How Do I Check Speaker Loads?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by PhuzzphayzZ, Jan 14, 2020 at 9:38 AM.

  1. PhuzzphayzZ

    PhuzzphayzZ Member

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    I'm not sure I asked that correctly.

    There's an old Peavey 400 with two PYLE DRIVERS, but I see no info on the speakers. I have the most basic RadioShack multimeter I found. Can I find out the speaker numbers 4...8...16... (would I say "resistance"?) so I can hook them up to my Traynor (which has a 4/8ohm switch)? I would just take the plug out of the Peavey and put it in the Traynor's second speaker output...?...!...

    I'm ASSuming that each speaker is 16, load is 8, hook it up and switch to 4... but you what happens when we...
     
  2. VICOwner

    VICOwner Supporting Member

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    Measure the dc resistance at the plug. 12-16 ohms is 16 ohm load. 6-8 ohms is 8 ohm load. 3-4 ohms is 4 ohm load. Select the impedance accordingly.
     
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  3. PhuzzphayzZ

    PhuzzphayzZ Member

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    Amp OFF. 1/4" from speakers unplugged. Tips of probes to inside of 1/4" hole in amp. Reading: .2-.5

    Amp ON. 1/4" from speakers unplugged. Same basic reading, never shooting over 1.0...

    So obviously I'm doing it wrong (since that's what I seem to be good at!- YES, I AM this ignorant. I should either be taken under someone's wing, or SHOT!!!)

    I'm tired of feeling (being) a complete idiot. Complete and utter.... disgusted with myself that I can't even do this simplest of things...

    kids, stay in school
     
  4. EdFarmer

    EdFarmer Member

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    Who told you to stick anything inside of the amp? You're trying to determine the impedance of the cabinet/speakers.

    Leave the amp off. Unplug the speakers and look at the plug. It has two connections, the tip and the rest of the plug. Measure the resistance THERE and use the information explained above.
     
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  5. PhuzzphayzZ

    PhuzzphayzZ Member

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    I gotta tell ya, I don't know if I have brain damage, but any question of me being a complete and utter spazz and (fill in the blank) were just extinguished. Had you seen me perform what you just laid out was worthy of Inspector Clueless. I did ASSume that the REDtip/TIP...BLACKtip/SLEEVE...(yes, I have to learn every.last.thing apparently)

    1) Must one remain absolutely perfectly still with the tips?, because if there was the slightest movement the numbers would re-scramble. I finally had one tip above, one below, stabilized, and then I got a reading of 3.8 for a while... this would jockey between 3.6-4.1...

    2) HOWEVER, if I moved the black pin farther up the sleeve towards the cable, I seemed to be getting semi-stable/moving reading between 4-6.6...


    Look, I'm sitting here screeching at myself because NOTHING I've learned here has been easy for me, so I more than anyone need perfectly neat numbers, so obviously I can't have 3.8 and 6.6 floating in my brain, I must have one or the other, and "fear is the mindkiller" is STRONG with me, I AM a former DarwinAward winner

    sorry, let me take a breath...

    I can go try some more stable readings. It seems to generally say 3.8, but if I try a different positioning, it can jump into the 5-6.6 but it's not as stable there


    Ultimately, if my amp is 8, and these speakers are 8, then they add to 4; if the amp is 8 and the speakers are 4, what does that equal

    I'm literally sitting here telling myself "I can't do math, I just can't do math.." wtf is wrong with me?


     
  6. pdf64

    pdf64 Member

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    What reading do you get if you short the meter's probe tips tightly together? ie red to black.
     
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  7. PhuzzphayzZ

    PhuzzphayzZ Member

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    0.0-0.2
     
  8. pdf64

    pdf64 Member

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    That's impressive :)
    Looks like the speakers are wired up for a 4 ohm load.
     
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  9. tarweed

    tarweed Member

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    2 "Pyle Drivers".
    How are they connected - series or parallel?
     
  10. PhuzzphayzZ

    PhuzzphayzZ Member

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    both wires go from the left speaker to the right speaker, then they both turn into the output cable with the 1/4" at the end...

    lol, last time I got this wrong,... drumroll,... I'm gonna say PARALLEL... if it was Series, one wire from each speaker would have gone to the amp?...

    I'm sorry, this must be like pulling teeth for you guys
     
  11. PhuzzphayzZ

    PhuzzphayzZ Member

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    back of the Peavey says " (2)SPEAKER JACKS PARALLELED' and "4OHM MINIMUM AMPLIFIER LOAD"
     
  12. PhuzzphayzZ

    PhuzzphayzZ Member

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    gotta go to work...thanks to all so far
     
  13. EdFarmer

    EdFarmer Member

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    Well . . . You will be happy to hear that you have answered some of your own questions: The meter indicates that you have a four ohm load. This makes sense as you likely have two 8 ohm speakers wired in parallel. This matches what you now tell us is on the back of the amp.

