I'm just curious because all the DTSES DVDs say 5.1 compatible. What do I lose not having that extra rear? or do I lose anything?
Thanks

The sounds from the rear center channel speaker(s) is mixed into the right and left rear channels, meaning you will still hear the sounds from the rear center channel, you will just lose the directionality of the sound eminating from directly behind you, and it will come from your exisitng surround speakers.

Thanks. The main reason I was asking is that I was actually considering buying a EX/ES receiver despite being really low on cash. I'll wait. Thanks!

Not exactly true. With EX/ES you have:
LEFT SIDE (= REAR in Old DD.5.1!)
RIGHT SIDE (= REAR in Old DD.5.1!)
LEFT REAR
RIGHT REAR

In order words: if you play a non EX/ES-title in DD5.1 mode, only the sides will be used assuming that your receiver doesn't have a mode to 'fill' the rear channel. If you play a non-EX/ES-title in EX/ES-mode you can get unpredictable results (which are sometimes nice but other times crappy).

Mark

You know, I think I'm going to wait at least until next year to see if 6.1 sticks around. I don't think it's worth investing right now. I don't want to invest in a dying/dead format.

I don't think 6.1 is going away. There's just a lull with titles not being released that way. Look at the theatrical releases with 5.1EX or 6.1 and there's not many coming up right now. I guarantee that The Phantom Menace will be EX and the Indy and SW Trilogies could be too. Cast Away will be EX, The Mummy Returns is likely to be EX, etc.

Look at how many titles are available in 5.1EX or 6.1 and it's more than you think. I think it's support will be similar to dts from a couple years ago. Back then, there were few titles with dts sound. Now there's tons more.

Also the equipment will be getting cheaper. I wouldn't make the move to EX for at least another six months to a year. This way the DTS discreet stuff gets straightened out and the prices will begin dropping. Then there's Pro-Logic II which will help out the older Dolby Surround titles. Give the companies time to make the gear to do all of it.

Most EX/ES receivers have the option of using the EX speakers like a second set of rear speakers for 5.1 material. Instead of one Left Surround you have two. That's what the Onkyo 989 does and I'm sure others do too.

[Edited by William Ward on 03-21-01 at 11:26 AM]

I was under the impression that Dolby mixes the sounds from missing channels in with the ones you have. dts on the other hand doesn't - you only get the channels for the speakers you have, no mixing in... is this right?

What's not true? I never mentioned anything about speaker configurations, and the assumption was made that only EX/ES titles were being discussed.
Also, there is no mandate that there <i>has</i> be two rear speakers used for the rear center channel. One or two speakers is the option. And considering the fact that regardless of how many speakers you use, it's still <b>one channel</b> for the rear, be it discrete or matrixed.
THX recommends two speakers for EX/ES use, but most of THX's other recommendations for HT are crap, so take it as you wish.

You said "meaning you will still hear the sounds from the rear center channel" which is not true for non EX/ES-titles but is true for EX-ES/titles.

About the mandate for two rear channels: that's NOT TRUE! With this information you can confuse someone who doesn't have technical knowledge.

"The Surround EX® Factor...

The latest addition to the THX family is an enhancement to Dolby Digital and DTS 3/2.1 (commonly referred to as "5.1") soundtracks known as Surround EX.
Surround EX is fully backward-compatible with both Dolby Digital and DTS. An additional channel known as Surround Back is matrix encoded into Surround
Left and Surround Right, which undergo a +/- 45º phase shift. The channel is recovered using a matrix similar to Dolby 3 Stereo.

In the home, official Surround EX processing will be limited to THX products (processors and receivers) and there will not be add-on boxes for existing hardware, no matter how many inputs that hardware may have. Products from ADA and Circle are not strictly Surround EX compliant.

Two Surround Back channels are used; while both carry monaural information, they can be individually time aligned and bass management applied accordingly. Surround EX processing is only available within the THX Cinema mode, in which case adaptive decorrelation is disabled and re-equalisation applied to the Surround Back channels as well as the Centre.

The Surround Back loudspeakers are placed behind the listening position with the Surround Left and Surround Right ‘speakers to either side of the listening position. THX suggest dipoles for all four, arranged so that adjacent drivers are in phase, but monopole Surround Back loudspeakers could be used as a compromise for upcoming discrete music formats such as DVD-Audio and SACD."

(source: http://www.smr-home-theatre.org/Interface.html)

Pay attention to: "Two Surround Back channels are used; while both carry monaural information, they can be individually time aligned and bass management applied accordingly."

