# THX listening modes



## THX-UltraII

I just found out that on my AVR I can only get *Audyssey FLAT* by using a THX listening mode and disabling RE-EQ. What happens when I select Dolby PLIIx THX Cinema, Neural THX Cinema, THX Cinema or THX Ultra2 Cinema when a Dolby Digital or Dolby TrueHD track is running and what happens when I select DTS Neo 6 THX Cinema, Neural THX Cinema, THX Cinema or THX Ultra2 Cinema when a DTS or DTS-master track is running?

No, I m not looking for an explanation what THX is, I want to know what the DSP does in this mode. Are there any delays applied etc etc?


----------



## Jungle Jack

THX-UltraII said:


> I just found out that on my AVR I can only get *Audyssey FLAT* by using a THX listening mode and disabling RE-EQ. What happens when I select Dolby PLIIx THX Cinema, Neural THX Cinema, THX Cinema or THX Ultra2 Cinema when a Dolby Digital or Dolby TrueHD track is running and what happens when I select DTS Neo 6 THX Cinema, Neural THX Cinema, THX Cinema or THX Ultra2 Cinema when a DTS or DTS-master track is running?
> 
> No, I m not looking for an explanation what THX is, I want to know what the DSP does in this mode. Are there any delays applied etc etc?


Yep. I am not sure why Onkyo does not offer a Flat Curve for general use. I am grateful that THX mandates a Flat Curve. To get the Flat Curve on a DTS-HD track, just engage THX Cinema. And I always disengage ReEQ anyway so it has never bothered me, This situation has been well known for years.


----------



## THX-UltraII

But what is actually done by the Onkyo when THX mode is selected? I know what THX is and that is sets certain standards for bigger rooms etc. but like I want to know what (technically) happens in the Onkyo AVR when selecting a THX mode. eg. are there extra delays or something applied to channels?
I don t mind running the THX mode if I can get the FLAT Audyssey curve with it but I do want to know what happens in this mode. Also there s the LPF of LFE setting which in a 5.1 setup you want to have on 120Hz instead of the standard 80Hz (THX) setting. I HAVE it on 120Hz but maybe this setting also gets changed automatically to 80Hz (THX) when running in a THX listening mode. 
btw (for the ones that don t know this): this last setting I am talking about (LPF of LFE) is NOT the Xover setting of the mains/sub! This setting affects only the bass of the LFE signal and has nothing to do with the Xover.


----------



## THX-UltraII

No ideas anyone?


----------



## Jungle Jack

Check out this 6 Part Series:http://www.hometheaterhifi.com/volume_13_1/feature-article-thx-1-2006-part-1.html
LPF of LFE should be set at 120hz and only older Onkyo's use an 80hz default if memory serves. I have recommended to untold Onkyo Owners in the past to change this during the initial setup. Engaging a THX Mode does not change this. Also, there is not added delay with THX Cinema. 

However, THX keeps much of their Post Processing Technology proprietary. The Secrets link I gave provides the best overview I have come across. Just trust your ears in respect to whether or not you like what it does.
I do use THX Modes to get an Audyssey Flat Curve and I have always disliked ReEQ so disengaging it to get the Flat Curve was never a sacrifice for me.


----------



## THX-UltraII

> LPF of LFE should be set at 120hz and only older Onkyo's use an 80hz default if memory serves. I have recommended to untold Onkyo Owners in the past to change this during the initial setup.


I knew this but thanks.



> Engaging a THX Mode does not change this


THIS is important and good



> Also, there is not added delay with THX Cinema.


not sure about this. Will explain later in this reply



> I do use THX Modes to get an Audyssey Flat Curve and I have always disliked ReEQ so disengaging it to get the Flat Curve was never a sacrifice for me


ReEQ does something similar like the Audyssey Reference curve which is roll-off the higher frequencies if I am correct. This is exactly NOT what I want/need in my professionally acoustically treated HT room.

