Dual high output and LFE connection to sub?

Cross-posted in AVS Forum:

Hi - buying my first subwoofer (Martin Logan Dynamo), and trying to figure out the best way to connect it for 2-channel music as well as movies.

The advice I've received on the AVS forum is basically set all speakers to "Small", connect the sub via the pre-amp Sub Output/sub .1/LFE In, and let the receiver do all the bass management (mine is an older Onkyo Integra DTR7.1, so has a fixed 80Hz cross-over to the sub).

My front left/right speakers are fairly full ranged Mirage OM-7's (honking big floorstanders, with a stated range of 30Hz to 20,000Khz) ... nice sound. I'm wondering - for 2-channel music - if I should try and set it up to allow the sub to do some bass mgmt (via low pass filter and level controls) - and twiddle with the cross-over via the low pass filter on the sub (I think the high pass filter is fixed at 70Hz).

The Martin Logan manual indicates that you can hook up both high level inputs (via RCA jacks or speaker wire) and LFE input. The diagram shows the LFE input coming from "Processor" and the high level inputs from "Pre-Amp/Receiver" (if that makes any difference).

So - to do so, I ASSUME I would do the following:

1. Use "DIRECT" mode on the receiver, which disables the Sub output from the Receiver (forcing the receiver to send signal via the high level outputs).

2. Use "STEREO" mode on the receiver, set Sub-woofer to "No" for stereo mode only, again - forcing the receiver to send signal via high level outputs.

3. For all multi-channel modes (THX, Dolby DTS, all multi-channel audio modes, etc), leave sub-woofer set to YES, so all LFE output is sent via the sub out to .1/LFE in.

I guess my questions are:

1) - Is there any reason to do this, or should I just leave well enough alone and rely on the receiver bass management for all modes?

2) - Is there any chance I could blow up the receiver or subwoofer by hooking up both the high level outputs and LFE outputs, and setting up the system as above.

3) - I only have ONE speaker size set-up, so - if speaker size is set to "SMALL" and "no subwoofer" is selected or sub output is disabled (for stereo/direct mode), would my receiver still be sending a full range signal to the speakers - or would it enforce an 80Hz cut-off on the signal (even without a connected subwoofer)? (The Integra receiver manual states that fronts are set to Large automatically if subwoofer is set to "No" - however, I'm not sure if it does that on the fly depending on the selected listening mode).

Basically - I know for best bass management for movies, all speakers should be set to small - but can I leave them set to small for when listening to 2-channel with bass management on the sub, or would I be missing some dynamic range? Would I actively have to set speaker size to large each time I wanted to listen to music?

Sorry for possibly basic questions, but I'm still trying to get a handle on all the tweaking for a first-time sub user.

Cheers,
Reg

What worked best for me was to set my front left and right speakers to large and then use line level or speaker level L/R inputs to the sub (for 2 channel music). Then for HT connect the sub out to the LFE in. ML subs allow you to hook both up at the same time. Don't forget to set your pre-amp for NO-SUB for 2 channel listening and with sub for HT.

Good luck.