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Old February 1st, 2014, 12:18 AM
SME SME is offline
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Bass dynamic range on Denon AVR3313CI (likely other models and brands too)

Whilst integrating a pair of MBMs with my VTF3-MK4 and VTF-15H true subs using a digital device, I discovered something surprising and remarkable: The way my Denon AVR3313CI was configured, my bass output was effectively limited to ~111 dB peaks. That number looks pretty big, and it is for continuous signals in the audible bass region, but there are two significant reasons why this isn't enough:
  1. Heavy bass transients get clipped and are less powerful than they should be. Many film soundtracks have very powerful bass transients. There is a thread on the forums at data-bass.com that reveals bass impulses mixed into several channels at once hitting well over 115 dB at reference volume.
  2. Also varying from soundtrack to soundtrack, much bass energy consists of subsonics that get filtered away by the subs but consume valuable headroom in the AVRs processing.
So why was my dynamic range limited? They key is in how the "sub level trim" function is implemented by the AVR. Essentially every gain control within the AVR, including the master volume and trims is implemented digitally. Digital signals have a hard maximum that cannot be exceeded. It is up to the system designer to decide how much headroom to provide within the signal pathway.

Unfortunately, in this AVR and probably many others like it, headroom is relatively limited. Because the sub level trim is implemented in the digital domain, the higher it is set, the less dynamic range is available.

Note that I keep using the term dynamic range here. There's nothing that stops a user from cranking the gain knob on his/her sub(s) to get more output. This does not increase dynamic range and results in loud but poor quality bass.

The key to maximizing dynamic range is to set the gains on the subs such that when calibrated, the sub trim will be set close to its minimum. For my AVR, a calibrated level trim of 0 offers peak output at around 109 dB. My system now calibrates with a sub level trim close to -10 dB, so theoretically, I am now able to pass 119 dB peaks. I may attempt to get this up to 120 dB, which is still not high enough to avoid all clipping, but it's a huge improvement over where it was.

Subjectively, the improvement is enormous, but varies with material. With music, there's little if any difference. With heavy bass movies the difference can be enormous. For example, the film "Samsara" depicts a volcano, in which the bass had seemed kind of quiet despite subtle hints of infrasonics. After the optimization, the deep bass energy is no longer subtle as the room pressurizes and the floor trembles. I believe the track has so much subsonic energy that the audible bass was getting squeezed out within the AVR.

So to summarize: the best bass dynamic range is obtained when the sub gains are set so that the calibrated sub level trim is as close to the minimum value within its range as possible. This can potentially to apply to any AVR model that implements these controls digitally. The question is how much headroom they built into their design, and how low the sub level trim control can go.

One more note: I only tested one particular condition. I synthesized multichannel full scale sine wave FLAC audio files and tested them with the subs turned off. My DSP device gives a level reading that I could monitor for these tests. I adjusted the master volume and watched the level increase until it didn't anymore. In another instance, I put 27 dB of attenuation on the line from the DSP device to an MBM and listened. The onset of distortion as the master volume was increased was abrupt and indicates hard digital clipping. It is possible that the AVR has other stages with clipping and/or limiting that influence output in earlier stages in the digital pipeline. My study does not rule out those possibilities.

Last edited by SME : February 6th, 2014 at 8:03 AM. Reason: update to quoted maximum dB of transient
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Old February 1st, 2014, 7:19 PM
SteveO SteveO is offline
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I enjoy reading your post's about your home theater system, I find them informative and interesting. But having said that I am hoping to not have to spend that much time and energy on mine cuz I dont have the patience for it.

I would like to get a receiver that has audyssey multeq xt32 and subeq ht and let it do the work for me and hope it sounds good enough to not have to mess with it. Unfortunitly multeq xt32 and subeq ht only comes with the receivers flagship models and I would end up paying for a bunch of features I dont need.
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Old February 5th, 2014, 8:00 AM
elwaylite elwaylite is offline
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I always run Audyssey with my sub gain set to where the AVR ends up with a -5db target for level. I then always boost inside the AVR menu to 0.0, because I run my sub 5db hot.
X4000/Outlaw Amp/Klipsch RF82 II's/RC62 II/VTF-15H (2)
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