Axiom Home Page Forums General Discussion Home Theater I'm Confused--Dolby? THX? Pro Logic IIx? EX?

I am still on the low side of the learning curve regarding home theater. I have learned from this message board to buy Axiom speakers and the Yamaha RX-V1400 receiver and I am enjoying them immensely with my front screen projector, Denon DVD player with farouja processing, and Comcast HDTV. The hardware seems pretty straightforward.

My confusion concerns selecting the proper sound processing mode in my Yamaha Receiver. What is my best strategy to hear the best sound possible for 5.1 HDTV, DVDs and audio CDs? Should I use THX, Dolby Surround, Dolby EX (whatever that is) or Dolby Pro Logic II and IIx? I can go 7.1 but I have not yet set up rear speakers. I'd hate not to be taking full advantage of my audio system so any help or referral to a good article would be appreciated.

I'll kick this off. THX is more of a certification than an actual processing mode. Put that off to one side.

Dolby Digital 5.1, DTS 5.1

For DVDs there are two 5.1 standards -- Dolby Digital (DD) and DTS. All DVDs must include Dolby Digital although it can be 2 channel instead of 5.1 (surround). DTS is optional. You choose the standard via DVD menu (the DVD, not the DVD player) and the receiver switches automatically to the right mode.

If the DVD you are playing has both give DTS a try, some think DTS sounds a bit better. Both DD and DTS take 5.1 data from the DVD and play it on 5.1 speakers, ie no expansion from 2 to 5 channels etc...

I'll talk about DD 2.0 later.

Dolby Digital EX, DTS-ES (>5.1)

Dolby Digital and DTS both have new modes to support 5.1 and 7.1. I think Dolby EX is the 6.1 DD and DTS-ES is the corresponding DTS 6.1. The receiver will auto-switch into these modes but I think you have to enable them first on a Yamaha. I'm pretty sure it's the same surround "modes" which can take 5.1 content and process it to 6.1 or 7.1.

General consensus seems to be that a good 5.1 system will be better than cutting any corners to get 6.1/7.1, but a 6.1/7.1 system can sound a bit better than 5.1 but you need lots of space around/behind your listening position to get the benefit.

OK, so far we've talked about playing 5.1 DVDs on 5.1 speakers (DD / DTS), 6.1 DVDs on 6.1 or 7.1 speakers (DD-EX, DTS-ES) and 5.1 DVDs on 6.1 or 7.1 speakers (same).

Dolby Pro-Logic II (expanding 2 channels to 5)

Dolby Pro-Logic (PL) is an older surround processing mode, pretty much replaced by PL II (and, I assume, PL IIx). It takes two channel inputs from CD, DVD (the 2 channel track), FM, tape, phone etc..) and synthesizes 5.1 channels by processing the two channels against each other.

Multi-channel sound tracks can be "processed down" to matrix more channels onto a 2 channel recording; most DVDs with 2 channel soundtracks are processed this way and the hidden info can be extracted via PL II Movie mode.

PL II Music mode is intended for stereo input which does NOT have multiple channels encoded down to two channel. In other words, most 2 channel DVDs should be heard using PL II Movie while everything else should be heard using PL II Music.

Logic 7 is HK's proprietary equivalent to PL II Music but was introduced quite a bit earlier. DTS Neo6 is the DTS equivalent. In other words, PL II Music, Logic 7, and Neo6 are all interchangeable. Most people have a slight preference for one of the three but the difference seems to be partly a function of how loud your center channel is set

Again, all of these modes take two channels on DVD or other media and expand them out to 5.1. I imagine you can also go 2 channel to 6.1 or 7.1 but I don't know which mode would do that.

Bottom line :

- you have lots of choices with 2 channel input. Use DD PL II Movie for most DVDs; use DD PL II Music for all other 2 channel input. Try Neo6 as an alternative to PL II Music and use whichever you prefer. If you readjust speaker levels do the Neo6/PLII Music compare again.

