SPOTLIGHT ON UPGRADING TO EX SURROUND by Shane Buettner

The release of Austin Powers: The Wrath of Khan, er excuse me, Austin Powers: The Spy Who Shagged Me marks the debut of a potentially important new feature of 5.1 channel soundtracks, THX Surround EX (THX-EX. I thought I'd outline for you the steps taken to upgrade my home theater to take advantage of this new technology.

If you read my earlier report on THX-EX, you'll recall that this feature is currently being implemented exclusively in THX Ultra certified equipment, employed in a "7.1" channel configuration in which the traditional left and right surrounds will now be directly to the sides of the listening area and the EX back surround channel will employ two speakers placed at the rear of the listening area. As Lexicon has long recommended this configuration with its processors and even builds them as full 7.1 channel processors with eight equally high quality delta-sigma 24 bit DACs. This made Lexicon a natural fit for the THX-EX configuration and they have brought the first THX-EX upgrades to existing processors to market (and their MC-1 and DC-2 processors now ship with THX-EX integrated.) Where this played into my hands is that I am the proud owner of an MC-1 and began working Lexicon on getting an upgrade chip for my MC-1 as soon as it was announced at the CEDIA show back in September. On october 25^th I became the first kid on my block (and perhaps anywhere) to get the upgrade EPROM chip for the MC-1 in my hand.

While I threw on an anti-static wrist strap and popped open my MC-1 and performed the upgrade myself, I absolutely do not recommend this route for anyone. It is very easy to make a mistake and damage the unit (which is as painful as it sounds.) The pins on the chip are very, very delicate and if bent or broken will not work. If any static builds up or you put the chip in the wrong way, it could fry the whole chip and perhaps even the processor board. And you also know that any such undertaking will most likely void the warranty on this very expensive piece of gear. In fact, what am I thinking? If any of the good folks at Lexicon customer service are reading this what I meant to say is that I didn't perform my own upgrade either. Crank call, crank call!

The THX-EX upgrade for the Lexicon also upgraded the system software to version 4. Functionally the piece still works the same, with some new menu items relating to THX-EX as well as some menu items moving around slightly. One of the most notable additions is that if you've got a complete THX speaker setup you can one step the speaker configuration by selecting the THX Surround EX speaker setup which automatically selects THX EX spec 80hz crossovers at all (7) speaker positions. Also interesting is that THX spec for the 7.1 channel THX-EX config is dipole speakers at the sides and bandwidth limited direct radiators at the rear. When THX Surround EX is chosen as the speaker setup this configuration is the default and cannot be altered in any way. But also note that any other custom speaker setup of speaker types and crossover points can be used in conjunction with THX Surround EX with Lexicon processors.

Also of note with Lexicon is that the DTS THX film mode now defaults to Surround EX being in the ŠOnÔ position. Given that THX Surround EX is joint venture between Dolby and THX I wasn't sure where DTS support would fit in, but at least in the Lexicon EX can be enabled for DTS soundtracks as well as Dolby digital. This is important when considering that any EX encoded film's 5.1 channel printmaster will have the EX back surround channel matrixed into the surround channels prior to any kind of digital encoding. Any soundtrack sourced from that printmaster will automatically carry the matrixed back surround channel. So a DTS DVD encoded from such a source will indeed have the back surround channel embedded in its surrounds which can be matrixed back out and played back via THX Surround EX decoding. The only thing that is unclear at this point is whether EX-encoded DTS discs would carry a digital flag that will alert THX-EX processors of it's presence so the THX-EX processor can auto-switch to THX-EX mode as the Dolby Digital THX-EX DVDs will.