And for just in case you didn't know: EX is actually called THX Surround EX so you can think whatever you want about THX, but EX is part of their standard!

Mark

PS. It seems that you are offended or something. Don't take everything so personal.

Mark, I'm not offended by anything you said at all, don't assume so much. ;)
To clarify what I said in my initial post:
<i>"meaning you will still hear the sounds from the rear center channel"</i>
This is TRUE. Myabe I wasn't clear on my explanation, but since I was trying to eliminate technicalities from my explanation, I guess maybe I should have stated that you <i>will</i> still hear the sounds that were mixed for the rear center channel. If you only have a 5.1 set-up (meaning controller/receiver and speakers), and you put in a 6.1 title (let's say Gladiator, for example) you will NOT lose the rear center channel's worth of information from the soundtrack, it will now come from the rear surrounds along with the rest of the rear channels. As was stated in my other posts, I thought it was obvious he was talking about EX/ES titles only...hence the question originally asked which included the phrase <i>'5.1 capable'</i>, which is not something you find on a non-EX/ES title. It was obvious to me that the poster was asking about EX/ES title playback on a 5.1 system, and that's how I directed my reply.
As far as THX claim about <b>must</b> having two speakers for EX playback. *sigh* THX can claim all they want, but the fact is, you are talking about <b>one channel</b>! If you think you would benefit from a mono signal being sent to the same speakers (ala DPL), be my guest. But to make it sound like it is unnacceptable to use one is ludicrous.
If you put that much faith in THX guidelines (demands?) I feel for you. As I stated before THX HT guidelines are a joke, but of course...YMMV. If you want to pay more for a product because it bears THX certification, and follow their demands, er guidelines to the t without thought to try otherwise, full steam ahead. Reading right out of the info you posted, THX makes it sound as if no product that isn't THX certified will work for 'official' EX sound. Ha!
Again, I take nothing personally, and everything I state is just my opinion, which happens to be based on my personal experiences.
Also, 'in case you didn't know'...THX Surround EX is the theatrical format for 6.1, and is actually called Dolby Surround EX for home use. THX has no surround format in use in home theaters today. You've got DD, dts and PCM...no THX.

Over the past 8 months or so, I have seen a million discussions on the whole "one or two speakers for the EX/ES channel" debate. I don't understand why anyone would support the idea of one speaker at all. Is it to save money?As soon as you can find a descent rear speaker that is sold as each instead of a pair, let me know.

So what is it then??
 

One or two rear center speakers?!? -rolleyes-

j/k! :eek:

I can't even afford DTS-EX anyway...

I'll reply here (also on DVD_O_Rama's post) because obviously things get very confusing! I don't think that there is a single product on this planet that support EX/ES with one speaker. Hence, you need two speakers. Here's some more info: 1999 saw the introduction of Dolby Digital Surround EX® (known in the home as THX Surround EX® as it is licensed for domestic use by the THX division of Lucasfilm Inc.) THX Surround EX adds a monaural surround back channel to the usual complement of five full-range and one bandwidth limited channels of a 5.1 system. This is achieved by matrix encoding the surround back (SB) channel into the two existing discrete surround channels, surround left (SL) and surround right (SR). A decode matrix then extracts the channel upon playback via a SR + SL = SB sum (similar to the way in which a Pro-logic® system extracts a centre channel) and conveys it to two loudspeakers.

It has been stated that DTS Extended Surround (DTS ES) is a competing but compatible format, this is however incorrect. The name "DTS ES" applies to Digital Theater System's theatrical EX adapter, the competitor to Dolby's SA-10, and not to a 5.1 format enhancement. When an additional surround back channel is delivered by DTS, it is done so by using the technology developed by Dolby and DTS pays a license fee accordingly. Therefore, the correct name for an EX-encoded soundtrack delivered by DTS is: DTS Digital Surround Dolby Digital Surround EX. This is not to be confused with DTS ES 6.1 Discrete, an entirely different format which is indeed correctly described using the term "6.1" as it does deliver six discrete channels of full-range information plus an LFE channel.

To explain why THX Surround EX is not a "6.1" format we need to understand the two abbreviation systems used to describe discrete and matrix systems.

