Is THX a scam?

[jtg]

Im relatively new to the field of pro audio, so forgive my lack of experience. Lately Ive been curious about THX certification. I was somewhat skeptical as to the merits of it because there is huge money associated with the THX name, and I often see it being used as an excuse to charge double or triple what a product is worth.

I notice on wikipedia, it says:

"The THX system is not a recording technology, and it does not specify a sound recording format; all sound formats, whether digital (Dolby Digital, SDDS) or analog (Dolby SR, Ultra-Stereo), can be "shown in THX." THX is mainly a quality assurance system. When a film's producer has it mixed in THX, this means the film's soundtrack will sound, when shown in THX-certified theaters, exactly as the mixing engineer intended."

Which initially sounds like its a reference standard to basically ensure flat frequency response, which is all well and good. But the next sentence:

"THX also provides certified theaters with a special crossover circuit whose use is part of the standard."

Now that sets off some red flags. To me it sounds like that means they throw this in to "color" the sound in a specific way. This means when a mix is created on THX gear, it is assumed to be a flat reference, and as they claim it will sound perfect on other THX gear. But, only because other THX gear is similarly colored (which essentially negates the coloring). But then when it is played on a truly flat system, lacking the special THX proprietary crossover, it isnt actually flat. It sounds like theyre trying to create a captive market with THX gear and alienate other audio. Now, I dont have any knowledge of this "special circuit", but suppose it deliberately cut a specific pattern of frequencies by a specific amount. It would basically act as a "key". To pass the THX certification and be "guranteed compatible", all gear needs the same "key", or those frequencies will be artificially boosted when playing on a non-THX system because the original THX engineer was compensating.

I dont know if it follows a similar principle or not, but the fact that they have a special proprietary circuit, and the huge money around those 3 letters makes it pretty suspicious. It would actually be fairly obvious as a tactic from a purely business standpoint.

Anyone have further insight?

[Pascal Sijen]

The THX cinema crossover, is just that - a crossover, designed to match the THX Approved screen channel speaker systems made by companies such as JBL, EV etc. The unit also incorporates some screen loss HF compensation and the newer digital unit also offers some EQ etc. Final EQ and calibration follows all SMPTE standards.

In general, the THX Theater Certification program focuses on the complete design of the theater, both sound & picture. THX attempts to ensure that the theater achieves certain baseline standards for such things as isolation, background noise, SPL, monitoring angle, response, coverage, seating / viewing angles, light level on screen, etc. These standards are well understood and are fully compliant with SMPTE and other industry recognized standards.

More information can be found here:
http://thx.com/mod/services/cinemaServices.html

I hope that helps...

Cheers!

[gsilbers]

its really usefuull. we are all used to it by now, but before any greasy greedy old guy will get cheapo speakers and just hang them anywhere in thier movie theatre. and thats really what happen and happens in developing countries without that stanbdard. so youll get a movie that was mix by this awsome engineering in a theare space with all this gear and all this great job to be later heard in crappy spakers. totally ruins the mood and the art.

[danasti]

Originally Posted by jtg

Im relatively new to the field of pro audio, so forgive my lack of experience.

Now, I dont have any knowledge of this "special circuit", but suppose it deliberately cut a specific pattern of frequencies by a specific amount.

So you are new to pro audio and you don't have any knowledge of what exactly is going on in THX?

Interesting theory. I just wonder how you thought it all up. Maybe you should go work for George Lucas.

Seriously though, all it is there for is for people who make wonderful sounding productions to give their customers a standard for which to buy their gear. THX certified amps are tested for a minimum s/n ratio and dynamic range. Speakers are tested for frequency response.

THX gear is good for playback and it's a standard that makes me happy knowing that if I produce something then I'll know, to a certain degree, how someone out there will hear it.

I wish they'd do this for Mastering music on audio CDs. Then we wouldn't have these mangled, distorted blocks of cheese that the major labels seem to call music.

Originally Posted by jtg

It would basically act as a "key". To pass the THX certification and be "guranteed compatible", all gear needs the same "key", or those frequencies will be artificially boosted when playing on a non-THX system because the original THX engineer was compensating.

Props for being creative though!

[taturana]

to me thx always semeed like a great idea...

[jtg]

Originally Posted by danasti

So you are new to pro audio and you don't have any knowledge of what exactly is going on in THX?

