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Inductor values for AR3a?


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Are you sure they aren't on the schematics I have online here? I know quite a few years ago my dad had Madisound do some custom coils, I could have sworn those values were on the schematics we had.

If they aren't .. if someone could forward those to me I'll make sure to get the information up. Did the coil values stay consistent across the entire AR-3a run?

Mark

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>Does anyone know the values of the coils in the AR3a

>crossover? They don't seem to appear on any of the

>schematics I've found.

>

>Thanks --

>--Daniel

Daniel,

Just curious, are you changing the coils? And if so, why? Are you fabricating new crossovers? Coils rarely ever burn out or change in value unless someone plugs the speaker into a wall socket. The originals used in the AR-3a are air-core chokes, and essentially cannot be improved upon for the intended purpose here. But anyway, here are the values:

AR part #805001 0.044 mH part number

AR part #805004 0.88 mH

AR part #805009 2.85 mH

You should be able to take the schematic and match the inductor numbers to those values above.

--Tom Tyson

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Hi Tom -

I'm not planning on changing the coils. I am interested in the crossover design in general to get a better handle on what the results might be if I (temporarily, non-destructively, respectifully) experimented with different drivers. I'm completely new to this, so please go easy on me, but I am interested in exploring alternative drivers for a pair of 3a's that my neighbor put out on the curb a while back (I've had the woofers re-foamed already). I've actually gone ahead and installed a pair of (gasp!) Hi-Vi wide-dispersion ribbon tweeters to replace the blown originals (just to experiment, y'unnerstand...), but I really don't want to just toss components in willy-nilly without understanding the electronic (as well as sonic) implications. OK, I admit it, I already did some of that, and some crude frequency response tests (pink noise CD, Radio Shack SLM) revealed that the mid wasn't rolling off at ~5000 Hz as it should, and then I got a bit more into it and I determined that the replacement mid was 8 Ohms, and if the original was more like 4 Ohms I may have effectively shifted the crossover frequency out to the 10K region, which would explain the wicked peak at 8K...Too curious, not educated enough. But willing (eager, actually) to learn.

If you (or anyone else) is up to it, I'd be very interested in the calculations that show how the crossover frequencies are derived given the component values and the driver impedances! On that subject, I'm not a EE, but I wonder if the impedance of each driver is actually a bit variable depending on the position of the corresponding level pot, thus also affecting the crossover frequency?

Any and all input gratefully welcomed.

Best --

--Daniel

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>AR part #805001 0.044 mH part number

>AR part #805004 0.88 mH

>AR part #805009 2.85 mH

Hi Tom

Do you know the resistances of theese inductors?

Otherwise what is the wire diameter of each inductor?

I need these information because inductor resistance affect the croosover points and as I have the original AR drivers

I would like to rebuild a 3a as closely to the original as possible.

Do you also know if Ar 3a crossover schematic canged during the course of its production?

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>

>

>

>>AR part #805001 0.044 mH part number

>>AR part #805004 0.88 mH

>>AR part #805009 2.85 mH

>

>

>Hi Tom

>Do you know the resistances of theese inductors?

I used to have that information, and I have it on some of the original early AR drawings. I plan to go through several of the old schematics and cabinet drawings during the forthcoming holidays, and I will try to find that information up for you.

>Otherwise what is the wire diameter of each inductor?

I think that the choke wire is 16-gauge (possibly 14-gauge) solid-core, lacquered bell wire. Knowing the "turns" is also helpful.

>I need these information because inductor resistance affect

>the croosover points and as I have the original AR drivers

>I would like to rebuild a 3a as closely to the original as

>possible.

All the die-hard AR devotees applaud your efforts!

> Do you also know if Ar 3a crossover schematic canged

>during the course of its production?

There were some minor changes in the AR-3a, but essentially the speaker remained unchanged from October 1967 until somewhere around 1975, the latter version being characterized by the velcro-attached grill panels and the "back-wired" tweeters, a la AR-10Pi, AR-11. The paper capacitors were replaced by the newer electrolytics, etc. The lower crossover was originally 575 Hz., but some of the newer literature shows 525 Hz. as the later crossover. By the time AR began making changes, the AR-3a was beginning to be phased out because of the Advanced Development Division speakers coming on stream.

--Tom Tyson

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