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Thread: Small but perfectly formed JBL home cinema

  1. #301
    JBL 4645
    Guest
    I just chatted on the Phillips consumer support by (text chat) the issue has been resolved for the player. I uploaded new firmware this morning not knowing what type of firmware it might be? So I asked a simple question and got simple answer and thatís all there is to need to know.

    Great so I an get Terminator Salivation on bluray again and it should play.

  2. #302
    JBL 4645
    Guest
    Okay Iím going to do an experiment to find a way around this centre issue. Iíll report back in short while.
    http://www.audioheritage.org/vbulletin/showpost.php?p=276811&postcount=675

  3. #303
    JBL 4645
    Guest

    Improving on centre channel with anti-phase centre

    Okay what Iíve done is sent centre from the main AVR decoder to the Yamaha DRP-100 seen in the diagram. The centre invent is helped from the left and right from the main AVR decoder.

    The role of the task is to get a signal sent to the Yamaha DSR-70Pro Dolby pro-logic to place an anti-phase signal to cannel or reduce the amount of signal on the (centre main signal) which shouldnít be on the (main centre channel of Ď2010í).

    There is downside since the signal will reduce some portions of the signal and (will inject a signal from centre phantom left and right). If there is signal of similar sound / frequency or mirror image it will be cancelled out thus freeing the centre front by a small degree.

    The test signal I used was the dts calibration music and demonstration set-up disc (track 14, all-channels) which is a wideband pink noise signal.

    I activate the Yamaha DRS-70Pro which sends out the same pink noise that is being sent to left and right front. I then adjust the centre level on the Yamaha DRS-70Pro so that the pink noise will cancel out the centre. Its only reduced (all or part of the lows) mid and highs are reduced down to very faint sound. Reason is the Yamaha DRS-70Pro has limited bandwidth down to 100Hz so tiny bit low end is heard but its reduced most of the directional.

    Now before most of you start jumping around up and down, this doesnít wreak the sound no worse than it already is. This helps by reducing the centre main will still perform most of its original level.

    There it is, simple. I guess this can be improved upon with fancier audio electronics.

    This can also remove normal half panned sounds from the centre for clearer left and right stereo sound field. Often the phase tends to have you shifting around in the sofa to catch a clearer left and right sound.

    I tired this out a few years ago, with ĎBeverly Hills Copí (1984) when Foley gets tossed out a window and then cops show-up. Thereís subtle effects left and right that had half panned sound filed mixed onto the centre and I found it distracting at the time.

    Today I place a little delay on the DCX2496 centre LF/HF to gain a clearer left and right sound filed, or I can extend it further with the approach that I have just shown you.
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  4. #304
    Member coruphius's Avatar
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    Dude u never sieze to amaze me thats for sure! loong time no see hey!

  5. #305
    JBL 4645
    Guest
    Okay two waterfall graphs of Jerry Goldsmith Star Trek the motion picture main title opening on CD.

    The differences between the stereo 2 channels and Dolby stereo pro-logic and I can see some work still needs to be done on the EQ or each of the two playback modes, not a big deal to sort out.

    I used no sub bass extension I muted the sub, so only the two sides stereo only JBL control 5 are playing and then the three JBL control 5 in Dolby stereo mode.

    Note: around 230Hz on the stereo only a nice warm spot. It’s less on the Dolby stereo mode but that’s just down to maybe placement and a little bit extra EQ to be applied.

    Note: above 250Hz between the two waterfall graphs it’s more or less the same, or varies not a huge big deal as I can see.
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  6. #306
    JBL 4645
    Guest
    The graph shows my diy JBL 4645 sub which is located at the front left-hand side 7 Ĺ feet away. As you can see there is a bit of null between 40Hz and 60Hz.

    If the sofa is moved a few feet forwards its different story where the null will even out, but the lower extreme drops away. Room size is an issue with 15 feet length 10 feet 7 feet 8 inches height.
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  7. #307
    JBL 4645
    Guest
    The graph for the smaller sub Eltax A 12-R which is located 4 Ė 5 feet depending on the angle or where youíre sat on the sofa.

    The response is good across 35Hz to 80Hz where the crossover is set at. It should play find for LCRS sub bass extension on discrete Dolby / dts 5.1 with LFE.1 playing discreetly as to not over taxi the rest of the low end on high impacting film soundtracks.
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  8. #308
    JBL 4645
    Guest
    The two subs summed together JBL 4645 and Eltax A 12-R ďit takes two tangoĒ or even out the frequency response for a smother feeling.

    All is needed now as little parametric EQ smoothing to finalize the level and additional adjustment on the audio mixer to get the rest of the levels LCRS to match up smoothly with the rest of the primary loudspeakers.