- you don't have a lot of choices with 5.1/6.1. Whatever the disk is recorded in is what you play in, but many DVDs have the option of more than one surround mode, selected via DVD menu.

- don't rush into 6.1/7.1. Make your 5.1 system as good as you want first. If your room is too small don't even bother

- if you buy 6.1/7.1 speakers and you don't seem to be getting back channels check to see if you have to enable something on the receiver via remote. If I remember correctly it's one of those stupid "only on the remote" things.

- if the surround modes sound crappy with 2 channel content (CDs) then your speakers may not be matched properly, either different brands with different sounds or the setup levels are not right

- and finally, the listening room probably makes more difference than all this stuff combined. Make the room sound good in stereo first (placement, wall coverings, carpets, etc...) before you start looking for improvements via surround modes.

Enjoy !!

Ok, I'll take a stab at this one, ahhhh, what Bridgman said above

Really, her pretty much covered it all. I will say I like my Pro Logic IIx mode as it makes use of all seven speakers for 2 channel and 5.1 material. I think it is similar to Logic 7 on HK receivers...

good luck, Randy


m60tis vp150 ep350 4-qs8's
Denon 2805
Sanyo Z2 projector
Toshiba P.S. DVD
Samsung OTA HD receiver

Sparky, to summarize some of what John and Randy have said, if you're playing a DVD you'd use Dolby Digital or DTS 5.1, depending on what's available on the DVD. Playing a regular CD, you wouldn't be able to use DPLIIx until you got the speakers for 7.1, since what DPLIIx does is to take 2 or 5 channel material and expand it to the back 6th and 7th speakers. With a 5.1 speaker setup, you should consider making full use of them on CDs and other 2 channel material by using DPLII Music, which takes the ambience naturally present to varying degrees in 2 channel material(no artificial reverberation or anything else is added)and steers it to the surround speakers where it belongs.It also steers sound equally strong in the left and right channels to the center speaker, forming a real rather than a "phantom" center image. You should experiment with the center width and dimension controls on DPLII to get the most pleasing results with various source materials.

>>You should experiment with the center width and dimension controls on DPLII to get the most pleasing results with various source materials.

I had forgotten about them. Thanks !!

I use the rx-v 1500 Yam which is basically the same as your 1400. The room is pretty big. I have a 7.1 config. and use (for movies) dolby PL-IIx mode. It did take quite some time to get the 7.1 mode sounding right. speaker adjustment, db adjustment etc. Also as stated above you must tell (set-up mode) the receiver you are running 7.1 or whatever you decide on. I was very disappointed initally with the 7.1, but now that it is right, I love it. It took some time/tweaking. However, on some material there is no benefit. put in any LOTR, harry potter stuff, and WOW. But again the room size/layout must facilitate 7.1 for it to be worth while. Also if you use PL-IIx and the Yam displays "surround enhanced" this is a normal switch the Yam makes from PL-IIx, and is still providing 7.1 it does it on certain encodings of some DVD's.

Thanks everyone for the valuable information. So when do I ever use THX?

I didn't know you could "use" THX. It's just a rating.

I did hear that there is some sort of high end roll off (or enhancement, maybe?) specified by the THX standard. None of the other modes use it so maybe this option on your reciever turns that on.

At any rate, I'd only try it when watching a Lucas film. George is THX's "daddy".

I don't think you can "use" THX. It started as a set of standards for movie theaters -- there are now versions for home theaters but I would argue it's mostly a gimmick.

Oh, you can use THX--it's just another DSP. I don't really know how good it was, but I'm not overly fond of DSPs in any case. Given that, I use DTS:Neo6 for TV watching, so go fig.

What does it do ? I assume it's "stereo to surround" processing since I've never seen anything "encoded in THX"...

Is there a button for it or something ?

Usually. I'm not sure what it does, as I don't own a THX receiver.

