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LITTLE HELP WITH IMPEDANCE PLEASE!

Discussion in 'Amps [BG]' started by martinpopelka, Nov 23, 2012.

  1. martinpopelka

    martinpopelka

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    Hi everyone.

    Im thinking about buying a Peavey Mark VI head.
    That head gives 250W RMS into 4 ohms, and 400W RMS into 2 ohms.

    My question is: can I match it with some other cab which is not 4 ohms, let's say, the PEAVEY 410TX, which is 8 ohms (nominal) and 6.9 ohms (minimum)? And if I can't, what if I do?

    or do I really need a 4 ohm cab?
    :meh:
  2. megafiddle

    megafiddle

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    If this is a solid state head, you can always use a higher impedance cabinet,
    but you will lose power.

    In this case, an 8 ohm cabinet will give you about 125 watts.
    But, no, you don't have to use a 4 ohm cabinet.

    About matching, you don't have to match impedance. But you will lose power with higher impedances.

    You do want to make sure the cabinet can handle the output power that will be available with that
    particular power output though.
    So the 8 ohm cabinet would want to be able to handle at least 125 watts.
  3. Downunderwonder

    Downunderwonder

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    Any 8 ohm bass cab worth a damn will work. You would get a bit more than half of the 4 ohm power, not a lot more. End of day, loudness is more about the total speaker area than the impedance. Look into "sensitivity" in the all amps ohms etc sticky.

    I believe Peavey do both 8 and 4 ohm 2x10 which is half a 4x10. Stack two of those up and you'll be well loud enough for rocking a vocal PA bar gig. A lot of guys would disagree but they either don't give a flying **** about their vocals and acoustic drum tones or they have always played big places with full on PA.

    You don't have to have peavey cabs to get a good sound out of a peavey amp. They have decent EQ so you can get a good sound from many cabs.

    Asking about old Peavey pegs you as a beginner so here's another 50c of free advice. 4x10, 6x10, 8x10 have crappy dispersion characteristics whereas a vertical pair of 2x10 is as good as it gets in budget cabs with bonus points for not being blow everyone off the stage loud.

    Beware getting into a band with young turks with Marshall stacks. The rig that can play a stadium stage is not what you want down at your local.
  4. line6man

    line6man

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    If the cab is 8 Ohms with four speakers, it is likely that each speaker is 8 Ohms. So why not wire it for 2 Ohm operation?
  5. Downunderwonder

    Downunderwonder

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    Because it would melt the coils or throw them out of the cab.
  6. Arjank

    Arjank

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    Possible.
    But if the speakers in that Peavy cab can handle the 400watts why not wire them all parallel to get 2ohms?
    I think it's a good point made by line6man.

    Edit: just checked on the specs of the Peavy, it's rated 350watts RMS. They will probably not melt. My only concern would be the mechanical limits of these drivers. They don't look like modern xmax monsters.....probably only 2-3mm of xmax(these cabs are from 1997)
  7. Downunderwonder

    Downunderwonder

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    So getting distorted with 150W or so. Case rested, even if you wanted a killer 4x10 for cheap.
  8. martinpopelka

    martinpopelka

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    Thanks a lot guys. I think I'll stick with the 8 ohms 4X10.
    But I now have a new question about using two 2x10 cabs. Because in that case, the amp outputs 400w at 2 ohms, so... isn't that the same kind of problem?

    and also: what happens if I connect an 8 ohm cab and in the other output I connect an 4 ohm cab?

    PS: I'm completely new at this, and also english is not my native language so, correct me if I'm wrong.
  9. B-string

    B-string Supporting Member

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    The total load on the amp will be 2.667 ohms.
  10. BogeyBass

    BogeyBass

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    Alot of modern amps dont go below 4ohms min.