Yes, as opposed to being an experienced veteran in pro audio and still lacking knowledge of it. I figure its widely accepted that newbies havent learned a lot yet so its acceptable for them to ask questions. Or am I missing something? Im not sure what youre implying exactly with that and your comment about working for Mr Lucas, but its an honest question, Im not claiming much here.


Im familiar with THX of course, but not aware of exactly what the certification process entails. I realize its a strict set of measurements for various applications, but I wasnt aware that THX certified setups are only certified after they have additional exclusive THX circuitry.

If it was merely a standard, it shouldnt require new hardware. I mean if your setup can acheieve perfect reference level results, why do they require you add something to it to change it before you can wear the THX badge? Obviously it depends on the components too - THX certified cables arent going to have anything new in them, Im not that much of a conspiracy theorist, but wanting to change other otherwise perfect gear seems shady! Thats why Im asking more about the reasoning for that.

Also, Im curious what the cost of the certification process is. How much cost is added to the bottom line of a speaker just to carry the badge?


Is it only theaters that require the THX crossovers or other THX hardware? Or is it a requirement for studios, or amplifiers, or anything else?

[TREMORS]

Originally Posted by jtg

Is it only theaters that require the THX crossovers or other THX hardware? Or is it a requirement for studios, or amplifiers, or anything else?

It is not a requirement.
Maybe a post, or surround sound studio, but not a typical recording studio.
Mackie HR824's, and 624's (which I like) are "THX" certified.
What does that mean for mxing in two channel stereo?
Not much.
Perhaps 5.1 or 7.1, or DTS, Dolby digital mixes and theatre/cineplex sound, yes.
So, it certainly isnt a "scam" by any means.
I too am curious to learn more about it, if anyone else weighs in on this thread.



-D

[Pascal Sijen]

There are two basic difference between "Professional THX" and "Consumer THX". With a consumer system, the hardware is "certified" to meet a certain performance criteria. For professionals, the hardware is "approved for use in a THX Certified studio / cinema". Therefore, in order to have studio 'THX Certified', you need to work with THX on the design and implementation of the complete studio or theater and then the theater or studio is tested against industry / THX standards. So, even after using THX approved gear, you may not get certified. This could happen, for example, if the HVAC system is way too loud (common problem in theaters).

The cost for a manufacturer to have product THX "Approved", in a professional application, is considerably less, as compared to THX Consumer certification. The THX Consumer certification is a licensing program, not just a testing and "approval" program.

I actually worked for THX Professional for a little over 5 years, when THX was still part of Lucasfilm Ltd. I can tell you that the people who work there do genuinely care about quality. Additionally, the mandate given by George Lucas, was to find ways to both improve the quality of movie playback and make it more consistent between all venues. It certainly wasn't a big profit center for Lucasfilm and was never intended to be "scam".

Anyway, the THX website has a lot of information about the processes involved (www.thx.com)
... also this link has some good information on the consumer side of things.
http://www.hometheaterhifi.com/volum...06-part-1.html

Cheers!

[jtg]

^Interesting. Personally I think their use of it in consumer products hurts their brand. It is hard to take seriously when you see brands like Monster cable plastering it on their package to justify charging $200 for a $20 cable. Though, thats a different issue altogether.

Theres no way the consumer side of things has a primary goal of consistency if there are licensing fees though. Thats purely cash-cow You dont "license" a certification, thats just renting an endorsement.

[Pascal Sijen]

Originally Posted by jtg

^Interesting. Personally I think their use of it in consumer products hurts their brand. It is hard to take seriously when you see brands like Monster cable plastering it on their package to justify charging $200 for a $20 cable. Though, thats a different issue altogether.

Theres no way the consumer side of things has a primary goal of consistency if there are licensing fees though. Thats purely cash-cow You dont "license" a certification, thats just renting an endorsement.

Although, I do agree that there is a risk of devaluing the logo / brand, I believe the consumer program has brought many benefits to consumers and to the licensees.

For example, consider a product such as a consumer surround receiver: These products are very complicated, with many features and the integration of all these features in a product like this, is not easy (Dolby Digital, DTS, analog audio, analog video, digital video with audio, user interface, post processing, amplifiers, speaker configurations, switching etc). THX's work has been key to manufactures, and the various competitive audio / video formats, to make products that are both user friendly and have a high level of performance. It is important to point out, that these standards and benefits have also worked their way into non THX products, so the industry as whole benefits from this.

