Surround Processing and Bass Management

The AVR-5805 is fully armed with all the latest surround modes including PLIIx, DTS Neo, DTS 96/24, THX Ultra 2 as well as their own proprietary surround modes which I found to be unusable especially after hearing some of the awesome modes that Integra Research and Yamaha offer in their flagship products. Denon realizes this and has no desire to offer a multitude of artificial DSP modes. While I can see arguments from both camps on this topic, to be honest I only utilize such DSP on rare occasions such as when viewing older concert DVDs and VHS tapes which usually benefit from a good DSP mode. In those instances I found partial salvation using PLIIx M usic M ode. What's re a lly cool is that you c a n overl a y PLIIx over virtually any audio signal or format (i.e. Dolby Digital, DTS, DVD-A a nd SACD tr a nsported through IEEE 1394!) Now you can have your cake and eat it too by taking advantage of all 7 speakers in your setup regardless of what format is being decoded.

All of the THX options are also present, including Ultra 2 Music, Cinema , EX, and the newest THX Games mode. But be warned, engaging any of these modes automatically restores the bass management to a global 80Hz crossover setting. Thus, if Audyssey determined more optimal settings for a better splice between your speakers and subwoofers, it will be lost when engaged in THX post processing modes.

Learn More About the Different Levels of THX Certification at:
http://gamma.audioholics.com/education/audio-formats-technology/thx-select-and-thx-ultra2-certification-general-questions

Bass Management

The AVR-5805 bass management system is by far the most sophisticated and flexible system we have seen in a receiver or even a dedicated processors for that matter. In fact, it uses one dedicated 32 bit TI chipset just for that function! It allows user adjustable speaker group crossover frequencies independently of e a ch other from 40Hz to 250Hz and independent subwoofer delay and level settings for up to three subwoofers! It even allows for independent subwoofer crossover settings for two-channel audio. I proceeded with caution based on my p a st experience with systems th a t a ttempted, but failed, to successfully offer this type of multiple crossover system. The problem with most multiple crossover systems is when you configure one speaker group's crossover to a much higher setting than the main channels, the bass from those speaker groups don't get recombined to the sub and are lost entirely. This is because most systems only incorporate one fixed LPF setting for the subwoofer channel which is usually derived from the main channel's setting. Knowing the kind of company Denon is, I didn't suspect the AVR-5805 truncated the bass like this, especially since it has a separate LFE crossover setting.

To test my assumption, I used the Audio Precision SYS 2722 Audio Analyzer to run some measurements via the analog two-channel inputs of the AVR-5805 configured in two-channel and multi-channel surround modes. What the SYS 2722 told me was that the LFE crossover setting only a ffects LFE info as stated in the menu. This is a good start, implying if you set all other channels to a lower frequency, critical LFE info will NOT get truncated. M any processors unfortunately do truncate LFE bass under this circumstance but thankfully the AVR-5805 is not one of them.

Discrete Multi Channel Measurement

Red Traces: Main CH set to 80Hz and corresponding subwoofer output

Green Traces: Center CH set to 150Hz and corresponding subwoofer output

This is a plot of the subwoofer LPF and Main Channels HPF when set to the THX recommended 80Hz crossover setting (in red) and the center channel set to 150Hz along with its corresponding subwoofer output (in green). Notice in the red trace the HPF is down -3dB at 80Hz with a 12dB/Octave slope while the subwoofer is -6dB down at 80Hz with a slope of 24dB/Octave as per THX. Similarly for the center channel and corresponding subwoofer output at 150Hz the -3dB point of the HPF is 150Hz and the -6dB point of the LPF is 150Hz. Basically the AVR-5805 bass management is intelligent enough to have discrete LPFs corresponding to the HPF settings of each channel group. For 2CH sources, the LPF of the subwoofer is based on the HPF setting of the main channels as it should be.

A few notes about bass management logic for the AVR-5805

• If you set Mains Small, all other speakers default to Small
• If you set any speaker to Large, the bass will not go to the subwoofer, except if you select "LFE + Main ".
• If "LFE + THX" is selected then bass from the Mains will not be directed to the subwoofer if the Mains are set Large, even in 2CH mode.
• The AVR-5805 has completely independent bass management settings (ie. crossover, distance compensation, level, etc) for 2CH mode. Not since the days of the Aragon Soundstage have we seen this sort of flexibility, especially in a receiver!

PLIIx Measurement with Analog Two Channel Source

The Green Trace represents the subwoofer output while the main channels are set to 120Hz while all others are set to 40Hz. Notice the subwoofer output that appears to be rolling off at 120Hz which is based on the main channel setting.

The Red Traces represent all channels set to 80Hz. Again notice the subwoofer crossover point remains at 80Hz based on the main channel setting.

Let's take a closer look at the subwoofer output while varying the multiple crossover settings between the main speakers having high and low crossover settings, while the other speakers have low and high crossover settings, respectively. The AVR-5805 is configured in PLIIx Music Mode.

In the Blue Traces, we set all channels but the mains to 120Hz (extreme case), while the mains were set to 40Hz. Notice how the subwoofer crossover -6dB cutoff remains at 40Hz based on the main channels setting and we see no weird summing like we did in the Integra Research RDC-7.1. Granted, ideally it should have extended to the frequency of the satellite speaker with the highest crossover setting (in this case 120Hz), but I suspect Denon limited the cutoff of the LPF of the sub to the main channels setting to avoid excessive bass energy from a single source which is localizable at frequencies above 80Hz and to avoid having too much overlap of the speakers with HPFs set to a lower value.

Essentially the bass information from any speaker groups set above the main channels crossover point will not recombine bass back into the subwoofer. In other words, that information will be lost or extremely attenuated. In actuality the function is proper since the AVR-5805 was receiving a two-channel source and deriving a multi-channel surround output. It was defaulting the LPF of the subwoofer to whatever setting the main channels were configured too.

Overall, this multi-crossover system is the most flexible bass management system to date (a requirement for properly integrating the Audyssey MultEQ room correction system), and can be very effective if used within confined limits. We would suggest to always select satellite speaker systems with a -3dB point of 80Hz or lower, especially when using a product of this caliber in a full-blown high performance home theater system. We also suggest maintaining a difference of no greater than 20Hz between crossover settings of all speaker groups and using caution when setting the main channels' crossover setting too low (especially when listening to two-channel sources in surround sound) to avoid loss of bass information from the other channels. Always start at the 80Hz reference point and only deviate when absolutely necessary for your particular situation. In my system, I set all channels, including the LFE, to 80Hz (THX setting) except for the main channels which I set to 100Hz because I achieved better acoustical bass integration with my subwoofers and main satellite speakers.