Which cab for Orange Micro Terror?

Ninja_RebornNinja_Reborn Posts: 124Member
Here's a quick question - which I hope someone can help with. I have an Orange Micro Terror on order for delivery in January.  I've bought the matched cab so that I have a portable solution. But I also have a pair of Backstar  40w 16 Ohm Cabs, which work with my HT-5. As I understand it the MT has a speaker output rated at a minimum 4 OHMs; which if I understand correctly should be fine driving 8 or 16 Ohm speakers (I'm assuming running 2 x 16s with give a rating of 8 Ohm).  The only drawback being it may not deliver the full 20 watts. Just want to make sure this makes sense and that I'm not going to blow something up! Advice as always welcome! EDIT: Further research seems to indicate that the MT can pretty much work with anything (I suspect because of S/State Power Stage?)

Comments

  • LesterLester Posts: 1,575Member, Moderator
    edited August 2016

    Running your two 16 ohm cabs in series will give the amp a 32 ohm load; running them in parallel will produce an 8 ohm load. A valve amp will be able to drive your cabs but quite how much it reduces the volume and alters the tone I cannot guess.

  • Ninja_RebornNinja_Reborn Posts: 124Member

    Thanks Lester

     

    This is where I get totally lost as I'm very unclear on series vs parallel.  I understand that series increases resistance and parallel decrease, but have no idea how this is achieved.

     

    Currently on my HT-5 I have two output options - if I am using one cab I plug into the 16 Ohm output. If I use two I plug each one separately into sockets rated for 8 Ohms. (am I correct in assuming this will be parallel as it is halving the power?)

     

    As the MT has just one output I was planning in running a Y cable out into the back of each speaker.  I'm assuming this would be a in series and therefore giving greater resistance?

     

    Does that sound reasonable logic? 

     

    Now if my logic is right it would make a lot more sense to run the MT through a single can rather than the 2? (less resistance? so less impact on volume and tone?)

     

    (This is why I've generally stuck to combos!!!)

     

  • LesterLester Posts: 1,575Member, Moderator
    edited August 2016

    It sounds to me like the HT-5 needs a 16 ohm load and the internal wiring runs the two 8 ohm sockets in series: 8 ohms + 8ohms = 16ohms, a simple calculation whatever the individual speaker impedences.

    A Y cable is a splitter cable and that would be a parallel load. If you have two speakers of the same impedence you just halve the value of one to get the combined loading. The forumla for calculating a parallel load is (R1 x R2)/(R1 + R2).

    As both of your guesses have been the wrong way round it will be worth double-checking with someone before getting your soldering iron out.

    Just make sure you meet the amp's required minimal load, ie. 16 ohms for the HT-5 and 8 ohms for the Micro Terror. It would make sense to run the MT through a single 8 ohm speaker, two 16 ohm speakers wired in parallel or two 4 ohm speakers wired in series.

  • JockoJocko Posts: 6,871Member, Moderator
  • Ninja_RebornNinja_Reborn Posts: 124Member

    I understand it now!

     

    Thanks guys I finally get this - which is massively important to me as I'm not at all clued up on electrical matters.  I'm quite happy to use volts and amps, but I generally have no idea how they work!

  • Reg SoxReg Sox Posts: 3,121Member
    Originally Posted by Jocko:

    Well, it's nearly all there

     

    The calculations are valid, but it conveniently ignores resistance versus impedance.  In the speaker example, because it's an AC circuit we're talking impedance (even though a resistor is still called a resistor, and is exactly the same component!).

     

    So when we are talking about a DC circuit it's resistance.  When we are talking about an AC circuit it's impedance.  That's why speakers are described as having 4/8/16 etc ohm impedance, not resistance.  Of course more confusion for people trying to understand this stuff comes from the fact that both impedance and resistance use the Greek symbol, omega.

     

    But I'm just being overly pedantic.  The link Jocko shared is excellent and illustrates the solutions to your whole series versus parallel question.

     

    So you can ignore what I've written above in terms of working out how to link your speakers/cabs - just use the info Lester and Jocko shared.  But it is useful to know when talking to the occasional a-hole who will start sniggering if you use anything but the absolutely correct terminology.  We all know those people, and they can make you feel 2 inches tall sometimes!

     

    I usually find the component with the biggest impedance in any amp circuit is me, holding my guitar.

     

    Cheers, 2 Inch Tall Reg.

  • JockoJocko Posts: 6,871Member, Moderator

    And impedance is frequency dependent so the speaker has a different impedance when you play a high E as against a low E. I hated AC Theory at college. Spent a whole term on it. Formulae still stuck in my head after almost 50 years. No amount of defragging will clear out.

  • Reg SoxReg Sox Posts: 3,121Member

    Yep, hence the phrase "Nominal Impedance".

     

    I should have an "O" Level, and possibly an "A" Level in all this stuff.  Our poor old physics teacher had a brain tumour and was off for two whole school years (I guess early 1970s diagnosis and treatment weren't as good as now).  But still a lucky man to have recovered.

     

    Anyway we all came into 4th year physics lessons for our two year course with the physics teacher newly back at work.  We spent two years learning a predominantly electronics and components theory based "O" Level course.  We all confidently went into the exam and were faced with a bunch of questions relating to electronics systems (I recall it was heavily geared towards car ignition systems), rather than theory and components.  Every single one of us failed apart from the kid whose dad owned a garage.

     

    Turns out that while the teacher was off sick, the school changed the exam board with a syllabus more geared towards practical application rather than pure theory.  Except the school forgot to tell him on his return and he proceeded to teach us exactly the same course he had been teaching for 30 years.

     

    The other thing that was different in the early 1970s was a complete lack of comeback - there would be outcry and headlines in national newspapers these days.  Back then, it was "tough crap", oh and you can't do "A" Level Physics now you've failed your "O" Level.  Could have done a retake but would have had a massive amount of cramming on the new syllabus, or pay to take it on the original exam board if I could find somewhere local teaching it (note the "If I" could find somewhere, not the school!).  So I swapped to "A" Level Computing Science instead.

     

    Cheers, Reg.

  • JockoJocko Posts: 6,871Member, Moderator
    Originally Posted by Reg Sox:

    So I swapped to "A" Level Computing Science instead.

    And look where that got you!

  • Reg SoxReg Sox Posts: 3,121Member
    Originally Posted by Jocko:
    Originally Posted by Reg Sox:

    So I swapped to "A" Level Computing Science instead.

    And look where that got you!

    Indeed, sat on my backside in front of a PC for around 10.5 hours a day. It used to be fun when I was on the cutting edge, helping develop international standards, getting patents, designing products.  The more senior you get, the less hands on you are, and the more boring it is.  Nowadays it's shuffling spreadsheets around containing budget and revenue numbers so large they would never bear any passing relation to my bank account.  Here's the Reg Sox career trade off ratio:

     

    .....          Boredom + Hassle

    Salary =  ----------------------

                    Job Satisfaction

     

    Or simply put, the more fun your job is the lower the salary is likely to be.  A bit easier to understand than Impedance.

     

    I took note of your comment months ago about a retirement counter.  According to the one I set up I have another 914 working days to go.  Which by my calculation is about 900 too many!  At least the current purgatory of my job will allow me to retire early.  Therefore I still consider myself lucky as many people are not in that position.

     

    Cheers, Reg.

     

     

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