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Bass drastically different between PLII Music vs PLIIz Height

post #1 of 20
Thread Starter 
Just happened to notice this today while listening to some music recorded in 2 channels. The bass is significantly fuller and overall louder in PLII Music 5.1 as opposed to a thinned bass response in PLIIz Height 7.1

Was hoping someone could shed some light on this, as I do prefer the soundstage of the additional height channels, but very much dislike the lacking of bass.
post #2 of 20
^^ IIRC PLII has Movie and Music modes, while PLIIz is a Movie mode. If you compare PLIIz to PLII Movie, does the bass sound more similar?

PLII Music sets the Center Width to spread the center channel across L/C/R so the center bass also gets picked up by L/R bass management. Make sure you have the center speaker set to small so it will feed the subwoofer even in Movie mode.
post #3 of 20
Whether it's 2CH (in the OP's case) or MCH both PLIIx and PLIIz modes apply bass management so I don't see how the centre channel is set explains the bass discrepancy the OP hears between them.
post #4 of 20
maybe your receiver's amps are running out of steam with the two additional speakers.
post #5 of 20
Thread Starter 
Quote:
Originally Posted by Kilian.ca View Post

Whether it's 2CH (in the OP's case) or MCH both PLIIx and PLIIz modes apply bass management so I don't see how the centre channel is set explains the bass discrepancy the OP hears between them.

Exactly my thoughts. I have all speakers set to an 80Hz crossover. And as far as I know, the only listening modes that don't implement bass management are Direct and Pure. Also, FWIW all of the listening modes I'm talking about are under the MUSIC subcategory on the receiver's menu.

I was thinking perhaps PLII Music was boosting the bass as an added effect of processing for music specifically, but the bass response between PLII Music and 2.1 Stereo is essentially identical. PLIIZ Height, which you think would simply apply surround effects to the 2 height channels, would produce the same (if not more) bass considering the height channels are crossed over at 120hz.

Quote:
Originally Posted by Roger Dressler View Post

^^ IIRC PLII has Movie and Music modes, while PLIIz is a Movie mode. If you compare PLIIz to PLII Movie, does the bass sound more similar?

Also, PLIIz vs PLIIx does not indicate movies vs music modes as Dolby describes both technologies being tailored for movies AND music. It seems that Z refers to height channels specifically, while X refers to converting stereo/5.1 --> 6.1 or 7.1 surround without mention of specific placement of the surrounds.
post #6 of 20
Thread Starter 
Quote:
Originally Posted by nismo604 View Post

maybe your receiver's amps are running out of steam with the two additional speakers.

This was my first thought. But I'm not sure that it makes complete sense with the Onkyo TX-NR808 considering 5 speakers crossed at 80 and the last two at 120hz. Not to mention listening volumes WELL BELOW reference. The difference is apparent even at about -28 from reference (on my receiver)
post #7 of 20
Quote:
Originally Posted by mannetti21 View Post


Also, PLIIz vs PLIIx does not indicate movies vs music modes as Dolby describes both technologies being tailored for movies AND music. It seems that Z refers to height channels specifically, while X refers to converting stereo/5.1 --> 6.1 or 7.1 surround without mention of specific placement of the surrounds.

Are you sure that Dolby recommends PLIIz for music listening? That last I remember Dolby engineers couldn't get what they consider an "acceptable" result with PLIIz and music material, hece no recommendation. I believe that's why you'll find both movie and music modes for PLIIx but not for PLIIz.

Cheers,
SB
post #8 of 20
Thread Starter 
Quote:
Originally Posted by SpotcheckBilly View Post

Are you sure that Dolby recommends PLIIz for music listening? That last I remember Dolby engineers couldn't get what they consider an "acceptable" result with PLIIz and music material, hece no recommendation. I believe that's why you'll find both movie and music modes for PLIIx but not for PLIIz.

Cheers,
SB

Just double checked and PLIIz is definitely under the MUSIC Listening Mode subcategory on the receiver, as well as the MOVIE modes. Furthermore, with my additional 2 channels set as height channels in the receiver, PLIIx isn't even an option.

