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SVT 810e impedance issue

Discussion in 'Amps and Cabs [BG]' started by doomloop, Jul 20, 2012.


  1. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR
    Hi...got a question about reading resistances with my voltmeter...

    I just got an Ampeg SVT 810e...it's from @96 and has one 1/4" jack on the back...I'm guessing it should be an 800 watt 4 ohm cab...when I read the resistance I'm getting around 4.6. I'm pretty sure I should be seeing around 3.6. The speakers all seem to be working fine and sound great!

    I'm wanting to run my SVT classic head into this cab and wondering...is it okay...

    The impedance is slightly high for the amp, I'm running it at it's 4 ohm setting, and I don't want to screw it up.

    Is this the correct reading or could there be something going on with a speaker or something else!

    Thanks...looking forward to getting LOUD with my new cab and posting some pics cuz it's looking sweet!!!
     
  2. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Impedance constantly changes when you play, and as long as it measures somewhere in that 4 ohm ballpark, it's fine. As long as all the speakers are working, enjoy the cab and don't give it a second's thought.
     
  3. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR
    Thanks!

    I think I'll do that tomorrow at practice! Got a gig on Saturday and my 4x10/1x15 combo was giving my some buzzes and I thought it'd be time to get real with the 8x10!

    I did the reading with no amp plugged in, I suppose that's the only way to do it, and just wanted to make sure I wouldn't wear out the amp as I've heard a higher rating can do...
     
  4. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    All the speakers in the 810E are in parallel so you could theoretically have one or two connections that have come loose and could be causing the low reading. Just try it out and check all the speakers, make sure they're all producing sound, not just moving as it could be sympathetic movement in a sealed cab. You could also try a battery test. Clip one end of a 9V to the one end of a guitar cable and then tap the other side to complete the circuit and all the speaker should jump the same way. If any don't or move opposite the rest then the wiring is a little wonky. Otherwise don't worry about it.
     
  5. The resistance varies with frequency, like JimmyM said, as long as you're pretty close to 4 ohms, you'll be ok. Rock that 810.
     
  6. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    Do you know for a fact that your meter measures low resistances correctly? Does it read 0.0 when you short the leads together? Can you measure a known resistance (or known good cab) as a sanity check?

    The DC resistance of a speaker should be a bit less than its nominal impedance. If it's really 4.6 ohms for a 4 ohm cab, something's not quite right.

    The 9V battery test is a great idea, get the grill cloth off so you can see the cones and be sure they all move in the same direction.
     
  7. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR
    Hey all...thanks for the responses...

    When I use my meter on my 8 ohm cabs it reads @7.xxx
    When I use it on my other 4 ohm set ups it reads around 3.4-3.6
    This cab is reading around 4.9 and fluctuates from 4.5 to around 5.1


    I'm pretty sure all the speakers are producing the proper signal and that it's not just sympathetic movement.

    It's certainly reading a higher resistance than it should for a 4 ohm cab and based on previous threads on TB it seems that running high, or low, can be a problem for this amp...SVT-CL...and I am NOT taking it easy on this gear...I am playing in a loud heavy rock band...not doomy and distorted really but I am rocking it hard which is why I stepped up to the Ampeg cab.

    So I am tempted to go with what Jimmy said because I'm excited about the gear but the last thing I wanna do is screw up my amp so I guess that means breaking out each speaker and testing each one, checking the connections, etc...

    I've never done the battery test as I'm pretty familiar with using my meter to test individual speakers but will probably give it a shot. Can I use a speaker cable and attach the battery ends to it just like I would a meter to test all speakers at once or should I test each individually?

    So...if I did leave it as is...could I really blow my amp right away? Could I get away with a couple practices or is it better to play it safe. I understand I'll get differing opinions but I can handle multiple POV's pretty well so hit me!

    Thanks for all the hints...TB is the best place for bass!
     
  8. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR
    UPDATE:

    I just called LOUDTECH service and they said it is normal and fine to run at this nominal impedance reading...

    Any thoughts?
     
  9. Did you do the battery test???
     
  10. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR
    Not yet...do I need to do that for each individual speaker or can I do it on a speaker cable...someone above in the post mentioned doing it via cable which is why I ask...

    I haven't opened the cab up yet...
     
  11. Tim1

    Tim1

    Sep 9, 2005
    New Zealand
    Just play the darned thing, sit back and enjoy the big smile on your face. You are totally worrying unnecessarily. I recently checked the impedance on several of my cabinets and the only one that read exactly 4 ohms om the meter was one Bergantino cab - this was absolutely normal and nothing to worry about. No you do not "have " to do the battery test - I seriously doubt that a speaker connected out of phase would have any influence at all on impedance reading as the signal still goes through the voice coil. Further, you have no reason to think that one is out of phase and it would be very unusual if one was. Just play it and enjoy :bassist::!!!!
     
  12. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    You can do the battery test for the whole cab since there is no crossover, just touch the negative end to the sleeve of a speaker cable, the positive to the tip, and see how the speakers move. It's easier if you have some clip leads or something like that but you should be able to make it work with a speaker cable. The relevance of this test would be that you could be sure all speakers are hooked up and wired in phase quickly and easily. Just do it quick, you don't have to leave it connected.
     
  13. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR
    Yeah..I do that sometimes...thanks!

    So, for my peace of mind, did any of your cabs read 'higher' than they are rated for?

    ...and I will do the battery test just for fun...never done it before so may as well see what it's all about...
     
  14. ahc

    ahc

    Jul 31, 2009
    No. Virginia
    It'll take you longer to pull off the grill off than to do the battery test. And much longer to type a post to TB. :D :D :D
     
  15. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR
    Battery test was a pass...no problem there...
    When I pulled of the input plate and tested the bare speaker wires they measured around 4.2...

    Gonna go for it!
     
  16. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR
    Interesting...called LOUD again just to bug them and they gave me a bunch of technical jargon and of course as with all impedance questions no specific answers..it's like filling out a W-4...I pulled a speaker and tested it wired up and it reads 3.9...that's more like it so maybe a weird connection near the jack creating increased impedance...?!
     
  17. Tim1

    Tim1

    Sep 9, 2005
    New Zealand
    No no no. Stop worrying :rollno: :scowl:. All is fine. Your amplifier will deal happily with minor changes in impedance. IIRC one of my cabs was 3.6 another was 4.3. It did not bother me or my amps at all - it is normal. Also I believe there is such a thing as acoustic impedance which means that the design of the cabinet can affect the overall impedance, but I am not too sure on this - read about it once. For God's sake stop being anal and just enjoy the bloody thing :).
     
  18. doomloop

    doomloop

    Mar 1, 2011
    Portland, OR

    LOL..yeah no doubt :oops:...okay it's off to practice and the big gig tomorrow night...first show for the new band I'm in...:hyper:
     

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