Sub power/bass mgt with speaker level connection. (1 Viewer)

[Steve_Ma]

I plan on experimenting with switching to the speaker level connection rather than the LFE out, in order to play with my sub's x-over settings and placement. The sub is a powered (120W) B&W ASW1000. AVRec is a Marantz SR7000.

1. In my AVR, if I set my mains to large and sub to no...What happens to any bass material with the surrounds/center? DO I leave them to small and does their bass get re-routed to the mains/sub?

2. MY AVR puts out 100W per ch. If my sub now drives my sub and my mains, will this be too much for my 120W sub? Is there any benefit derived from using the power coming from my AVR and the sub together or does the AVR's power simply get wasted?

Thanks,

--Steve

 

[John Kotches]

Steve,

If you define the speakers as large, you will be "wasting" the portion of the receivers power that is used for amplification of frequencies below whatever crossover point you select on the subwoofer.

For example, if you set the subwoofer crossover to 80Hz, and run the speakers large, your receivers amplifier will still amplify below 80Hz, and the subs crossover will also amplify from crossover frequency and below after a stepdown from speaker level to line level.

The lower the frequency, the more power is required for driving to a given SPL. As such, running speakers full range, you might very well find that your receiver has less "usable power" than with the speakers running bandwidth limited aka small.

It's certainly a worthwhile experiment to see if it gives you pleasing results, if you don't like them you've learned something. If you like them, you've learned something.

Also, test levels carefully with a disc like Stereophile's Test CD or a VE or AVIA frequency sweep. Be warned you will see peaks and dips from room interactions.

Hope this helped.

Regards,

 

[Steve_Ma]

Thanks John,

So the Rec will still be amplifying the mains above the X-over, and the sub will amplify below? Which makes me wonder about having less juice for the mains, and placing more of a load on the sub's amp. Not sure that I like that as I'm happy with the power the SR7000 sends to the mains (for now).

Maybe I'm over thinking/over tweaking. I suspect that any change I'll experience with regard to a lower x-over (the SR7000 = 100), will probably be minimal compared to the change due to placement alone (for better or worse).

Thanks again,

--Steve

 

[BruceD]

Steven,

I don't know how the B&W ASW1000 sub handles a high-level speaker cable input with respect to your mains and the xover frequency, or a low-level input and output with xover.

Does the sub manual explain this well? see below.

Your sub might also support low-level interconnect cable pass-thru in your setup if the Marantz SR7000 AVR provides main L&R pre-out and main L&R amp-in jacks.

Here is how:

1) Main L&R pre-out from AVR -> sub L&R input (RCA low-level)

2) Sub L&R output (RCA low-level)-> AVR L&R amp-in (xover set on sub)

3) Main L&R AVR speaker out (high-level) -> main L&R speakers

Anyway, I use this same setup scheme as you, except with low-level interconnect cables between the processor, an electronic xover, and the amp channels.

You could also use low-level interconnect cables with an electronic xover in your setup if the Marantz SR7000 AVR provides main L&R pre-out and main L&R amp-in jacks.

1. In my AVR, if I set my mains to large and sub to no...What happens to any bass material with the surrounds/center? DO I leave them to small and does their bass get re-routed to the mains/sub?

Answereing point #1, this means all bass re-directed from center and surrounds (set as small) + LFE bass is sent to the main L&R channels and then split appropriately by the xover (electronic or maybe the sub's internal) to the mains and sub. This means you can custom select the best xover frequency for bass in your particular room with your specific main speakers and sub.

I found this to be the best way to overcome the lack of bass xover flexibility in many of today's HT processors.

The benefit is that it also allows for the use of the sub in 2-channel.

 

[John Kotches]

Steve,

In your wiring scenario, speaker level to sub, sub internal crossover to subwoofer and speakers, the receiver will amplify a full range signal for the mains.

Your reply (receiver handling above crossover (maybe it's a typo?) is not correct.

Regards,

 

[Steve_Ma]

Thanks Bruce/John,

I think I'm getting there. John, I was looking at the following quote when I made my previos mistake:

If you define the speakers as large, you will be "wasting" the portion of the receivers power that is used for amplification of frequencies below whatever crossover point you select on the subwoofer.

Based on your response I take this to mean the AVR has no idea whether or not there is a sub "in-line" and will send the juice downstream regardless. BUT. the sub is also driving power to the same region and there is a certain amount of power that will be wasted in the process. Am I getting warmer?

Bruce, I need to get a closer look at the manuals when I get home, to see if I have the L/R pre-out and amp-in jacks on the SR7000.

--Steve