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Using speakon adaptor in bridge mode

Discussion in 'Amps and Cabs [BG]' started by Batsquatch, Mar 1, 2016.

  1. Batsquatch


    Feb 20, 2016
    Used a speakon to 1/4 adaptor in bridge mode and Hartke kilo head kept over heating. My two cabs have 1/4 only therefore the adaptor was necessary. Others have suggested that this can't be used in bridged mode. I don't see that in the Manuel and the GC geniuses didn't think it would be an issue but I have my doubts now. Thanks
  2. wcriley


    Apr 5, 2010
    Western PA
    It's not that you "can't" use it...it's just not a very good/safe thing to do.

    Doubt it caused you amp to overheat, though.
    BasturdBlaster likes this.
  3. wcriley


    Apr 5, 2010
    Western PA
    Interesting that neither the back panel nor manual mention anything about which Speakon terminals are used in bridged mode...
    Bob Lee (QSC) likes this.
  4. If I recall properly, when I got a Speakon cable to allow my Crown XLS1000 to power a cab in Bridge Mode, I had to rewire one of the ends of the cable. A standard Speakon cable wouldn't work... I can't recall how I had to rewire it, but I'll try digging around.
  5. Here's my old thread about it:

    Re-wiring a Speakon cable

    Please be aware this was for my equipment and I'm not positive it is the same for yours. Check with the manufacturer before powering this up.

    Also, I wrapped a piece of blue electrical tape around the cable at the amp end to identify which end was which.
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Generally, when a connector is dedicated to a bridged output only, it uses the conventional 1+/1- wiring standard. That way you do not need a specially wired cable.

    When a SpeakOn is used for multiple purposes, such as on a stereo amp, and carries both channels, the bridged signal is carried on the 1+/2+ terminals. This is the case where a special cable is needed, wired 1+/2+ at the amp end (to match the amp) and 1+/1- at the speaker end (to match the speaker cabinet).

    (Correct typo)
    Last edited: Mar 1, 2016
  7. What’s the matter OP? Do you think I don’t know what I’m talking about?? :)

    In the other thread I told you that in bridge both the tip and the sleeve of a phone plug are live referenced to ground. Between the tip and the sleeve there is twice that voltage. It’s dangerous and can give a healthy shock - right @agedhorse,?

    iF a grounded object such as a guitar cable or microphone contacts the plug, your amp gets shorted out - not good. When a phone plug is removed from a socket the tip and ring are shorted momentarily. that shorts the outputs of both amps together. Even worse for the amplifier.
    Last edited: Mar 1, 2016
    gumtown, tjh, B-string and 3 others like this.
  8. I only use Neutrix Speakon connectors for my Kilo. Both cables are wired 1+/1- on both ends. They work for both bridged & stereo modes.
  9. RoadRanger

    RoadRanger Supporting Member

    Feb 18, 2004
    NE CT
    I've class D power amps here that need +1/-2 as the output stages are out-of-phase to prevent power supply pumping I guess. Must be an extra inversion stage in channel 2. Anyways the "neutrals" that are tied together internally to chassis ground are -1 and +2.
    Last edited: Mar 1, 2016
    wcriley likes this.
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    And I think you are right!!!

    RoadRanger likes this.
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Yes, this is all correct. These reasons were all motivating factors in the industry migrating towards SpeakOn connectors.
  12. wcriley


    Apr 5, 2010
    Western PA
    Now the industry needs to migrate towards PowerCon connectors.
  13. rufus.K


    Oct 18, 2015
    Why don't you retrofit SpeakOn connectors onto your cabinets then, or even just one of them and daisy chain them from there
    mbelue, gypsyfelon and Deezer Butler like this.
  14. ArtechnikA

    ArtechnikA I endorsed a check once... Gold Supporting Member

    Feb 24, 2013
    I think this probably has little to do with the cable and everything to do with the 2 cabs...
    What's their impedance ?
  15. mc900ftj

    mc900ftj Supporting Member

    Jan 21, 2014
    It all depends the equipment. There is no universal standard. Read the manual. Period.
  16. Toddbass65

    Toddbass65 Supporting Member

    Oct 21, 2012
    I had same question a while ago....yes you need to have the one end rewired to work properly in bridge mode. Then mark that end so you know that it goes into
    the amp. Good to go then...at least in my amp. Check your specs to see the wiring requirements and it should tell you how it should be wired.
  17. gjohnson441496


    Dec 14, 2014
    There was another thread very similar to this one and the guys discovered that the culprit was the outlet the guy was using. I believe the home was somewhat older and the wiring in the room he was playing in was bad. He tried another, newer outlet and everything was ok.
  18. popgadget

    popgadget Commercial User

    Sep 4, 2005
    Eastern, PA USA
    Authorized Greenboy Designs Builder, Scabbey Road
    That was my guess. Even if they're 8 ohm cabs his amp is seeing the minimum 4 ohm load on the bridged output, if they're 4 ohm cabs that's the problem for sure.
    RoadRanger likes this.
  19. There is also an issue that some speakers present an impedance that is lower than their nominal rating. For example, an 8Ω speaker can have an impedance of 6 or 7Ω in a certain frequency band. Here is one example, the Eminence Alpha 15A. It just happened to be the first speaker I looked at and this is not a rare example. It is rated for 8Ω but its impedance is below that between 60 and 500Hz. It is about 6Ω in much of that range. Two of those will be 3Ω in that range and that can be a problem for an amp rated for 4Ω in bridged mode where it will have its maximum current draw.
  20. BasturdBlaster

    BasturdBlaster Supporting Member

    Feb 19, 2012
    Crandon WI
    Both amps (Hartke) that the OP is asking about both have a dedicated "Bridge only" Speakon output that is wired in a "conventional" manner i.e. 1+/1- unlike the more often seen style that is basically a 4 connector speakon out that doubles as a single plug stereo out or used as a mono bridge out using the 1+/2+ setup as Aged Horse has stated quite well. In this situation, this adapter would be wired correctly for the Hartkes.

    I know nobody including myself is going to recommend or advocate the use of the adapter in a bridge situation, its all the juice any amp has in one connector that could very easily and accidentally become shorted and become a shock and loss, bad deal if that happened. Though I can't remember the last time I have held any speaker cable in my hand when the amp was on. Mute button and volume down don't count as off. The thought of a (drummer's) mic stand somehow tipping over and touching the 1/4" jack body (which is hot in bridge mode) scares me, I can see that being a bad deal.

    The OP cabs are both 8ohm so a 4ohm bridge is seemingly do-able but what Vince said could easily be a part of the equation and lets face it, bridging an amp at 4 ohms really is asking alot of the amp since both sides are actually at 2ohms. QSC will even admit that they prefer their (maybe just older) amps to only be bridged at 8 ohms even when they give 2ohm per side specs.

    I think the best bet for any bridge use is to use a complete speakon to speakon cable set-up. Even if it means adding them to your cabs. They stay locked in at all connections and no exposed amp juice on the body of the connector like a 1/4 end would have.
    Last edited: Mar 1, 2016
    agedhorse likes this.

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