Now, the upgrade of the processor having been performed left me another task: to add the requisite two additional channels of power amplification and two speakers. I wasn't previously running my Lexicon in its full 7.1 channel configuration, which left me with some more work (and shopping) to do. As my current surround channels are direct radiators placed to the rear of the listening position I decided I would leave them where they are and add the two speakers directly to the sides of the listening position. For this setup I really wanted bipolar surround speakers. I think bipoles are terrific in this kind of setup, as they are more spacious than direct radiators, but also don't suck the life out of directional sound effects the way dipoles do. This put me in a bind as NHT, the speaker manufacturer that makes my current five speaker setup only makes direct radiators and dipoles. Dipoles I wouldn't even consider, leaving me to choose between direct radiators by NHT or bipoles from another manufacturer. NHT direct radiators would obviously be a timbral match for the rest of my system, which is attractive, but these speakers would be placed so close to the listening area that I think it would really too much having another pair of direct radiators pointing at me. Bipoles would seem a nicer fit, not being so Šin-your-faceÔ directional at such a close distance, but I'm also very big on having a tonally matched system. Well, even if NHT were to build a bipolar surround speaker, I still think it would sound at least a bit different. Thus, I decided to go bipolar.

Where surround speakers are concerned bipoles are built a lot like dipoles, generally with two identical high frequency drivers on opposite sides of the enclosure, with a null or sometimes a low frequency driver in between them that will typically be facing the listener. But the key is that the drivers fire in-phase with each other in a bipolar design, not out of phase like dipoles. Once the decision was made to go with the bipolar design I immediately thought of Mirage, a Canadian loudspeaker company that has built terrific bipolar speakers for years. My current reference subwoofer is Mirage's bipolar BPS-400, a choice I've been very happy with for over two years now. The speaker I chose for this particular duty is the OM-R2, a wall mounted 2-way 3 driver design of the type described above. The build quality of these relatively diminutive speakers completely belies their modest price of $500 per pair.

Any concerns I had about going off-brand with the surround channels have been alleviated by listening experience with the Mirage OM-R2s in my room. Like the NHTs, their emphasis is clearly on natural, accurate reproduction of sound with low coloration. The image that comes from the sides is exactly what I wanted, fat and non-localizable, nicely filling in the sides but never calling undue attention to themselves. To further investigate their potential I ran them as the only surround speakers in a 5.1 configuration, listening to a variety of soundtracks and multi-channel music courtesy of DTS CDs. The results were no less impressive. As I said, the surround image with the OM-R2s is wide and does a nice job of filling the room with sound, but also retains enough directionality to serve discrete surround duty with 5.1 channel material. I highly recommend bipolar speakers for 7.1 channel configurations, as well as 5.1channel home theater installations in which the surrounds are to placed at the sides of the listening area. I also highly recommend that anyone heeding this advice consider the Mirage OM-R2, a fine surround speaker and a genuine bargain.

For the additional two channels of amplification I wanted something with enough oomphh to keep up the dynamics of the 200w per channel Sunfire Cinema Grand, but I also didn't want to break the bank. (Even technical editors have budgetary constraints to be considered.) Given that these speakers would be crossed over at 80hz given their low frequency capabilities I decided on the Parasound HCA-1000A, a THX certified stereo amplifier rated at 125w RMS with both channels driven, and also an affordable choice at $600 retail. Parasound has made a reputation offering high quality amplifiers at a reasonable cost to the consumer and the 1000A is no exception. I listened to this amplifier with my system running in a 5.1 configuration using the Mirage OM-R2s and the NHT 1.5s that are in the rear of my room separately before I set it up in the 7.1 configuration. The results were outstanding any way I used the 1000A. Outstanding dynamics and detail, and a wide and deep soundstage that was clearly evident on the best 5.1 soundtracks and DTS music CDs, even on the NHT 1.5s which are slightly more difficult to drive than the Mirage OM-R2s.

All in all, I'm very happy with the performance of the new components I've added to my system to upgrade to 7.1 channel capability required for THX-EX. Any concerns I had about going off-brand with the speakers and amplification were assuaged by the relatively neutral sound quality of the two components in question. I look forward to the upcoming releases of THX Surround EX encoded material, as well as experiencing Lexicon's Logic 7 surround mode in it's full 7.1 channel configuration. You can expect upcoming reports on both.