Axiom Home Page Forums General Discussion Technical Questions How to wire a vintage AX120 Subwoofer

Hello JohnK,

I agree with you. I was thinking along those lines. The first `guess` should be taken care of by looking inside the cabinet and following the wiring as Alan suggested.

I appreciate your thoughts JohnK and as I mentioned in my reply to Alan I will post an update once I get the connections correct and do some listening comparing the AX-2 by themselves and then with the bypass filter and the AX-120 added.

James

Hello Terzaghi,

I agree with your interest on seeing the vintage designs of speaker companies. The design in this pair of subwoofers makes me wonder why the binding posts are on the front of the speaker with no cover to hide the wiring. I am not sure what the primary reason to do this would be by Axiom.

I understand that the subwoofer can be placed out of sight and work effectively but in our situation this setup will be used in a small apartment/university dorm room and therefore will be stacked for space saving underneath a set of AX-2 speakers that have the same isosceles trapezoid (near a triangular) shape. We won`t be able to turn the speaker around to hide the wiring because of the distinct isosceles trapezoid shape of both speakers. One trapezoid backwards stacked underneath another trapezoid facing forward would look weird and be unstable.

I bought the speakers for my son from different sellers because they were cheap given the vintage and I wanted to hear what old Axioms would sound like. He has been playing the AX-2s in his bedroom (about 10 square meters) and they sound good. By themselves my wife thinks they have more than enough bass but you know us guys. We can never get enough clean bottom end. That is what brought on the experiment with the AX-120s.

I will post an update sometime later on the sound check once they are wired up.

Cheers

James

If you don't want to take the back off there *might* be an easy test...

Hook up the speaker wires from your receiver/amp to the top left/right terminals, play something with some bass, then move the wires to the lower left/right terminals and play the same track again.

My guess is that one of those hookups will give a lot more bass than the other -- the "more bass" hookup is the one you want. The other one should provide less bass because the high pass filter is blocking bass from the subwoofer (rather than blocking bass from your mains as it was designed).

You could probably test with just a single channel and get the same results.

I suspect the binding posts are actually on the *back* of the speaker and the woofer is supposed to face the wall... but when pictures are taken the speaker is turned around because otherwise the pics would be really boring. Is the other side of the speaker finished or is it "the ugly side" ?

Did a quick search on having subwoofer driver face the wall or face the listener... to the extent there was a pattern, it seemed to be "maybe sounds a tiny bit better with driver facing the wall, but then I have all those ugly wires visible" (since most subwoofers have the driver on one face and the wires on the opposite face).

AFAIK at subwoofer frequencies there is no directionality to speak of, and no real concern about the wall absorbing more sound when the woofer is facing it. A couple of people have told me that "the primary reason for having the subwoofer driver face the listener is because some people like to watch it move".

John, on your first suggestion to try it both ways, there might be a problem. If there's a polarised capacitor for the high-pass filter, connecting it backwards can cause it to explode. If the enclosure was opened, the presence of the filter(which would also have a directional indication if polarised)connected to one of the terminals would answer the question.

As to what you suspect about that actually being the back of the sub, I tend to agree(by about a 60/40 margin). Looking at the picture I linked from the earlier thread, the "right" terminals are shown to the left. This would seem to be illogical(requiring the wiring to the mains to cross over each other)unless that was intended to be the back and it would then actually lead toward the right main.

You found left/right markings ? Good catch !

re: polarity, isn't the speaker signal going to be AC, no significant DC component ? My assumption had been that direction wouldn't matter in that case but maybe I missed something...

i think the signal is DC.

Actually, since audio signals are AC waveforms, speakers use AC to reproduce them. DC can only move a speaker driver in one direction from their neutral point -- outward (or inward if wired that way). Note how all the energy in the red dc line lies above the horizontal axis:



If you send a mixed AC and DC signal to a speaker, the DC component will effectively move the speaker's neutral point outward (or inward depending on how the speaker is wired) and increase the likelihood of distortion.

Here is an update on the Axiom AX 120 vintage subwoofer. I finally had the time to look inside the speaker so while referring back to the pictures I posted this is what I found. The lower terminals have wires that go to the upper terminals and what I believe is a crossover filter. The upper terminals have wire that goes to the woofer. I am going to run input wires to the lower terminals from my receiver and then output wires from the subwoofers to my AX2 speakers. I will let you know how it sounds after some listening tests.

If the upper terminals go straight to the woofer, then it's the lower ones that that are actually behind the crossover filter.