Subwoofer On-board Amplification Gain Setting

[Buckster]

Put this in the Monolith thread as thats what I've got - but its more of a generic query really.

Daft question but is there a relationship between "subwoofer" actual gain, and amp subwoofer LFE output gain - wrt to audio quality ?

the reason I ask - is that for my BFD to register anywhere near the top of its scale (you need it relatively high otherwise your effectively getting a rather poor SNR) - then the gain on my LFE outpu from AV amp has to be high (+8 or so out of a maximum 10) - and subwoofer gain very low (like a 1/4).

are the Monoliths and current gen subwoofers like some of the old RELs - where the amps on the sub themselves need to be fairly high (like around 1/2 or more) to give the subwoofer some punch ? IE high-ish gain on subwoofer (actual) and low-ish gain from amp.

does this make sense ?

when amp set to +8 (to get reasonable volume reading on the BFD) - volume control of sub via amp is very un-sensitive - ie you have to move up and down at least 2dB to hear even a slight change in volume of the sub. amp set to 0 and gain up to 1/2 on the sub - then becomes much less sensitive - ie even 0.5dB gain changes on the amp are very apparent.

Mark.

[Gregory]

I'm a bit of a newby at playing with a BFD, but one bit I'm aware of is the avoidance of clipping in the BFD. I started with the sub output in my amp where it used to be and simply connected the BFD on bypass to see what levels I got. It looked fine (low bars, but visible). The I put a DVD with serious LFE on (the very start of toystory 2 as it happens). I found that I needed to dial back a fair way to be only just tipping into clipping in the BFD - now, on normally telly level sound the BFD hardly lights up the bottom bar, and the -40dB signal indicator on the amp also only occasionally lights (my old sub with it's signal detection standby would just go into standby on this!). This felt so low that I have put it back up a little on the AV amp.

BUT, I do notice that the LFE feels less 'crashy' than before, so it is entirely possible that it was simply distorting before, but is now just fine. By conclusion from that is that the LFE channel power can be so high that you need simply huge headroom to avoid distortion. And, unsurprisingly, that means that for most of the time the levels on the various signal lines are very low, with the SNR issues that might come with it. I guess you take your choice - either go with distortion on the LFE but lower SNR for the rest of the time, or keep linear even during heavy LFE and accept that there is a SNR hit. I reckon that the latter option is better, if only because distortion when operating at already high power during LFE sounds like a driver damaging thing to do.

Greg