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connecting one amp to two cabs

Discussion in 'Amps and Cabs [BG]' started by Bruce Calin, Jul 2, 2020.

  1. Bruce Calin

    Bruce Calin

    Oct 15, 2002
    I need to buy or build a speaker cable that connects a single amp speaker out to two cabs of the same impedance that have to be connected separately(one outlet into two inputs). If I build it, what do I need to be aware of? Is it a common connector that I can buy? All of the connectors would preferably be speakons. I have okay soldering skills. Sorry if this has been covered somewhere already.
  2. Warpeg

    Warpeg Supporting Member

    Jun 20, 2005
    At least one of your cabs does not have a parallel speaker jack?
  3. SidNitzerglobin


    Feb 12, 2019
    Typically w/ 2 8 ohm cabs you'd want the wiring to be parallel to give you a resulting impedance of 4 ohms. Most any bass amp I've seen will handle a 4 ohm or 8 ohm load either automagically or w/ the flip of an impedance switch near the speaker jack(s). Many of the Class D amps won't put out their full power until you have a 4 ohm load connected.

    To do this you wire it exactly the same as a single speaker cable (w/ a 1/4" TS hot is tip & ground is sleeve on both sides of the cable), but hook up 2 cables/jacks to one end of it. Sorry I don't mess w/ Speakon unless I have to so not familiar w/ wiring them, should be the same deal once you figure out which terminal is hot & which is ground.

    The approach I've taken previously to this is to build a small box for the interconnection. If you want to get fancy w/ it you can make the cab side of the box switchable for series/parallel.
  4. JimChjones


    Aug 6, 2017
    SE England
    Well, you could fabricate a Y cable I suppose, but it would be much better to put a second speakon in one of the cabs. If that were really impractical I think I would make a box with 3 speakons all connected in parallel in preference to using a Y cable. I have an objection to using non-standard cables.
  5. abarson


    Nov 6, 2003
    Santa Cruz
    Which amp and which speakers are we specifically talking about?
    The only cabinets I've seen that don't have two connectors are 4 ohms, and most amplifiers won't handle a 2 ohms combined load.

    Note: If using Speakons, don't solder the wire tips.
    2tonic, AudioTaper and BassmanPaul like this.
  6. lug

    lug Supporting Member

    Feb 11, 2005
    League City, Tx
    It's always better when seeking answers on gear related questions to actually name the gear you are asking the question about.
  7. Michedelic

    Michedelic MId-Century Modern

    What lug said, plus if you are able, post some clear, well-lit pics of the back side of your amp, and the imput jacks of your cabs
    2tonic likes this.
  8. Bruce Calin

    Bruce Calin

    Oct 15, 2002
    Thanks for all the info. I like the box idea. The cabs only have the one input so I need the two wires. Trying to modify the cabs is beyond my skills. I also think I will use 1/4in connectors with speakon adapters unless someone thinks that's a bad idea. The amp is a tc electronics BQ500. I'm not sure what cabs yet but all are 8ohms.
  9. JimChjones


    Aug 6, 2017
    SE England
    Using jacks is indeed a bad idea. Many if not most Class D amplifiers deliver voltage down both conductors, and the power of that amp vastly exceeds what 1/4in jacks were designed for. It has only Speakon for a reason...

    You know, unless your chosen cab has a crossover or other complications installing a second socket in an existing cab is probably no more arduous than building a dedicated junction box. You may well even be able to get a pre drilled plate that's a direct replacement for the current one - many manufacturers use third party ones that are available retail.
    2tonic, AudioTaper and abarson like this.
  10. SidNitzerglobin


    Feb 12, 2019
    Here's a layout a while back I did for series & parallel speaker boxes w/ 1/4" jacks, hopefully helps a little if you go that route:
    You'd want the parallel one for 8 ohm cabs connected to the TC amp.
    paco facile likes this.
  11. abarson


    Nov 6, 2003
    Santa Cruz
    If your amp has Speakon and your cabs have Speakon, use Speakon connectors. Don't throw 1/4" into the mix. Using a box might be an easy solution but I think it would be just as easy to modify or exchange the cab control plate.
    2-pole Speakon uses +1 terminal as signal and -1 terminal as ground. @SidNitzerglobin 's drawing for Parallel connection is a good illustration.
  12. SidNitzerglobin


    Feb 12, 2019
    Can anyone elaborate on why Speakon should be an absolute necessity for any amp aside from mitgating risk of an unintentional partial or full disconnection of the leads while in operation? I'm genuinely curious & am more than willing to accept my ignorance :thumbsup:

    I've not had a Class D (or Class AB or Class A) catch on fire using 1/4" yet. Only advantage I can see to Speakon is the locking nature of the connection. Sending power down either side of a Speakon or a 1/4" seems equally viable given similarly insulated & gauged leads.
  13. Bruce Calin

    Bruce Calin

    Oct 15, 2002
    Thanks again for the info. I'm always glad to learn what I don't know about things that seem deceptively simple.
    2tonic likes this.
  14. The Speakons I've dealt with weren't even soldered, just screws. It certainly helps to solder the ends of the cable though. And if you want to get really crafty a single speakon can actually carry 2 completely individual signals. It's not just for mono. But I believe you have to purchase them as 2 cable variety, the mono ones only have 1 set of screws, same exact package.

  15. bassgrackle

    bassgrackle Gold Supporting Member

    Aug 17, 2010
    I think we need to see photos of the back of the amp and speakers. This sounds a bit odd.
  16. stigbeve


    Sep 24, 2014
    Your post made me curious as well. Found this really quick.

    The Top 3 Benefits of Using SpeakON Cables vs. 1/4" or XLR cables - Bonsai Audio | DJing Simplified
  17. delta7fred


    Jul 3, 2007
    1. Damage to the amp - As already stated both connectors on class D amps are live so if you accidentally short the metal jack plug casing to ground you stand a good chance of damaging the amp.

    2. Damage to the operator - The voltage generated in the higher power amps are sufficient to give you an electric shock. If you use a jack this will be on both the tip and the screen so if you touch the screen don't be surprised if you get a shock.

    3. The current generated for high power at low impedance is more than a jack is rated for. Jacks were designed for handling a few milliamps in manual telephone switchboards.

    4. No risk of accidentally getting pulled out.

    5. Whoever thought that using the same connector for signal level inputs and speaker level outputs was not thinking clearly. We had a keyboard player who would pick up any jack lead and used it for either input or speaker output. In one case he blew the PA amp by linking the input to the output.
    2tonic, S-Bigbottom and agedhorse like this.
  18. Ric5

    Ric5 Supporting Member

    Jan 29, 2008
    something like this


    or one of these

    Zbysek and JeezyMcNuggles like this.
  19. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    NEVER tin the wired of a binding screw connection. The solder will cold flow under pressure and the connection may become intermittent. This is a problem we see regularly when troubleshooting intermittent issues with customers. This, and cheap off-shore parts that are either knock-off or counterfeit with poor quality.

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