In a matrix system – Dolby Surround® being the obvious example – a given number of channels are folded on encode into a smaller number and then extracted on decode. In the case of Dolby Surround, left, centre, right and surround are added to a carrier with just two channels, they’re then known as left total and right total (Lt and Rt). Because four channels have been combined into two, the system is abbreviated as 4:2. On decode, the Pro-logic matrix extracts all four channels, so this is known as a 2:4 system. More information about the Dolby Surround format can be found at the Dolby web site: http://www.dolby.com/tech/whtppr.html

In discrete systems such as Dolby Digital and DTS, in simplistic terms, each channel is encoded individually and they remain so throughout the entire signal path through to decode. The Dolby Digital system is also outlined within a white paper upon Dolby's own web site at the following URL: http://www.dolby.com/tech/ac3flex.html

Because both Dolby Digital and DTS most commonly transfer five channels and a bandwidth limited low frequency effects (LFE) channel, they’re known as "5.1" formats. This in itself is a shortened version of the true abbreviation which would be 3/2.1. The figure before the oblique indicates the number of discrete channels in the front half of the room, the figure after the oblique those that can be found in the rear of the room and once more the LFE is indicated as present: ".1". Two-channel Dolby Digital is written as 2/0.0 (no centre, no surrounds and no LFE) whereas a DTS music disc quad mix is represented as 2/2.0 (no centre and no LFE), the region 1 Dolby Digital release of 'La Femme Nikita' has mono surrounds and no LFE, so is 3/1.0... and so on.

As THX Surround EX combines both discrete and matrix encode systems, for it to be correctly represented numerically we must combine both abbreviation conventions. "6.1" is commonly used, but as we have learnt that indicates six full-range discrete channels plus an LFE, which is not the case given the matrix encode and decode of the new surround back channel. If we are ever to see a true discrete 6.1 system, then describing EX as "6.1" will prove to be even more misleading. Dolby’s own policy is "...to never use "6.1" in our literature..." and they agree about the current state of confusion.

Surround back is matrix encoded into surround left and surround right, so three channels have been folded into a two-channel carrier. They are recovered in the same way – a 2:3 decode system (two discrete channels containing a third matrix encoded channel). Dolby Digital Surround EX soundtracks do of course still have three discrete front channels and an LFE channel, so we must add the 2:3 rear channel abbreviation to the whole – 3/2:3.1 being the result.

My conclusions:
1. You DO need two speakers. Period
2. THX Surround EX is the official name for home use (why do you think that EX-units are so expensive? They need THX Ultra/Select certification!

Mark

PS. I am also not a fan of most THX products but IMO amps, recievers and processors are the only units which DO benefit from THX-certification.

Just out of curiosity, do you also use two speakers for your front center channel as well? If not, why?

[QUOTE]Originally posted by exm

Quote:

---

My conclusions:
1. You DO need two speakers. Period
2. THX Surround EX is the official name for home use (why do you think that EX-units are so expensive? They need THX Ultra/Select certification!

Mark

PS. I am also not a fan of most THX products but IMO amps, recievers and processors are the only units which DO benefit from THX-certification.

---

Mark, I'll respond to the part of your post that you wrote, and not the stuff from the SMR website as it's not adding anything that hasn't been repeated ad nauseam.
On your conclusions:
1) Was this based on you having set up one rear speaker and listening, and then hooking up another to reach this conclusion? Just for a frame of reference, what equipment was used (speakers, processor, amplification, etc)

My experience with an ES/EX set-up used one rear center, simply for space reasons. I have not said that 'one is better then two' or vice versa, because I haven't tried it both ways. I like to base my opinions on personal experiences, rather then what someone else thinks. And by the way, this was never a '1 versus 2' type of post...my whole point was that it CAN be used either way, there are countless posts on the HTF saying exactly this, posted by users who have 1 center surround speaker in their set-ups.

<i>(why do you think that EX-units are so expensive? They need THX Ultra/Select certification!</i>

Why are they so expensive? For one YOU ARE PAYING EXTRA FOR THE THX LOGO. Period. There will be dozens of processors/receivers that come out this year (or soon thereafter) that do EXACTLY what the current crop do, and will be substantially cheaper. This is how technology works. Of course, I'm sure there will be plenty that aren't THX certified...I bet they won't be as good, right? I can gurantee they will be cheaper ;)

[QUOTE]Originally posted by DVD_O_Rama

Quote:

---

Originally posted by exm

Quote:

---

My conclusions:
1. You DO need two speakers. Period
2. THX Surround EX is the official name for home use (why do you think that EX-units are so expensive? They need THX Ultra/Select certification!

Mark

PS. I am also not a fan of most THX products but IMO amps, recievers and processors are the only units which DO benefit from THX-certification.

