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Thread: JBL Master Reference Monitor

  1. #1621
    Senior Member grumpy's Avatar
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    I did start with -if-

    and if not disturbed, the fibers don't break or have (very small) bits wandering off.
    I'd personally not be put off using fiberglass for cabinet sound absorption/damping,
    particularly if following a known formula (e.g., M2).

  2. #1622
    Senior Member 1audiohack's Avatar
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    Hi Grumpy;

    Sorry, I meant people in very general terms. The stuff just doesn’t float around is all I wanted to say.

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  3. #1623
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    I think the loose fiberglass and blowing bits concerns are overstated. I recently used the old school fiberglass and there was very little if any shedding, and it was due to the cutting. I think the amount of any fiberglass coming out the ports will be minuscule and unmeasurable (and maybe imaginary). This was the stuff used, from the Widget's 2004 post:#7

  4. #1624
    Senior Member grumpy's Avatar
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    Ha! No need for anyone to apologize to me (pretty much ever)
    Did someone respond to gbadaut regarding M2 insulation thickness?

    I'd expect it may not be uniformly placed (or the same thickness throughout)
    I've not had one to open up and investigate.

  5. #1625
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    It sure looks like 1-inch fiberglass to me. Here is a page that shows a bit of the interior of the cabinet and the insulation. Note the HF network is mounted on top of the insulation and pushes it down so it isn't going to be more than an inch thick to compress down plus looking at the various pieces of wood and how the uncompressed insulation sits relative to that.:

    http://www.audioheritage.org/vbullet...l=1#post375530

  6. #1626
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    New system with M2 and Lexicon

    Just before driving to LA for Annie's uncle's funeral, FedEx dropped this off.
    Attached Images Attached Images  
    Out.

  7. #1627
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    I posted this over on AVS regarding the RV-6, and I'll just quote it here. I expect it to be at least a month before I have anything else to say about it or the M2 fronts.

    Since the amplification isn't needed, I got it primarily as a new front end to utilize with three M2s with a pair of SDA4600 amps. The rest of the system will utilize all Synthesis® amps, surrounds, and, if I'm ambitious, ceiling speakers, plus a pair of S1S-EX subs. Since I can't spatially recreate my old Synthesis® system in this house, I'll "live with" what Dirac can do and get rid of the old Synthesis® pre-pro and SDEC units, plus, maybe, the SAM1HF/SAM2LF front LCR speakers.

    The recent deaths in the family have inspired me to "get it while I can," and make the best system I can in the available rooms rather than pipe-dreaming that someday I'll build that new room that rivals or exceeds the old one.



    Out.

  8. #1628
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    Amp try-outs for the M2s

    I have been running my M2s with a BSS Soundweb BLU160 and Crown CTS1200 amps for a year now and I am very happy. I chose the CTs1200 because I had them already and my gut-feeling prefers class A/B when the speakers play mids/highs.

    But I have been thinking lately if there are any improvements by going for other amps.

    An obvious choice would be the Crown MA5000i which is recommended by JBL Pro if a BSS unit is used. Do you think there would be any noticable change in sound? It's a Class I/BCA amp which I know have exceptionel performance on subs (I'm using a 12000i on subs). But what about mids/highs?

    JBL bundles the M2s with Mark Levinson amps when purchasing through Synthesis. Old-school A/B amps with a big torodial power supply.

    What are your experiences with the various amps? Do they all sound the same if not pushed or is there potential improvement here?

    (Fan noise is not an issue as I have the amps in an equipment room)

  9. #1629
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    For mine, I auditioned QSC DPA-Q (Class-D) and QSC DCA (Class-H) and preferred the DCA series. It wasn't a good/bad. It was a good/better situation. The lower-power DCA series are Class-A/B but the ones I settled on are the DCA-2422, which is Class-H.

  10. #1630
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    Quote Originally Posted by sguttag View Post
    For mine, I auditioned QSC DPA-Q (Class-D) and QSC DCA (Class-H) and preferred the DCA series. It wasn't a good/bad. It was a good/better situation. The lower-power DCA series are Class-A/B but the ones I settled on are the DCA-2422, which is Class-H.
    The DCA-amps are very similar to my Crown CTs1200 actually.

    What differences did you notice between the two?

  11. #1631
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    It just sounded a little tighter/cleaner to me...both the LF and HF just seemed tighter and a little quieter.

  12. #1632
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    Quote Originally Posted by pos View Post
    Here is a comparison of the magnitude response of the BSS measurement Grumpy send me (thanks!) and the FIR one directly derivated from the EQ settings with rePhase :

    Attachment 72274

    As can be seen there are some differences, especially up high, and some trends that appeared in measurements also appear here.
    The Q in the BSS appear higher than normal up high, with other defects, which is a often the case with IIR units.
    rePhase EQs are exact whereas the ones from the BSS suffer from biquad approximations.

    Of course the target response is the BSS one, as this is the one JBL wanted to achieve, and any defect or approximation in the way EQ are handled in the unit was factored in...
    I will try to adjust settings in order to approach the BSS (and hopefully Crown, which should be identical) response curve with rePhase.

    Of course if another IIR DSP unit were to be used, things would be different (not necessarily in a good way )

    Stay tuned!
    Hi POS.
    Have you ever compared the presets from the BSS to the presets from the Crown amps? Do they differ? I can see the presets in the BSS Soundweb and they are not the same as the Crowns filter-by-filter. The slopes are different, no gain on HF/LF EQ and the crossover slope on LF is also different (But 18db/oct instead of LR36 on Crown).

    I also see on JBL Pro site that for DCi and iTech amps the presets are Version 1.1 and RevB where the BSS is RevA. I really hope that JBL optimized the settings for both the Crown and BSS and not just the Crowns.

  13. #1633
    Senior Member pos's Avatar
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    Hi Jonas,

    Barry was kind enough to do some measurements on his crown amps, but incompatibilities between our measurement software got in the way.

    I would be very curious to see those BSS settings. How did you get to them?

  14. #1634
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    Hello,

    Do someone know the purpose of these pieces ? Do they serve for the mounting of the panels ? Or are they part of the bracing to control the modal behavior of the enclosure ?

    Name:  jbl.jpg
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    They are also used in the JBL 4367 :

    Name:  jbl-4367-review-new2.jpg
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  15. #1635
    Senior Member Ian Mackenzie's Avatar
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    I think they hold the bracing in position during the assembly process.

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