How do you level match surround back speakers

[AcuDefTechGuy]

Say you are watching a DTS track and you turn on PLIIx your 5.1 signal stays in DTS or whatever the source is playing, but your two rear speakers get a matrixed signal based on the original and that is what PLIIx does for you. (I do the same thing as Glocks during movies and turn PLIIx on.

Basically you get DTS+PLIIx (or XXXXX-PLIIx) which is exactly what my receiver shows when I do so .

PLIIx is overlayed on top of DD or DTS, it's not like the old pro logic. You can have PLIIx on top of THX on top of DTS-ES or DD if you want.

Ahhhhhhhhhhhhh. Now I get it
So when you watch a movie with TrueHD 5.1 or DTS-HD (HR or MA) 5.1, you turn on that PLIIx to get a matrixed 7.1!
That's a good invention.
But it's really a 5.1 Surround Sound with 4 surround speakers.

Because my preamps have dual outputs, I have two left surround signals and two right surround signals, so I never needed PLIIx.

Now here's the question: If you have all seven INDIVIDUAL speakers' sound level matched---say 75 dB, and you use PLIIx (or similar), wouldn't the SURROUND channels be way too loud?
I don't know how sound waves add (or subtract) to each other. But if it were 100% linear (without substraction), wouldn't you theorectically have 150 dB (75 + 75) for your surround left and right?

I guess sound waves will add and cancel one another, but the surround channel levels will now still be much higher than the front channels, right?

 

[AcuDefTechGuy]

Yes, my receiver is THX certified, and I do believe the internal tones aren't reliable, hence my originaly question of how to properly level match the rear surrounds since Avia doesn't have surround back tones.

I can't recall exactly how far off the front and back were when using just the internal tones, but it was significant. Ithink the left and right levels were pretty close it was just the front and back that weren't good.

You say match all channels with avia and forget it, but I can't since avia doesn't have tones for the surround back.

Is it possible that your DVD player is the one at fault, not the more expensive THX certified receiver? Maybe the channels through the DVD player is not all matched?

Personally, I would trust a $1K+ receiver's test tones over a less expensive DVD player. I mean the Avia disc/software may be great, but how can you be sure the DVD player's internal channel gains is not the issue here?

 

[GlocksRock]

Ahhhhhhhhhhhhh. Now I get it
So when you watch a movie with TrueHD 5.1 or DTS-HD (HR or MA) 5.1, you turn on that PLIIx to get a matrixed 7.1!
That's a good invention.
But it's really a 5.1 Surround Sound with 4 surround speakers.

Because my preamps have dual outputs, I have two left surround signals and two right surround signals, so I never needed PLIIx.

When you level match your speakers, you match them one at a time, so each channel is playing at the same volume.

I say you should give PLIIx a try, you say you don't need it, but it's not just playing the same thing through the rear surrounds as what is playing in the side surrounds, nor doesn't make any of the speakers too loud. Say you have a 7.1 setup with surround speakers to the left and right of you, and a rear surrounds behind you, and a helicopter is flying in a circle all around you, when using the PLIIx decoder it creates a stereo surround back (which is why you may want to overlay PLIIx on top of DTS-ES discreet 6.1, it makes the rear channel stereo instead of mono) so the pan is even from left to right and all behind you, you don't hear as much of a jump from the left to the right. It almost makes it so that you don't really need a discreet 7.1 setup... but I would still prefer it.

 

[GlocksRock]

Is it possible that your DVD player is the one at fault, not the more expensive THX certified receiver? Maybe the channels through the DVD player is not all matched?

Personally, I would trust a $1K+ receiver's test tones over a less expensive DVD player. I mean the Avia disc/software may be great, but how can you be sure the DVD player's internal channel gains is not the issue here?

I don't know... I'm using a nice Oppo player using the digital coax output. I'll try playing the avia disc through my xbox 360 which has an optical digital output, and is using a different input on the receiver and see if I get the same results.

And just because it's a $1000 receiver, doesn't mean that it has a good test tone generator... it may have the same tone generator as their low end receivers.

 

[AcuDefTechGuy]

When you level match your speakers, you match them one at a time, so each channel is playing at the same volume.

When using the PLIIx decoder, it doesn't make any of the speakers too loud. Say you have a 7.1 setup with surround speakers to the left and right of you, and a rear surrounds behind you, and a helicopter is flying in a circle all around you, when using the PLIIx decoder it creates a stereo surround back so the pan is even from left to right, you don't hear as much of a jump from the left to the right. It almost makes it so that you don't really need a discreet 7.1 setup... but I would still prefer it.