    So yes a 8ohm 410 is a great choice, because you could add another 8ohm 410 if needed. and the pair would then be 4ohms, which is the limit of many amps.

    but 2 4ohm cabs would be 2ohms and many amps are not 2ohm stable.

    well anyways, good thing the peavey is 2ohm stable

    because now you can run 4 8ohm cabinets if needed.
    for a total load of 2ohms

    so save up and have fun melting peoples faces off.:bassist:
  11. line6man

    line6man

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    Impedance is not inherently linked to power handling capability. That has more to do with exceeding the current a coil's wire is designed to handle. If we assume that voltage is constant, current increases as impedance decreases. You have indicated an output of about 7.75A at 4 Ohms and 14A at 2Ohms, at 250W[SUB]RMS[/SUB] and 400W[SUB]RMS[/SUB], respectively. (I= [P/Z][SUP]0.5[/SUP])Whether or not this doubling of current will be enough to cause damage is not known to me off hand without checking spec sheets. Perhaps someone else can check.
  12. Downunderwonder

    Downunderwonder

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    If 400w RMS, peaking 600 to 800w, gets thrown at 3mm of xmax do you wanna buy the kid a set of recones?
  13. martinpopelka

    martinpopelka

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    Well, finally I ordered the Mark VI with the peavey 410 TX (8 ohms) cab.

    For a total of $272 plus tax, I think it is a great deal.
    Here in Chile, to get a set like that you have pay at least $600, so I'm pretty happy with this. What do you think?

    Maybe when the shipment arrives in like 1 or 2 months, I'll post a video of the amp.

    I was new in this forum, and I didn't expected such a great answer, so thanks a lot.

    :)
  14. B-string

    B-string Supporting Member

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    IMHO you did darn good!
  15. martinpopelka

    martinpopelka

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    Well, I have another question:

    How can I connect four 8 ohms cabs if the amp has only 2 output jacks?

    Splitting both cables and connecting two cabs into each outputs?
  16. Downunderwonder

    Downunderwonder

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    Most cabs have a parallel jack enabling you to link another cab. This is called daisy chaining.
  17. delta7fred

    delta7fred

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    Good score, it is a nice sounding amp and cab.

    I have that same amp and cab. I picked them up in a hurry about 12 years ago when my main rig self combusted and gigged with them while I was repairing my main rig, then used them for rehearsals until a few months ago.

    Don't boost the bass too much, and put a bit of low frequency shelving on it so you are not wasting power with bass frequencies that the cab cannot reproduce and lighting the DDT light (Peavey limiting system).

    In fact don't boost any frequency too much as it will light the DDT light up which reduces the gain to limit the output power, which limits the available volume.
  18. martinpopelka

    martinpopelka

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    Wow. Thanks, but can I deactivate that DDT? I like to boost some frequences to have a little overdrive on the mid tones...

    Also: does in any case boosting the bass or other frequences will damage the cab? As far as I know this cab can handle 350 watts... So I shouldn't have any problems about that.. right?

    And about that daisy chaining, I think this cab does not have such jack. So I'm screwed, right?
  19. delta7fred

    delta7fred

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    You cannot deactivate the DDT, there is no point as once it comes in you have reached the maximum output from the amp. It just reduces the audible distortion by reducing the gain. If you want mid distortion then use a pedal for that not the amp, solid state amp clipping distortion rarely sounds good.

    I would not boost the bass as it just wastes power with little or no audible gain, but try it when you receive your rig. If you want to get into bass boosting you need a cab that can reproduce those frequencies and handle a lot of power without farting out (hitting the driver/s xmax), and have plenty of available amp power. See my sig for what I use now, with that you can boost the lower frequencies without running out of power or farting out.

    I don't think you will damage the cab but I suspect that the 350W figure is probably the thermal limit, not something you want to be hitting regularly.

    I don't have my cab here but I thought there were 2 paralleled jacks on it. I may of course be wrong as it is a few months since I saw it, it is out on loan to a young band.
  20. martinpopelka

    martinpopelka

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    Ok, thanks a lot.

    What is "xmax"???

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