Because the THX certified consumer products incorporate technologies which are owned by THX (see the link in my previous post), they need to be licensed to the manufacturers. This is not a "cash-cow", but is essential to THX having a sustainable business model. They are not a not-for-profit organization, although they did recently launch one: http://www.thxbpl.org/

Anyway, just trying to give the THX point of view... ...not that I represent them, anymore.

Cheers!

[WTMNMF]

I was at Skywalker Ranch when we were bringing the rooms up and the guys are having a rough time with a film mix one day and bitching about the system and what we might have done to F' it up so badly when who should walk out from behind the screen?? TH himself, he had been "improving" the settings on the THX eq's!!!!! The fact that a film was being mixed at the time didn't seem to worry him in the least

[Pascal Sijen]

Originally Posted by WTMNMF

I was at Skywalker Ranch when we were bringing the rooms up and the guys are having a rough time with a film mix one day and bitching about the system and what we might have done to F' it up so badly when who should walk out from behind the screen?? TH himself, he had been "improving" the settings on the THX eq's!!!!! The fact that a film was being mixed at the time didn't seem to worry him in the least

Ouch...

That must have been more than 10 years ago...

[drBill]

Originally Posted by jtg

I notice on wikipedia, it says:

"....snip....When a film's producer has it mixed in THX, this means the film's soundtrack will sound, when shown in THX-certified theaters, exactly as the mixing engineer intended."

Now that's a good laugh! In the 50+ films I've been involved with, it's a joy and total surprise when I walk into a theater - anywhere - and it sounds like the dub stage. THX or not.

A few years ago, an guru audio designer friend of mine who builds super high end tweaky amplifiers submitted his amps to THX to have them "approved" because one of his clients (a very large post house here in LA who shall remain nameless) had dozens of his amps and needed THX approval for their clientele. Long story short, he bought back all the amps from the facility because he wouldn't degrade the electronics enough to get THX spec. Now, they have THX approved amps, but it doesn't sound like they like it. Oh well.....such is the case so often with "standards".

[MichaelPatrick]

Pascal, I use your monitor speakers and love 'em. Thanks!

[Pascal Sijen]

Originally Posted by MichaelPatrick

Pascal, I use your monitor speakers and love 'em. Thanks!

Cheers!

[minister]

Originally Posted by jtg

Which initially sounds like its a reference standard to basically ensure flat frequency response, which is all well and good. But the next sentence:

"THX also provides certified theaters with a special crossover circuit whose use is part of the standard."

Now that sets off some red flags. To me it sounds like that means they throw this in to "color" the sound in a specific way. This means when a mix is created on THX gear, it is assumed to be a flat reference, and as they claim it will sound perfect on other THX gear. But, only because other THX gear is similarly colored (which essentially negates the coloring). But then when it is played on a truly flat system, lacking the special THX proprietary crossover, it isnt actually flat.

i think pascal has made the case already....

personally, i don't really follow THX, or care .. and there are many in the film community who disagree with a lot of what TH is doing.

[Pascal Sijen]

Originally Posted by minister

i think pascal has made the case already....

but, do you know what a crossover is? Pascal can tell you about his Fourth-Order Linkwitz-Riley crossovers — which as you know are comprised of two cascading Butterworth filters for a slope of 24/dB per octave. These are quite common these days. The StudioComm units employ 2nd order Sallen-Key — and, any order Linkwitz-Riley filters can be implemented by a cascade of 2nd order Sallen-Key filters.... With 78/79, there is a steep cutoff for LFE with a more gentle 12/per for hi and lo pass to the mains. The MartinSound MultiMax unit does not discuss what crossovers it uses...that I could find....maybe seriousfun will enlighten.

What you are referencing to is related to bass-management, which is not the same as the crossover that I am referring to. THX provides THX Cinemas and THX Dubbing stages with a product called the D1138 (being / has been replaced by the D20). This product provides the crossover filters for the front screen channels approved by THX (2-way / 3-way etc). It also provides some EQ and also screen loss compensation. The D20 does allow for bass-management, although it is not common for most cinemas or large film style dubbing stages to use this type of feature.

Anyway, there you go...

Cheers!

[danasti]

Originally Posted by jtg

Yes, as opposed to being an experienced veteran in pro audio and still lacking knowledge of it. I figure its widely accepted that newbies havent learned a lot yet so its acceptable for them to ask questions. Or am I missing something? Im not sure what youre implying exactly with that and your comment about working for Mr Lucas, but its an honest question, Im not claiming much here.