Interesting article that you send me. There are some important things clarified there:

_- All THX Controllers include one or more THX modes which are NOT surround sound decoding schemes or codecs. When engaged, the THX modes apply a set of processes or filters to the soundtrack AFTER it has been Pro Logic, Dolby Digital, or DTS decoded._

I ve also read the enable a THX mode includes a few processing things done (after the DTS-MA or TrueHD decoding like I learned):
*1. Re-Eq, or ReEqualization*: This is not a problem because this can be disabled in the Onkyo TX-SR876
*2. Adaptive De-Correlation / De-Correlation*: from what I read in the article you send me some processing is done to the surround channels whenever the surround channels receive the exact same information at the same time. This option cannot be turned off in the TX-SR876.
*3. Timbre Matching* This applies a generic HRTF (Head Related Transfer Function) to reshape the surround sound speakers' sound so that it is a closer match to what we hear from the front channels, closing the "seam" between the front of the room and the rear. This option cannot be turned off in the TX-SR876 either.
*4. 'override function'*: _Part of the THX Cinema mode is that it "overrides" any superfluous alterations of the program. For example, if bass or treble controls have been engaged, or an alteration made to the level of a speaker (outside of the master calibration), any such "impurities" are zeroed out whenever the THX button is pressed, assuring you that the movie is in fact being presented as it should._
This would mean that the levels that Audyssey set are disabled and set to 0!

These are the 4 things that I ve found it the article that are done as for processing when you enable THX cinema mode. Like I said RE-EQ can be disabled but Adaptive De-Correlation / De-Correlation, Timbre Matching and the 'override function' cannot be disabled. Maybe even more processing is done when engaging THX cinema mode in my Onkyo TX-SR876........ 
So what I want to find out, and I think I can only find this out by getting in contact with the engineers of Onkyo I think, is WHICH processing is done when engaging THX mode. Maybe you would ask why this is so important. Well, I ultra-finetuned my SPL response and time alignement of my entire system with REW and a cross-spectrum calibrated mic and the THX processing COULD mess this up I think.


----------



## Jungle Jack

Hello,
Glad you enjoyed the articles.. Exactly what you write of is why is always try to make the distinction of THX being Post Processing. However, with Onkyo AVR/SSP's it is the only way to get an Audyssey Flat Curve.
J


----------



## THX-UltraII

When using an AVR only as processor as I do (I own a separate 5-channel amplifier), do you think that it is a smart move to go from the Onkyo TX-SR876 to a Denon 2809 (which has Audyssey XT like the Onkyo but does have the opportunity to choose FLAT). I ask this because I can make a deal by trading my Onkyo for that Denon.


----------



## Jungle Jack

THX-UltraII said:


> When using an AVR only as processor as I do (I own a separate 5-channel amplifier), do you think that it is a smart move to go from the Onkyo TX-SR876 to a Denon 2809 (which has Audyssey XT like the Onkyo but does have the opportunity to choose FLAT). I ask this because I can make a deal by trading my Onkyo for that Denon.


I do the exact same thing, but use a 3008. However, due to my speakers dipping down to less than 1 ohm, I could not use the AVR if I wanted to. Provided you have even reasonably easy to drive speakers, the Amplification Stage in the Onkyo is in a whole different league than the Denon in the event you should ever need to send in your 5 Channel Amplifier for repair.

In addition, the 876 has a better Video Processor in Reon and you can get around the Flat Curve with the Onkyo and ReEQ is the most noticeable change to me when THX is engaged and can of course be defeated. If it was a newer Denon, I would be more inclined to say yes, but given it is around the same age it is mostly a downgrade.
Cheers,
JJ


----------



## THX-UltraII

I don t any features on the Onkyo like video processing etc. Also the amplifier part does not bother me (IF my NuForce amplifier ever goes into repair, I can live with the Denon for a few weeks). So in my case I would not downgrade at all am I? I will only benefit from the Denon that has Audyssey FLAT as manual option. 

EDIT: I just checked the Denon 2809s manual. I can t find anything about a LPF of LFE setting. Would this assume that the Denon sets this by default on 80Hz and cannot be changed? If so, the Denon is a no-go if you ask me.


