LFE signal, what's in it?

EricH

I'm wanting to run my HT set-up full range, but the manual for my AVR says that, excluding the mains, large speaker settings send no signal to the sub.

My question is this: What information is being sent to the sub from the LFE pre-out? If all speakers are on large, the sub gets nothing? Or is there still some sort of LFE signal being sent regardless? Thanks in advance, Eric.


HK AVR 630
RTi70 mains
CSi40 center
CSi30 surrounds
RTi38 rear surrounds
Velo CHT-15 sub

Dr. Spec

Setting all speaks to large and the sub to yes/on does the following: All speakers get the full range signal in that channel, with no redirected bass. The subwoofer gets only the LFE channel (".1" in 5.1 and 6.1).

Setting all speaks to small and the sub to yes/on does the following: All speakers get high passed at the selected xo frequency, and the bass gets redirected to the subwoofer. In addition, the sub gets the LFE channel.

The ".1" LFE channel is dedicated to bass effects only. In theory it goes to 120 Hz, but in reality it goes to 80 Hz and then gets rolled off.

I saw in your other thread you set the xo to 60 Hz with the h/k. Doing so will lop off the top of the LFE channel unless your pre/pro can set the xo for the LFE channel separately (and most can't). If you're setting your speaks to small, it's best to keep the xo at 80 Hz or higher to preserve the entire LFE channel.

Typically the way a pre/pro does BM is it takes all 5 channels and high passes them at the selected xo. Then it takes a duplicate set of of all 5 channels, and the LFE channel, and low passes them (again at the selected xo) and sends the resultant signal to the subwoofer.

So you can see if the LFE channel is low passed at say 60 Hz or 40 Hz, you'll lose everything above that point since the LFE channel is not high passed and redirected to any surround speakers.

Doc

johnny_utah

Originally posted by Dr. Spec
it's best to keep the xo at 80 Hz or higher to preserve the entire LFE channel.

just wanted to ask a quick question.

I have my xo set to 80, and speakers (csi3, rti6's, fxi3's) set to small. Would it be better to set the xo to 100, would I gain anything? Right now my sub clips at pretty high volumes, would this make it clip more at not as high volumes? Thanks for any replys.

EricH

Originally posted by Dr. Spec
Setting all speaks to large and the sub to yes/on does the following: All speakers get the full range signal in that channel, with no redirected bass. The subwoofer gets only the LFE channel (".1" in 5.1 and 6.1).

So even on large settings, the sub does receive a signal. What signal information exactly is "only the LFE channel"? Is it indeed a low frequency combination of all other channels, or a stand alone signal, separate of the other channels?

Concerning the 60hz setting, at this time my sub gets boomy if the crossover is set over 60 hz, so upper bass is not achievable through the sub. I am adding on to the room and will be able to move it out of the corner in the future.

Dr. Spec

I have my xo set to 80, and speakers (csi3, rti6's, fxi3's) set to small. Would it be better to set the xo to 100, would I gain anything? Right now my sub clips at pretty high volumes, would this make it clip more at not as high volumes?

Setting the xo higher reduces the load on the speakers, and increases it on the subwoofer. But most of the work the sub does is in the 20-50 Hz region, anyway.

If the sub is already being overdriven, raising the xo from 80-100 will slightly worsen the situation, but it sounds like you'll need to get a bigger sub or turn it down, regardless.