I just finished several fruitless hours searching the THX site and the Web. Although the 5.1 standard is explained (i.e. an Ultra configuration specifies dipoles for the left and right surround channels), I could find no mention of what type of speaker(s) should be used for the new rear center channel, whether using a single speaker or a pair of speakers. Does anyone know?

BTW, if you know that one, could you also explain what the Select specifications are? :)

-Bruce

Bruce; You may be able to get your answer by inference.
Spec out an existing total THX system package.
RE rear centre: I was told to try & match my front centre as close as possible so I chose per size & type of speaker & materials & the specs. I have never seen a speaker sold identified as a "REAR" centre.
RE Select: It seems to be on some pretty inexpensive (low cost) models.
Question: Dolby 6.1 vs DTS 6.1 are the rears supposed to be dipols for both? I was told to use Bipolar because of the DTS ??
Dougofthenorth (starting to question everything "I was told")

Bruce, I don't have the specifics in front of me, but the main difference between Ultra and Select is the intended volume of the space. I do remember from reading that my room, at 16x26x8 is within the Ultra (larger of the two) range, if I'm not mistaken. However, I'm still happily without any THX-spec'ed equipment.

Larry
www.fineelectricco.com

This message was edited by Larry Fine on 12/18/01 13:13.12.

I also can't remember specifically, but I believe Select is 2000' and up. Ultra is 3000' and up. That's cubic foot.

According to my Maculator, 26x16x8=3328. Yup, I'm in the Ultra-zone.

Larry
www.fineelectricco.com

Thanks everybody for your input so far.

Doug, I took so long to reply because I was waiting for some response from THX, Dolby, or DTS to my e-mails. (The silence is deafening, at least so far. To give THX credit, they state they don't reply to most mail). Also I wanted to study DTS before I tried to talk about it.

Anyway, re your question about dipole/bipole DD 6.1/DTS, etc... Both DTS and Dolby go to great lengths to explain that THX is not a competing standard. At the risk of over simplifying, Dolby and DTS concern themselves with getting the sound into the system (often referred to as the "A" path), and THX is a standard for playing that sound back into the theater (often called the "B" path).

Therefore, the THX standards are compatible with both DD and DTS playback. The requirement to use dipole surround speakers only applies to a Home THX Ultra setup, by the way: THX Select allows direct radiating surrounds. And as Larry has often pointed out, you can get great sound without a "THX certified" setup, too.

BTW, anyone know what the THX Ultra2 standard consists of? Sheesh...

-Bruce

Bruce; Thanks for the info - my setup is good then.
Bye the way - what format was the deafening response in?
Re: Ultra2 -THX Ultra2 uses seven channels of amplification to play back any multi-channel-encoded program through a single fixed seven-speaker/one subwoofer layout. In the new THX Ultra 2 Cinema mode or THX MusicMode, all program material with 5.1 channels or more is auto-detected and proprietary processing is applied that blends the directional and ambient surround information prior to replay through four surround speakers — two at the side and two at the back. Ultra2 receivers and controllers also feature switchable Boundary Gain Compensation (BGC) to alleviate "boomy" bass performance that can occur with near-wall listening positions.

[Link: thx.com]

Dougofthenorth

This message was edited by Dougofthenorth on 12/20/01 07:36.23.

I return the favour of a lot of info I have recieved from many of you. This is what I researched - hope it helps
THX ULTRA Speaker Systems:
Feature: Front Speakers feature focused vertical directivity.
Benefit: Listeners enjoy a sound of unparalleled clarity, with minimal intrusion from the effects of the listening room.
Feature: All THX Ultra Front Speakers in a system must have a virtually identical sonic signature.
Benefit: Listeners hear the exact position of front images and pans.
Feature: Fronts, Surrounds, and Subwoofers are required to reproduce substantial continuous sound levels.
Benefit: THX Ultra Home Theatre owners enjoy a large dynamic performance margin, and can play at or above reference levels with any program material (producing 105 dB and beyond) with no distortion

THX SELECT Speaker Systems
Feature: THX Select Front Speakers have a simplified and refined directivity pattern.
Benefit: THX Select Speakers may be smaller and easier to place, yet have superb tonal balance and clarity, and encompass a much wider range of speaker design philosophies and sound types.
Feature: All THX Select Front Speakers in a system must have a virtually identical sonic signature.
Benefit: Listeners hear the exact position of front images and pans.
Feature: THX Select Front Speakers can have bass extension beyond that of THX Ultra Speakers
Feature: The dynamic capability of the product is better suited to small listening rooms and multichannel digital audio.
Benefit: The THX Select specification permits greater flexibility in design and choice of speaker components, so the Fronts, Surrounds, and Subwoofer can be smaller and less expensive, yet have the same peak sound level as existing THX products (105 dB).

ULTRA2:THX Ultra2 uses seven channels of amplification to play back any multi-channel-encoded program through a single fixed seven-speaker/one subwoofer layout. In the new THX Ultra 2 Cinema mode or THX MusicMode, all program material with 5.1 channels or more is auto-detected and proprietary processing is applied that blends the directional and ambient surround information prior to replay through four surround speakers — two at the side and two at the back. Ultra2 receivers and controllers also feature switchable Boundary Gain Compensation (BGC) to alleviate "boomy" bass performance that can occur with near-wall listening positions.
THX Ultra2 LCR and rear surround speakers have been revised to minimize any changes in perceived timbral balance over the widest possible listening area, and Ultra2 subwoofers now have bass extension down to 20Hz, to better reproduce the very low frequency information increasingly found in modern digital multi-channel recordings.
Ultra2 SUBS: To pass the Ultra2 specification it had to extend to 20 Hz at its -6dB point. The response also had to tightly follow a target of a Linkwitz Reilly sixth-order shape to within 1dB.
Dougofthenorth








This message was edited by Dougofthenorth on 12/20/01 08:36.55.