---

Mark, I'll respond to the part of your post that you wrote, and not the stuff from the SMR website as it's not adding anything that hasn't been repeated ad nauseam.
On your conclusions:
1) Was this based on you having set up one rear speaker and listening, and then hooking up another to reach this conclusion? Just for a frame of reference, what equipment was used (speakers, processor, amplification, etc)

My experience with an ES/EX set-up used one rear center, simply for space reasons. I have not said that 'one is better then two' or vice versa, because I haven't tried it both ways. I like to base my opinions on personal experiences, rather then what someone else thinks. And by the way, this was never a '1 versus 2' type of post...my whole point was that it CAN be used either way, there are countless posts on the HTF saying exactly this, posted by users who have 1 center surround speaker in their set-ups.

<i>(why do you think that EX-units are so expensive? They need THX Ultra/Select certification!</i>

Why are they so expensive? For one YOU ARE PAYING EXTRA FOR THE THX LOGO. Period. There will be dozens of processors/receivers that come out this year (or soon thereafter) that do EXACTLY what the current crop do, and will be substantially cheaper. This is how technology works. Of course, I'm sure there will be plenty that aren't THX certified...I bet they won't be as good, right? I can gurantee they will be cheaper ;)

---

Interesting discussion though... :)

Anyway, it seems that you dislike THX for their program and you're partly right, especially on software. On laserdisc you knew THX meant quality but on DVD... Uhm, no. For Home Theater equipment THX means that is has met certain standards and from there one you can improve the product. For me THX doesn't mean quality by default, but is does mean performing on a certain level.

You said your experience is with one speaker? How did you manage that? As I stated, I don't know a single unit with one REAR-connection for EX. Are you telling me that you only used one out of two? As you read earlier in this thread, the two speakers might look being driven parallel (mono) but just like THX-processing on analogue sources, some decorrelation process is being used to create a more spatial sound.

Mark

Flipping through the latest issue of Widescreen Review, you'll find a review of the Yamaha RX-V1 receiver. On page 96, there is a picture of the rear of the unit, which among other things shows the binding posts, including the pair for use with the rear center speaker. <i>Speaker</i>.
One set of binding posts.
I make no claims about the quality of this unit, as I am not a fan of receivers in general, and haven't heard this in use. I only mention it to show there is at least one that uses one connection for EX. I am sure I can find more, and would love to detail my own experiences with the Denon 5800, but I have painting to do this weekend and grass to mow. Perhaps if I'm on later we can continue this discussion, and I'm glad to see it hasn't gotten into any sort of pissing match.

OK, so let me try to summarize what the original questioner wanted to know:

(Please correct me if I'm wrong)

1 - Dolby Surround EX is matrix - meaning that when you play it in a 5.1 system the back center channel will be matrixed out to the other two rear speakers.

2 - DTS ES is discrete - so when you play it in a DTS 5.1 system, you essentially lose a channel of sound because it does not get matrixed out to the other rears.

Is that all correct?

We ARE talking about Yamaha here who doesn't have 'official' EX/ES but their own interpretation!!!

1 - Correct due to downwards compatibility
2 - No, it's downwards compatible (just like 1).

You'll never lose information, you can only GAIN information!

Okay, so now it's only 'official' EX products we are talking about. Fair enough.
Also in the current issue of Widescreen Review is another review of an EX capable receiver (this one emblazened with the THX logo on it), the Marantz SR-14EX THX Surround EX Receiver.

In several diffeent places, the reviewer comments on using <i>'6 or 7 channels'</i> in a THX Surround EX setup. Was he mistaken? If he was, it was more then once because mention of using the SR-14EX's <i>'surround back channel(s)'</i> came at least twice in the review.
In another issue of WR, the first to feature a look at the Denon 5800 back in September of 2000, it was stated <i>'the AVR-5800 carries seven channels of on-board amplification, allowing <b>one or two</b> speakers to be deployed to reproduce the back surround channel'</i>. Again, was this reviewer mistaken, as well? Do you know something they don't? And I asked once, and didn't get a response...what exactly is your experience with surround EX? I asked if you have compared using one or two speakers, and didn't get a response. You may have missed that. Do you even have an EX/ES system, or are you just going by the literature of others?

I haven't read the reviews in WSC so I can't comment on that and besides, it's not for me to judge reviewers. The only thing I know and what I consider as standard (besides this forum I also participate in SMR Forums, HVT Forums and AVS Forums) is that you need 2 back channels for PROPER EX/ES-reproduction. There is a lot of confusion, mainly because sometimes the rear is called center rear and people confuse that with the real center speaker.

