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Gallien-Krueger Neo 112-II - test for blown driver or crossover

Discussion in 'Amps and Cabs [BG]' started by 9985, Feb 17, 2020.


  1. 9985

    9985

    Mar 22, 2018
    I have an older GK Neo 112-II cabinet, purchased used 2 years ago in good condition, use it with a GK MB Fusion 500 head. Blew the woofer at band practice yesterday. Was playing at about 50% master level on the MBF 500, hitting it pretty hard with a Fender Elite J-Bass with 18v active pickups; the cabinet suddenly produced a few ugly farty sounds, followed a few seconds later by cutting off all but very slight sound out of the horn only - I immediately shut everything off. the MBF 500 head tested out fine on another cabinet, so problem is definitely in the cabinet.

    Troubleshooting steps: pulled the cabinet's crossover - the 2 lamps (fuses) in the crossover visually look fine, and both test good on a multi-meter. Took off the front grill & pulled the woofer - doesn't show any obvious rips or separations- but it tests dead right at its terminals when cable is disconnected from crossover.

    The horn tests fine, multi-meter reads about 7 ohms at its terminals when disconnected from crossover.

    Using a 1/4 speaker cable connected to the crossover set to full range, it seems fine- tests about 6ohms through to to the horn- even temporarily connected the horn to the woofer terminals on crossover & get same 5-6 ohms reading there too- I am 90%+ sure crossover itself is good & issue is only the woofer. This is the older part number woofer, 082-0340-A - found a TB post that said there were early QC issues with that version when being pushed hard- newer model replacement listed on GK site is part# 082-0340-B (vs "A").

    So- two questions:

    1) Before I order a new woofer, is there anything else I need to test? I had a blown Neo 410 horn and a blown LM3886 treble amp on a 700RB-II in 2018, so I am sadly fairly familiar with the troubleshooting drill, although this is the first time I've ever killed a woofer.

    2) After I get the 112-II fixed - is running the MBF 500 hard into it w/active pickups, boost/EQ pedals, etc. asking for trouble? That head puts out 350 watts @ 8 ohms. The latest revision of the Neo 112-II cabinet is rated at 400 Watts @ 8 ohms per the GK website; the sticker on back of my older model say it is only rated for 300 watts @ 8 ohms, maybe due to the older revision of the woofer. I love the small size/portability of that cabinet for practice, really don't want to have to get a 1x15 or 2x10, or god help me muscle my 4x10 up & down basement stairs.

    thanks all -
     
  2. Wasnex

    Wasnex

    Dec 25, 2011
    Pretty sure the crossover is only an HPF section and switching, so you can bypass the HPF if you want to use the biamp capabilities of the RB series amps. Pins 1+, 1- of the speakON should be a dead short with the woofer terminals.

    350W is a lot of power for a single 12" driver, especially if you are cranking up the low end. Often manufacturers provide the thermal rating of the voice coil without providing the mechanical power handling capability of the cab. Below 100hz the mechanical power handling is often less than the thermal power handling. So yes if you are running the MBF into clipping and pushing heavy lows, it is possible you may blow the replacement driver as well. Keep in mind the amp is rated for 350W clean, so if you are pushing it into clipping and it does not have a built in limiter the amp may actually be making substantially more than 350W.

    Another thing is the mechanical power handling of ported cabs drops off exponentially below the port tuning frequency. You may want to consider getting an HPF pedal so you can roll of the extreme lows that are below the cabs intended pass band. The listed -3db point for Series II Neo 112 is 51hz. You don't want to force the cab to operate very far below 51hz as it can't produce sound efficiently in this range, and the driver will be jumping around like crazy.

    I have an old 700RB/112 combo. The amp makes 225W into the internal speaker. What I have noticed is that it reaches a certain point and it won't go any louder, it just gets more and more compressed. Rather than pushing the rig into heavy compression and risking the driver, I bring an extension cab when I need to be loud. Generally we I am playing in a cover band I need the extension speaker. The combo alone is good for jazz trio.
     
  3. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    You can scratch the last part of that about the active pickups, boost, and pedals out of the equation.

    A single Neo 112-ii is not a lot of cab for many situations, and an MBF 500 is more than capable of doing nasty things to one regardless of what the wattage ratings are.

    You probably need another 112.
     
  4. 9985

    9985

    Mar 22, 2018
    Thanks for the reply. MBF does have a limiter switch that was on, and it wasn't running to clipping. I have an Empress EQ pedal that I can use to cut the low end below 51Hz with that cab, great suggestion. Will also be careful about keeping bass on 3 band EQ dialed a little lower, and Deep setting off (it was on when it blew), and the master level a bit lower, this is only a practice cabinet, but definitely not a jazz trio... old Judas Priest song was being enthusiastically butchered when I murdered the driver :)
     
    Wasnex likes this.
  5. 9985

    9985

    Mar 22, 2018
    Thanks for the suggestion. The MBF 500 was an impulse buy for a lighter practice rig & as a backup for my 700RB-II, I got it used for a silly low price, super convenient to tuck into gig bag.

    Rather than get a 2nd 112, what do you think about switching to a single GK 210 CX cabinet? They are only slightly larger/heavier than the 112. Just too much crap to haul 2 of the 112s to practice where I have to load in & out every time. I'll keep it lower and the EQ pedal for now. Other option would be to switch heads & go back to using the (bulky and heavy) 700RB with the 112.
     
