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Advice on long subwoofer signal cable runs from switch box

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Re: Advice on long subwoofer signal cable runs from switch box

Postby DC-Choppah » Thu Sep 19, 2019 1:09 am

The Outlaw receiver and the both subwoofers are double insulated. No ground wire on the A/C plug of any of these components.
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Re: Advice on long subwoofer signal cable runs from switch box

Postby ef37a » Thu Sep 19, 2019 7:41 am

In general if you are using two core screened cable as single core it is better to tie the "cold" core to the screen and use a single hot core.

This gives the minimum core to screen capacitance, not an issue for a sub woofer feed but can help in other applications such as a guitar cable.

The configuration also greatly reduces microphonic thumps from cable impacts in the latter usage. The screen/cold core can of course be dissed if an earth loop is experienced.

Dave.
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Re: Advice on long subwoofer signal cable runs from switch box

Postby Hugh Robjohns » Thu Sep 19, 2019 9:28 am

DC-Choppah wrote:The Outlaw receiver and the both subwoofers are double insulated. No ground wire on the A/C plug of any of these components.

Oh wow! That's unusual! Normally, the receiver/amp is the only grounded unit in a hi-fi system, which makes a lot of sense... I don't think I've ever come across a system which has no solid earth reference at all!

Oh well... at least that means you won't be troubled by ground-loops via the mains supply. There could be other issues to resolve, but let's see what happens when you wire up the subwoofer's line feed with the appropriate screened cable first.

H
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Re: Advice on long subwoofer signal cable runs from switch box

Postby DC-Choppah » Sat Sep 21, 2019 12:28 am

Wonks wrote:Do you know what all the filter frequency points are, and if the ones in the amp are adjustable at all?

Both the amp and the subwoofer crossovers are adjustable. I have them both set at 80 Hz.

Although the subwoofer signal wire runs through the basement, the listening room is on the ground floor and is a 25’ x25’ room with vaulted ceilings and cork flooring and one wall full of windows. I also record instruments in this room as it has a very appealing sound.
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Re: Advice on long subwoofer signal cable runs from switch box

Postby DC-Choppah » Sat Sep 21, 2019 10:22 pm

Hugh Robjohns wrote:
DC-Choppah wrote:
Oh well... at least that means you won't be troubled by ground-loops via the mains supply. There could be other issues to resolve, but let's see what happens when you wire up the subwoofer's line feed with the appropriate screened cable first.

H

Success. Using this cable, with black wire connected to the screens on both ends solves the hum problem.

https://drive.google.com/open?id=1rp6Dt ... Z3djOa1o65

The subwoofer switch needs to be SPDT with the wires shorted together when off to get rid of the hum. If left open circuited at the switch it still hums (faintly) with the shielded cable.
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Re: Advice on long subwoofer signal cable runs from switch box

Postby Hugh Robjohns » Sat Sep 21, 2019 11:55 pm

I love it when good science predicts correct outcomes... ;-)
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Re: Advice on long subwoofer signal cable runs from switch box

Postby funky54 » Sat Oct 26, 2019 4:47 am

I’m a low voltage integrator. I wire 200-300’ runs of rack to room RG59 and 14/4 all the time. I can’t tell you how many years it’s been since I experienced 60 cycle hum when wiring subs. Are you sure your amp is grounded?

I don’t run any sub with any of my personal two channel gear, maybe it would be more sensitive than typical AVR or Crestron amps.. try a long LFE wire or make a 100’ out of RG6 and find out.

Edit: Never-mind, just read the thread.
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