So in other words, in PLIIx mode, the sound coming out of the Surround Left will be DIFFERENT than the Back Surround Left? If they were to have dialogue in the Surround Left, would you hear the dialogue in both the Surround Left and the Back Surround Left?

 

[AcuDefTechGuy]

Oh, and I hear that sound mixers usually will put "Ambien Sound" in the Back Surround channels and put "Background Music" in the Surround channels.

 

[GlocksRock]

So in other words, in PLIIx mode, the sound coming out of the Surround Left will be DIFFERENT than the Back Surround Left? If they were to have dialogue in the Surround Left, would you hear the dialogue in both the Surround Left and the Back Surround Left?

Yes, re read my previous post that I just edited. As far as dialog in the left surround being played in the left surround back, I don't think it would do that. The PLIIx decoder is actually very good, I'm not sure how they do the algorithms that tell the surround back what to play and when, but so far I've been very impressed.

It might be time for you to switch from all analog inputs/outputs and give your digital inputs/outputs a try using the PLIIx decoder... it will make you want to watch all of your movies again.

And since the surround back channels get used all the time with PLIIx, I want to have them level matched as best I can... hence my original question.

 

[MDS]

Probability that the internal test tones of a THX certified receiver are 'defective' - ZERO.

The AVIA test tones are not only at a different level they are not the same as the THX standard used by receivers (even non-certified). If the purpose is to level ALL channels then you must use a test tone that can play over all channels.

This may seem like an interesting academic exercise but there is a lot of misinformation so far. You cannot calibrate some channels with one tone and others with a different tone. This combo AVIA/internal tone approach is no better than doing it all by ear.

 

[GlocksRock]

So you are basically saying the the tones on the avia disc are no good?

 

[MDS]

So you are basically saying the the tones on the avia disc are no good?

Of course not. They are no good for your purpose - unless you were calibrating a 5.1 system.

 

[GlocksRock]

I think people are misunderstanding what I'm doing.

That's what I was saying before about using avia to level the 5.1 then measure using the receiver... but keeping all the levels the same on the receiver. But I'm getting inconsistent numbers, if I calibrate with avia, then use the internal tones, all the speakers should read the same db, just at a lower overall db. with the receiver's tones... but that's not what's happening.

 

[AcuDefTechGuy]

It might be time for you to switch from all analog inputs/outputs and give your digital inputs/outputs a try using the PLIIx decoder... it will make you want to watch all of your movies again.

Ah, no................I think I will just get another RL-11 and be ready for DISCRETE 7.1

 

[GlocksRock]

Ah, no................I think I will just get another RL-11 and be ready for DISCRETE 7.1

I wish they would hurry up with the discrete 7.1 already, and make it the new mandatory format instead of 5.1. My receiver can handle 7.1 analog inputs, so as soon as either Bluray or HD-DVD wins, and they make an affordable player with 7.1 analog outputs, I'll be good to go... till then I'll stick with what I have now.

 

[tcarcio]

I had the same problem when I set mine up using Avia, so I just used the recievers pink noise to set all the levels. Seems to work fine that way for me.

 

[GlocksRock]

I had the same problem when I set mine up using Avia, so I just used the recievers pink noise to set all the levels. Seems to work fine that way for me.

When you did that, did you go back to avia and see if the levels for your 5.1 were matched? When I did that I get inconsistent results.

 

[Buckeye_Nut]

Glocks,
Are you using a SPL meter? You wont get repeatable results by ear. Also, subtle changes in the orientation or the location of the meter can effect the results.

I think of such variances(Glocks & others) are SPL-meter user error too. Whether or not you hold the meter vertically or horizontally will also make a difference.

My 2 cents.... Use the Yammi Mic as instructed in the manual, and it will level all 7.1 channel SPL levels accurately. Of course....user error can foul up those results too.

 

[GlocksRock]

I'll work on it more later on when I have a chance. Thanks for all the replies.

 

[Buckeye_Nut]

Ahhhhhhhhhhhhh. Now I get it
So when you watch a movie with TrueHD 5.1 or DTS-HD (HR or MA) 5.1, you turn on that PLIIx to get a matrixed 7.1!
That's a good invention.

Yep....it's awesome.

 

[tcarcio]

When you did that, did you go back to avia and see if the levels for your 5.1 were matched? When I did that I get inconsistent results.

Yes, and I ran into the same problem as you. But someone mentioned before that they would trust the reciever first and I felt the same way so that is the way I left it.

 

[patnshan]

Maybe I should just rephrase my question... how did everyone else here with surround back speakers level match them?

I used internal test tones and an SPL meter on a tripod.

Pat