Field coil conversion - DIYAudio site

**bowtie427ss** · April 27th, 2012, 08:15 AM

Clearly the field coil is smoother and more extended, surprisingly (or not?) most at the bottom of the FR.

Logic should suggest this conclusion as lower frequencies require larger pulses of AC current to maintain a given acoustic output. It makes sense to me that it is in these critical low midrange frequencies that we would most likely sense(hear) differences that could be directly attributed to the reluctance and saturation characteristics of various motor types.

Beyond that, i just think it'd be cool to have a nice rack of glass cased wet cells to energize my speaker motors.

**Altec Best** · April 27th, 2012, 11:20 AM

Originally Posted by Coendert2011

As least as interesting is that the driver has a very straight FR from 150-15kHz! Very nice for any full range driver. Now you just only need a suitable horn, like an WE-15A

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Like these replicas.

home

**604man** · April 27th, 2012, 02:52 PM

JBL Technical Notes Volume 1 Number 9

This is the app note ; ALNICO Vs. Ferrite maginets and the shorted
turn mod to prevent modulation of the maginetic field. Notice the reduction in distortion.
No data is given for field coil drivers but I presume the field coil power supply is the
shorted turn.............GC

**Cal Weldon** · April 27th, 2012, 03:58 PM

Originally Posted by Altec Best

With nearly a 100,000 members that could be a daunting task.

AB my friend we have 219,331 members and yes, it is a daunting task. You have to spend 15-20 minutes moderating stuff before you even get to post anything of your own, even with around 10 moderators. The upside of it is that you attract a lot of talent. The downside is that not even the brightest minds are necessarily social aficionados.

**Altec Best** · April 27th, 2012, 08:57 PM

Originally Posted by Cal Weldon

AB my friend we have 219,331 members and yes, it is a daunting task. You have to spend 15-20 minutes moderating stuff before you even get to post anything of your own, even with around 10 moderators. The upside of it is that you attract a lot of talent. The downside is that not even the brightest minds are necessarily social aficionados.

I hear you brutha. I'm with you on that Cal (Social Aficionados)! But my gosh 220K members now,wow the last time I checked was quite awhile ago.Can't believe DIY has more than doubled since then.

And I thought I had it tough.

**slowmotion** · April 30th, 2012, 01:51 PM

Originally Posted by Steve Schell

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I won't get into the merits of field coil conversion except to say that IMO the results are worthwhile and not subtle. One thing I'll mention is that a mistake is often made when converting Altec or JBL compression drivers to field coil, and I see it happening again in this thread. The original Lansing 1930s field coil compression drivers used a constant diameter on the center pole from the voice coil gap to the back (actually front) plate. A sectional view can be seen at the bottom of this page:
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Thanks for the info and pictures, Steve.