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I just must be stupid (Impedance? AGAIN!)

Discussion in 'Amps and Cabs [BG]' started by tspallone, Mar 7, 2013.


  1. tspallone

    tspallone

    Oct 13, 2011
    Nanuet, NY
    I know what you're saying; "There are tons of responses concerning impedance. Just read stupid!"

    Well, I have. And, sorry, I still have questions. Specific to ME anyway.

    Someone please help me out here.

    I'll explain what my goal is and please tell me what I'm looking at.

    I have a head with TWO 1/4" outputs and one of those NEUTRIK SPEAKON connections. (450W into 1 x 4 ohms or 2 x 8 ohms.)

    I purchased this amp (Behringer) from a studio and was connected to a Peavey 115BX (800W) with ONE 1/4" input.

    I don't know what the impedance of the cabinet is.

    This is part of the problem. I'm about to purchase a Carvin V410T 8ohms cabinet. I would like to stack the 410 on top of the 115. Nothing new here of course.

    The amp manual advices that the TOTAL impedance be 4 ohms.

    Here's where I'm confused; the 410 cabinet has TWO 1/4" inputs. But, it states that its 8ohms. Am I to understand that I take both 1/4" out of the amp and connect to both 1/4" inputs of the 410? Is so, does that mean that one input of the 410 represents 16 ohm (maybe two speakers connected) and the other also represents 16 ohms, equalling 8 ohms?

    If I took ONE output from the amp and connected to ONE input of the 410....what would happen and what am I doing?

    Ok, next. How do I find out what the hell the impedance is on the Peavey 115? The technical information states that the cabinet can come in "either 4 or 8 ohms". Well, which is it? It certainly doesn't state it on anything. Must I open up the cabinet and look at the actual speaker? But, what does THAT really mean.

    So, I guess what I'm asking is, can I connect the 450w amp with TWO 1/4" outputs to the TWO 1/4" inputs of the 8ohm 410 and THEN connect the Peavey 115 using the NEUTRIK SPEAKON connection? Would the output still be 450w?

    Brutal. Back in the day, I'd just plug stuff in and see what happened but, I'm TRYING to be a little more intelligent about it.

    School me please.
     
  2. Jazz Ad

    Jazz Ad Mi la ré sol Supporting Member

    This cab comes in 4 and 8 ohms. The sticker on the back tells you what version it is. If it doesn't, you have to open the cab or use a multimeter to measure the resistance, from which you can easily deduct the impedance. You should roughly read 6.5 ohms for an 8 ohm cab or 3 ohms for a 4 ohm cab.
    The number of cables is irrelevant, you're still connecting 2 speakers in parallel and it's all that counts.
    My advice is to ditch the 15", which won't pair well with the 410 anyway.
     
  3. pbass6811

    pbass6811 Supporting Member

    Nov 10, 2008
    Indy, IN
    In a word, no. Never, ever, connect both outputs of your amp to one cab! The 2 outputs on the amp are for 2 different cabs and the 2 "inputs" on the cab are for daisy chaining cabs(amp into one input, then you run another speaker cable from the output of that cab to another cab). If its a 4ohm amp, you can either run one 4ohm cab or two 8 ohm cabs.

    Usually, a cabs impedance is on the back, near the inputs or the serial number, if the only thing back there is a single 1/4 input, then I'm not sure what to tell ya' besides contact Peavey and ask them. Someone on here probably has one and can give you some insight.

    Good luck!

    Also, a 410 and a 115 are a great combination, as long as you get the impedance right...
     
  4. Jazz Ad

    Jazz Ad Mi la ré sol Supporting Member

    You can connect both outputs to a single cab, it won't hurt anything. It's just useless.
     
  5. funkingroovin

    funkingroovin Conquering A-D-D,and all the other notes as well!

    Apr 19, 2009
    Hawaii
    OK..You really,really need to find the impedance of your 15 cab. The ohm rating will be stamped on the speaker's basket or magnet. You can either remove the jack plate to get a look inside w/a light or remove the speaker and have a look.

    The dual jacks on your cab are for chaining cabs together..Cable from amp to one (8ohm) cab jack--cable from other cab jack to second (8ohm) cab..

    The jacks on the back of your amp allow you to run two separate 4ohm cabs,one jack to each cab. If your cabs are 8ohm you'll need to chain them as stated above--From ONE amp jack to first cab,and a second cable from the first cab to the second cab.

    I hope that helps..
     
  6. pbass6811

    pbass6811 Supporting Member

    Nov 10, 2008
    Indy, IN
  7. Jazz Ad had it all covered.

    Parallel outs of amp can go anywhere and it won't make any difference.

