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speaker distortion

Discussion in 'Amps and Cabs [BG]' started by bassman_2_1, Apr 1, 2009.

  1. bassman_2_1


    Dec 31, 2005
    Hi, just wondering would anybody have any idea's as to why my speaker is distorting< i am currently using an ampeg svt4-pro my speakes cabinets are the Ampeg BXT4x10" and BXT1x15" both rated at 4ohm so i am running my rig at 2ohm. The 4x10" is not distorting tho only the 15" cabinet. i have taken the grill of the cabinet and there doesnt appear to be any tears in the speaker cone also took a quick peep inside the cabinet when i took the speaker out all the wires seemed to be in order too. Is this a classic sign that the speaker is about to blow or could there be any other fault that i am missing? is has been like this for a couple of months now and am kinda scared to use the speaker as i dont know weather i am making it worse? i use a modulus flea bass which also seem to run pretty hard on the gain section of the amp could never really turn the gain past 3 without it clipping(running in the red) but started using the tuner input of the amp which give -15db i think so you could supply more gain that way. But any suggestions would be great

    ohh forgot to mention--- svt4-pro has two amps inside that run at 600watt a side(1200 total) my 4x10" is a 600watt cab while the 1x15" is 300 watt could this affect it... not sure but i read that Victor wooten uses the same set up> i know he helped design the cabs too,
  2. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Yes, that could be exactly what's causing the distortion, Wooten or no Wooten. 600 > 300. Part of the situation may be your EQ settings--if you have the lows boosted a lot, then most of the wattage is pumping into a frequency range that the speaker just can't handle at that power level. It may be for example that Wooten uses EQ settings and a compressor which both prevent excess power, in the wrong ranges, from hitting his cabs.
    Errr.... what? The tuner input? That doesn't make sense.
  3. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    +1 There may be a tuner OUT, (which won't work with your bass), but no tuner in. What exactly are you plugging into?
  4. bassman_2_1


    Dec 31, 2005
    Sorry might have not made that clear-- on the svt4 you have your normal input and next to to that you have a tuner input, you can use this to decrease your input signal to the pre amp, possibly due some active pickups can run hot in your amp- but anyway to the speaker distortion I was using the normal input to my amp and as I mentioned my bass runs very hot on the gain section,I can't put the gain past like 3 on the amp without it clipping or running to hard, so now I use the tuner so I can run my gain section more-- but anyway doesn't matter which 1 I use I still get a distorted sound out of my 15" cab. Just hopefully I don't have to get it replaced ;(
  5. bassistgook


    Feb 5, 2009
    Check your speaker cable. A bad cable will give your cab distortion. Try switching your speaker cables around and see if it makes a difference on which cab sounds distorted.
  6. synterx


    Jan 24, 2005
    you blew the 15. It's that simple. If it sounds like you have a cheap distortion pedal on, but you can still hear your notes, it's blown.
  7. hrgiger


    Jan 11, 2009
    +1. you cannot see anything by looking at it, it will look like brand new. On a Peavey Black Widow I got screwed on, the guy said it was tested good, took it home put it in and tried it, distortion on low notes that was obvious, took the basket off and looked at the voice coil. SHOT. But before inspection it looked perfect.
  8. MIJ-VI

    MIJ-VI Banned Supporting Member

    Jan 12, 2009
    According to the SVT-4Pro's downloadable Owner's Manual there is an INPUT jack and a TUNER OUT jack on the amp's front panel.

    All basses should be plugged into the INPUT jack only.

    There is a -15db input pad located below the MUTE button which should be engaged if one is using an active bass whose output is quite hot in order to avoid clipping the amp's input stage.

    Amp literature can be enlightening... :)


    EDIT: Your 15's voice coil is likely cooked (overheated and deformed causing it to make contact with the sides of your speaker's voice coil gap) from feeding it 2X its power rating.

    To test for this, place your thumb & fingertips along the edges of your 15's dust cap (the dome-shaped center of the speaker cone) and gently push the cone in slightly. If you feel/hear it scraping, your speaker's voice coil is cooked.


    - Take your cooked 15 to a competent repair shop and have it re-coned (or buy a new speaker) and then use your amp's crossover FREQUENCY control to send only those frequencies which fall below ~ 60 Hz to the 15" cab and use the CROSSOVER BALANCE to blend the 15" with the 4X10" in a manner which does not overpower the 15, or

    - Cut your losses and sell the empty 15" cab, and then replace it with another 4X10" to match the one that you already have and run both cabs full range (no crossover) if your SVT-4 Pro allows this.

    Aside from having two cabs whose RMS rating more closely matches the output of the SVT-4 Pro, your rig will yield a more focused wall-of-sound by eliminating its current speaker mis-match.​
  9. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Check it out, as bizarre as it sounds, the OP is right! From the manual you just linked:

  10. MIJ-VI

    MIJ-VI Banned Supporting Member

    Jan 12, 2009
    :eek: Well! Holy hoist & petard Batman, that's sure a eyeopener for me!

    Thanks for setting me/this straight bongomania (and I hope that you can locate a recent copy of your 'Preamps explained!' piece too). :)

    I stand corrected OP.

    I will now resume playing my passive bass guitar through my tweeter-less amp. :bassist: :D
  11. woodsideh


    Feb 19, 2009
    Charlotte, NC
    I had speaker distortion also and finally figured out that I was using the monobridge cable that comes swith the amp in one of the speaker connections. This cable is wired only to work on the monobridge connection.

  12. How does one determine if their active pickups output are too hot to the point that the -15db pad is needed. I see where many SVT4 PRO users say they never use it, even with active pickups.

    I play a Modulus Genesis 5-string with Bartolini active pickups, NTMB active tone system and I have been using the -15db because it does seem to suppress a distortion, not just volume, that occurs when I don't depress the -15db pad.

    Is it just a matter of hearing distortion when testing the -15db button, or is there a measure to show if the active pickups are too hot, whereas you should use it?

  13. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    It's really just about listening for clipping at the input stage of the amp (as opposed to speaker farting for example). You can further narrow down the location of any clipping by removing any pedals, setting the EQ to "flat", lowering the output volume of the amp, etc.
  14. akaTRENT


    Jan 10, 2009
    New Jersey
  15. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    That's because you're putting an equal amount of power into one fifteen in one cab and four tens in another. That's a mismatch. A better match would be one fifteen and one or two tens. Or a 4x10 and a 2x15.
  16. Thanks. I've gone back and tried that (Flat EQ, no pedals, back the output volume down a little to where it sounded relatively the same volume as with the -15db pad depressed) and found that the I had to move the Gain back from around 3:00 to 12:00 before the red peak light came on.

    I spoke with Dino from Ampeg and he said he usually advises to not use the pad unless "...you can't get the GAIN knob past say, 9 o'clock before the clip light comes on, then your bass is really hot and you can use the -15db pad. However your ears are the ultimate judge on this.
    You won't hurt anything by overdriving the preamp. Like you've noticed, you'll just introduce more distortion into your sound by doing so. Some players actually dig this. The only detriment may be that you'll be changing out preamp tubes a bit sooner"

    Thanks again for the response.
  17. Plucky The Bassist

    Plucky The Bassist ZOMG! I'm back from the dead! Supporting Member

    Jul 30, 2010
    Houston, TX
    Not debating whether or not this is true....but WHY WOULD THEY DO THAT??? :confused:

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