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Arcam AV9 - DTS Processing - 7.1 Query

Buckster

Distinguished Member
I've been tempted with buying a 2nd hand AV9 for ages

question though please after looking at manual today. I run a 7.1 setup - and always tend to use DTS + PLIIx extension for bluray playback - so I get full "simulated" 7.1 with the 2 rear centres.

I'd sort of assumed all processors that did PLIIx and DTS could do this - but on looking in the AV9 manaul - its not mentionned at all ?

is there anyway on the AV9 to "extend" DTS from 5.1 (DTS 5.1 is pretty standard "core" for Blurays) to 7.1 ? other than using the THX Ultra 2 mode ?

manual seems to suggest you can do it for D.Digital, ie you can have D.Digital + DPLIIx, but no such mode for DTS ?

THX Ultra 2 mode apparently can be applied - andwould be ok for me to use, but my speakers are fairly warm anyway, and I find the RE-EQ dulls the sound far far too much when I've used THX in the past.

are there any other modes which add the rear surrounds to DTS on the AV9 ? I couldn't see any listed in the manual, it mentions DTS-ES of course, but specifically only if its "flagged" and encoded on the track.

I had thought my AVR350 did DTS + PLIIx but I can't find it in manual either - but perhaps my memory eludes me - wasn't playing as many Blurays those days.

my current Pioneer certainly can apply PLIIx to DTS and had sort of taken it for granted.

whillst I think 7.1 in a small room like mine is pretty overkill - its quite handy in our room layout, as the Rear L/R are parallel to the sofa, wheras the 2 rear centres are about 1 1/2 m behind, and it gives more of a rear depth to the sound.

thanks for any help,

Buckster.
 

KelvinS1965

Distinguished Member
There is a setting where you can have the same signal sent to the rears as the side surrounds and the AV9 will automatically apply 3db reduction to compensate. I use the THX Ultra2 mode on mine and even though I used to find similar RE-EQ on other amps used to make it too dull, I don't seem to have that issue with the AV9 and that's using fairly 'warm' PMCs at the front.

I'll have a check in a minute and see if there is any way of getting a 7.1 signal from a 5.1 DTS source but I'll just have to put a BluRay in to check this...I'll be back (or smoke me a kipper and I'll be back for breakfast :)).
 

Buckster

Distinguished Member
thanks for taking the time to reply and find out Kelvin much appreciated :)

I'd assumed the RE-EQ on THX was the same on all processors/amps - perhaps not, I'm used to it only on Pioneers. I had heard its about 6dB drop in some higher frequencies (on a curve) - but I may have heard wrong
 

KelvinS1965

Distinguished Member
Just done a quick check using Back to the Future so it's a DTS 'core' soundtrack via coax into my AV9: The only options I could find were variations on DTS modes like THX Ultra2, THX Cinema, THX Music Mode and THX off (using the THX button). Using the Mode button I could change to stereo, mono downmixes or 3/2.1 (ie 5.1).

If you're using a DD signal then you can select the PLIIx type matrixing for the rears, but as most BluRays seem to be DTS MA these days then I guess you have to use Ultra2 mode, Cinema or THX off. As far as I can tell these modes use the setting in the setup menu for 'Speakers' where you select what the rears do for 5.1. The choices are to have the side surrounds on only, the rear surrounds on only or both as I mentioned previously which 'shares' the signal between both surrounds and applies 3db reduction.

I'm not sure if the Ultra2 mode does anything 'special' with the surround rears, but I'll have a read up in the manual to see what it says.
 

KelvinS1965

Distinguished Member
I just re read the section in the manual and this is what it says regarding THX Ultra2 mode:

THX Ultra2 Cinema
THX Ultra2 Cinema mode plays 5.1 movies using all 7.1 speakers giving you the best possible movie
watching experience. In this mode, ASA (Advanced Speaker Array)™ processing blends the surround
speakers and surround back speakers providing the optimal mix of ambient and directional surround
sounds. See ‘About THX Cinema Processing' for more information.
DTS-ES (6.1 Matrix and 6.1 Discrete) and Dolby Digital Surround EX encoded soundtracks will be
detected automatically if the appropriate flag has been encoded on the DVD.
Some Dolby Digital Surround EX soundtracks are missing the digital flag that allows automatic switching.
If you know that the movie that you are watching is encoded in Surround EX, you can select the THX
Surround EX playback mode manually.

And also:

ASA (Advanced Speaker Array)™
ASA is a proprietary THX technology which processes the sound fed to two surround and two surround
back speakers to provide the optimal surround sound experience. ASA is used in two modes; THX Ultra2
Cinema and THX MusicMode.

Which seems to answer the question that the AV9 does matrix the rears from a 5.1 source when in THX Ultra2 mode.

Finally the re-eq notes, which confirm that there is some treble reduction going on, but as I said before I don't find it too dull, though I do tend to watch films at around -15 to -10db on the master volume which is quite loud so no trouble hearing the treble at this level. For lower level day to day listening I've setup a second preset (the AV9 has upto 5) as this is where the AV9 is so flexible: I have the tone controls switched on and a few tweaks to them and the surrounds and sub levels increased by 3db to help give a better result at around -30db master volume:


THX technology
Re-Equalization™
The tonal balance of a film soundtrack will be excessively bright and harsh when played back over
audio equipment in the home because film soundtracks were designed to be played back in large movie
theatres using very different professional equipment. Re-Equalization restores the correct tonal balance
for watching a movie soundtrack in a small home environment.

