Originally Posted by rebop
Thought about not posting this until I test further, but running out of time before I travel tomorrow for business. Will chat with Oppo as well, but appreciate any insight....
OK, the project for yesterday and today is bass management revisited. Something is VERY wrong. And difficult to explain. And possible I am missing something.
I use primarily the analog 5.1 outs of the Oppo. There are times I use bass management in my proc (Parasound AVC-1800). So I want levels to match on both. Or at least relative speaker levels.
The goal is to use MCH analog outs from the Oppo for all discs - DVD, Blu-ray, Blu-ray Audio, CD, SACD, DVD-A, etc. So this is more important than having bass management in the proc "right on".
I used three different discs (Disney WOW, DVE, S and V) as well as internal pink noise on the proc to set bass management using SPDIF out from the Oppo. And a Rat Shack SPL meter adjusting just a little for inaccuracy in the low end of the meter. Everything balances well. I use the sub input level to trim the sub level. Not only does it measure accurately, it SOUNDS accurate. All front and surround set to small, btw with 80 Hz crossover set on both the proc and the Oppo.
Now, same tests tones from discs on the Oppo using analog outs. Fronts, surrounds all balance about the same. But sub is 10-15dB below the sub level compared to using the Parasound to decode. Only way to get close is drop fronts and surrounds a little and raise sub 8-10 dB. And then, levels are closer with test tones, but some
discs are 10 dB hot on the LFE channel. And there is a different quality of the LFE as well. The proc decoding seems to have more low frequency in the LFE tone and the Oppo sounds like it is missing the bottom octave. There is no doubt the frequency response of the SPDIF out and analog out LFE is different. No doubt.
Direct a/b shows this easily. I have not yet tried a Stryker disc and checked 20 or 25Hz with Oppo analog and Parasound SPDIF to see, but may if I have time today. Should show the freq difference I am hearing.
So, it seems the analog LFE or Sub output of the Oppo is greatly too low and on SOME material (Inception) it boosts Sub output to be unlistenable. But worse, the frequency response. And even where the bass is not boosted, the quality of the LFE on analog out is missing impact.
This could be a deal breaker now for me.
I am hoping someone will point out something I am just doing wrong, but I have thought through all this quite a bit and if I am, I am missing it.
Could anyone check a good Blu-ray with bottom end and compare SPDIF out with analog out and see if they find the same.
Unfortunately, I will be traveling for 5 days on business starting tomorrow, so will only have some of today to test any suggestions the next Friday will be my next opportunity. And the last day to return if I cannot solve this.
The sub output on the analog multi-channel outputs is down -15dB compared to the other channels by design to keep loud bass on that output from clipping the input on your pre-amp (or sub amp). -10dB of that comes from the nature of LFE itself on movie discs which is recorded -10dB down to provide more headroom. I.e., LFE is not so much for bass -- the other speaker channels are perfectly capable of carrying bass -- it is for *LOUD* bass.
The remaining -5dB is to allow additional headroom for steered bass in case you have any speakers set to "Small" in the player. Due to recommendations from Dolby the -15dB is maintained even if all speakers are set to "Large".
Note that the above applies *ONLY* to the multi-channel analog outputs.
+10dB boost is "standard" in pre-amps for LFE input. For the digital audio paths (such as S/PDIF) that happens automatically. For the multi-channel analog path you may need to turn that on. In any event, there is an additional +5dB that also needs to be accounted for on the multi-channel analog path.
Apparently your problem is that you are trying to match levels from the analog outs against levels for digital audio output.
If your pre-amp/processor is typical, it will not provide level adjustment on its multi-channel analog inputs but WILL provide it on the digital audio path. If that assumption holds true for you, then a common approach to solving this problem is:
1) Get a calibration disc and use that for making these adjustments. I recommend the AIX audio calibration Blu-ray. To keep things simple, use the 7.1 or 5.1 LPCM tracks from that.
2) Set volume trims in the Oppo for the multi-channel analog outputs EXCEPT FOR the subwoofer. Leave the sub output at 0dB trim.
3) Adjust the sub level for multi-channel analog using the volume knob on the sub. Typically this will mean RAISING the volume knob on the sub +5dB or +15dB depending upon whether your pre-amp does or does not provide the "standard" +10dB boost on LFE input already for the multi-channel analog inputs. Whatever the case may be, use the sub volume knob to get the sub in balance.
4) Now this means you have just screwed up the sub for your digital audio. So now go into the setup for your digital audio path and LOWER the volume trim for the sub output for those in your pre-amp/processor to compensate for the change you just made to the sub volume knob.
The upshot is that the levels are correct for multi-channel analog because of the adjustment you made to the volume knob on the sub, and the levels are ALSO correct for digital audio because of the compensating reduction you've made in sub output trim in the pre-amp for those sources.
NOTE 1: Don't just raise the sub volume trim in the Oppo as that will defeat the purpose of making sure that output won't clip the input of your pre-amp. However, as stated, the extra -5dB attenuation is to allow headroom in the sub analog output if you have bass steering going on -- i.e., if any speakers are set to "Small" in the Oppo (and you are not playing SACD discs using DSD-direct-to-analog). If in fact you have all speakers set to "Large" then no such bass steering is happening in the Oppo and so it is safe to add up to +5dB of sub output volume trim in the Oppo itself.
NOTE 2: The SACD spec is screwy. It has an LFE channel but does NOT record it at -10dB down compared to the other speaker channels. This is silly on the face of it since there's no point in an LFE channel in that case. The other speaker channels are perfectly capable of carrying bass themselves. Indeed some older SACD discs are recorded with LFE -10dB down just because of this (compounding what is already a silly situation). And PentaTone records their latest SACD titles without using the LFE channel (except in test tones) because of this confusion. They carry all of their bass in the main speaker channels. Anyway, in the Oppo, SACD LFE is automatically attenuated -10dB so that it matches the level settings you have for LFE from other sources.
NOTE 3: As previously posted SACD DSD-direct-to-analog bypasses any processing including bass steering. If that's what you are using then you will need to take extra care in setting sub volume trim. As stated in my earlier post above, if you are trying to use the multi-channel analog outputs BOTH for SACD DSD-direct-to-analog output AND for "normal" audio processing for movies and such, you have an interesting challenge figuring out how to account for the lack of processing on the DSD path.
NOTE 4: I recommend the test tones in Tracks 43-48 of "Stay in tune with PentaTone", SACD, to test SACD levels. Just to give you an idea of how people can screw this up even when they are trying to be careful not to do it, even this PentaTone disc has a problem. As the write up that comes with it correctly states, the levels in Tracks 43-48 are "right" -- those are the ones to use for set up. But the channel-ID tracks also on that disc (starting around Track 19 as I recall) have the LFE test track recorded +10dB too loud. I'll be charitable and suggest that instead of a bug, this is something PentaTone did deliberately on those channel-ID tracks to make sure folks still hear that bass channel-ID tone if their system has the error where their sub is -10dB too low.
NOTE 5: There have been recent reports here that there is a problem with the built-in sub channel test tone in the Oppo in the current firmware. I haven't seen details on that. If true, this is of course just a bug. Using a calibration disc as I recommend is the workaround.