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How to connect monoblocks to a single REL sub with ONE RCA input

I just purchased two Quicksilver 60w Monoblock amplifiers and a LineStage Preamp by QS.
To connect this REL 328, normally one uses connect their Speakon cable (Red, Yellow, Black ends that connect to Right+, Left+, and Ground) or a SINGLE "low-level" RCA in. But this preamp doesn’t have a single sub out.

REL’s advice is to buy a second sub and attach one sub to each monoblock. Well, maybe I’ll do that, but in the meantime, I’d like to be able to hook up what I have.

Should I orient the amps so that the speaker terminals are close enough together to attach the strands of the Speakon cables? I have been warned by REL not to hook up high level to monoblocks because it will create a ground problem.

An alternative is that I get a Y cable that will bring two RCA outputs from my Preamp into the single RCA input on the REL?

Or is there another alternative?

Advice appreciated. (But please try not to tell me to just buy a second sub.)
128x128hilde45

Showing 3 responses by ieales

ieales's avatar
ieales
1,201 posts
 
@ hilde45
you should NEVER use the high level output. Especially on a tube amp.
Their use is strictly lofi. No professional installation uses anything like them. No matter what anyone says, they cannot produce accurate bass. Especially on a REL328 with no phase control. It's actually a polarity control.

See  http://ielogical.com/assets/SubTerrBlues/TubeAmpSpkrV.png and read  http://www.ielogical.com/Audio/SubTerrBlues.php and https://www.soundoctor.com/whitepapers/subs.htm

What you plan to do will be  H U G E  compromise over what is correct.
ieales's avatar
ieales
1,201 posts
 
@daveyf
which system page? please post impulse and phase plots. I had a look. I find the Sonus intolerable. The low end is just awful in every system I’ve heard. [I’ve never owned a ported system]. I didn’t care for Nordost speaker cables in any demo.

@almarg
The QS have low output impedance, but if one looks at response into a real load, it is nowhere near flat.

Additionally, current drives the loudspeaker and voltage drives the sub. For any non purely resistive load I & V differ by an ever changing phase angle. Hence, a sub driven from the LS out can N E V E R be time correct with the mains.

@lalitk
I hear no compromises in bass production or lack there off.
I'm sure there is plenty of level.

I must admit that Time Coherence is my grail and systems without it are uninteresting. IMO, frequency response is, and always has been, overrated.

ieales's avatar
ieales
1,201 posts
 

NEVER use high level outputs to drive a subwoofer. It's a Band-Aid that should be banned.

According to the REL S/812 manual, it has two low level inputs. You can simply Y off the main pre out if there are not two sets of outputs

Ideally, you should roll the lows out the mains with a passive HP filter. Doing so will tighten up the low end and effectively double the apparent power of the PLs

That being said, you should flog the REL and get a pair of subs with real controls. IMO, REL markets bling, not good bass and are not serious about proper system integration due to their dearth of controls making them impossible to integrate properly. e.g. 180° phase inversion is equivalent to moving the sub about 25 feet @ 40Hz. Fixed XO slope will only integrate properly in a tiny subset of rooms and systems. 

Martin-Logan X series and JL Audio are excellent offering full control.

 

 

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