On to your question (which I indeed overlooked): I own a Lexicon DC-1, which has DTS ES Matrix and THX (or DD as you like) EX. The Lexicon has it's own surround modes which always suggested 7 speakers so adding ES/EX only added an extra mode. So to anwer your question: no, I haven't tested it with one rear channel and to be honest, I don't see any reason why I should. As stated earlier, although indicated as a single channel, there is/can be a difference in steering both rear channels so using one channel only limits the sound.

My question to you is: what are your experiences?

One extra point (after some extensive researh) that I noticed: in the 'theater' world there is such a thing as a single rear channel while for home theater use THX added an extra rear channel for improved steering. So I don't know where your information comes from, but it is (as usual!) confusing.

[Edited by exm on 03-26-01 at 06:22 AM]

My experiences with ES/EX have been limited to say the least. I am currently have been using a Sunfire Theater Grand II, amplified with a Sunfire Cinema Grand (soon to be replace by a Cinema Grand Signature, or perhaps the Theta Dreadnuaght), and when ES/EX made it's big splash a while back, I was dead set on getting an ES/EX unit, only to find that there were only two models that did dts ES Discrete at the time- of course the Denon 5800 and 3801. The 3801 was dimissed quickly, so after hearing the hype on the Denon, I got a unit from my dealer to audition in my home. I have never been a big fan of receivers, and even after hearing what is arguably the best receiver currently available, I still am not.
The sound on the 5800 was not horrible, quite the opposite in fact, but not up to par with the Sunfire. It was the ton of useless 'bells and whistles' that I could live without. Personally, I don't need my 2 channel music to be bastardized by some DSP that simulates a 'hall' by drenching it in digital reverb.
There are many other reasons I passed on the Denon as well, but the actual lack of software as of late clinched it for me. I see no need in investing that much in something there is no software for. I remember this same discusssion when dts hit a while back, and there was nothing available at the time, so perhaps ES/EX material will be bountiful one day as well, and there will be more then a handful of titles available.
One thing...when you said <i>"So I don't know where your information comes from, but it is (as usual!) confusing.
"</i>...
Any 'inforamtion' I gave was from my readings (which I listed the sources of, so you could try reading them for yourself). You said it's not up to you to 'jugde' reviewers, and I didn't expect you to, I just was curious to how you felt about what was written (that one speaker is possible for EX/ES use). You seemed to gloss over that, for whatever reason.
Don't know what you find 'confusing' about anything I said, as anything I said was either quotes from recent magazine articles, or my personal experiences. As I said, maybe you know something we don't. Enjoy your EX set-up. Maybe if you pay them enough, THX will give you a little plaque or soemthing; you sound very loyal to their guidlines. ;)
BTW, I guess you aren't a fan of dts ES Discrete, as it has nothing to do with THX?

When will it end? Before too long, we'll have Super Extended DTS Dolby Digital 15.4 surround.

My opinion is this -- there are VERY few discs with 6.1 capability now. Waiting a year, they're going to have very few 7.1 or 6.2 systems. You can't just wait for years -- because you'll end up 'waiting' your life away.

I think you should just go ahead and get one...you're missing out already!

I have been quite satisfied by 5.1, and thought that EX and ES were overkill. However I'm now starting to really like the idea of steering sound directly behind your head rather than simply to the sides. Imagine the bullets and explosions passing right THRU you, from front center to the rear center speakers.

Here's a couple articles that sold me on EX/ES sound: http://hometheater.about.com/gadgets.../aa061400a.htm
and http://www.homecinemachoice.com/fram...199912EX.shtml

The THX logo does not impress me, especially after hearing a THX-certified Dell computer. The Altec Lansing speakers sounded pretty good for a computer, but hardly stereophile quality. Hopefully the THX royalty requirement will soon be dropped to provide an affordable DD-ES receiver.

I'm also getting excited for DPL2. I look forward to effectively using all of my speakers while listening to music or watching TV. Getting "near 5.1" sound from a current TV broadcast would be great indeed. Check out http://www.widescreenreview.com/attr...qrevdolby.html and http://hometheater.about.com/gadgets.../aa062900a.htm and http://www.hometheatersound.com/features/soundoff/

So how about it Denon, a 3801-x with DD-ES & DPL2?

