M19 crossover inductor measurements

A comment on another thread lead me to starting this one. As most people feel their original inductors superior to after market versions I thought it would be interesting to list out measured values as a comparison for the archive.

These are the measurements from one of my stock crossovers and of the replacements. Stock were measured with a BK 875A and BK 2890A. Replacement with a bridge meter by North Creek and the BK 2890A for resistance.

Stock:
L1, 0.18 mH, 0.04 ohms
L2, 2.43 mH, 0.37 ohms
L3, 0.61 mH, 0.12 ohms

Replacement (North Creek Music 12 awg air core)
L1, 0.30mH, 0.07 ohm
L2, 2.62mH, 0.28 ohm
L3, 0.77mH, 0.14 ohm

Stock total resistance: 0.53 ohm
Replacement: 0.49 ohm

The total difference in inductor resistance is trivial. As a mentor of mine expressed, you can always add resistance.

As far as the total crossover goes, it makes sense to have closely matched values vs. the 20% deviation as one member stated that Altec might have used. My goal is 1% matching between parts on the externals I'm building. Once finished and burned in for a while I'll post some listening impressions.

Quote:

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Originally Posted by johnsonad

A comment on another thread lead me to starting this one. As most people feel their original inductors superior to after market versions I thought it would be interesting to list out measured values as a comparison for the archive.

These are the measurements from one of my stock crossovers and of the replacements. Stock were measured with a BK 875A and BK 2890A. Replacement with a bridge meter by North Creek and the BK 2890A for resistance.

Stock:
L1, 0.18 mH, 0.04 ohms
L2, 2.43 mH, 0.37 ohms
L3, 0.61 mH, 0.12 ohms

Replacement (North Creek Music 8awg air core)
L1, 0.30mH, 0.07 ohm
L2, 2.62mH, 0.28 ohm
L3, 0.77mH, 0.14 ohm

Stock total resistance: 0.53 ohm
Replacement: 0.49 ohm

The total difference in inductor resistance is trivial. As a mentor of mine expressed, you can always add resistance.

As far as the total crossover goes, it makes sense to have closely matched values vs. the 20% deviation as one member stated that Altec might have used. My goal is 1% matching between parts on the externals I'm building. Once finished and burned in for a while I'll post some listening impressions.

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WRT to 20% tolerances is WRT the Model 19 Crossover which was from the mid seventies early eighties I'm sure that improved as the components got better Capacitors,inductors,etc...

Personally I prefer iron core to air core is there any difference in sound "Who Knows" but to my ears I think there is, they just sound better to me IMHO.As other members have noted that when they replaced their inductors with air cores sound changed.When the old Altec Iron Cores replaced it also brought back the Altec Sound !! The rule of thumb here is go with what sounds best to you.As music is nothing more than personal preference you can't get any more Individual than that IMHO. :2thumbsup:


Best Regards !

Thanks for the measurements Johnsonad. It confirms my thought that the original inductors probably weren't what the schematic claims them to be.
You didn't say if the new inductors sounded much better to you but I assume they do if your still using them and your happy with the sound.
Hard to say if they all fall into where yours and mine do unless more people post measurements.
But now to ask another question, I wonder if that was on purpose or just a function of tolerance/cost effectiveness in the manufacturing process?
With no other change other than the 2.7 inductors, I went from very listenable to annoying tonal balance with new inductors that read 2.7 on the money and not all that less in resistance than the original so it is a mystery to me.
It's hard for me to believe that a fraction, maybe .15 of a ohm in a woofer crossover can account for such an obvious change in tonal balance, not SPL, and I'm more inclined to believe that the difference in the inductance is more of a factor as to where the highs start to be rolled off in the woofer.
As for very tight tolerances, I'm not sure I see a need for that in passive xovers because they are more or less all over the place depending on drive and frequency aren't they?

I'm still in the building process thus why I haven't posted any listening results. The 19's will also receive some horn damping and increased bracing in the cabs. I've got little to no experience as compared to most of of the usual suspects on this board and as anything goes in this hobby, what sounds good to me may not to you. At worst it will turn out a fun experiment. The crossover boxes I'm building have enough room to roll different caps including oilers and putting the crossovers back to original will be as easy as changing out 4 wires.

More to follow but when you guys get time post the values of your inductors.

Aaron

Thanks for the followup and I'd love to hear what you think of the results of what your doing versus stock 19's with just new caps.

Quote:

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Originally Posted by DNV47

It's hard for me to believe that a fraction, maybe .15 of a ohm in a woofer crossover can account for such an obvious change in tonal balance, not SPL.......

I'm more inclined to believe that the difference in the inductance is more of a factor as to where the highs start to be rolled off in the woofer.

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It can't, using AB's averaged specs only changes Qts ~0.185%, so would require a very high resolution just to measure the response plot difference.

Agreed since this shift would be high enough up to be in our acute hearing BW.

GM

Thanks GM.
I guess its just personal sonic taste because there are people who have used very expensive air core inductors closer to the schematic values and liked the results even with motor run caps.
That's out of my sonic comfort zone for sure.

Johnsonad
I suggest you tune your air core coils to the same freq as the iron core coils.
Use the same set up as we use for speaker impedance .
You can buy 1% caps or parallel small values of cap. to match your caps.

To match the coils, remove or add turns of wire to the air coils.
See below for the coil tuning setup

X-Over
Don

Hey Don, i was looking at the X-over and noticed those coils are side by side touching one another.Shouldn't those coils be one down the next up on edge to prevent interference/crosstalk from one coil to the other ???

Like in fig. 6-6a -7 on this page.

Inductor Coil Crosstalk Basics — Reviews and News from Audioholics

Altec Best
Thank you for your comments . Yes , the best way to orient the coils is to alternate one up one down.
The latest XOs I have built are up & down. The measurements I have made show minimal cross talk with all the coils flat since they are tuned to different frequencies . So it really is not a problem . But to be a purest mount them up & down.

Don