    I would ditch the 4x10 and get another 1x15 if it's 8 ohms. You can cover any gig with that.
     
  8. The two inputs on the 4x10 are simply parallel connections to let you link another cab to it, same as the outputs on your amp, all parallel.
     
  9. GrowlerBox

    GrowlerBox

    Feb 10, 2010
    Nude Zealand
    They might sound OK together, although the odds are against it in most situations. If you are going that way, I would suggest putting the 115 on top, so you improve your chances of hearing it fart out before the 410 really gets going. Depending on the particular drivers involved, it is unlikely to take more than half the power of the 410 before giving out, so be gentle.
     
  10. tspallone

    tspallone

    Oct 13, 2011
    Nanuet, NY
    I think I got it but, if I just want to test a single 8ohm 410 cab just to see if everything's working, should I NOT plug in the amp that's looking for 4 ohms at all? Can I get away with it for a second just to get a little sound out of it? Or, should I seek an amp that can be matched with a single 8ohm cab?
     
  11. Solid State amps only care about the MINIMUM impedance (in your case 4 ohms).

    Using a single 8 ohm cab is fine, and just results in less power from the amp.
     
  12. The 4 ohm minimum on the amp is saying (on a SS amp) DO NOT go below this. You can connect a 8 ohm or even a 16 ohm cab no problem (except loss of output power) safely all year long.

    The lower the number with impedance the less it impedes the flow of voltage (and the higher the strain on an amp.).
     
  13. cjp3044

    cjp3044

    Oct 10, 2008
    Clovis, CA
    Your amp will work just fine with a single 8ohm cab, however you won't have full power out. I believe you said the amp 450 watts at 4ohm, so at 8ohms it's probably only putting out around 250 - 300 watts.

    You're going to get a lot of people saying the 410/115 combination is great and others telling you it's horrible. IME it's horrible - you're putting the same power to a single 15" driver that you are to the 4 10" drivers and the 15 will likely fart out on you before you get the full realization of what the 410 can do, however if you like it, that is ALL that matters.

    My personal recommendation would be to buy a 4ohm 410 cab (or other 4ohm single cab solution) - I would venture to guess that your 15 is probably 8 ohms, but without seeing any markings on the back or testing with a MM, it would be hard to tell. A single 4ohm cab solution will give you all the headroom from the amp, and realistically a 410 is fine for most gigging situations and a single cab is SO much easier to schlep around.

    Just my .02

    Oh, and it was already said, but the speaker outputs on your amp are for connecting multiple cabs - you won't necessarily damage anything running two cables into the cab, but it's pointless. The 2 connectors on the cab are for "daisy-chaining" to another cab as well - just gives you multiple options. And make sure you use a SPEAKER cable, not an intrument cable to plug into the cab!
     
  14. The difference in output between the 4 ohm and an 8 ohm version of the same cab are negligable.

    Getting a single 4 ohm cab does nothing for him other then make it so he cannot add another cab if necessary.
     
  15. SoLongJake

    SoLongJake Supporting Member

    Jul 1, 2007
    Des Moines, Iowa
    This isn't entirely true, he would be able to get more wattage out of his amp if the single 410 pushes enough air.
     
  16. And even with the difference in wattage, it would amount to maybe +2db (negigable).

    And that is even *IF* the cab could make use of the extra wattage (most can't, it gets burned off as heat).

    So again, it does nothing but limit his future expanding.
     
  17. Agree with this fully. Extra power that may just provide useless power compression from the cab is waste of resources. The negligible difference between 350 and 500 watts only "LOOKS" big by the numbers, not in actual use.
     
  18. Agreed. Or you can use a digital multi-meter in Ohms mode (the capital Omega character) and refer to JazzAd's post.

    Um, NO!!! The two outputs on the back of the amp ARE NOT to run to two separate 4 ohm cabinets, that would be a 2 ohm load and would burn out the amp. The outputs on the back of the amp are in parallel just like the jacks on the 410 cabinet are. You could run from each jack on the amp to a single 8 ohm cabinet for a net load of 4 ohms.
     
  19. Simple. The three speaker outputs on the amp are all the same--they all go to the same place and are all connected to each other in parallel. They're there to allow you different connection options. You only need one of them.
    The input jacks on the cabs are the same way--redundant/connected in parallel.
    You must know the impedance of both cabs so you don't accidentally present the amp with less than a 4 ohm load. For example if the 1x15 happens to be 4 ohms and you connect it and the 8 ohm 4x10, the amp will see 2.6 ohms, which is bad. Do not go below 4 ohms.
    Search internet for 'impedance calculator' to figure different loads.
     

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