John (and Sparky). This should answer some of your questions.

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I'm not overly fond of DSPs in any case. Given that, I use DTS:Neo6 for TV watching, so go fig.

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Same here... on both accounts... watch stereo (Dolby Digital - have digital cable) program sources in Neo6 Cinema for television and Neo6 Music (pans the centre wider) for music channels, etc.

Bren R.

THX....Besides being a certification which also will do post production automatically, it is also a DSP as mentioned. There are tons of movies that have THX encoding listed on them. Use it on these movies, and your amp will switch to THX-EX(if DD also). This is a tremendous choice for those THX encoded dvd's

That article that Jack linked to explained what I was referring to.

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I did hear that there is some sort of high end roll off (or enhancement, maybe?) specified by the THX standard.

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"Re-Equalization generates a slight roll-off of the high-frequencies in movie audio to compensate for an artificially boosted high frequency used due to movie theater acoustics. Movie theaters roll-off the highs slightly due their design so a little high frequency signal boost is applied to compensate, however, that boost is not need in a home theater resulting in an overly bright sound."

I think this is the only audible difference between THX and DD.

Just a quick comment on ProLogic II. I would disagree that you need a 6.1 or 7.1 set up to benefit from this. My kids love it when I pop in one of their pop/dance/house thumping CDs (2 channel) and I set the receiver on Pro Logic II or DTS Neo 6. Even though I have a 5.1 set up, the sound is a nice improvement over the 2 channel version.

So I would say that even with a 5.1 set up you will hear a nice, positive impact using Pro Logic II or DTS Neo 6.

Personally, I LOVE DTS. I have been using DTS for about 6-7 years, back when not many people knew what it was, so I am a little partial to the DTS Neo.

As for THX, it is supposed to be just a certification, like other have said, of a certain level of ability for a piece of equipment to meet some fiarly strict (depending on the level of THX - Select, Ultra, Ultra2) guidelines in that equipment's (receiver, speakers, and so on) ability to reproduce sound. With that said, you will find some receivers that have a THX Cinema (or something similar) DSP mode. I have not looked to see what benefit it has being a DSP mode, but if the hardware can handle THX, it should be able to reproduce a "fuller" sound spectrum than a non-THX piece of hardware. I think that the THX DSP mode just tried to compensate for sound nuances that are often lost in the recording, or in the average home set up. To me, the THX DSP is just one system's estimate of what you may want to hear. I like the more "true" modes like Dolby Digital, and DTS for movies, although like I mentioned above, I do use some others to create simulated sound for my center, rear, and sub channels.

Last note, you should get something that can handle 7.1 and DTS (Dolby Digital is always included, and DTS is there on any good quality receiver, and on some cheap junk). THX will be there if you start getting into the $500+ market for a receiver. Not all will have it at that price, but you will start to see it.

Since I was starting from scratch, I went with a THX Select receiver that could handle 7.1 and DTS. I figured if I was finally getting some nice speakers like Axioms, I should have a nice receiver too, and the THX certification just means a little piece of mind to me in sound quality.

Now, you could go all out and get THX certified speakers too, but why would you want to with great products like Axioms.

THX Surround is closely related to Dolby Digital...

http://www.thx.com/mod/techlib/surroundEx.html?print=1

...so I guess technically it is a format. I have seen some AV receivers with the THX Surround logo (I believe it was a Kenwood). Whether or not there's a difference between the two, I don't know.

nickbuol Wrote:

Personally, I LOVE DTS. I have been using DTS for about 6-7 years, back when not many people knew what it was, so I am a little partial to the DTS Neo.
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I'm in the same boat. I used to surf the DTS website and special order DVDs that were formatted in DTS that weren't being sold in stores. I remember getting Saving Private Ryan in the mail and testing it out in both DD and DTS and the difference was HUGE!!!

