If DVD's have DD and/or DTS soundtracks, what is the purpose of selecting THX as a surround mode on a THX certified DVD? Would it sound any better than say a DTS soundtrack? Does one need THX certified speakers? I have a THX Ultra receiver if that makes any difeerence.

Tom: very good question; one I've asked myself. I haven't got a clear-cut answer yet, but I can tell you from my own experience....

I have a friend who owns the Onkyo TX-DS989, also Ultra rated. This guy actually lives in a house (what a hassle!) It has a THX surround mode and an EX surround mode that kicks in when you hold the surround button down during a THX-EX enhanced movie.

I find repeatedly that DD5.1 and DTS both sound a heckuva lot better than this THX mode. It's like the THX mode is "fake" like "hall" or "disco". When THX is selected, the sound level drops way down, and there is far less surround effect. This is particularly noticeable on a powerful soundtrack like "Gladiator".

If there are THX-certified speakers, I don't think it matters. TheDude

This message was edited by StreetDude on 11/12/01 08:39.29.

You do not need THX cert speakers. Although you obviously need good speakers.

In a receiver, THX actually does a little processing now. Re-Eq is a THX process for reducing brightness that is inserted into a THX recording to compensate for the dynamics of a movie theater. Assuming your home theater isn't the same size/shape, the extra brightness (emphasized highs) is not useful. I believe there are some other tweaks as well. You could try www.thx.com for info.

You may just hear the emphasized highs without THX decoding on and think it sounds better. Or maybe your calibration is off for THX purposes. As for the overall sound level dropping, can you compensate simply by turning it up?

Spiky: No and no.

Everything is changed in THX mode, from LFE on up to the top. Cranking up the volume only.... well, cranks it up. The surround channel effects are noticeably inferior and far less directional. My salesdude, who truly does have a lot of intelligent experience in this area, says he doesn't like it and doesn't use it.

I think what's happening here, and this is what I can't find out about on THX's website or anywhere yet, is that this is just a mode: it has nothing to do with what the soundtrack is recorded in. Here's an example: a DTS movie or DD5.1 movie may have a THX setup, but it never says that the movie is in DTS-THX surround. ... Mike

What we are really looking at here are two separate things:

1) The THX logo on the sleeve of a DVD
2) THX certified equipment

The confusing thing is they are actually two are completely different issues!

In effect when you see the THX logo on a DVD, it’s only indicating that the disc has been through a set of THX quality control steps. This should guarantee (supposedly) that the quality of the picture/audio reaches a certain set standard. If you really want to know each element that is measured check out [Link: thx.com]

Actual equipment that is certified as THX is a more complicated issue. If we look at just amplifiers for instance... They must also reach a certain standard in their specifications, but in addition they also offer THX post processing which, yes, is really only another 'mode'. However this is REALLY over simplifies what the processing does.

I really don't want to get technical and besides, all the info can be found on THX website [Link: thx.com]

Here's a quick summary of the main elements the processing encompasses...

Re-equalization
Timbre Matching
Adaptive Decorrelation
Bass Management

The main one most people notice is the re-equalization, which progressively rolls off the treble upto about 5db at it's extreme. If you do any A - B comparisons, this of course seems to remove detail (especially if you swap between modes mid film), but really only places the treble further down in the 'mix'. I've always found you can actually play a soundtrack much louder with THX engaged because of this!

As a test, just try listening to a whole track with THX and then without. I usually find on a lot of movies, when THX is engaged the overall sound, especially panning effects seems to 'gel' much more believably/smoothly. Any thoughts on this?

Overall, it really comes down to a matter of personal choice (as ever!). If you like it, great, if you don’t just switch if off ;-)

This message was edited by Phil Clelland on 10/07/01 08:54.54.

Phil, You seem to to be knowledgeable on this THX issue, so I wanted your opinion regarding receivers. I am in the process of upgrading to either the Yamaha RX-V1 or the Denon 3802 and trying to decide which one is better. Any insite on these two?? Thanks, Julian

Hi Julian,

Sorry, I haven't had the chance to listen to either of the two you listed. I'm currently using a Denon AVC-A10SE (but only using it's onboard amps to drive the rear channels, the fronts are ouput through my Hi-Fi amp).

Your best bet would be to get a demo of the two at a local dealer (maybe even a home demo) and see which you prefer and suit's you need best. You could also try a post on the Home Theater forum, I'm sure someone must have tried them side by side and could give you their thoughts/advice.

Good Luck,
Phil.

Phil - I was hoping to draw again on your THX knowlegde. I have a new Sony STRDB 1070 - not sure if you know the model or not BUT yuo might be able to help me with a THX question.

It has no THX logos or stats on it whatsoever. Sony do not advertise it as having DD THX 5.1 EX decoding capabilities - but it is a 6ch amp.

Now I was cool with this thinking it was just standard 5.1 processor. But when I put my new Star Wars Episode 1 DVD in and select THX set up the 1070 perfectly decodes 5.1 EX through the centre rear during the 'Phase' test.

The little fine print down the side says "EX system - sound shuold come from Centre rear only when in phase and surround rears when out of phase". This happens like this on my system when I have "6.1" selected.

