JBL N-Center

Discussion in 'Archived Threads 2001-2004' started by BryanJ, Aug 29, 2001.

  1. BryanJ

    BryanJ Auditioning

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    Does the JBL N-center sound good for movies ?
    does it compete with the center channals that the movie theaters have ?
    How is the dialog durring movies ? is it good does it sound real does it have good midrange, highs and bass ?
     
  2. Jack Lee

    Jack Lee Extra

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    The N-center is not supposed to have very good horizontal dispersion (many horizontal centers don't). On axis, it's a little more treble peaked than the N-24 bookshelf.
    If you already have N-24 bookshelfs for fronts, you could use another N-24 as a center. It has a low enough profile and is a better speaker.
     
  3. Jack Lee

    Jack Lee Extra

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    No Sean.
    A horizontal MTM array will usually limit horizontal dispersion. There is interference around 1-3Khz (so-called combing effects) between the side mid-woofers and tweeter for frequencies near the crossover frequency. The effect of combing is to place a node (ie. dip in SPL) on either side of the tweeter for these frequencies, leading to poorer, i.e. narrower, horizontal dispersion pattern right at the top of the mid-range. The nodes vary in space with frequency leading to complex "picket" fence or comb pattern.
    (ASIDE: In a certain sense, this is in direct contradiction to one of the main reasons why Dolby recommends using a center speaker in the first place. "When identical information is played through two speakers instead of one, there is contructive and destructive interference near 2KHz that effects the intelligilibilty of dialog." The very combing effects that are supposed to be reduced by using a center speaker can re-emerge w/a horizontal drive array!)
    Your usual vertical tweeter-midrange has a null over your head (or down at the floor), so it doesn't usually limit performance.
    The ugly truth is that most horizontal speakers are made horizontal to fit on top/below a TV - there usually is no performance advantage.
    This does not mean all horizontal center speakers have problems, just that it is an inherent issue to design arround in order to make the speaker convenient. There are several designs to minimize combing effects (vertical TM w/side woofers, offset tweeter, close arrangement), unfortunately the JBL N-center has not been measured to do especially well:
    http://www.soundandvisionmag.com/SoundAndVision/Article/Features/priceri ght0130/priceright0130p13.html
    "JBL's N24 left / right satellite had smooth, uniform response over the entire ±60° window. There was some roughness between 2 and 8 kHz, and there was a tweeter resonance just below 20 kHz. The N-Center had a rising high-frequency characteristic and a deep notch near its crossover frequency at 15° off-axis. Tom Nousaine"
    Note this is from the SAME article that Phil Iturralde references w/the frequency response graphs he posts below. Averaging over +/- 45 degreees has a tendency to hide deep notches at +/- 15 degrees.
    Notice the frequency response curves: the N-center (blue) has a peak near 10Khz in the high treble range.
    The idea of identical speakers for L/C/R is to have (nearly) seamless front stage performance. If Bryan already has N-24 fronts, IMO using another N-24 for a center will be better. Even on axis, the N-24 is cleaner than the N-center.
    If you want, I can privately mail you general references on MTM design and combing effects. You can do a search and see that some people go out of their way to place their center speakers vertically to avoid poor horizontal dispersion.
    Sean,
    Sent you a PM about N-26's. Sorry to hear a single bookshelf didn't work out better. It was worth shot. Seems like most people are happy enough with the N-center.
    [Edited last by Jack Lee on August 30, 2001 at 07:23 PM]
    [Edited last by Jack Lee on September 01, 2001 at 04:03 PM]
     
  4. Phil Iturralde

    Phil Iturralde Screenwriter

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    Personally, I agree with http://www.geocities.com/p_iturra/NSP1_Review.html
    Frequency Response
    N-24 front left/right...... 89 Hz to 18.9 kHz ±2.7 dB
    N-Center....................... 89 Hz to 20 kHz ±5.5 dB ***
    N-24 surround............. 89 Hz to 18.4 kHz ±3.2 dB
    quote: IN THE LAB: ***The (N) center speaker's response was averaged over ±45°, with double weight directly on-axis, where the primary listener will sit. - Tom Nousaine[/quote]
    The N-Center blends very nicely with the JBL N24's, "making movies seem more like I was hearing them in a real theater" (to quote Brent), . . . it fit's on top of my http://www.geocities.com/p_iturra/HT_Room.html ) has no complaints!
    Phil
    ------------------
    http://www.geocities.com/p_iturra
    [Edited last by Phil Iturralde on August 30, 2001 at 10:04 PM]
     
  5. Jack Gilvey

    Jack Gilvey Producer

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    As I've stated in various threads on the use of "phantom" center channels, I find it ironic that the typical MTM center sounds worst to those whom it is supposed to benefit, the off-center viewers. The MTM design decision, as used horizontally in a center channel, is by-and-large a marketing and aesthetic one, not a performance one.
    Having said that, I own the JBL NSP-1 system, and I don't find a very noticeable null, at least at the ends of my sofa. The performance of my last center, the NHT SuperCenter, was vastly inferior in this regard. I did try one of the N24 satellites in the center position, and preferred the N-Center due to its good off-axis performance and slight "presence peak", which helped a bit with dialogue intelligibility. I'll also admit that it did look better than the N24 on top of the TV. [​IMG]
     

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