I hope this is of some help.
 

Mark.Yudkin

Distinguished Member
THX Re-equalization is one of those subjects that seems to be misunderstood, and no doubt the fact that one has to pay to obtain a copy of ISO 2969 ("Specifications and measurements for the B-chain electro-acoustic response of motion-picture control rooms and indoor theatres") doesn't help. I'll try to give a summary / reference.

The ISO 2969 roll-off curve:
Specified are characteristics of the B-chain response of motion-picture studio dubbing theatres, review rooms and indoor theatres. They are intended to assist in the standardization of recording monitor and reproduction characteristics of the motion-picture sound in rooms with volumes of at least 150 m3. Not included are conditions where the recorded sound is intended for reproduction in domestic surroundings, i. e. radio and television broadcasting, tape and disk.

Now a reference:
This paper from JBL gives an easily read introduction to the basics of ISO 2969 on pages 4-5, and the need for re-equalization (i.e. compensation) in the home environment for sources conforming to ISO 2969.

The THX curve:
The ISO 2969 curve, dating from the 1950's, is based on measurements rather than psycho-acoustics. As a result LucasFilm tried to determine a psycho-acoustic curve. This yielded a second, slightly different re-equalisation curve. The THX re-equalisation curve is the average of these two curves.

---
Note that THX Re-EQ is not intended to be applied to television, CDs, sports broadcasts or the like, or to films that have been pre-equalized during the DVD transfer. It is targeted at source material standardized to the ISO 2969 roll-off curve.
 

KelvinS1965

Distinguished Member
Some useful links Mark, which I'll take a longer look at tonight. However those charts seem to imply a roll off from 5Khz upwards at 3db/oct according to chart 'c' on page 5. That seems quite a strong cut to treble, which doesn't seem to be case when listening...perhaps my ears are worse than I thought. :D

I have a signal generator and an RMS meter somewhere in my loft. I'm tempted to try to measure the frequency response, but of course this would be using an analogue source (the sig genny) so maybe not directly comparable. In any case it sounds good at higher volume levels and I don't have a screen in front of my speakers.

The hardest thing to find out though is whether the disc is recorded/mixed for use with re-eq engaged or not and therefore whether it should be engaged or not.
 
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Mark.Yudkin

Distinguished Member
However those charts seem to imply a roll off from 5Khz upwards at 3db/oct according to chart 'c' on page 5. That seems quite a strong cut to treble, which doesn't seem to be case when listening...perhaps my ears are worse than I thought. :D
Sorry. I tried my best. Really I did. I quoted the ISO spec's title and abstract. I differentiated between roll-off, equalization and re-equalization. And failed. Miserably :(.

ISO 2969 is a specification / measurement of the cinema - it is a roll-off curve of how the cinema affects the sound. Film soundtracks therefore need to be equalized (altered) to compensate for the cinema - to achieve a flat response in the cinema - just like any room equalization. When played in your small room at home, that same soundtrack will necessarily be too bright, as it was carefully and deliberately equalized to an international standard to be just that, to compensate for the cinema. Accordingly, when replayed in your home, that same sountrack needs to be re-equalized, as your room, not being a cinema, will not measure to the ISO 2969 roll-off curve.

As you say, the hard part is knowing if re-equalization was applied during DVD mastering, in which case it obviously does not need to be applied during replay.
 
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KelvinS1965

Distinguished Member
I don't think you failed. :)

The response I refered to is showing how the cinema effects the frequency response? If so then the mastering will need to be equalised in the opposite direction (ie to boost at 3db/octave from 5Khz) to achieve flat response when playedback in the cinema. If this recording is then played at home, to achieve a flat response the re-eq would have to roll off at 3db/octave from 5Khz. Unless I'm missing something or looking at the wrong response graph?

I'll have to dig out my old test gear and do a frequency response plot for the AV9 (I'll limit it to the centre speaker if that's OK?). I'll measure with and without THX Ultra2 engaged if I can achieve this using an analogue input.
 

Buckster

Distinguished Member
Thanks for taking the time to test kelvin very much appreciated

Thanks to other posters for info on thx I will have a good read through

Still not clear if studios re-eq before bluray is mastered of not

Cheers buckster

=KelvinS1965;13439355]I just re read the section in the manual and this is what it says regarding THX Ultra2 mode:



And also:



Which seems to answer the question that the AV9 does matrix the rears from a 5.1 source when in THX Ultra2 mode.

Finally the re-eq notes, which confirm that there is some treble reduction going on, but as I said before I don't find it too dull, though I do tend to watch films at around -15 to -10db on the master volume which is quite loud so no trouble hearing the treble at this level. For lower level day to day listening I've setup a second preset (the AV9 has upto 5) as this is where the AV9 is so flexible: I have the tone controls switched on and a few tweaks to them and the surrounds and sub levels increased by 3db to help give a better result at around -30db master volume:




I hope this is of some help.[/QUOTE]
 

Mark.Yudkin

Distinguished Member
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