JBL Northrige owners....upgrade your sound for $5!

Discussion in 'Speakers & Subwoofers' started by Frank Carter, Jan 7, 2004.

  1. Frank Carter

    Frank Carter Screenwriter

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    I started this small project mainly because I got bored. On another forum I read of someone complaining about the quality of the N24 so I got curious and decided to take my parents JBL Northridge speakers apart. What I did was pick up two cans of rubberized undercoating from Walmart, it cost me a whopping $2.50 a can. It's in the automotive section and it comes in a red can. Click on the link below to see what the can looks like. I sprayed it on the inside walls of the speakers to help deaden the enclosures. I ended up using one and a half can's on all five speakers. I took some pictures along the way to help encourage some others to try this out.
    http://www.bondo-online.com/catalog_...sp?itemNbr=484

    If you've never used rubberized undercoating before, it can be a pain to clean up so make sure you properly tape off everything you don't want to get it on. I highly suggest you wear gloves when you do this because I let some sit on my skin a little too long and it took about 20 minutes of scrubbing to get it off. I found it was easiest to wrap the whole speaker in newspaper, cutout the holes with a sharp knife, then use masking tape. I taped the corners and edges because the paper kept ripping.

    Taped up speakers
    Newspaper wrapped N26

    As some of you might know, the enclosures of these speakers are made out of plastic(N26II's are now wood). The plastic seems to be about 1/8" thick with plastic ribbing running through the inside to help strengthen it. While playing music through them I could feel a good bit of vibration through the cabinets(the N26's were the worst) so that's what prompted me to do this. The N26's also have a metal tube that goes from the front to the back of the enclosure as well.

    N26 tube

    The JBL NCenter has one vertical brace in the center of the enclosure.

    NCenter brace

    There's also one piece of polyfill that's probably around 1.5" thick that's big enough to line most of the back wall of the enclosure.

    N24 & N26 polyfill
    JBL NCenter polyfill

    After I unscrewed the drivers, I simply unscrewed the crossovers, and pulled off the wires from the back side of the binding posts. Here's a few pics of the crossovers

    JBL N24 crossover
    JBL N26 crossover 1
    JBL N26 crossover 2
    JBL NCenter crossover
    JBL NCenter crossover inside of enclosure

    Before I sprayed the inside I taped up the screw holes for the crossover, and the connections on the back side of the binding posts. On the NCenter make sure to cover the inside of the port opening unless you want a black stuff spraying on something through the back of the enclosure.

    JBL N26 inside tape

    I found that you really need to shake the can very well and for a long time to get it to spray smoothly. If you don't it will work just find but it comes out kind of clumpy. I did the NCenter last and you can see it's coated much smoother than N24 and N26. Here's a few pics after I've sprayed them with the rubberized undercoating:


    JBL N24 inside after spray
    JBL N24 closeup inside
    JBL N24 closeup inside 2

    JBL N26 inside after
    JBL N26 close up

    JBL NCenter inside after spray 1
    JBL NCenter after spray 2
    You can also see the two holes that for the crossover that should be covered up before you spray in the above pic.

    Here's a few pics of the drivers:

    JBL N24 closer to the camera, N26 farther from the camera
    JBL NCenter drivers



    Ok, so you see all the pictures now how exactly did it change the sound? Well I'm not one for subjective mumbo jumbo so I'll keep it short and sweet. For a comparison, I did one N24 and one N26 at first so I could directly compare them side by side. The first thing I noticed was that the sound stage was seemed to be more forward on the and the bass actually decreased. I'm guessing the cabinet resonating was adding to the perceived bass. These speakers aren't meant to produce lots of bass anyways so it's not a big deal. Vocals seemed to be clearer and I could turn the speakers to a higher volume before things seemed to get "muddy". One thing I hear people say a lot when it comes to tweaks is "it was like a blanket was lifted off of my speakers", well that's not what this is going to do for you. With what I did, it's more like a lifting a silk sheet from the speakers giving them a clearer and more forward presentation.

    I noticed the biggest difference in the N26, probably because it had the largest panels to vibrate. Before I did this I always thought preferred N24's because I thought the midrange was better than the larger N26, but after spraying the undercoating the midrange on both seems to be about the same but now I prefer the N26's overall tonal balance. The same tonal differences I found on the N24 and N26 applied to the NCenter.

    If anyone in the DC area wants to compare their Northridge speakers to mine to hear the difference just shoot me an email or PM.
     
  2. Geoff L

    Geoff L Screenwriter

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    Hey Frank

    Glad to hear the messy stuff was worth it Frank....Shake twice srpay once, right, kidding....

    Can't just leave well enough alone can you. [​IMG] Oh yes, the nature of DIY, and now your tweaking on JBL's plastic work.

    Seriously:
    Very nice documentation of your afternoons tweak work. Nice to know the idea brought forth a noticeable (surely to the good) audiable difference to the folks JBL North/R speaks.

    Now don't you have another killer sub to build or something! [​IMG]

    Cheers
    Geoff
     
  3. Steve*W

    Steve*W Agent

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    Thats really interesting considering that I'm all but decided on N24's as my new rears. Think i'll have to give that a try when I get them. Thanks for the tip.
     
  4. Frank Carter

    Frank Carter Screenwriter

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    No problem. I noticed the least amount of difference on the N24's but the difference is still audible.
     
  5. Geoff L

    Geoff L Screenwriter

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    That rubberized undercoating can be used for allot of different stuff. Those that may try this or maybe some other tweak using it, be sure and let it dry completly before assembly. The fumes can eat on driver parts while drying.
    Especialy likes foam surrounds

    A little off subject:
    Wow Frank, thought you would have blew that sub together already.

    Yes, cold, very cold here also. Like -6 right now! Warmer tonight...[​IMG]

    Did you notice that the nice 250-amp find you got, has dropped in price even further. They also have picked up a 500-watter now too. Ain't that always the way...

    I'm sure it will be an excellent sub for the parents rig when you do get to finish it....

    One of my Rythmik amps is giving me some trouble, so I'm glad I still have the PE's laying around. Was just about to put them both up for sale... Threw one in while Brian puts a fix on the (most likely going out smaller 80V caps). I picked that Rythmik amp up before he made the change over to the 100V's...

    Be sure and take a few pic's of the parents subage unit when it's finished!

    Regards
    Geoff
     

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