Anyone know what these are

I picked these up at an estate sale recently, and am wondering if anyone can explain their purpose. They weren’t hooked up when I bought them, but the estate included a high-end Linn / Legacy / Conrad Johnson system, so I thought they might be interesting.

Circuit looks like a capacitor, a few resistors, and a wound spool of wire, all on a basic switch. There are two of them. Guessing maybe some sort of filter that goes between an amp and speakers? Thanks.
hard to say w/o tracing it out but that is a good sized inductor in there

sell it to a copper recycler
Without being able to see all of it, it looks like a speaker level low pass filter, with a  bypass switch.

I can't tell if there are also resistors or caps involved. However, if it's just an inductor in series, that's what it is.


OK, so it's a little more complicated. It looks like there are 4 resistors, which I assume are in series with the coil.

Not sure what the switch will do exactly. It could bypass everything, or just the resistors, or just the coil.

Was this system using horns/pa type of setup? if so maybe the user was experimenting with the bass configuration.

It is probably very cabinet specific, and my guess is it was more of a hack/experiment.


Does the other one (not pictured) have a red or black binding post? Are they identical inside?
I don't see any capacitors involved. Since there is only one in and one out, it's safe to say the entire circuit is in series. Nothing shunts to ground. Therefore the circiut is something like this:


with "vvv" representing a resistor and "uuu" representing a coil.  "0" and ">" representing the input and outputs.

Somewhere around there the switch bypasses some or all of it.

Clearly someone was playing with a bass cabinet somehow.


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 Yes there are electrolytic caps. Low pass passive crossover in my estimation.
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Thanks @grannyring I see it now.

Ok, with more coffee and less fuzzy vision than I had yesterday (comes and goes) I can see most of the circuit.

It seems that all parts are in parallel. However, 2 of the resistors are switching in or out, changing the parallel resistance from 5 Ohms (10 Ohms / 2) to 2.5 Ohms (10 Ohms / 4). Lowering the parallel resistance reduces the effectiveness (depth) of the notch filter.

This makes it most likely a shunt-type notch filter. Impossible to tell what exactly it’s doing without full analysis of the driver as well as knowing the coil and cap values.

It could have been an experiment to remove ringing in a driver, with the switch allowing for different levels of suppression.

In any event, this is clearly a DIY hobbyist’s experiment which would only be useful for his particular speaker/experiment. No use at all for anyone else. If I purchased this (I wouldn’t) it would be for experimental parts only.

This could all be confirmed with an Ohm meter. If you want to understand more about this type of circuit (or whatever it ends up being) come over to the DIYAudio / multi-way forum where we can post pictures and discuss with a number of speaker builders. :)


Thanks for all the responses.  I really just bought these on a whim.  They were only $5, so I figured worst case, I could keep them around for parts.

I'll try to dig up more details on the exact parts used in these.
Not exactly sure, but they look a lot like the low pass filters from Legacy Audio used for some of their late 80s early 90s loudspeakers. Classic, Focus......etc. Bill from Legacy would just give them to you if you asked, if you had a problem with too much bass in your room caused by standing waves. This is a few years before they came out with the Steradian.
Well, now it's an interesting paperweight you've bought.

You could call it an early prototype 'mouse' and see who takes the bait... ;)
Put it on eBay.

If some nitwit is willing to pay major money for a Cheeto that 'looks like Something', you'll never know unless you run it up the flagpole....

You can thank me later...*L*
Did you see the other components? What model were the Legacy's?

I would send some photos to Legacy, there might be owners of early Legacy speakers who might want to try them.

My curiosity is up?
That is not, but looks like a BMW car speaker crossover. My 528 has the wire wrapped around the woofer magnet to save parts and space. The tweeter connects to the wire where it exits from the wooder magnet. The swithch probably offers a rooloff choice, like Acoustat Spectra 1100's.