Oppo BDP-83SE / BDP-83 Blu-ray Analog Audio Measurement Supplemental

When Oppo announced a hot rod version of their highly regarded BDP-83 Blu-ray player, it piqued our interest.  Considering the stock player demonstrated stellar audio and video performance via the HDMI outputs and respectable analog audio performance, we figured it would simply be icing on the cake for Oppo to offer a supped up version and evidently they agreed, hence the BDP-83SE was born.  Think of it as a BDP-83 on Red Bull.  The power supply was completely upgraded as was the digital to analog front end. 

Check out our Oppo BDP-83SE First Look article and Oppo's tabulated spec sheet for comparative differences of their two Blu-ray players.

We were a bit concerned with Oppo’s choice to use an ESS Technology DAC solution since it was relatively new and hasn’t been proven in the home theater market yet.  We were curious to see how it would handle full scale digital audio reference levels (0dBFS) and how it would stack up against their stock BDP-83 player and thus tested accordingly.

We utilized the industries most advanced HDMI Audio Analyzer – the Audio Precision APx585 along with their Blu-ray test disc which has Dolby TrueHD and DTS HD test signals varying from 48kHz /  8 channel to 192kHz / 6 channel.  Channels #1 – 5 represent the 5 main speaker channels while channel 6 represents the subwoofer channel for all tests unless otherwise

 
Oppo Frequency Response BDP 83SE (left graph) and BDP-83 (right graph)

With all speakers set to “large” and subwoofer turned to “on”, we measured the frequency response of both players using a Dolby TrueHD 192kHz / 6CH test signal.  Interesting both players sent a fullrange signal via the subwoofer output.  We didn’t understand why this was the case until we pinged Oppo.  They explained to us this was purposely done to accommodate users playing Chesky 6.0 DVD-Audio discs that require a full range subwoofer channel because those discs use the center and subwoofer channels to carry the surround channel information.    If you do run fullrange on either player for all other source material, we recommend engaging your subwoofers internal crossover else you will be sending a fullrange signal to that channel which could result in boomy, highly localizable bass.

The graph of the BDP-83SE is ruler flat for the entire audio bandwidth (20Hz to 20kHz) with a measurable -3dB point slightly below Nyquist frequency of the test signal which in this case was around 80kHz. 

The standard BDP-83 shows some unusual behavior we were not expecting.  Apparently with all speakers set to “large” the brickwall output filter characteristics seem to drastically change causing fairly large frequency peaking above 20 kHz.  With standard CD and DVD playback this is not really an issue since the sampling rate limits the frequency response to 22kHz where only moderate peaking exists.  Until Oppo can resolve this issue, we do NOT recommend running fullrange on the Oppo BDP-83 for 192kHz DVD-A playback. 

We were initially concerned about how this would affect SACD playback given the intrinsic out of band noise DSD exhibits but we didn’t have the proper test signals to measure it.  We consulted with Oppo and they informed us that the analog DSD filter is engaged for SACD playback with a -3dB at 50kHz with a  27dB/oct rolloff as indicated in the data sheet excerpt below.

  

 Oppo Bass Management BDP 83SE (left graph) and BDP-83 (right graph)

Oppo only gives you one choice of crossover frequency; 80Hz, which is supposed to apply for the subwoofer Low Pass Filter (LPF) and the High Pass Filter (HPF) for all speakers set to “small”.  This is fine for most applications and we like to see the filters exhibit the following roll off characteristics per THX for optimal subwoofer to satellite speaker blending.

HPF: Fc = 80Hz 12db/Oct roll off with -3dB pt at 80Hz

LPF: Fc = 80Hz 24dB/Oct roll off with -6dB pt at 80Hz

Unfortunately neither player followed this recommendation.  In fact, they were both different from each other which again was puzzling though not surprising since no DVD / Blu-ray players we’ve bench tested with the exception of Denon flagships (ie. DVD-5910CI, DVD-A1UDCI) actually exhibit the correct specified cut off frequency and roll off characteristics.

Tabulated Oppo Bass Management Comparison

We are hopeful Oppo can improve their bass management filters and also offer end users adjustable crossover points in 20Hz increments between 60Hz to 120Hz to accommodate a wider variety of speaker options.

Next up we wanted to measure distortion levels of both players.  If the hot rod version was truly better, it should be self evident in distortion measurements.