As asked earlier, the difference B/W DD and DTS is the compression ratio. DTS provides higher fidelity than DD because the format only uses 1/16th compression whereas DD uses 1/4th compression. That is also why when you start a movie in DTS, you have to turn down the volume because it plays much louder. The lower compression ratio as explains why earlier DVDs formatted in DTS did not include any extras due to lack of disk space, but that was years ago and things are different now.

To this day, I look on the back of a DVD to see if it was formatted in DTS and if it was, it is a HUGE purchasing criteria, even if I wasn't necessarily interested in the content of the movie.

The Eagles "Hell Freezes Over" DTS DVD is a GREAT DVD to showcase your system.

DTS all the way...DD is too soft (fidelity wise) in comparison.

Now having said all of this, there are DTS mixed DVDs where the engineers did a horrible job of mixing and there is no real difference b/w either DD or DTS...these are usually the movies that include both a DD and DTS soundtrack.

Find the movies that are strictly DTS format and you can be rest assured that the mix will be amazing.

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As asked earlier, the difference B/W DD and DTS is the compression ratio. DTS provides higher fidelity than DD because the format only uses 1/16th compression whereas DD uses 1/4th compression.

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Actually, DTS tracks do use a higher bitrate than Dolby Digital - as for exact numbers, there are flavours of each and I've never really seen hard evidence (due to secrecy and closed doors in both camps) of exact numbers. Where did 1/16 and 1/4 come from? And what are those fractions of? Full 44.1K/16 PCM audio? DTS, Inc. and Dolby Labs use different models for compression - in the beginning, yes, DTS took up a lot more DVD real estate for its audio tracks, but most of what you have on the market now is the lower (some call it "half") bitrate DTS encoded audio stream. That way you don't have to give up the 4 audio programs of Director's Commentary and the 8 extra hours of footage shot "Behind the Scenes" with a DVX-100 so they can put a starburst on the front of the packaging that says "Wow! 8 Hours of Previously UNRELEASED Footage!"

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That is also why when you start a movie in DTS, you have to turn down the volume because it plays much louder.

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From an engineer's standpoint, a higher resolution digital audio stream cannot play any louder than a lower resolution stream. 0dBFS is the same digital ceiling (at which clipping occurs) whether the source material is raw PCM, DD, DTS or even a Windows Media file. DTS simply cannot play louder because it is DTS. It can be compressed - which reduces dynamic range in a recording in order to make the entire recording louder on average (This is a pretty good layman's description of compression)

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The lower compression ratio as explains why earlier DVDs formatted in DTS did not include any extras due to lack of disk space, but that was years ago and things are different now.

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This is pretty accurate, I'd add that DTS compression in the early days was the full bitrate flavour and dual-layer DVDs were not yet common.

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To this day, I look on the back of a DVD to see if it was formatted in DTS and if it was, it is a HUGE purchasing criteria, even if I wasn't necessarily interested in the content of the movie.

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Again, something that seems odd... not to poke a thumb in your eye, but I've never picked up a book and decided to read it based on the fact it was typeset in Caslon on Weyerhauser Cougar Opaque stock. For me, I guess the medium isn't the message, the message is the message.

Bren R.

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Actually, DTS tracks do use a higher bitrate than Dolby Digital - as for exact numbers, there are flavours of each and I've never really seen hard evidence (due to secrecy and closed doors in both camps) of exact numbers. Where did 1/16 and 1/4 come from? And what are those fractions of? Full 44.1K/16 PCM audio?

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That is what I remembered reading on the 'old' DTS website, for which I surfed before making my post to make sure those numbers were correct, but they completley revamped the site and I was unable to find it. As far as the technical details on that claim, they did not list the details, just the compression comparison of 1/4 to 1/16th.

