Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Eden's Impedence!!??

Discussion in 'Amps and Cabs [BG]' started by Rockbobmel, Jan 10, 2003.


  1. Rockbobmel

    Rockbobmel Supporting Member

    Well, I discovered something very interesting... When I tested my 1-18 cab today to see if it was 4 or 8 ohm, it came in at 6.9-7.0 with a multimeter. So I figured that I can daisy this with my 8 ohm Eden.
    Out of curiosity, I tested the 8 ohm Eden. It tested 5.6 Ohms!!! I wonder what the 4 ohm model tests at. Maybe that's why they are so efficient!!--You know 106db...

    Anyway so now if you add these together it's around 12.6
    then the imp is around = 2.8?. Or if I run both 4-10s 2.5?, So the amp should be run out of the 2 ohm tap (less or equal to the speaker load), to be safe, instead of the 4 ohm tap. I normally would have used the 4 tap because the speakers are knowb as 8 ohm cabs.

    Am I all wet here?? Or do I have something??:confused:
     
  2. DigMe

    DigMe

    Aug 10, 2002
    Waco, TX
    Your multimeter is testing for DC resistance. That should only read about 75% of your cab's AC resistance. So if the cab is 8ohms then it should read about 6 ohms and if it's 4 ohms it should read about 3 ohms on the multimeter.

    No idea why it would be reading around 7 for one but the 5.6 is close enough to 6 to make sense for the other one. My guess is that the first cab is 8ohms. You could plug them up in parallel and then check resistance again and see if it gives you about a 3 reading. That would mean that together they are 4 ohms, also meaning that alone each one is 8.

    brad cook
     
  3. Rockbobmel

    Rockbobmel Supporting Member

    I had no idea there was different impedence types.

    So, I should run them in parallel off the 4 ohm tap?

    The Eden cab has a tweeter in it. Maybe that drops it down a little?

    What does "nominal" impedence mean? Average?
     
  4. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    If I'm not mistaken, in a tube amp, you'll want your actual impedance to be lower than the tap. Example. If you had to run a 2.67 ohm load, you would want to run it off of the 4 ohm tap and not the 2 ohm tap. if you run a lower impedance than the tap is rated for, you'll lose a bit of power, but will operate safely. However, if you go too high above, damage can be done. In reality, you'll probably be ok running an 8 ohm load on a 4 ohm tap, but would you want to do it if you could run it on an 8 ohm tap? Probably not. Also, consider what DigMe said about your actual impedance. You shouldn't have anything to worry about.

    Also, your meter should read your impedance on the parallel load as 3.0912 - 3.1111 ohms based on your numbers. Looks fine to me. Hope that helps you out.

    Tom
     
  5. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    to answer your question:

    Yes, you would want to run the cabs in parallel off of the 4 ohm tap.

    add the reciprocals of your cabs' rated impedance:

    1/8+1/8=1/4

    Take the sum and reciprocate once again to find your total impedance for the cabs in a parallel circuit:

    1/4 -> 4 ohms

    Tom
     
  6. Rockbobmel

    Rockbobmel Supporting Member

    Thanks Tom.
    Could you double check on the impedence lower/higher thing? I thought it was; amp can be lower than speaker, not higher...:confused:
     
  7. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    With solid state, yes. However, I'm almost positive that the opposite. There are limits in both directions as far as I know, but it's technically safer to be a little bit lower than the tap is rated for (same example, run a 2.67 ohm load off of the 4 ohm tap and not the 2 ohm tap). I'll see what I can dig up to make the explaination more clear without getting uber technical. Psycho Bass Guy could probably do a better job. That's all I can do for now. Good luck!!!
     
  8. DigMe

    DigMe

    Aug 10, 2002
    Waco, TX
    Honestly I'm not familiar with these "4 ohm tap" and "2 ohm tap" terms. Maybe it's an Eden thing (I'm assuming we're talking about the WT-1000 mentioned in your profile). Most amps just have a minimum impedence rating and outputs for bridged or stereo (unless it's a mono amp). Does your power amp have impedence-specific outputs or something?