Oppo THD + N vs Frequency BDP 83SE (left graph) and BDP-83 (right graph)

 With all speakers set small the distortion below the HPF is understandably higher and should be ignored.  For the five main channels, both players exhibited excellent distortion characteristics with the BDP-83 in the 0.02% level for the entire audio range above its HPF and the BDP-83SE about half of that for the surround channels and 1/3^rd that for the main channels.  The distortion reducing benefits of doubling up on the DACs for the main channels was clearly measurable here. 

What was perplexing however was the outrageously high distortion from the subwoofer channel of the BDP-83SE.  We double checked this with the built in digital Oscilloscope feature of the Audio Precision and could see visible clipping of the test signal.  The output signal level was 2.7Vrms so we knocked the subwoofer trim down -10dB figuring the opamps were hitting the rails causing it to clip, and retested.  The sub output level dropped to around 1Vrms but was still clipping hard.  We retested using a -20dBFS test signal and boosted the subwoofer level to +10dB which would give us about the same 1Vrms output level that clipped the subwoofer channel before.  This time the distortion levels were similar to the other channels (< 0.05% THD + N).  What this told us was that the BDP-83SE was not properly handling 0dBFS digital output levels when recombining into the subwoofer channel. 

Please note our various articles discussing the importance of properly handling 0dBFS signal levels in digital audio playback systems:

Issues with 0dBFS+ Signals on Digital Playback Systems 

The Case for NOT going above 0dBFS

Update Regarding 0dBFS

2/11/2010

We have recently discovered that not all BD players handle 0dBFS in a similar matter.  We've found that when testing at 0dBFS levels, the summed subwoofer output of some players exceeds 0dBFS and thus causes the distortion problem we've previously documented.  It is unclear if this is a real world test scenario so going forward we will be testing at -20dBFS based on Dolby Labs recommendation.

For more information, check out our article:  0dBFS & Bass Management of DVD / Blu-ray Players 

Oppo THD + N vs Frequency BDP 83SE (Fullrange)

Interestingly we retested the BDP-83SE at 0dBFS signal level with all channels set to “large” and the subwoofer channel exhibited no distortion issues.  It’s clear that the 0dBFS distortion issue we previously observed was happening in the digital summing process of the bass management circuitry of the ESS chipset.  Until Oppo can resolve this issue, we recommend setting all channels to “large” and engaging external bass management as necessary to your speakers and subwoofer.

Oppo Crosstalk BDP 83SE 

Using a 10kHz test signal Dolby TrueHD test signal we ran all of the 6 channels but the one under test as the noise disturber and measured the residual noise of each channel individually.  This is the worst possible test scenario and despite that, the BDP-83SE was able to achieve anywhere between 101dB to 105dB of isolation.  With only one channel driven as a disturber, the adjacent channels measured a between 3-5dB even better.  In comparison the standard BDP-83 was only 2-3 dB worse in every test scenario which is also excellent performance.  These are excellent numbers, and certainly beyond audibility.

Wrap Up

Please note the issues we found while testing these fine players may never be audible in real world usage but they are important to note when configuring the players to match your components.  Until Oppo resolves these analog audio issues on both players we recommend the following setup guidelines for each.

Oppo BDP-83 Recommendations

• Run “small” for all speaker settings when playing back 192kHz DVD-A
• Utilize the subwoofer crossover when all speakers are set to “large” for all formats other than the Chesky 6.0 DVD-A recordings.

Oppo BDP-83SE Recommendation

• If you experience distortion via the subwoofer output when playing DolbyTrueHD or DTS HD source material, set all speakers to “large” and utilize an external bass management solution (ie. A/V receiver, external crossover system, etc).

It is also important to note that these issues only reside in the analog domain when utilizing the 7.1 analog RCA outputs.  If you are using the HDMI output for all of your audio needs, then there is no cause for alarm for any modes of operation at this time. 

Fellow BDP-83 and BDP-83SE owners panic not about these findings, especially if you aren’t experiencing any notable performance issues as a result.  We have never known an electronics company more dedicated to customer service and support than Oppo.  You can rest assured that as you are reading this, they are working on solutions. 

Once Oppo resolves these analog audio issues, we will do a follow-up article with listening tests to compare the analog audio performance of both players.

For more information on Oppo Digital products, visit:  http://www.oppodigital.com

We would like to thank Audio Precision for making it possible for us to conduct such detailed and accurate measurements and their guidance in assuring our test results are as accurate as possible.