4.) Scotty, We Need More Bass!
The final configuration step in getting good sound from a multi-channel analog configuration is getting the subwoofer level right. This is often the toughest part of setting up analog audio. The LFE (Low Frequency Effect) channel is designed to play back 10db higher than the other channels, for maximum impact. But, that extra 10db may clip during transmission to your receiver, causing audible distortion. So, the LFE channel is generally mixed at the same level as the other channels in the soundtrack, with the understanding that it will be boosted 10db (decibels) by the receiver. With digital transmission of multi-channel audio, the software adds the boost to the signal automatically. With analog, the user (that's you) needs to apply the boost to the signal, but it can't be done in the player (again, due to the risk of overloading the analog inputs of the receiver) -- it must be done in the receiver.
But wait, there's more! One more complication, that is. When using bass management in the player (setting any of the speakers to "small" in the previous step), the subwoofer channel is dropped another 5db to "make room" for the redirected bass information from the other channels. This means the subwoofer level actually needs to be boosted by about 15db in the receiver in order to get it to the "correct" output levels.
Many preamp/processors and receivers offer an adjustable LFE boost (or cut) for the subwoofer channel of the multi-channel analog input. Pictured is the setting from an Integra DTR-9.8 preamp/processor.
Many (if not most) receivers and preamp/processors have a special setting to boost the subwoofer for the multi-channel analog inputs. This may be called "subwoofer sensitivity" or "subwoofer level" (and it's different from the level controls for the digital inputs). Some receivers even apply this boost by default. But, other processors don't make this level adjustment so easy. If your receiver doesn't have a way for you do the required LFE boost and you think the bass sounds a little weak, you still have a couple of options.
You can simply turn up the sub. Most powered subwoofers have a level or volume knob on the back or bottom which raises the overall output level of the subwoofer. Of course, that will give your digital sources too much bass. So, if you take this approach, you will need to recalibrate your receiver by reducing the sub output for the digital inputs. If you ran an auto-calibration routine such as Audyssey or MCACC, then you'll need to run it again with the subwoofer at its new, higher volume so that proper balance is restored to your digital sources.
The other choice is lowering the output of the non-LFE channels in the player, which has the same effect as boosting the sub. Of course, now your overall volume will end up too low and you will need to crank it up in your receiver. While this approach will get the proper bass balance, it raises the noise floor, which may not be the ideal solution.
More info here on how to setup your BD55. The first thing to check in your Yamaha manual is for a setting to boost the subwoofer signal while using the multi-channel analog connections +10 or +15 if you can. Note this is a separate setting from your normal bass managment settings in your receiver.
http://www.bigpicturebigsound.com/How_To...s_And_Why.shtml
