LFE, Bass Management & Room EQ software

A lot of people can easily get confused with Low-Frequency Effect (LFE) and Bass Management (BM). They are not the same thing. LFE is often used interchangeably with bass and that is not correct. LFE itself is a full bandwidth channel, hence the (.1) channel. The LFE for movies is usually mixed up to 120Hz. By default, most AV Receiver/Amp manufacturers will set a Low Pass Filter (LPF) for LFE at 120Hz. This is unlike the bass being re-directed from the speakers to a subwoofer at a specific crossover point - e.g. THX level at 80Hz. Anything beyond 80Hz, the bass becomes “localizable” and this is something we try to avoid that. The key is to make the bass “blend in” with the rest of the speakers so that it becomes indistinguishable or “disappeared” where one is unable to tell where the subwoofer is located within the listening space.

During calibration, all speakers are set to small (usually at a crossover of 80Hz or higher) in order for the BM module in an AVR or AV Amp to do its work. We have seen Audyssey almost constantly set a wrong crossover point for the Center and Mains to around 40Hz because of its proximity placement to the wall. This somewhat “confuses” the Audyssey calibration mic when picking up pink noises during the calibration process. Consequently resulting in a less than ideal crossover setting for the LCR. Fortunately, Audyssey does allow users to change the crossover point to a higher point (not lower) after post-calibration. In this regard, most of the computer-aided Room EQ like Anthem ARC, Dirac Live with BM, RoomPerfect EQ to name a few, perform better than Audyssey as it factors in the room mode (room gain) during the calibration process to determine the best crossover points for each speaker.

If you really want good bass performance from your investment, look out for an AVR or AV Amp that comes with Dirac Live or Anthem ARC (which I am currently using) as it will vastly improve your listening experience when the bass is done right. Considering now that the latest Onkyo models come equipped with Dirac Live and the price is almost on par with some of the higher-end Denon and Marantz models that still utilize Audyssey as the Room EQ. Try something new for a change and I promise you will not regret it.

But what is wrong by setting the crossover frequency lower at 40 Hz or so if the spakers are trully capable of producing the sound?

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80Hz is a general rule of thumb…besides it will be good for dedicated subwoofer(s) to handle the bass so as to relief the mains, particularly those bookshelf speakers which are unable to reproduce bass an efficient manner.


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