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Proprius with a subwoofer.
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discrete badger View Drop Down
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In a word - yes.

Resolved by also having a low-level (RCA) connector to my home cinema amp. (RELs offer the possibility of dual simultanous connection so that sub can effectively do two roles - low pass for high level speaker connection and unfiltered for LFE effects in home cinema). REL recommend borrowing the home cinema amp's ground for this purpose.

For me this provided an adequate ground reference for the REL. So then the yellow/red potentials don't actually "float". But you may not have a home cinema setup, so ... 

Unplugging the low-level connector produced horrible hum. So I connected the black wire to the 0v output of one of my amps (not Proprius). I also tried chassis ground (i.e. turntable ground terminal) and that also worked fine. 

I think with this "don't connect the black wire" advice, REL are worried about two things, neither of which I believe apply to the Proprius.

1. That the "-ve" terminal is not actually locked to 0v, but actually moves around just as much as the "+ve" terminal, but at the opposite polarity. This is the case with a balanced output stage, which the Proprius doesn't have, only a balanced input stage. So you can connect the black wire to the "-ve" terminal of either Proprius because it's a 0v ground.

2. That many PWM switcher amps reference their "-ve" to actually "+10v" or thereabouts and the "+ve" terminal moves around relative to this. The Proprius isn't a switcher so its -ve terminal will actually be at 0v, so this doesn't apply either.

But - bigger picture! For a pair of (presumably identical) subwoofers you have the golden opportunity of subwoofer stereo. If that works for your room layout, then why not forget all the above and just wire red+yellow to speaker +ve, black to speaker -ve on each side, one subwoofer exclusively per speaker. The result should be superior.
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Mikeh View Drop Down
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Originally posted by discrete badger discrete badger wrote:

In a word - yes.

But - bigger picture! For a pair of (presumably identical) subwoofers you have the golden opportunity of subwoofer stereo. If that works for your room layout, then why not forget all the above and just wire red+yellow to speaker +ve, black to speaker -ve on each side, one subwoofer exclusively per speaker. The result should be superior.

Thanks for the information.
 

My intention is to install one sub per Proprius. Whenever I tried connecting the Speakon black wire to Proprius -ive ground the hum returned. I did try connecting  a RCA cable between a spare Majestic port and the REL low input to provide a ground but this did not remove the hum. Only with the two Speakon +ives to Proprius +ive gives a connection without hum.  Which I don't understand but I guess just have to go with.


Edited by Mikeh - 18 Oct 2021 at 6:10pm
Mike

Technics sl1210g with Victor U-2
Accession MM, Majestic + Proprius, Solo ULDE
Cambridge Audio CXC CD player
Lindemann Limetree Bridge streamer
Harbeth P3ESR XD paired with 2x REL t5x
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discrete badger View Drop Down
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I think what's happening there is the unconnected yellow is free to float and pick up hum from some source close to the cable. Connecting it to amp +ve effectively pins it to 0v (which it will be when playing no signal, when you're listening for hum) and removes the hum.

The REL amp sums L and R signals relative to ground, so on paper you could try connecting it to amp 
-ve! That should halve the REL output. I just tried it on one of mine (an older REL). When I disconnected the yellow from the amplifier +ve, hum appeared. When I connected it to amplifier -ve, hum disappeared and half output.
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Mikeh View Drop Down
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Originally posted by discrete badger discrete badger wrote:

I think what's happening there is the unconnected yellow is free to float and pick up hum from some source close to the cable. Connecting it to amp +ve effectively pins it to 0v (which it will be when playing no signal, when you're listening for hum) and removes the hum.

The REL amp sums L and R signals relative to ground, so on paper you could try connecting it to amp 
-ve! That should halve the REL output. I just tried it on one of mine (an older REL). When I disconnected the yellow from the amplifier +ve, hum appeared. When I connected it to amplifier -ve, hum disappeared and half output.

That's interesting. I'll give it a try. Just seems so wrong to connect +ive Speakon wire to -ive Proprius but if I works and your's hasn't blown up (!) it would remove the need for a resistor and simplifying installation.
Thanks!
Mike

Technics sl1210g with Victor U-2
Accession MM, Majestic + Proprius, Solo ULDE
Cambridge Audio CXC CD player
Lindemann Limetree Bridge streamer
Harbeth P3ESR XD paired with 2x REL t5x
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discrete badger View Drop Down
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Feels weird I know!

But if it helps, imagine what happens with black wire on 0v (speaker -ve), yellow wire on left +ve, red wire on right +ve. Now imagine music on right channel only, and silence on left channel (perhaps via the balance control) 

Normal REL-advised connection scheme. Normal signal conditions. Subwoofer won't explode, but play right channel bass only.

Yet yellow wire is at 0v potential, same as if it were connected to speaker -ve!
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Fatmangolf View Drop Down
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Great example of a real world solution.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Points: 541 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Mikeh Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2021 at 5:27pm
Originally posted by discrete badger discrete badger wrote:

Feels weird I know!


Tried your suggested connections to new RELs and it works a treat, halving the input to sub gives its amp more chance to warm up.  Straight out of the box they aren't very subtle but after proper break in period and setting up I suspect there will be significant improvement. 
Thanks for the supportClap
Mike

Technics sl1210g with Victor U-2
Accession MM, Majestic + Proprius, Solo ULDE
Cambridge Audio CXC CD player
Lindemann Limetree Bridge streamer
Harbeth P3ESR XD paired with 2x REL t5x
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