As far as DTS format being louder...I guess I mostly notice it in the older DTS formatted DVDs, but whatever makes the sound seem louder, I know that I have to move the volume down a 1/4 inch when changing over from DD to DTS *shrugs in ignorance*

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That is what I remembered reading on the 'old' DTS website, for which I surfed before making my post to make sure those numbers were correct, but they completley revamped the site and I was unable to find it. As far as the technical details on that claim, they did not list the details, just the compression comparison of 1/4 to 1/16th.

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Unfortunately both companies are making it difficult to compare apples to apples, and it works in DTS Inc's favour. Most people, myself included, prefer the sound of a DTS-encoded soundtrack - though no one can seem to put their finger on quite what sounds better about it.

Doing the math on 5.1 PCM audio - 6 discrete channels at 44.1/16 gives you a bitrate of 4.25MB/s, and if the claims above are true - that DTS uses 4:1 compression (encoding compression - not compression/limiting) - means they use about 1.06MB/s for what you hear on a DTS track. At 16:1 compression Dolby Digital would be using 0.27MB/s for their track. Since Dolby Digital sounds better than 1/4 as good as DTS, that would be proof that Dolby Labs' compression model is better than DTS' at a given bitrate.

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As far as DTS format being louder...I guess I mostly notice it in the older DTS formatted DVDs, but whatever makes the sound seem louder, I know that I have to move the volume down a 1/4 inch when changing over from DD to DTS

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Which makes perfect sense if you're listening to a heavily compressed (now we're talking about compression/limiting) source - the loudest parts of the source still can't be any louder than an uncompressed source, but the average levels of the source are higher.

Dolby Labs really started the whole "compressed audio" evil with Dolby A Noise Reduction on cassette tapes. If you make the average level on a recording louder, you get a better signal to noise ratio (against tape hiss), and when the tape is played back in a Dolby A capable player, it has expander technology in it to pull the dynamic range back to somewhere near what it was.

So in an orchestral recording, your quiet flute upon recording would be forced up to, say twice it's actual loudness (which doubles the signal to noise ratio - the inherent noise floor of magnetic tape stays constant, but the program audio level is doubled) - then when the tape is played in a Dolby A deck, it's "expanded" to fill the dynamic range again (which in effect, gives you less "divisions" of range, but it cleans up the hiss, wow, flutter, etc)

Sadly I think the "engineers" of today listening to Dolby A Noise Reduction on non-Dolby equipment has led to the push to see how big they can get the "wall of sound"... how many times have guys here complained about digital clipping on new albums - Norah Jones was a big culprit from what I remember. Whether it's old analog guys assuming they can squeeze maybe just a dB or two of headroom out of a digital master (the answer is NO - there is NO headroom on a digital presentation) or if it's just the career-college mass-produced ProTools jockeys that have scuttled into the industry like cockroaches - audio mixing and mastering has suffered.

As much as I hate arena/prog/classic rock - the 70s Todd Rundgren era still exhibits some of the best engineering ever. I'm going to go wash my mouth out with soap now.

Bren R.

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Doing the math on 5.1 PCM audio - 6 discrete channels at 44.1/16 gives you a bitrate of 4.25MB/s, and if the claims above are true - that DTS uses 4:1 compression (encoding compression - not compression/limiting) - means they use about 1.06MB/s for what you hear on a DTS track. At 16:1 compression Dolby Digital would be using 0.27MB/s for their track. Since Dolby Digital sounds better than 1/4 as good as DTS, that would be proof that Dolby Labs' compression model is better than DTS' at a given bitrate.

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That probably explains why DTS now advertises a separate 96kHz/24 bit encoded disks...a format I haven't heard yet. Figures that they are now essentially admitting to the now lower bitrated sampling their basic logo represents on current DVD releases which have both DD and DTS available. I guess now I have to look for DTS 96/24 to know that it is a higher bit rate than DD.

I absolutely agree that in as little time a four years, digital mixing has gone to hell in a hand basket and it is now rare to find a well-mixed DVD.

I will give it to Disney however, as their THX certified DD disks always sound incredible!