1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

DPL and Sony 930

Discussion in 'AV Receivers & Amplifiers' started by S, Jul 9, 2001.

Tags:
  1. S

    S
    Active Member

    Joined:
    Jul 9, 2001
    Messages:
    237
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +8
    Hello all,

    I've got a STRDB930 which I use to drive two pairs of Tannoy MX2s and an MXC. It sounds great playing 5.1 soundtracks but I'm a bit disappointed with its prologic performance.

    From what I understand of the prologic decoding process, the centre channel signal is basically the component of the stereo signal that is common to both left and right channels. With most two channel sources (especially NICAM) this seems to represent just about everything - with the result that most of the sound is channelled through the centre speaker.

    The MXC is great for dialogue but it just doesn't quite have the response of the MX2s and the overall sound is pretty gutless. I've tried changing the centre speaker setting on the '930 from 'LARGE' to 'SMALL' to force the bass frequencies through the fronts but the difference is barely discernable.

    Is this just par for the course with DPL or is there anything I can alter within my current setup to improve matters?

    (On a related topic, do the MX2s qualify as 'LARGE' or would I be better setting each speaker to 'SMALL' and investing in a sub?)

    Thanks in advance.

    S
     
  2. cozzer

    cozzer
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    s,
    i also have the 930 and have had mixed results from pro-logic. strangely, i get better results from analogue sources than digital ones?!
    having decided to take the plunge and start rebuying my buffy and x-files vhs box sets on dvd, i was expecting to be blown away by the supposedly improved sound quality......
    not a bit of it. the pro-logic sound from the videos was superb - clear and warm with excellent sound from the rears. the dvd sound was , imho, a lot 'thinner' and i had to boost the sound levels to the rear speakers to hear anything like what i heard from the videos!! talk about disappointed. but as i said this is only what i think and i'm sure that many others disagree!! even the picture quality isn't what it should be, but this isn't the fault of the dvd, rather the quality of the video the programmes were originally shot on.
    so the poor pro-logic performance you talk about, was that from dvd or vhs?
    and has anyone else had better pro-logic results from vhs than dvd?
     
  3. Reiner

    Reiner
    Active Member

    Joined:
    Jul 16, 2000
    Messages:
    3,315
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    61
    Location:
    Germany
    Ratings:
    +13
    I think I must clear up some confusion: NICAM/Stereo may give some effect when Dolby Pro-Logic decoding is activated but it must not be true DPL unless the (stereo) soundtrack actually contains a DPL encoded signal.
    When you listen e.g. to CD you will find that there is something coming out from the center and rears, but IMHO it's all rubbish.
    And I think that is similar to what you are experiencing.

    I know people who swear it sounds good and that CDs are even mastered in DPL, but nevermind ...

    The MX2 are good speakers (I assume this based on the fact that I owned M2s before) and must be set to LARGE since you do not have a subwoofer, else you will loose out on the bass / LFE.
    At this stage check that the subwoofer is set to NONE in the 930, else setting the center to SMALL will route the bass into nowhere.

    However the effect may not be that great since the cut-over frequency is probably somewhere around 80-120Hz (depending on model/make of the AV amp) only, so higher frequencies than that will still come out from the center.

    Only thing I can recommend is to switch off the DPL processing and listen to plain ol' stereo instead. Not what you actually want to hear I guess ...

    Ah, and yes, I would highly recommend a sub, that's where homecinema fun really starts!

    As to cozzer's problem: I think you disappointment is based on the fact that X-Files was originally in DPL only, so if now offered in 5.1 (I assume that's what you mean with "digital sound") I don't think they actually have remixed the soundtrack but just recorded the DPL channels into the 5.1 channels, the rears are therefore probably mono only, even though they are discrete now.

    I rekon to balance the soundlevel of all speakers with a SPL meter, else any comparision of what sounds "better" (louder doesn't mean it's better or correct) is of no use.
    Then again if you like your rears loud(er) why not just increase their level?

    Note that DVDs are not necessarily mastered in the same way, hence speaker levels on DVD might differ from each other.
    In real life this would mean you would need to calibrate your levels for each DVD, but that's hardly practical, isn't it? And unless each DVD provides a reference signal it's pretty much impossible.