----------



## THX-UltraII

From the Onkyo TX-SR876 manual:

_*THX Cinema*
In this mode, THX Loudness Plus is configured for cinema levels and Re-EQ, Timbre Matching, and Adaptive Decorrelation are active._

Louness Plus and Re-EQ can be turned off but Timbre Matching and Apaptive Decorrelation cannot...... So it s going to be the Denon I think......


----------



## jaddie

THX-UltraII said:


> ReEQ does something similar like the Audyssey Reference curve which is roll-off the higher frequencies if I am correct. This is exactly NOT what I want/need in my professionally acoustically treated HT room.


ReEQ is pretty much the same as the Audyssey Ref curve, and similar in purpose. 

This is a rather incomplete explanation of Re-EQ, but it comes from THX:
http://extranet.thx.com/technologies/reeq.html

And something about the Audyssey Ref curve...note a vague similarity:
https://audyssey.zendesk.com/entries/94162-multeq-target-curves

You do realize the guy who invented THX, and invented THX Re-EQ is one of the founders and a former director of Audyssey, right? The point of the Audyssey curve is that if you don't have a THX processor or AVR, you still might need Re-EQ, so he put it back into Audyssey, which is why there's a funny glitch sometimes in THX receivers where they're trying to avoid applying both at once. 

Here's an explanation of why we may NOT want Re-EQ (or the Audyssey Ref curve), and a better explanation of why it became necessary in the first place:
http://homethaternews.blogspot.com/2011/04/update-on-re-equalization.html

What's wrong with your statement is that you are saying you wouldn't need either Re-EQ or the Audyssey Ref curve because your room is professionally acoustically treated. The need for Re-EQ actually has nothing to do with the fact that your acoustics are treated, it has to do with room size and the fact that films are mixed in theaters with the X-curve, which was an attempt at pulling the large-room-sound into parity with small-room-sound. But the X-curve, standard though it is, is just a little bit wrong! Anyway, the last link above X-plains the X-curve and Re-EQ problem, and why it's a mess today, and why, at least in some cases, you might still want it.

On a personal note, I first tripped over the need for Re-EQ back in about 1983, setting up a surround decoder I built (there were no commercial decoders for home use). I found that all film soundtracks of the Laser Disc era sounded too bright at home, and built an equalizer, tuned by ear, that fixed it. Back then you needed it for all soundtracks, no question, and the need didn't start to go away until quite recently.

Last note, turning on THX processing does not disable Audyssye's room cal, it just disables the Ref curve because of the availability of Re-EQ. At least, that's the idea.


----------



## jaddie

THX-UltraII said:


> Louness Plus and Re-EQ can be turned off but Timbre Matching and Apaptive Decorrelation cannot...... So it s going to be the Denon I think......


The original Tambre Matching idea was to be built into _speakers_, not the processor. I found it strange, and misguided of THX to build it into a processor without a bypass, because what happens if you have tambre-matched THX surround speakers? Double-tambre matching creates non-tambre matching. Should be defeat-able, but it's not. Fortunately most people don't have tambre-matched surround speakers, so in general it's ok to leave it on.

Decorrelation was always in THX processors, and stemmed from the problem of playing the old 4.1 sountracks (Dolby Stereo had a mono surround channel), in small rooms. Large theaters had many surround speakers, thus even a mono surround track created a diffuse field effect. In the home, a mono surround pops to the surround speaker you are sitting closest to. Decorellation simply made the Ls and Rs outputs dissimilar using a very slight pitch bend, just enough to make them impossible to correlate into a phantom mono signal localized between two speakers. Adaptive decorellation, at least in theory, applies decorellation where necessary based on surround content. It's a way of doing decorellation only when needed. It's OK to leave it on.

Yes, turn of that Loudness Plus thing. Not done well, and without regard for specific SPL. Audyssey Dynamic Volume and Dynamic EQ are much better, and know the specific SPL at any given moment, and respond properly. Both set out for the same purpose, Audyssey did their homework.


----------

