Page 1 of No Subwoofer

I have a Sony 940 amp, KEF speakers but no sub. Do I need to bridge the subwoofer terminals on the back of my amp to the main speaker terminals to ensure I don`t lose the low frequencies ?

Extremely BAD idea! You will probably end up blowing up your amp.

I don`t have or know the Sony 940 amp but I`ll assume it`s a 5.1 capable amp so some general comments.....

First off, if you linked your subwoofer terminals to the main speaker terminals you would parallel your Sub, Left & Right outputs together and you would lose stereo. If you really wanted to go the whole hog you would link the centre channel as well but I think you would be a little disapointed at turning your 5.1 system into a 3 channel one (Front + Left Rear + Right Rear)

While we`re here, let`s deal with another misconception...that LFE (Low Frequency Effects or the .1 of `5.1`) equals sub-woofer output. It doesn`t! All the LFE channel is, is a dedicated channel for low frequency effects. How this gets reproduced in the home (or at certain cinemas is a different matter)

All Dolby Digital amps include a `Bass management` facility where the low stuff from ANY channel gets routed to amplifier channels with suitable loudspeakers. Normally you have to tell the amp which amplifier channels are `Large` (ie have full bandwidth speakers) or `Small` (generally have poor bass response below 80Hz) If you tell the amp you have a subwoofer then the amp should route the LFE + all the low stuff from the `small` channels to the sub woofer output. As an exteme case, setting all channels to small, telling the amp you have a sub but not actually connecting it would lead to an extremely lightweight sound as all the low stuff would get routed to a non-working sub! Telling your amp that you don`t have a sub and have large main speakers should be enough for it to route the LFE (and possibly low stuff from the surrounds) to those large speakers. As an experiment also try setting the centre channel to `large` it MAY sound better. For a final bit of fun (if they are capable) try setting the surround channels to large as well.

The other way of looking at it is that film mixers are told never to put anything critical to the plot in the LFE channel alone (remember this is an EFFECTS channel!) If this low frequency noise/thump/whatever IS critical, then it should also appear in the main channels as well.

Check out the Dolby web-site, this has loads of info about LFE + Bass management - www.dolby.com

This item was edited on Wednesday, 31st January 2001, 11:19