    [ 10-07-2001: Message edited by: Reiner ]
     
  4. cozzer

    cozzer
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    reiner,
    cheers for the response and sorry to hijack this strand from s!!
    when listening to pro-logic from dvds i do boost the levels from the rears but it gets a right pain in the backside to then have to swicth them back when watching a full 5.1 disc (i know, i know but i'm lazy!).
    has anyone ever listened to the same soundtrack from different sources - ie the exact same dolby stereo soundtrack, played through pro-logic decoding, from both a video and dvd, as in the case of the buffy or x-files soundtracks, and noticed the difference?
    obviously there will be a difference, but i much prefer the analogue version of the soundtrack on the vhs to the dvd version.
    could this be like people staying the vinyl sounds better than cd???
    what does everyone else think?
     
  5. Nike

    Nike
    Active Member

    Joined:
    Feb 27, 2001
    Messages:
    654
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    bournemouth, UK.
    Ratings:
    +17
    S, What you have just described is the effect of putting a 2channel signal with no surround encoding through a DPL processor; everything is routed through the centre speaker and it sounds crap.
    My Yam DSP-E800's default setting is prologic and if I play a stereo signal through it (ie only 2 channel L & R) I have to select 'effect off' to avoid this. Not knowing too much about how DPL works I get the impression that it is trying to decode something that's not there.
    This can be annoying particularly if watching a film on terrestrial TV that IS in DPL and then switching to another channel where the programme is in 'plain' 2ch stereo.

    Please correct me if I am wrong on this.

    Do some processers detect the difference between conventional 2channel stereo and DPL/Surround and avoid this?
     
  6. Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    There is no analogue (vhs/terrestrial/sky) "flagging" system adopted. The Pro-Logic chip will simply try to "draw" the matrix from any given source material be it mono, two channel mono, stereo, Dolby surround, Dolby Pro-Logic. It simply "looks" for out of phase information recorded within the (stereo) soundtrack, (90 degree's left and right or leading/lagging if you like at +3db respectively contains center and surround channel informations) a modified Dolby B reduction circuit "seperates this "matrix" and (nowadays) DSP's direct and control "leakage" and "break-in" to deliver the relevant info to the seperate output stages of the amp. IT will do this forever and a day with anything you give, Reiner is correct in that the results are unpredictable with anything but specifically encoded, typically you will here a "pumping" effect across the center/surround speakers as the chip evaluates the phase relationship of the music itself as opposed to specific out of phase info on "proper" sources. NICAM (Near Instantaneous Compounded Audio Multiplex i believe) is not relevant to the Dolby process.
    A digital (dvd) Pro-Logic source (while obviously still dependant on the quality of the code) should "in theory" give a better quality in sound over analogue (vhs/t.v) given it's lower noise floor etc but will still be limited by the restrictions of Pro-Logic decoding (lesser dynamic range, leakage and inherent phase errors) commo to this form of matrix encoded soundtracks.
    This also extends to the newer formats, i have a R2 (dts es discrete) and R2 (dts es matrix) copies of Gladiator and when listen to the back surround channels only the difference (unsurprisingly enough) is exactly the same as comparing (for instance) a surround channel of a Pro-Logic film and a surround channel of the same film in Dolby Digital.
    Does this help at all?

    SteveEX
     
  7. S

    S
    Active Member

    Joined:
    Jul 9, 2001
    Messages:
    237
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +8
    Thanks for all the responses.

    I guess the bottom line is that DPL decoding doesn't sound so great when its applied to sources that aren't DPL encoded.

    I really only use DPL for TV but it's a bit irksome having to constantly swap between stereo and DPL to decide whether a broadcast is encoded or not.

    The disappointing thing is that I know DPL can be made to work effectively with straight two channel stereo with a bit of tweaking. My car stereo has a prologic decoder which has been adapted to suit the car cabin: part of the centre channel signal is fed back to the left and right channels to create two mid-impressions (one on front of the driver and one in front of the passenger) while the rears are fed with the surround channel AND the low-frequencies present in the original stereo signal (filtered off prior to the decoder). I was extremely sceptical at first but I have to say that the effect is amazing (much better that I get applying DPL to CDs with the '930). If anyone's interested, have a look at www.imicon.or.jp/kcc/volvo/showroom/c70/c70_audio.html. The article also includes a really good description of DPL and surround sound in general.

    As regards the sub, I think I'll take the plunge and order an MxSub10 to go with the other MXs. Shame Tannoy only do it dark oak.

    Cheers

    S


    PS. I think the C in NICAM might be 'companded'.
     
  8. S

    S
    Active Member

    Joined:
    Jul 9, 2001
    Messages:
    237
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +8

Share This Page

Loading...