Looking at Dolby's website, PLIIz and PLIIx are indeed both marketed as being suitable for music and movies. Based on my understanding, PLIIx is available when you have front wide surrounds, or additional rear surrounds, whereas PLIIz is implemented when the additional surround channels are front height channels.....neither of which should affect the bass response IMO.
post #9 of 20
Quote:
Originally Posted by Kilian.ca View Post

Whether it's 2CH (in the OP's case) or MCH both PLIIx and PLIIz modes apply bass management so I don't see how the centre channel is set explains the bass discrepancy the OP hears between them.

Allow me to explain further. In playing 2-ch sources in PLII (or PLIIx) Music mode, the CW control spreads the center signal to include the L/R (and C) speakers. The sum of all three are power compensated to be the same as the C channel alone if coming from the center speaker (as would be the case with Movie mode).

For example, when two satellite speakers play the same signal, the SPL increases 3 dB. So when PLII steers a phantom vocal signal to the center speaker, it is 3 dB louder than either of the 2 original speakers so it maintains the same loudness in the overall mix.

However, as wavelengths increase, the power compensation would need to change. Two subwoofers playing the same signal can increase the SPL as much as 6 dB (if near each other), and even when spaced it is more than 3 dB. Dolby and THX found it was typically 4.5 dB in real rooms.

On top of that, bass management uses electrical summation which adds the L/C/R bass following the "6 dB" intensity law (not the 3 dB power law). So just taking the stereo signal and summing the bass to feed the subwoofer by itself adds a degree of bass elevation relative to each channel played alone, and adding a third component from center adds a little more.

However, when we designed PLII, we chose not to mess with applying gain shifts or filters to attempt to compensate any of this added bass from the use of three channels vs two.

You can prove it for yourself. Play 2-ch music in PLII Music and Movie modes. Music will have a little more bass.

Quote:
Originally Posted by mannetti21 View Post

Just double checked and PLIIz is definitely under the MUSIC Listening Mode subcategory on the receiver, as well as the MOVIE modes.

That may be true, but it does not mean that the Center Width control is supported individually as it is in PLII Movie/Music. Can you adjust CW in PLIIz? If so, where is it set? If not, you can easily find out:

Play some mono program (AM radio or whatever). Select PLII Music. Notice the sound comes from L/C/R.

Switch to PLII Movie. Notice the sound comes only from C.

Switch to PLIIz. Where does it come from?

Quote:


Furthermore, with my additional 2 channels set as height channels in the receiver, PLIIx isn't even an option.

That's because there are only 2 surround speakers. PLIIx needs 4. But PLII Movie/Music still works in your setup.

Quote:


Looking at Dolby's website, PLIIz and PLIIx are indeed both marketed as being suitable for music and movies.

Well, how would it do to tell people that their shiny new PLIIz mode did not work for music?

Quote:


Based on my understanding, PLIIx is available when you have front wide surrounds, or additional rear surrounds

Only for additional rear surrounds. PLIIx/z do not understand about wide speakers.

Quote:


whereas PLIIz is implemented when the additional surround channels are front height channels.....neither of which should affect the bass response IMO.

Neither should, I would agree. But as I explained above, they might.
post #10 of 20
manetti21,

You'd do well to listen to Roger instead of relying on the propaganda as put out by Dolby (or the manufacturer of your receiver)

No insult intended, just some worthwhile advice

Cheers,
SB
post #11 of 20
Thread Starter 
Quote:
Originally Posted by Roger Dressler View Post


That may be true, but it does not mean that the Center Width control is supported individually as it is in PLII Movie/Music. Can you adjust CW in PLIIz? If so, where is it set?

Thanks for the thorough reply. I'll probably need to read it a few more times to completely understand.

As for the center channel...when I go into the Dolby audio adjustments, there are two headings PLIIx Music and PLIIz Height Gain.

PLIIx Music
Panorama: On
Dimension: 0 (-3 to +3 scale)
Center Width: 5 (0-7 scale)

PLIIz Height Gain
Gain: Mid (low, mid, high)
post #12 of 20
Quote:
Originally Posted by mannetti21 View Post

As for the center channel...when I go into the Dolby audio adjustments, there are two headings PLIIx Music and PLIIz Height Gain.

