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.

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.

So a slow Friday??

Rob

[4313B]

You got it!

(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.

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.