My question is - does this mean the 1070 definately has EX decoding or is it the Sony 6.1 DCS directing the THX center rear channel by co-incedence ?

Thanks in advance for you help if you know.
Craig

Craig, the fact that the proper channel steering depends on proper phasing of the rear channels indicates that the rear signal is not that of a discrete channel. It is similar to the use of a DPL decoder in 3-channel mode in the rear channels to extract a rear-center.

To answer your question, it's not coincidence; it's doing exactly what it should be doing. I have the setup I described, with a DPL decoder, and my playing with the THX tools on my Star Wars, Episode 1 disc did exactly what yours did: produce a rear-center sound separate from the side surrounds.

Larry

Larry - one last question if I may.

I understand that it is doing what it is meant to (as nicely explained by you above). What I need spelled out for me is : Does that mean my reciever has a genuine 5.1 EX decoder in it ?

Or is it just that the Sony DCS system is producing the same results.

Reason I ask is because Sony do not claim Dolby(THX)5.1 EX decoding for this machine !

Hope I dont sound stupid here.

Craig, don't worry, stupid has no sound. : - )

If by EX, you mean an actual discrete sixth channel, I doubt it. It's probably being extracted, as in my setup. I tried the Gladiator DVD which has a discrete rear-center channel in DTS, and I heard - nothing at all! I had to use DD to get sound.

I don't know your particular unit, and your manual would be the best source of info, as would Sony tech support.

Larry

Man, this thread, and many other similar ones posted here at Remote Central, make me think that our toys are getting too complicated and that the manufacturers are doing a very poor job of explaining the AV whiz-bang technology de jour.

It’s no wonder that most folks in my age range (old) are still using their TV speakers.

I have every light in my house controlled by a JDS X-10 controller, my AV gear is controlled by a JDS IrXpander, I have a HT with a Sony XBR Wega, five AR speakers and a Velodyne sub, the first computer program I wrote was in 1961 in machine language for a vacuum tube computer that UCLA had– it was obsolete and non-functional at the time but at that time, one wrote programs with pencil and paper – and I have been dinking around with small computers since 1984 and ran a BBS for nine years, so while I am far from an engineer, I sure don’t consider myself a technophobe either but I don’t understand half of the AV acronyms I read.

Not only don’t I understand what all the acronyms stand for, more importantly, I don’t what the features are that they stand for (someone, perhaps Noel Coward, once said that ‘A preposition is okay to end a sentence with’).

And while I am on my soapbox, I think that Sony, and probably other manufacturers (I only own Sony equipment), do a dreadful job of explaining what the considerations are in selecting options for the setup for their equipment in their manuals. What’s the use of a feature if they don’t explain its use?

I suppose this topic, assuming anyone cares to pursue it, deserves a new thread.

Cheers, Jim.

I go to www.audioreview.com to get many opinions on equipment.

Jim, I have to agree with you about Sony. I have a sony receiver, cd changer and wega TV and love them. But their operator manuals are just horrible! Who writes them? It seems like I have to read the manual several times and in the end I have to wing it to get the best quality out of it because its not explained well in the manual.

Anyway, not to get off track. I read and have been told by people in hi-fi audio stores that THX is not a soundfield at all. Like Phil, said its just a certification. Which means that if you have THX certified equipment and THX certified DVD that you are getting sound pumped out to you the way it was meant to be heard (ex. same sound as if you were in a theater).

This message was edited by JohnY2050 on 06/19/02 20:44.35.

John,

Actually, no, it's not just a certification. As Phil mentioned above, "certification" only applies to equipment. The confusion factor is that the term THX is used in so many ways. As Phil also stated, a quick summary of the main elements the THX _processing_ encompasses includes Re-equalization, Timbre Matching, Adaptive Decorrelation, and Bass Management.

To paraphrase your statement above: "This means that if you have THX certified equipment and a DVD with a THX soundtrack, you are getting sound pumped out to you the way it needs to be modified for a home listening setup, to replicate the original theater soundtrack engineer's intentions as closely as possible, given the limitations of the standard HT setup."

You cannot get the "same sound as if you were in a theater" without a number of additional speakers and a source that provides appropriate signals to those extra channels. Even then, you might find that you didn't like the sound because of the size and furnishings in your listening room...

A "THX" label on a DVD indicates that the material on the disc contains a soundtrack which has been _processed_ using the THX standards mentioned above.

THX equipment _certification_ is an entirely different issue. It means that the equipment in question meets the THX standard for that type of equipment. Examples: A THX surround speaker must be able to pump 80Hz - 20KHz at a consistent 95 decibels; a THX amp must be able to drive a THX speaker to that level with no more than a certain level of distortion; etc.

You do not need THX certified equipment to play a disc with a "THX processed" soundtrack. Larry's system is a classic example: As far as I know, none of his excellent components is THX certified.

Similarly, there is no reason why THX certified equipment cannot play a DVD that is not "THX processed." DTS discs, non-THX Dolby Digital discs, etc. play just fine on THX components.

Whether the receiver can handle the disc format (as when Larry played the Gladiator DVD) is not a function of whether the receiver is THX certified, only what options it offers.

I hope I didn't just add to the confusion :) -Bruce