Doug,

All Right! So, it appears there is no Select or Ultra standard for the rear center speaker(s), because they only address 5.1 configurations. I guess I'll just match them to my other surrounds.

And reading between the lines of that press release link, I see that all four Ultra2 surrounds are identical dipoles, At least the Snell system is. Published September 7th, huh? I guess I was asleep when I scanned that page (oops :)

I wonder what the Ultra2 speakers "revision to minimize changes in perceived timbral balance" entails? The original standard already calls for "Timbre Matching" circuitry in the processor.

Do you think "Select2" will follow? Aargh! Stay tuned...

-Bruce

This message was edited by Bruce Burson on 12/20/01 08:41.32.

RE: CENTRE REAR SPEAKER
I researched all over & went through makers of speakers and makers of complete sets of THX (& other)
surround setups. findings 1) 7.1 -forget it 1) 6.1 rear centre - no specifics or direct references to a centre rear spec- only inferences that it would be the same as centre front - however the way THX deals with its surround speakers & speaks of balancing I would not be surprised to find it may not be like the centre front. I have "asked around" & have been told to use the same (matched) speaker for my rear as I use for the front. But hey the Yam don't have DPL2. Could there be a diff in speaker type between DPL & DPL2?
NOTE: 1)On this journey I have garnered that DTS & Dolby treat the rear speakers different: DTS - "direct", & Dolby "difuse". (I don't know the Bipolar/Dipolar thing enough yet to comment using those reference terms, I think there is a 3rd as type well.
Bruce; RE CENTRE REAR: (I wish I knew the diffuse/direct/direct radiating/bipolar/dipolar terms to explain this correctly but I'll try my way.
As the front speakers LCR front & rear are type "A"
& if one buys a THX system with a centre rear they are sold a speaker identical to the front type "A" I think you can't go wrong with doing so.
But as per M&K THX Ultra (not Ultra2) "gives you the choice of dipole or tripole radiation to best fit your room and source material." so using a dipole or a tripole is allowed for.
Therefore there is a diffence in the way Select/Ultra/Ultra2 present sound.
I wonder why the centre rear type spec is not just stated not just by inference??
Also it appears DTS address this issue in a different way & uses type "B" speakers. Yam also uses a "C" type speaker for the 2 Front Proprietary speakers.
Not just Snell try [Link: atlantictechnology.com]
& Also M&K [Link: mksound.com]

This message was edited by Dougofthenorth on 12/20/01 10:52.07.

Bruce;
Since you are such a great guy I'll share a secret? (depends if you saw my post I put last nite before I deleted it) I responded that I was going to give you
the specs on Ultra2 but my "in the know" buddy had told me he would give me the !!THXII !! specs which would get you ready ahead of time & would address your Ultra2 concerns as it (THXII) was backward compatable! (heh heh) BUT I woke up this am & thought this type of "joking around" may not respect the tone of the discussions & focus on helping each other - so I deleted it. (heh heh) I thought it was pretty funny though!!! - thought I would share !!
RE: Select2 I will bet my Yam on the ever changing,
never stopping upgrade game. (by the way in computerland SCSI now has a ULTRA2 mode as well)
Select2 - hah! you ain't even close to where it's going! "many a word said in jest comes to pass" THXII -I'll bet my Yam on that to! Hopefully I'll lose it & then I can get an upgradeable A/V recv'r!!(heh heh)
RE: "timbral" matching - one of the high end makers has a proprietary built in circuit that compensates for the sound reflected off the TV screen!!
FLASH FORWARD IN TIME: Each person entering the room to listen to your HT setup is acoustically fingerprinted & you key in the sitting position of that person. The higher end ULTRA2 versions of the setup would have an AUTO SENSE to allow for the wife leaving the room to go for a pee. As customers have been complaining about sound & ambiance loss when pets enter & leave the room, the Vetenarian Association will be encoding information into the subcutaneous PET FIND chip to allow the A/V recvr's to AUTO SENSE pet movements.
REALITY: A thought; I know that one can "balance" a speaker configuration with the use of an equalizer & a microphone connected to an oscilliscope & using formulas (& Larry's Maculator?) to allow for room dynamics. Would it not then be technically possible to have the Recv'r generate a series of require test tones & have those sensed by reading the fluctuations in voltage/amperage to each speaker caused by the "acoustical pressure" acting on each speaker? Thus auto-balancing the acoustics to the required/desired parameters? I bet it comes down to a $ factor only.
Dougofthenorth (obviously felt frisky last nite!)

This message was edited by Dougofthenorth on 12/20/01 09:41.00.

Uh Huh... My brain hurts.

I used Snell because it was the only model mentioned in THX press release.

BTW, "Tripole" is a M&K special term. Please let me know if you encounter it anywhere else?

Flash Forward: Individual audiograms then programmed into separate multi-channel headphones. Tailor made to accomodate that 20db drop-off in your ears from too many rock concerts, immune to pets and other room resonance speakers, and you can't talk to me while I'm trying to enjoy the movie! Hook up a set of 3D projectors built into goggles, and I don't even need a TV anymore... and the wife takes the set with her to the loo, so she doesn't miss a thing. Kinda fun watching her fumble her way across the house -- no wait, I've got goggle on and can't see her.

I posted the info for tripolar on another thread in HT.
Dougofthenorth

Just got a reply from THX: The Ultra 2 standard allows for either direct or dipole speakers for the center rear channel. The individual who replied went on to say he personally uses dipoles for the sides and tripoles for the rears.