Axiom Home Page Forums General Discussion Home Theater An LFE question – I’m confused, again.

It has been confirmed that my blue ray player, the Panasonic BD 30 attenuates (lowers) the LFE channel on PCM audio tracks 5 DB’s.

I made the suggestion to users of this machine who happen to use a Denon (or other audio processor) that allows independent channel adjustment to raise their sub 5 DB’s to compensate. That is what I’m doing and it works great. The 3808 allows the user to set PCM multi channel input or analogue input differently than DD or DTS bitstream levels, so when playing a BR disk with the BD 30 and selecting the PCM audio track, it automatically adjusts the channels to whatever level you choose.

So anyway, some other folks responded (AVS) saying that that is not an “accurate” way to compensate and it screws up re directed LFE. I don’t understand what they are saying. Unless the speakers are set to large and the LFE is set to LFE+mains, I fail to see how the speakers set to small would be effected if the crossover is set at or around 80 Hz. Isn’t all the LFE going to the sub below the crossover point anyway? And also from what I’ve read, DD rolls off LFE at 80 Hz.

Am I missing something?

Mike, I haven't been following this issue, but isn't what they're saying that by boosting the entire sub level by 5dB(if you are)you're boosting not just the LFE(which is occasionally present during movies)itself, but also re-directed bass from "small" speakers(which isn't LFE, of course)which has been calibrated accurately and doesn't need any boost? So the question is whether the 5dB adjustment that you mentioned affects all the bass sent to the sub or whether it affects the LFE channel alone.

Ya John, I believe that is what the drawback is. I can’t help but wonder how significant that is though.

mdrew, i have been following this as well as I am interested in getting the BD 50 when it comes out (DTS HD MA internal decoding!!!).

I think the problem is that a lot of receivers can only REDUCE the LFE level, not increase it...your denon might be one of the new ones that can. I think the problem is when you try and boost the gain on the sub by +5db. You should only boost the sub by 2 or 3 db, 5 causes problems.

mdrew, have you checked out the AVS forum on the BD30?

The best work-around is to decrease all channels OTHER than LFE by various degrees (on or about 5 dbs).

Will you impact redirected bass output? Sure, But that's why its a called workaround rather than a cure

Keep in mind this is only when a lossless PCM track is selected on the disc. If you select any other codec, do not use this.

The BD 50 looks promising, but with Panasonic’s history with this LFE bug, I’d wait. I’m considering the Denon 2500 myself, but it’s quite expensive. If they had a universal player, I’d probably buy one regardless of price.

I have been following the BD 30 thread at AVS. That’s where I posted the suggestion. I think I understand why bumping the sub level up isn’t such a good idea. It works for now though. That’s more convenient that using the PS3 for PCM tracks and the BD 30 for DTS Master.

The Denon will not allow you to raise LFE, just lower it, or raise the sub level. It will let you configure channel levels differently per source or format though, which is really cool.

As much as I enjoy these BD and HD movies, I’m really getting tired of all the troubles that continue to rise to the surface. Now they're rolling these new profile BD disks out that don’t work. Why would anyone want to listen to some idiot in a little box telling you about why they filmed a shot the way they did when watching a movie anyway?? I suppose some folks like that crap and I should keep that in mind.....

Mike, if you leave all speakers set to large in the player (disabling bass management in the player) then there is no issue. Since your reciever is capable of processing the analog inputs you can then apply your crossover settings at your receiver with no worries.

The issue only bites you if you are using analog inputs on a receiver that can't convert the analog to digital in order to apply bass management/xover and surround mode processing. Most receivers on the market can't do this. When you can't apply bass management settings with the receiver you are forced to use the bass management of the player.

Using the player's bass management causes the player to mix redirected bass from the speakers setup as small into the sub out channel along with the LFE. The 5dB attenuation is by design because adding the bass signals from up to 5 simultaneous channels on top of the LFE channel can overdrive the analog input on any receiver. The attenuation itself is really not the problem. The issue is that by design the LFE channel recorded on DVDs/Blu-ray/HD-DVD is 10 dB below the reference level. The reason the LFE is recorded 10dB low is for the same reason as before, the signal level would be "too hot" for use with analog inputs/outputs. It is the surround processors job to apply a 10dB boost to the LFE (but not the other channels) to give it the impact originally intended.

If the player mixes in redirected bass from the speakers setup as small, this and the LFE are now sharing a single analog path into your receiver. There is no way for the receiver to apply the 10dB boost to the LFE and not also the redirected bass from the other channels. Thus throwing off the intended level balance.

Again, if your receiver is capable of sampling the analog inputs and applying bass management / surround processing- just leave the players bass management off by setting all speakers large. Then the analog output for the sub does not contain anything but LFE, and your receiver can boost it correctly, and handle the crossover settings for your other channels by mixing in the redirected bass to your sub.

well there you go

What? I'm still here. Where did I go to?

Dave,

The analogue outputs aren’t an option. The BD 30 will not decode DD:HD or DTS:Master. It sends those as bitstream only. This player, as well as the Panasonic BD 10, and the Denon 2500 (which shares a Panasonic Chip) all have this low LFE bug with play back of selectable, uncompressed PCM audio tracks on BR disks. Another problem with using analogue…. even if this player decoded all the formats, is that it would be limited to 5.1. There’s several 6 and 7.1 disks out now.

Thanks for the helpful post though……

The real problem is that Panasonic just needs to address this. It’s broke. Unfortunately, it would appear that Panasonic is denying it’s a problem, whereas Denon admits it and has promised to fix it.

I still have my PS3 that plays back PCM audio perfectly. I’ll keep using that for those particular disks and the Panasonic for the DTS:Master disks.