It's absolutely fine to ask questions. The Lucas comment was refering to the story you came up with. It's also fine to come up "what if" scenarios and theories, it's an open and friendly discussion. I just quoted back to you how you presented yourself in regards to your experience. However, I am saying that it's better to ask the question honestly, as in "what is THX? How does it work on both a commercial and professional level?"; opposed to "Is THX a scam?, suppose they cut a freq boost where playback on other systems would be put at a disadvantage". Basically, I'm pointing out that if you admittedly don't know something, why start by asking if it's a scam?

Not that it's wrong or incredibly aweful because it's an open and friendly discussion. Why start with a negative when you don't know enough to be sceptical.

I'm not all that familiar with THX except for a few products (mostly amps) that I've worked with. There were rumors about Bryston amps a while ago but Bryston assured me this was myth. The rumor was that certain amps badged THX were inferior to their regular ST amps. This was both an audiophile and recording facility rumor. I was told then that all it means to be THX is that they send in the amp model and pay a fee. The amp is then tested and inspected. Basically, if it's a good peice of gear it will get through. However, I'm no expert on this, It could very well be a huge scam and the THX people could be forcing companies to use certain parts they have chosen.

All and all, on a consumer level, I think it's great to tell the listener that a product is capable of playing back something as intended. Finding amps for consumers who aren't "in the know" is hard, most people begin by looking at watts, without understanding RMS and peak, and completely look over current, freq response, s/n ratio, power supply, etc... Companies like Kenwood and JVC would put anything and it might look ok and read ok and be really cheap but it could suck major arse playing back the movie or cd you bought.

I'm sure THX has it's problems but so does everything. I do believe it has noble intentions.

[jtg]

Originally Posted by Pascal Sijen

Because the THX certified consumer products incorporate technologies which are owned by THX (see the link in my previous post), they need to be licensed to the manufacturers. This is not a "cash-cow", but is essential to THX having a sustainable business model. They are not a not-for-profit organization, although they did recently launch one: http://www.thxbpl.org/

Ah, that is reasonable. They are licensing the technologies then, I interpreted that to mean they are licensing the certification. Fair enough.

Originally Posted by Pascal Sijen

Anyway, just trying to give the THX point of view... ...not that I represent them, anymore.

Cheers!

But you do make products that carry their badge, and Ive heard that the Skywalker Ranch was overhauled with your monitors, so you do have some interest in maintaining their value But seriously, youve provided good info though, thanks!

Just curious, why does your lower-end gear not have THX certifications? Is it because the manufacturing cost to bring it up to THX standards is not suitable for that price point, or because paying for THX certification itself on those products would drive the cost up?

Im always curious in general when shopping for gear, how much of a levy the THX logo carries. If you have a $4000 piece of gear with the THX logo, and the cost of that logo is $500 in that case, then it would be reasonable to assume that there are products of equal quality at the $3500 price point. Of course without the certification, you have no way of knowing for sure. But conversely, if the cost of certification is minimal, there is little excuse not to obtain the certification, so its easier to assume that products that dont carry it probably dont carry it because theyre inferior.

Judging by the cable market, which I understand is somewhat unique and wont be representative of other markets, the THX logo clearly carries a huge premium. I think Monster Cable is the only manufacturer that has deemed it worth it (aside from a few Liberty Cable products) and its not like their products are any better than most decent gear out there.

Originally Posted by drBill

A few years ago, an guru audio designer friend of mine who builds super high end tweaky amplifiers submitted his amps to THX to have them "approved" because one of his clients (a very large post house here in LA who shall remain nameless) had dozens of his amps and needed THX approval for their clientele. Long story short, he bought back all the amps from the facility because he wouldn't degrade the electronics enough to get THX spec. Now, they have THX approved amps, but it doesn't sound like they like it. Oh well.....such is the case so often with "standards".

Now that doesnt make much sense to me. THX are minimum standards, are they not? Surely gear that is of far greater quality meets and exceeds the test. Does the THX testing require that gear not produce results that are BETTER than specified? That wouldnt make much sense. Where were the discrepancies?

[danasti]

Originally Posted by jtg

Now that doesnt make much sense to me. THX are minimum standards, are they not? Surely gear that is of far greater quality meets and exceeds the test. Does the THX testing require that gear not produce results that are BETTER than specified? That wouldnt make much sense. Where were the discrepancies?

