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.