First of all, let me apologize for my typo error. I meant to say: So I don't know where your information comes from, but the information concerning ES/EX is (as usual!) confusing. Sorry for that, I'm only Dutch! :)

On to the topic: I agree with all your point concerning receivers. Before I bought the Lexicon I had the Marantz AV-600/5xMA-500 pre/power combination and I wanted DD/DTS (the AV-600 is a THX DPL Unit). At that time I listened to the Denon AVC-A1 (European 5800) and the Onkyo DS-939. While the movie performance was excellent, the music performance was so poor ('digital' is the correct term I guess). So I decided to stick with my combination. After some research I listened to a Lexicon DC-1 (at that time WITHOUT EX/ES) and I was blown away by it's performance. You mention DSP modes which are aweful for music: I agree UNTIL... you've heard Lexicon's Music Logic. This is IMO the ONLY DSP-mode on the market being able to reproduce a valid alternative to 2-Channel (DPL II is based on similar coding techniques). To be honest, I never listen to 2-channel anymore!

Now, the other advantage of the Lexicon has always been upgradability. Lexicon was the first to announce EX/ES so I immediately bought the upgrade for $100. Lexicon already supports 7 channels by itself so it was only a chip swap. The only thing the Lexicon is missing is Discrete ES. You know what? I don't care less. The only difference between discrete ES and Matrix ES is that with discrete ES the channel is carried on a seperate channel while matrix has to decode it. There's no such difference as quality since matrix is just as full-range as discrete! The fact that I think like this about ES Discrete has nothing to do with the fact that it isn't THX. Although, my Lexicon supports THX ES... Oh well!

Guess my dedication for THX goes way back to the time when they were really special. When you had a THX-approved laserdisc running in THX cinema which was and is far superior to DPL. I have to agree that, like everything nowadays, THX is being controlled by commercial benefit instead of creating the best possible experience at home. I am also disappointed by a lot of THX-products. But I still trust them enough to know that the THX logo on front of my Lexicon means something.

I do expect that the next Lexicon upgrade will include DPL II and DTS Discrete...)

Mark

PS: a comment on TOAD's posting: IMO you can wait as long as you like. You can buy a 1 Ghz computer now for $1000. A year from now that's probably a 2 Ghz. It's the same in the audio industry. Of course there will be a successor to ES/EX, to DVD and all other emerging technologies. But I want to enough all technologies as long as I can and if I'm still in the position to afford new technologies when they come out, I buy them. Oh, I still have my 'extinct' Laserdisc player which I enjoy a lot (not to mention when I play the Star Wars Trilogy in DD5.1)

Jeff, I agree with you on all points.

If, and I say IF, you have a room large enough EX/ES DOES add an extra dimension exactly as you gave an example for.

One thing (as I posted earlier): don't go blind for DTS Discrete since DTS Matrix can decode all Discrete DVD's and it's very doubtful that you'll hear the difference. The reason why I bring this up is the fact that I think that a lot of people buy the Denon's for discrete while their musical performance is lacking.

The example you gave about THX clearly states what I wrote earlier that THX is becoming to commercial and that they disappoint me with some products. A THX-speaker for your computer: go back in time (let's say 5 years) and say the same thing. I think you would be the Steve Martin of that time.

About DPL2: I've been enjoying Logic 7 on my Lexicon, which reproduces a 7-channel surround system similar to DPL2. Some Lexicon experts already compared the two systems and they seem to perform on the same level. If that's true than DPL2 will blow you away. Definitely 10000000x more important than getting Discrete ES over Matrix ES/DPL2.

Some more info:

http://www.homecinemachoice.com/fram...199912EX.shtml

Especially notice the following column:

Surround EX equipment will provide two Surround Centre channels, THX call them 'Surround Back Left' and 'Surround Back Right' in addition to what
we now recognise as Surround Left and Surround Right. The two Surround Back channels will each have their own set of output level and time
alignment adjustments plus the ability to select a suitable crossover option, sending either full-range signals to the Surround Back channels or
employing a standard THX low-cut filter at 80Hz. It's also worth noting at this point that just as with existing Centre, Subwoofer and Surround
channels, the option of None will be available and decoding adapted appropriately, for example if one purchases Surround EX equipment but cannot
accommodate the additional loudspeakers needed right away.

Why two Surround Back loudspeakers? There are two reasons for this. Firstly, if the THX 5.1 EX mode is selected but the software being played isn't
EX encoded, the results are more predictable for the listener, or more acceptable if you will, than if one loudspeaker were used. Secondly,
manufacturers of EX equipment will have more scope to experiment with seven-channel implementations of other movie and music modes. This is
nothing new to the likes of Meridian and Lexicon, but will come as a shock to those firmly entrenched with five channels.

[Edited by exm on 03-29-01 at 04:31 AM]