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A few amp questions...

Discussion in 'Amps and Cabs [BG]' started by bass_drum, Jul 16, 2005.


  1. bass_drum

    bass_drum

    Feb 13, 2005
    Alberta,Canada
    Hey! As you may have read in my other thread, I found out that someone was selling a traynor tube head and a traynor 2x15 cab for $80. Now I havent seent this exact one, but Ive seen toher traynor 2x15 cabs and they all seemed to be 16 ohms. So I'm guessing that the cab is run in series (making each cab 8 ohms, right?). I'm wondering how I could change the wiring to parallel to therefore make the cabs total impendance 4 ohms, therefore making it way louder. Do you have any wiring diagrams with a really really good explanation since I'm very new to this.

    Also, Im wondering whats a good way to test just the cab? I know that I should press on the sides of the cone lightly and make sure its a nice fluent motion, and to listen for squeeks/look for cracks and cuts, etc. But I dont know how to test the sound of it? I'm guessing that the cabs dont change the sound so much as project so should I even be worrying that much of how they change the sound or would it be such a minor difference that it doenst matter to much?

    Now, I also know a few thigns about testing the head. I know I should crank it up about 3/4 of the way (volume wise) and make sure it still sounds nice. And that I should slowly turn each dial and listen for any hising or static. What else should I do?

    Thanks for your time, ~JB~

    (P.S. If I lower the impendance of a cab, does the wattage of the cab increase? or does it jsut get louder?)
    Thanks again!
     
  2. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Wrong.
    Wrong.
    Cabs do voice the sound coming out.

    Wiring to 4ohm wont make you way louder. Hardly even noticably louder. To test the cab, take a head along, plug up and play a little bit, make sure the speakers move fine and don't distort etc.
    To test the head, just plug it into a cab and play. You don't have to crank it at all, for any reason. Play with knobs making sure they all work fine without noise, and test as many of the functions as you can.
    Lowering the impedence of a cab, which involves rewiring it, does not change the wattage of the cab, and as I said, wont make much difference in volume. This is espeically true with tube heads that put out relativly the exact same wattage at most loads. Also, they could be 2 32 ohm speakers already, making 16 ohms be the min load you can get out of that cab.
    About the cab; it can change the tone of any head/bass. Sometimes it's good, sometimes it's bad, depends on the person and situation. Some cabs are sterile, some have mid bumps, some suck mids out. It's a matter of trial and error, and having a good ear to hear which cabs do what. And, in effect, which heads etc. etc.
    Just my $0.02

    -Ray
     
  3. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    For $80 if the amp works you are already a winner.

    You have the right idea about testing the cab for cone rub.

    Don't worry about the impedance of the cab. Tube amps commonly have several output taps on the output transformer (solid state amps typically have no output transformer) and they are less forgioving about the load they drive. It's probably set at 16 ohms for a reason.

    BUT- do not run the head without a load attached- fast way to kill a tube head.

    .
     
  4. For clarification, if the cab does consist of two 8 ohm drivers wired in series, then wiring them in parallel would indeed produce a 4 ohm impedance.

    But this won't get you any louder since it's a tube amp, as the others have pointed out.

    If the head were solid state, it'd be a different story.

    There is a very real possibility the drivers are 32 ohms already wired in parallel. Just for curiosity I'd open the cab up and look, and test each driver to make sure it's not already fried (open resistance checking with a meter).
     
  5. bass_drum

    bass_drum

    Feb 13, 2005
    Alberta,Canada
    Well, I dont have another head, all I have currently is a combo amp (hartke b60).How else could I find otu how the cab itself sounds?


    How could I tell how the cab was wired (seires or parallel)? If I ever choose to change the head, I'd like to be able to have it as a 8ohm cab (just preference i guess).

    About the not having to crank it up and see how it sounds that way. I've played many amp where they sound great quiet but as soon as you crank them they dont sound distorted, they just sound wrong. My hartke combo for example, has a weird hum to it when cranked past 7 or 8 (cant rememebr right now wich one it is).
     
  6. bass_drum

    bass_drum

    Feb 13, 2005
    Alberta,Canada
    What would I look for, and how do I check to see if the drivers arent fried?
     
  7. If the current cab is 16 ohms, consisting of two 8 ohm drivers in series, you can only go to 4 ohms by having the two drivers in parallel. (8 ohms is not an option)

    If the two drivers are already in parallel and they are 32 ohms each, you're completely out of luck. Putting them the opposite way--in series--yields 64 ohms. (again, 8 ohms is not an option)

    This site http://www.colomar.com/Shavano/construction.html

    has an article on speaker wiring with charts showing you series versus parallel.

    Evidently you've never used an ohmeter, don't sweat it.... The meter checks for DC resistance, you just touch the probes to the object under test to see what the resistance is. If it's infinite the voice coil is open. The poor man's test, for those who don't have a meter, is to rig up a couple of wires to the driver's terminals and touch them to a flashlight battery. The speaker will make a thump if the voice coil wire is good. Note: to test each speaker individually, it must be isolated from the other speaker--unplug or unsolder it.
     
  8. You're probably in luck, if its 2 spkrs and a 16 ohm cab, its WAY more likely to be 2 8 ohm spkrs in series than 2 32 ohm pkrs in parallel. Never heard of 32 ohm spkrs, but anything's possible, may have been popular way back when.

    4 ohms vs 16 ohms doesn't make the cab any louder. 300W into 16 ohms = 300W into 4 ohms. File this under no free lunch.

    SS amps just put out more power at lower impedances, so you get more power to the spkr with a given amp at the lower impedance. Making it harder, more expensive to get amp that'll put out 300W at 16 ohms, where many put out 300W@ 4 ohms. A 300W/16 ohm amp would likely put out around 1000W@ 4 ohm.

    I'm assuming nearly double the power going to 8 from 16 since that's pretty high impedance, current won't sag power supply voltage much if the amp's designed to go to 4 or even 2 ohms. And a little over 50% gain going from 8 to 4 ohms. In a perfect world, half the impedance= twice the power.

    Randy
     
  9. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Annnnnnnnnnd twice the power is *only* a 3DB gain in volume. Hardly worth the effort.

    -Ray