That's a good question. Like I said, I had contacted Bryston who makes power amps, some thx certified, if they had to use specific components and they said, "no". I was told then that you just had to meet a minimum requirement of spec and build quality which they did easily. Like I said there was a nasty rumor about THX quality of the Bryston being lower which also made no sense.

I could be misinformed though. Who knows?

[drBill]

Originally Posted by jtg

ANow that doesnt make much sense to me. THX are minimum standards, are they not? Surely gear that is of far greater quality meets and exceeds the test. Does the THX testing require that gear not produce results that are BETTER than specified? That wouldnt make much sense. Where were the discrepancies?

Of course, THX is just a spec. I can't remember all the details, but I do remember that for Ralph's amps to qualify for THX approval, he would have to redesign and build them to a quality (lower) that he was not satisfied with. He refused to do it. For whatever that's worth....

[Pascal Sijen]

Originally Posted by drBill

Of course, THX is just a spec. I can't remember all the details, but I do remember that for Ralph's amps to qualify for THX approval, he would have to redesign and build them to a quality (lower) that he was not satisfied with. He refused to do it. For whatever that's worth....

I am not sure what THX asked him to change, but I doubt that it had anything to do with "lowering the quality" per se.

Here are all the items that THX evaluates when reviewing an amplifier. A manufacturer is certainly allowed to exceed the quantitative performance criteria:

Reference Output Voltage
Voltage Gain
Output Current
Output Source Impedance
Overload Restoring Time
Stability with Capacitive Load
Harmonic Distortion and Noise
Modulation Distortion
Difference-Frequency Distortion
Noise Output Voltage
Phase Response
D.C. Offset at the Output
Hum
Crosstalk
Acoustic Noise Level
Mechanical Noise
Input Sensitivity
Input Impedance
Output Impedance
Load Impedance Range
Voltage Output Capability
Current Output Capability
Transient Output Capability
Transient Overload Recovery Time
Asymmetrical Clipping
Frequency Response
Phase Response
Total Harmonic Distortion
Intermodulation Distortions
SMPTE IM Distortion
IHF IM Distortion
DIM 30 Distortion
Noise
Hum
Radiated Interference
Conducted Interference
Crosstalk

Cheers!

[Jim vanBergen]

Nice stuff here, people. Good thread!

I use some of NYC's nicer cinemas for special events (usually broadcast presentations), and I'm sometimes hired to mix or consult on systems for the presentations of previews/premiere showings of films in non-cinema locations. My personal opinoin, is that THX sets a standard, and provides a great framework for the many irregularities in movie theatres.

THX and Dolby Digital's system specifications help insure that what is pu down on the media translates back to the listener/viewer in a fashion that is relative to how is supposed to be experienced.

Standardizing components, speakers, as well as insisting on proper speaker placement and screen types (including the proper perforation of the screen) has a big impact on how people HEAR the movie.

I'm all for consistency, and the THX systems tend to be consistent from house to house IMO. Some are better than others, sure. But in general, it gives me a sense of confidence before I do a walk-thru and system check-out.

Jim

[drBill]

Originally Posted by Pascal Sijen

I am not sure what THX asked him to change, but I doubt that it had anything to do with "lowering the quality" per se.

Can't say. That's way outside my expertise, but I do know that he wanted THX certificationa and declined the "opportunity" to make amps that met the specs because he felt he couldn't make them the way he wanted to. ???

He built pretty much high end audiophile type mono block amps that cost several thousand a channel at the time.

I'm not saying that THX is junk or the spec is bogus. Just relating a personal anecdote. It's all good.....

bp

[initialsBB]

Off topic a bit but in college I went for a job interview at TMH labs which was Tom Holman's company at the time (still around?). He gave me a demo of some surround process they were working on which I believe was supposed to replicate theater type surround for mixing applications using only a couple of speakers? Something like that. This was before 5.1 was really around but I really didn't see the point although I was pretty clueless about this type of thing at the time. They gave me one of those helicopter flying around your head demos where it didn't actually sound like it was behind my head and I tried to pretend like I was impressed Nice guy though!

