SUB Connect Stereo Left/Right & Surround LFE

[ARNiTECT]

I would like to use my sub with the surround amp for LFE and managed bass.
I would also like to use the sub to extend the front left & right speakers for music.

My limitation is a single cable in the wall between hifi equipment and subwoofer.

I have the following equipment, but I expect this applies to most subwoofers and amplifiers.

Stereo Preamp: Audiolab 8200CDQ (with surround preamp front L&R pass-through)
Surround Preamp: Audiolab 8200AP (8 channels)
Single socket RCA-RCA cable in wall from hifi equipment location to subwoofer location
Sub: SVS SB2000 (inputs: Left & Right/LFE)
3-way Stereo input switch
single ended and Y-Splitter Cables

Proposed connections at hifi location - Option A (select: stereo or surround):
Stereo Preamp L&R > Y-splitter cable > R channel of input 1 of switch
Surround Preamp S > RCA cable > R channel of input 2 of switch
Switch R channel > single socket

Proposed connections at hifi location - Option B (combine stereo & surround):
(I don't currently have a Y-splitter 2female-1male cable, but this should be the same?)
Stereo Preamp L&R > Y-splitter cable > L channel of input 1 of switch
Surround Preamp S > RCA cable > R channel of input 1 of switch
Switch L&R channel Y-splitter cable > single socket

Proposed connections at subwoofer location - Option A (R/LFE input only):
Single socket > Sub R/LFE channel

Proposed connections at subwoofer location - Option B (L & R/LFE inputs):
Single socket > Y-splitter cable to Sub L & R/LFE channels

What is the best option here?

 

[ARNiTECT]

Thank you Ed,
the SB3000 is a nice subwoofer, but unfortunately doesn't fit in my joinery unit and there is no where else for it.
I spent a bit more time on this and came to the same conclusion of a miniDSP 2x4, perhaps with the '2 way Advanced 21' plugin. I already have a nanoAVR DL & HD and UMIK-1, so I might as well get this too.
I'm also not sure I can replace my 'input switch' with a Y-splitter cable. The stereo preamp will output from its LR channels to the sub at the same time as the surround preamp is outputting its LFE channel with LR already mixed in.

 

[Ed Mullen]

Presumably the AV preamp will be connected to the stereo preamp and when you are watching AV sources the stereo preamp will be set to pass through.

I'm not sure if the pass through outputs of the stereo preamp are different than the active outputs of the stereo preamp. If they are the same - that's certainly a problem.

Of that is the case, I would not use the pass through function of the stereo preamp and instead just use a 1M-2F splitter on each input of the loudspeaker amplifier.

 

[ARNiTECT]

The stereo preamp has one fixed stereo pass-through input, which is connected to the surround preamp variable Left & Right channel outputs.
The stereo preamp has XLR outputs to my power amp and also has RCA stereo outputs, which I would connect to a miniDSP 2x4 (crossover possibly set around 50hz for my PMC Twenty5 26) with a single mono output to a Y-splitter cable the subwoofer.
The surround preamp has a subwoofer output for LFE and bass management of the other surround speakers (crossovers possibly up to 120Hz) to the other leg of the Y-splitter cable the subwoofer.
If I set the surround preamp front Left & Right speakers to full range (no bass management), then the passed-through miniDSP 2x4 can take care of the bass management of the LR channels instead; therefore, no input switch is required?
So the Y-splitter cable would combine the miniDSP 2x4 low frequency output with the surround preamp LFE and managed bass.
Does this work, or is there a better solution?

 

[Ed Mullen]

I don't see a need to run the mains on full-range in the surround pre-amp. I would run the mains with a 60 Hz crossover in the surround pre-amp, which will send the re-directed bass to the subwoofer pre-out (along with all the other speaker channels which are bass-managed).

When you listen to the stereo pre-amp, it will be sending out a full-range signal to both the subwoofers (via the RCA pre-outs) and the loudspeaker amplifier (via XLR).

Only use the miniDSP 2x4 for the low pass function. The mains are typically not bass-managed in a 2-channel stereo application in order to avoid the AD/DA conversion. Agree with the low pass of about 50 Hz in the miniDSP 2x4, but let your ears be the final judge.

The LPF at the subwoofers should be disabled (set to LFE).

 

[ARNiTECT]

I don't see a need to run the mains on full-range in the surround pre-amp. I would run the mains with a 60 Hz crossover in the surround pre-amp, which will send the re-directed bass to the subwoofer pre-out (along with all the other speaker channels which are bass-managed).

When you listen to the stereo pre-amp, it will be sending out a full-range signal to both the subwoofers (via the RCA pre-outs) and the loudspeaker amplifier (via XLR).

Only use the miniDSP 2x4 for the low pass function. The mains are typically not bass-managed in a 2-channel stereo application in order to avoid the AD/DA conversion. Agree with the low pass of about 50 Hz in the miniDSP 2x4, but let your ears be the final judge.

The LPF at the subwoofers should be disabled (set to LFE).

For convenience, I’d like to leave the MiniDSP 2x4 on all the time; in which case it will low pass from the stereo preamp to the sub for both full range stereo use and the passed through surround high passed LR channels from the surround preamp.

If the 2x4 is low passing the high passed LR channels, this would double the overlapping LF and HF crossover area already passed through to the sub from the surround preamp Bass management.

I could reduce this by using a lower frequency for the stereo use and leave the rest to my nanoAVR DL Dirac to even out, or run LR channels in full range as above.

 

[Ed Mullen]

I don't recommend running the mains on full range for AV applications. I would not use the pass through as previously stated - it will force you to run the mains on full-range at all times. If you feel they can take it without distortion or damage, then that's OK.

 

[ARNiTECT]

I don't recommend running the mains on full range for AV applications. I would not use the pass through as previously stated - it will force you to run the mains on full-range at all times. If you feel they can take it without distortion or damage, then that's OK.

I’ll stick to bass managing the LR channels for AV applications then, and deal with any overlaps with Dirac.
The BM is being performed by a very flexible nanoAVR HD with a nanoAVR DL making the final room corrections (Source>DL>HD>AVR>)
I have just ordered the miniDSP 2x4, will take a week to arrive.
Edit:Considered the 2x4HD, but wasn’t sure what it would add for my requirements for the extra £100.