PLIIx Music
Panorama: On
Dimension: 0 (-3 to +3 scale)
Center Width: 5 (0-7 scale)

PLIIz Height Gain
Gain: Mid (low, mid, high)

That confirms there's no CW for PLIIz. It is running in Movie mode. If you compare your 2-ch content in PLIIz and PLII Movie, the bass ought to be similar. If not, something else is going on. Have you tried that?
post #13 of 20
Quote:
Originally Posted by Roger Dressler View Post

For example, when two satellite speakers play the same signal, the SPL increases 3 dB. So when PLII steers a phantom vocal signal to the center speaker, it is 3 dB louder than either of the 2 original speakers so it maintains the same loudness in the overall mix.

Thanks for the explanation of PLII Music. Are you implying PLII Movie and PLIIz don't do the same here, applying 3dB boost to the centre?

Quote:
Originally Posted by Roger Dressler View Post

So just taking the stereo signal and summing the bass to feed the subwoofer by itself adds a degree of bass elevation relative to each channel played alone, and adding a third component from center adds a little more.

Understand that, but how is this different with PLII Movie and PLIIz?
post #14 of 20
Quote:
Originally Posted by Kilian.ca View Post

Thanks for the explanation of PLII Music. Are you implying PLII Movie and PLIIz don't do the same here, applying 3dB boost to the centre?

No, the logic steering is identical in both modes.

Quote:


Understand that, but how is this different with PLII Movie and PLIIz?

They are the same. The OP was originally commenting on the bass difference between PLII Music and PLIIz (a Movie-like mode). My explanation of compounding bass was in reference to Music mode.
post #15 of 20
Possibly I didn't put my question clear enough. So, is this right?
PLII Music: C +3dB even for 2CH source
PLII Movie: C +0dB
PLIIz: C +0dB
post #16 of 20
Quote:
Originally Posted by Kilian.ca View Post

Possibly I didn't put my question clear enough. So, is this right?
PLII Music: C +3dB even for 2CH source
PLII Movie: C +0dB
PLIIz: C +0dB

Question was understood. Answer is the same. The logic steering is identical in Movie and Music modes. The L/C/R power compensation is maintained in all cases. You can verify with an SPL meter.
post #17 of 20
Quote:
Originally Posted by Roger Dressler View Post

The logic steering is identical in Movie and Music modes. The L/C/R power compensation is maintained in all cases. You can verify with an SPL meter.

In that case I'm still at a loss where the extra bass in PLII Music mode comes from compared to Movie Mode when you said earlier:

Quote:
Originally Posted by Roger Dressler View Post

You can prove it for yourself. Play 2-ch music in PLII Music and Movie modes. Music will have a little more bass.

If logic steering, power compensation and bass management all work the same way in both modes, where exactly does the extra bass in Music mode come from? I'm not trying to prove you wrong, just want to understand it as best as I can.
post #18 of 20
Quote:
Originally Posted by Kilian.ca View Post

In that case I'm still at a loss where the extra bass in PLII Music mode comes from compared to Movie Mode when you said earlier:

It comes from the CW control spreading the C signal the L/R, which means there are 3 C-ch sources instead of 1 (in Movie) that are electrically summed to mono by the bass management. See post 9 again.
post #19 of 20
On the basis of what you said above I think I understand the general principle. I presumably got confused by the power compensated wording to mean/imply the bass portion is also reduced accordingly before bass management is applied. As the CW has variable settings from 0 (no centre spread) to 7 so I presume the bass summation also varies. I'd understand it much better in equations (what fraction of this added to that) but this is probably trade secret and if so I'll leave it at that. Thanks.
post #20 of 20
Quote:
Originally Posted by Kilian.ca View Post

On the basis of what you said above I think I understand the general principle. I presumably got confused by the power compensated wording to mean/imply the bass portion is also reduced accordingly before bass management is applied.

That's the issue. The power compensation is based on mid frequencies (power law), but it is applied to the entire center signal in the CW control, which means the bass part is not compensated optimally (intensity law). So there is a little more bass. I would not characterize it as "drastic" as did the OP, but that's an undefined quantity.

If it really is drastically different, there might be something else going on.

Quote:


As the CW has variable settings from 0 (no centre spread) to 7 so I presume the bass summation also varies. I'd understand it much better in equations (what fraction of this added to that) but this is probably trade secret and if so I'll leave it at that. Thanks.

Not a secret. Power law means sum of squares = 1.
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