    I still say you should hook the cabs to each other in parallel (not to the amp) and test the impedence reading for both cabs together. It should show around 3 on the DMM readout. If that happens then you know for sure that both cabs are 8 ohms and you are running a total 4 ohm load with both cabs hooked up parallel.

    brad cook
     
  9. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    DigMe: Tube amplifiers have (require) an output transformer because they don't function like solid state amps.

    now, for RockBobby:

     
  10. Rockbobmel

    Rockbobmel Supporting Member

    I neglected to add that I'm running a Mesa 400+ all tube head. It has 2 2ohm, 2 4ohm, and 2 8ohm output jacks.
     
  11. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    Your total impedence should be represented by the outputs rated impedence.

    Example: If you have two 8 ohm cabs and will be running in parallel (which you will), your total impedance for the circuit will be 4 ohms and you should plug each speaker into a 4 ohm tap output. If you had two 4 ohm cabs, you would have a total impedance of 2 ohms and should plus each speaker into a 2 ohm tap output. Hope that makes sense. I keep trying!!!
     
  12. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    If you don't believe me, you should at least believe your manual!!! :p Here's my last attempt at clarification for you-

     
  13. coyoteboy

    coyoteboy easy there, Ned Supporting Member

    Mar 29, 2000
    Sactomato, CA
    I was told by Aguilar to set the impedence switch on my DB728 to the 2 ohm setting if I were to run a 4ohm+8ohm cabinet configuration= 2.6 ohms. If I were running a 5.2 ohm 3x10, I believe I would set the switch at 4 ohms, not 8.

    hmmm??
     
  14. Rockbobmel

    Rockbobmel Supporting Member

    That's what I was under the impression of.

    I hate it when you get conflicting reports.

    :confused:
     
  15. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    The way I see it:

    By setting lower, you compromise a tiny bit of power. By setting higher, you compromise your amp's safety. (Like I said, if you run 8 ohms off the 4 ohm tap, you probably won't hurt your amp, but that's on the borderline of where damage should/would begin to occur)
     
  16. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I think I see where the confusion is here. I'll try to clarify it.

    2 ohms is more resistance than 4. And 4 ohms is more resistance than 8.

    I think people get confused because to increase resistance, you have to use smaller numbers.

    If you run a 4 ohm load from the 2 ohm output, you will indeed lose some power. I can't remember the exact ratio but I remember that my 400w amp would run at 400w at 4 ohms but at 280w at 8 ohms. The actual volume drop wasn't signicant though, and was probably more to do with the fact that I was minus a speaker cabinet.

    My advice is to run 2 ohms amps at 2 ohm loads, 4 ohms amps at 4 ohms loads, and 8 ohm amps at 8 ohm loads. So use the 4 ohm tap and link the speakers in paralell. Easy.
     
  17. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    oh I forgot to mention that valve amps do indeed behave a little bit differently to solid state amps. The tubes kinda absorb some of the resistance, so they are more forgiving with mis-matched impdance loads. But I still wouldn't run 2 ohm load to a 4 ohm amp.
     
  18. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    getting warmer
    Huh? Now I'm totally confused because this goes against eveything I've ever heard, learned or been told. As impedance approaches zero, the resistance gets less. Maximum resistance is achieved with infinite ohms, i.e open circuit.

    The lower the ohm of the speaker the less resitance it presents to the amp which is why it draws more wattage through the amp. If your scenario was correct, SS amps would push more into 16 ohm cabs than 2 ohm cabs and we'd be able to blow away MSG with a 100 watt amp running into a 1Kohm speaker.

    Am I missing something here?
     
  19. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    You've got it backwards.


    That's good advice
     
  20. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    Yes, he has it backwards.