    Set the Traynor to 4 ohms and be happy . . .
     
  14. PhuzzphayzZ

    PhuzzphayzZ Member

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    Thank you much!...

    now, even if the Peavey speakers had been 16+16=8... to hook em up to the Traynor STILL would have yielded a "4"...no?

    No matter what, the answer would have been '4'?


    It was still good to go thru the cobwebs and at least TRY to jump start some of them thar brain cells, what are left!

    thanks again for everyone's patience and tolerance, I'm sure there may be something else lurking around the corner...at... any...minute...
     
  15. PhuzzphayzZ

    PhuzzphayzZ Member

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    Also, once I hook up the two extra speakers, I should put the amp's 25/90W switch to 90 to get the full effect of what the amp was made for/capable of? (understanding I CAN go between the two to taste for whatever situation)
     
  16. pdf64

    pdf64 Member

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    No, an 8ohm speaker load would indicate that the Traynor’s output should be switched to 8 ohms.

    Dunno what your rationale was above; if you try to explain it, we could advise where you’re getting muddled up.
     
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  17. EdFarmer

    EdFarmer Member

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    If you have two speakers rated at X ohms . . .

    Connecting them in series results in (2 x X) ohms where the amp would need to be set to (2 x X).

    Connecting them in parallel results in X/2 ohms and the amp should be set to that value.

    So, if your speakers are 8 ohms each, series=16 ohms and parallel=4 ohms.
    If your speaker were 16 ohms, the values would be 32 and 8.

    No, the answer is not always 4.
     
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  18. PhuzzphayzZ

    PhuzzphayzZ Member

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    I just meant in this particular case.


    Traynor = 2 CenturyVintage (Para) 16+16=8

    Peavey=2 PyleDrivers (Para) I'm assuming that if we assume the 3.8 I was getting on the meter is correct, then 8+8=4

    But (as an example) had the Peavey speakers been 16+16=8... adding either:

    Traynor @8 + Peavey @4 = 4

    Traynor @8 + Peavey @8 = 4

    ...would have yielded a "4". Isn't that correct? At least, that's what I meant! I'm using coffee for brain cells lately...
     
  19. EdFarmer

    EdFarmer Member

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    You didn't say that you are using the Traynor speakers as well . . . but your math still appears mixed up.

    8 and 4 in series is 12 and in parallel is 8/3 or just under 3, which you would set to 4.

    When two loads are connected in series, you add them together. When connected in parallel, you add their reciprocals and then take the reciprocal.

    So . . . 8 and 4? You add 1/8 + 1/4 and 3/8. Take the reciprocal and get 8/3 which is 2.666667 ohms.

    There are other issues with using mismatched sets of impedance.

    By the way "impedance" is similar to "resistance". In normal electrical parlance, impedance is used for AC circuits while resistance is used for DC circuits.
     
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  20. PhuzzphayzZ

    PhuzzphayzZ Member

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    I'm obviously waaay more confused than I even thought...

    So, I'm using the Traynor AND adding the "extra cab" option because I have that extra speaker output, along with the 8/4 switch, just because I had the extra speakers lying around (lol, 400lb Peavey is more like it!).

    So, using both sets of speakers, both going into their separate 1/4" jacks on the amp...if you put a gun to my head I'd say they're not running "one after another", but "simultaneously", so, I would choose 'Parallel'. Am I still alive?

    I get the feeling not...

    So basically any answer I give, the opposite is true?

    I can't go on like this.


    Lemme try this again:

    1) both amps are wired, respectively, in Parallel.

    2) when I hook up the second set of speakers, from the Peavey, into the 2nd speaker jack on the Traynor, the signal from the Traynor "splits" to go to the two separate destinations (or is it that the speakers themselves are 'drawing' the amp's juice cuz they're 'thirsty'?). This, too, is Parallel?

    Guys, I hate this, my brain is literally "crashing"... all I see is a jumble of numbers... it's flippin 8s and 4s, nice sweet whole numbers, and all I can see in my head is .666 .666 .666 .666...

    I'm not trying to be funny, I'm really distressed that this absolute child's play eludes my besotted brain.

    I've got the other Thread where this GroundLoop plague is destroying my faith in any type of scientific reasoning, and here I can't even get the simple math ...

    Sticking my finger in a socket isn't going to make me learn what 'Ground' is... it's just not. Not saying anyone has recommended that yet!!! I'm just having to forego the humiliation of ignorance and plow ahead.





    I TOTALLY SEE how a 100W Marshall head can power 4 speakers, 8 speakers, and 16 speakers, and how, the more speakers, the ohm numbers go from like 16 to 8 to 4 to 2...

    But since I'm even more unconfident now, I still haaave to ask if this is correct.

    I do appreciate you being there EdFarmer!! I'm sorry for any taxing of your patience and tolerance. I didn't really realize the scope of my learning issues until I joined TGP!!! Thank you thank you!!
     

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