[initialsBB]

Then again, looking at the TMH site now my recollection must be wrong because it looks like he's into using MORE speakers than 5.1 not fewer. Apparently 10.2 is the future? What do I know

[JBLpro4645]

I hardly think it’s a scam havening been to several THX sound system cinemas here in the United Kingdom, from the famous EMPIRE Leicester square to Warner West End to the once so called voted number 8 top best sounding THX cinema in the world CIC UCI High Wycombe.
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
Both of which are very pleasing and after seeing many films in substandard cinemas where a lot of the textures of the soundtrack is lost thus it becomes only a routine trip to that cinema. But with THX it’s a simple sign of guarantee the picture and sound is going to be top class.
<o:p></o:p>
I’ll be attending the EMPIRE Leicester square on Wednesday 11<SUP>th</SUP> July for the DIE HARD THX event with 56KW of JBL sound power too blow you though the back wall of the cinema!

[matthew.sawicki]

Originally Posted by JBLpro4645

I hardly think it’s a scam havening been to several THX sound system cinemas here in the United Kingdom, from the famous EMPIRE Leicester square to Warner West End to the once so called voted number 8 top best sounding THX cinema in the world CIC UCI High Wycombe.
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
Both of which are very pleasing and after seeing many films in substandard cinemas where a lot of the textures of the soundtrack is lost thus it becomes only a routine trip to that cinema. But with THX it’s a simple sign of guarantee the picture and sound is going to be top class.
<o:p></o:p>
I’ll be attending the EMPIRE Leicester square on Wednesday 11<SUP>th</SUP> July for the DIE HARD THX event with 56KW of JBL sound power too blow you though the back wall of the cinema!

Is there a reason you keep bringing back threads from last year?

[JBLpro4645]

Originally Posted by matthew.sawicki

Is there a reason you keep bringing back threads from last year?

LOL, Yeah, I’m the ghost of Christmas past!

[Xantis]

Originally Posted by jtg

Im relatively new to the field of pro audio, so forgive my lack of experience. Lately Ive been curious about THX certification. I was somewhat skeptical as to the merits of it because there is huge money associated with the THX name, and I often see it being used as an excuse to charge double or triple what a product is worth.

I notice on wikipedia, it says:

"The THX system is not a recording technology, and it does not specify a sound recording format; all sound formats, whether digital (Dolby Digital, SDDS) or analog (Dolby SR, Ultra-Stereo), can be "shown in THX." THX is mainly a quality assurance system. When a film's producer has it mixed in THX, this means the film's soundtrack will sound, when shown in THX-certified theaters, exactly as the mixing engineer intended."

Which initially sounds like its a reference standard to basically ensure flat frequency response, which is all well and good. But the next sentence:

"THX also provides certified theaters with a special crossover circuit whose use is part of the standard."

Now that sets off some red flags. To me it sounds like that means they throw this in to "color" the sound in a specific way. This means when a mix is created on THX gear, it is assumed to be a flat reference, and as they claim it will sound perfect on other THX gear. But, only because other THX gear is similarly colored (which essentially negates the coloring). But then when it is played on a truly flat system, lacking the special THX proprietary crossover, it isnt actually flat. It sounds like theyre trying to create a captive market with THX gear and alienate other audio. Now, I dont have any knowledge of this "special circuit", but suppose it deliberately cut a specific pattern of frequencies by a specific amount. It would basically act as a "key". To pass the THX certification and be "guranteed compatible", all gear needs the same "key", or those frequencies will be artificially boosted when playing on a non-THX system because the original THX engineer was compensating.

I dont know if it follows a similar principle or not, but the fact that they have a special proprietary circuit, and the huge money around those 3 letters makes it pretty suspicious. It would actually be fairly obvious as a tactic from a purely business standpoint.

Anyone have further insight?

Yes lets see, the THX process in some short notes, you have too re-equalize the source (Mono, Stereo, Multi Chan) all before it gets encoded into DD, DTS, SDDS etc .. I would say use a flat based EQ line and at 2 Khz you go down 1DB per Octave, at this point (The big note) would be a great help, in a surround mix insert a 47 hz bass in the center, set the front speaker wide (50 % or so) ; note that the 47 Hz in your center will be manage by your build in base manager and it will be send to the LFE out, Sub. The output for the lfe can be set at 80 Hertz for home use.
The side rears (bi polar) and the rear wall rears normal, and cut all frequency's off before 100 HZ for the rears thus no low Frequency at or bellow 100 hz for these speakers, the rear center (matrixed) same as i said, if not matrixed some Re-eq can be done in global, trim, adjust and listen. Ain't that bad even if you do only the above steps.

Frans