    LFE.1 discrete needs to cut in on the smoothly rest of the two subs even thou the LCRS will only be playing on the Eltax A12-R sounds confusing!
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  9. #309
    JBL 4645
    Guest
    The two subs summed together with 1/3 octave smoothing this is still before I apply the parametric EQ which has been already pre-programmed into the Behringer FBQ2496 last night when I ran the same sweep, only I didnít save the graphs till I made fresh frequency sweep this afternoon.
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  10. #310
    JBL 4645
    Guest
    A new picture of me and Sooty sat up front next to my vintage plasticity JBL control 5.
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  11. #311
    JBL 4645
    Guest
    Iíve got some thin MDF for the base platform for the fronts as soon as I get around to knocking it up. Also a few 2x1 or 9 foot lengths to be attached to the front length wall and a few off-cuts for the sidewalls to rest the MDF on.

    Cost was £24.00 sodden VAT!
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  12. #312
    JBL 4645
    Guest
    However Iím also testing out an idea for the soon to be MDF flooring, so I can minimize the SPL db frequency between those neighbours I have below me and vice versa.

    It tends to give smoother feel and was noticeable on the Foley of ďTotal RecallĒ (1990) bluray region 2, during the hand to hand combat between (Rachel Ticotin) Melina and (Sharon Stone) Lori, where Lori throws a few high kicks and sidekick while flipping Melina over her shoulder and flat onto her back with thud!

    The concrete like floor keeps most vibrations to minimum and only a few reach the sofa.

    Nulls and dips will decrees action effect, but with the sub resting on the MDF with a few beams underneath it and the sofa legs resting on the edge of the MDF allows some low frequency vibration transmission to be felt.

    Sooty has been showing slight curiosity of the MDF timber, while sniffing it.
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  13. #313
    JBL 4645
    Guest

    Smile Notarize speech bleed though on youíre sub

    Most of you may hear a little voice speech seeping though the sub on a few occasions. Itís mostly around the 100Hz to 200Hz range that manages to get though.

    Okay, then since the way I run the sound system here is a little different with the low end from LCRS sent from various processors from the main AVR so I can cheat or find away around of controlling the low end thou the 6channel audio mixer.

    The Eltax A-12R crossover high pass filter always lets a little audio low end speech (sound as an audible muffled tone).

    Okay, so how did I solve this? Answer used a few filters on the BFQ2496 and placed sharp cuts of -36db and a little Q to kept most of the male speech that often goes down to 100Hz while monitoring on the RTA.

    So that is it simple fast and it will kinder relax the energy on the subs amp by a few db where some tones are not need, they are however need over the LCR or surround depending on some crazy dialogue panning that moves around all-5 channels.

    Anyhow you donít have to set youíre BFQ2496 or DSP1124 to these frequencies its what I used to make it work here after trail and error of listening to the same moment from Bluray ďStar Trek The Motion PictureĒ chapter 12, thou it doesnít have to be this title or this chapter!

    I also tested the sub bass extension with crossover THX set ON which is around -24db down at the crossover if Iím not too mistaken. The AVR still allows a tiny hint of voice dialogue to filtering though it, (only a tiny hint)!

    With the THX crossover 80Hz turned off as it always since I run an DCX2496 for the LCR and the surrounds have there own amp and bass treble and EQ control my sound system wonít sweat it. So back to the normal way of running and with the (bypass mode turned back to ON the BFQ2496 its like having an extra filter, brick wall, placed right in front where the voices filter though.

    The subs high pass crossover must be very shallow, I doubt 24db more like 12db. Well now I have an extra 180Hz -36db 302Hz -36db 502Hz -36db to deal with it.


    Its all, trail and error!

    The graph below only shows a prediction of what it should look like.
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  14. #314
    JBL 4645
    Guest
    The JBL 4645 sub and the Eltax A-12R have been raised a tiny fraction off the floor with some timber beams placed underneath each sub that extends towards the sofa ware its rests on the timber beams.

    A noticeable difference in the sub bass lows, as the signal is vibrating/travelling the wood and given an extra buzzing feel to the soundtracks low end.

    Its not yet been perfected as I still need to get a load more timber and MDF 8x4 sheets to outfit the flooring.

    Also testing out the JBL control 5 stereo image as well as centre imaging as the height has been risen by 1 Ĺ inches.

    I might allow for an extra 18mm after the flooring is placed down (as and when I get around to that?)

    I have one whole length to place across the front at 8 feet. I need to cut a few feet of the other 8 foot length and attach so that it extends into the front corner.

    The front corner needs to be blocked off so that most of the lows around below 80Hz donít end up with huge dip around in-between the 70Hz range.
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  15. #315
    JBL 4645
    Guest
    Here Iíve moved left and right fronts (only) and placed each one in the centre location for testing.

    Between the three there is a slight difference in the level. With the DCX2496 I only switched off all the (PEQ) for this test, but made no changes to the output levels of LF/HF, even thou Iím only testing the LF range here. I had the HF in mute mode.

    Not much of big, difference its not drastically major, nothing a bit of PEQ canít fix.

    Iíll test one of the JBL Control 1, out later to see how much of difference there is between 40Hz to 2 KHz that was the sweep test I wanted to focus on for now.

    1/3 smoothing applied.
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