with AudioCap Thetas.

[bigredplane]

For caps I would charge couple either Solens (recommendation from G.T. at JBL) or Daytons bypassed with AudioCap Thetas.[/QUOTE]

Thanks I think this will be fun Scott

[4313B]

Hopefully you'll let everyone know how it all turns out.

[aust-ted]

The original question was about coils.

The recent excellent thread on capacitors "Yet More Capacitors" got me thinking.

The only things I can think of which might affect coils, are the coil's resistance and capacitance, which will depend on how it is wound, and the effect of the iron core if indeed it has an iron core. The resistance can be measured and compensated for in the circuit. Not so sure about the capacitance. Do any of you guys go to the trouble to measure coil capacitance or is it usually insignificant?

With iron cores I remember from my student days a hysteresis effect which may be analogous to that found in capacitors (re the discussion about battery bias). So perhaps we should stick with air cores.

This is ignoring questions about the quality of the copper (oxygen free, crystalline structure, etc) which I do not know how to start to discuss.

Regards
Ted

[4313B]

So perhaps we should stick with air cores.I figured that was a given for most values at this point. The Erse coils are quite fine for the larger values such as the 6 mH (250Ti) and 18 mH (4435) inductors.

[bigredplane]

]Hopefully you'll let everyone know how it all turns out]

Sure will

[aust-ted]

I figured that was a given for most values at this point. The Erse coils are quite fine for the larger values such as the 6 mH (250Ti) and 18 mH (4435) inductors.

Giskard, is there something special about these or it just a case that they are both reasonably priced and of acceptable quality for large value inductors? How would they compare to an equivalent laminated inductor from a genuine JBL xover?

Regards
Ted

[bigredplane]

O.K. guys. I have the mid-ranges fixed on my L96s and have had an opportunity to sit down and listen to them for some serious evaluation. Besides needing some serious cap upgrades, I felt they were heavy in the mids even having the L-pad turned down on the mids to a -6db. I feel there is too much mid coming through the woofer with it only having a 6db crossover. I think I need to remove some of the mid frequency from the woofer. My opinion is there is too much overlap. I need ideas on the best way to do it. The woofer has only a 2.5uf coil on it for a crossover. The rest of the drivers have a 12db crossover slope. I'm not sure why JBL did it that way, if it was for a small time alignment issue or not. It could also be causing the woofer to be 90 degrees out of phase. I am wondering if I should just go to a larger coil to just roll off the woofer more or change to a 12db slope on the woofer? I could then just lean them back to help with time alignment issues. If I did that, does anyone have ideas on the value of the coil and caps I should use? I'm thinking of using sonicaps due to their price point and performance in the reviews I have read. Does anyone have pros or cons on those? Any suggestions would be appreciated.

[4313B]

I've been over this before - use the 3113B network. Remember, the N96 filter was actually designed specifically for the L112. It was then used in the L96 and the L150A.

[bigredplane]

I've been over this before - use the 3113B network. Remember, the N96 filter was actually designed specifically for the L112. It was then used in the L96 and the L150A.

I think I found a copy of the 3113b network. It has a 16.5 cap on the mids instead of the 13.5 in the N96 and a 16.5cap and a 5.1 ohm res. paralleled with woofer then add all the .01 bypass caps. Do I have the right schematic? I see they reversed the prolarity on the tweeter on the N313B and the N96 doesn't Do I do that too?

Scott:) :) :o:

[4313B]

Yes, you have the right schematic.

Start with the N96 polarity - if it doesn't sound/measure right switch it.

[bigredplane]

Will do Thanks Scott

[bigredplane]

I've been over this before - use the 3113B network. Remember, the N96 filter was actually designed specifically for the L112. It was then used in the L96 and the L150A.

What about useing the resistors setup that JBL used in the L86 network for replacing the L-laps in my L96's as a starting point for replacing the L-Laps in them?

[4313B]

That's probably too much attenuation. The LE10H is a bit more efficient than the 8" in the L86 by 1 or 2 dB. You can try it though.

[bigredplane]

That's probably too much attenuation. The LE10H is a bit more efficient than the 8" in the L86 by 1 or 2 dB. You can try it though.

So a maybe lower the series resistor a little and sart there?

PS. I posted some pictures of my brothers 240's if you wanted to see them. He will take less for them, he's just looking for a fair offer now