  6. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    It might fare slightly better, though it still wouldn't be enough cab to make me personally comfortable for regular "loud" rehearsal use.

    I don't think that'll make any difference. It's really just a matter of the low-end volume you need, and the capability of the cab(s).

    Sure, reducing lows and bumping up low-mids can help reduce the stress on drivers, but only you can decide how much low-end you're willing to sacrifice before you begin to feel that the tone is suffering.
     
    Al Kraft and Bassdirty like this.
  7. 9985

    9985

    Mar 22, 2018
    No matter what, I'm going to fix the 112 - any thoughts on alternatives to the OEM GK woofer for the same price range, $150-ish?
     
  8. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    If it were me, I'd replace it with the same driver that the cab was designed around, especially if it's going to be pushed hard in the future. I wouldn't necessarily expect to get better performance from something different - at least not without some odd voicing sacrifices (like if you went with a 3012LF or something).
     
    Al Kraft likes this.
  9. mmbongo

    mmbongo Regular Human Bartender Supporting Member

    Aug 5, 2009
    Carolinas
    The Eminence 2512 is pretty similar. However, I'd get the right driver from GK as you know it will work and how it sounds. Plus if you get another 112, they will match.
     
  10. BassmanPaul

    BassmanPaul Inactive

    Too few speakers for what you were needing. Get the driver replaced and then get another identical cabinet to run with it.
     
    five7, Al Kraft and David Jayne like this.
  11. DWBass

    DWBass The Funkfather

    I'd replace with an OEM speaker from GK. I also suggest getting a second cab if you plan on pushing air! What are your amp/bass settings? You may need to dial back the lows as you bring up the volume. Those GK amps are ridiculously loud so you have to be careful with your settings.
     
    pcake and Al Kraft like this.
  12. 9985

    9985

    Mar 22, 2018
    Appreciate the input, I'll stick with the OEM Neo speaker.

    Edit - As far as settings, for this practice rig, have preamp EQ on Elite JB typically with mid bumped to about 2 o'clock , treble slightly cut, and bass bumped just above noon or flat, blend between neck /bridge depends on song (broad variety of classic rock & hard rock covers) generally flat on the MBF with treble cut a little.
     
  13. You can save yourself some troubleshooting: If you push the speaker cone in (gently, evenly and not on the dust cover) does it move smoothly? Or can you hear something rubbing?

    You may also want to look into reconing it if the speaker is blown.
     
  14. I roasted a Schroeder 15L with my MB500. It's rated to handle 600 watts, which I now understand is absurd. The little MB can really throw down and you just gotta have the speakers to handle it.
     
  15. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    One of the failure modes of those early Neo 12's that failed in service was realted to the leads from the speaker connection to the voice coil. IIRC it was a QA problem of inconsistency as not all speakers had the problem or failed.

    My recommendation would be to call GK and get a proper replacement for your cab. I would also suggest recalibrating your expectations for a single 112...even good ones like the GK Neos.
     
    Last edited: Feb 17, 2020
    wave rider, Wasnex, Kro and 1 other person like this.
  16. 9985

    9985

    Mar 22, 2018
    Thanks. I ordered a replacement speaker from GK today, price was reasonable, fastest way to resolve.
    My expectation is to be able to use it for practice in a friend's 15x18 rec room at reasonably loud volumes. I've used this cabinet for almost 2 years for that purpose without issue - this last time I pushed the level & low end of the EQ settings a bit too much, without understanding I was up against its max capability, possibly exacerbated by a known shaky woofer revision. Suggestions in this thread helped me learn its limitations better, I feel confident with some moderation/EQ tweaks I'll be able to get many more years of practice without resorting to doubling the size/weight, but I am keeping an eye open for another used Neo 112.
     
    Al Kraft, Wasnex and David Jayne like this.
  17. Best possible call IMO. I suggest you keep the low-end down a bit and bump up the low-mid instead. This lets you be loud without pounding the speaker too hard.
     
    Al Kraft and 9985 like this.
  18. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    Glad everything worked out and it sounds like you have a great plan moving forward. You may already do this, but using a HPF when you need to push an amp/cab/combo a bit harder than you want to can often times get you more volume without overstressing drivers. In addition it can buy you come clean headroom when you would otherwise be out of steam.

    Many speakers have only their thermal limit ratings shown and as you get to lower frequencies it's likely that you can run into mechinical power handling limits before the thermal rating. This is where that HPF can be very helpful and you may be as surprised as many of us were that the bass still sounds very full and rich even when attenuating the low end a bit. The sub-lows a HPF attenuates aren't even able to be reproduced by most cabs anyway, and they are certainly not good for speakers.
     
    DavesnothereCA and Wasnex like this.
  19. 9985

    9985

    Mar 22, 2018
    Update - got the replacement speaker from GK, just installed it and cabinet is back in business! The new B model speaker has a much thinner gasket built into the front, I was very careful about not over tightening the wood mounting screws, seems to be fine. Appreciate everyone's input and help.
     
    Kro, Al Kraft and Wasnex like this.
  20. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Apr 16, 2021

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