How to (Not) blow out a Cabinet

Discussion in 'Amps and Cabs [BG]' started by A_maz, Feb 24, 2020.


  1. A_maz

    A_maz

    Feb 24, 2020
    Hello, I just bought my first bass rig about two months ago. I got a Trickfish Bullhead .5K and an SWR Goliath I. Here are the specs:

    Trickfish Bullhead .5K: 700W @ 4Ohms, 500W @8ohms
    SWR Goliath I: 400W @ 8Ohms
    *note: I think those are the specs for the Goliath because I couldn’t find any Goliath that looked exactly like mine but it looks most like the Goliath I*

    I noticed on Saturday after my gig on Friday, I blew out my cabinet somehow, even though I set my gain properly using the LED signals on my the amp head and it sounded fine the whole gig. I thought that so long as the gain on the amp wasn’t driving the cabinet into clipping, I could put my master volume knob to whatever i wanted. But now(after some research I should have done before), I see that gain=/=volume. From the article I read, it seemed that the volume knob shouldn’t go past where the gain knob is, but I don’t know if that’s correct. I’m just very confused because I thought I would be able to hear any distortion or clipping in the cabinet, and in all the videos from the gig my rig sounded really good. How do I know what volume level I can properly set my amp at to not get clipping/distortion in the cabinet?

    Also I’m looking into buying an Eden D410-T(300$) which has max 540W @4Ohms and I want to make sure I’m not going to blow it out. Any help is appreciated. And in case anyone was wondering, the Trickfish head sounds amazing.
     
  2. bobyoung53

    bobyoung53 Supporting Member

    Unless that is a very odd amp think of the gain as a preamp volume control and the volume as a power amp volume control (master), in other words, the volume control will not limit the total volume. How do you know your cab is blown?
     
  3. A_maz

    A_maz

    Feb 24, 2020
    I’m honestly assuming it’s no issue with the head because it’s literally new and has significantly more power output than the cab, but the gain knob was only a quarter of the way to the max. The volume knob was about 3/4s of the way to max during my Friday night gig, so I just kinda figured it was the amp putting too much power through the amp somehow. I tried different instrument cables, speakon to quarter inch cables, another bass, and I plugged all of these into my practice combo amp to make sure they were fine so I figured it must be the cab. And I listened to each of the 10” speakers individually and it sounds like it’s the upper left one being blown.

    There is the slight chance that it could be my bass, because there was some funky stuff going on with my bass where it sounded super quiet but also blown out through someone else’s amp. Never heard that before. I replaced the 9 volt to make sure it wasn’t the pre amp being dead, so I honestly had no clue what that was about. But then I plugged it into my combo amp and it sounded fine so...??

    Again, I’m new to the whole head/cab thing so I don’t know if I’m doing any of this right but I thought I did my research.
     
  4. A_maz

    A_maz

    Feb 24, 2020
    Ok sorry for that incredibly long reply, but I’m just confused about the gain knob then. Why does the LED light up red if the gain is turned too high?
     
    bobyoung53 likes this.
  5. Wasnex

    Wasnex

    Dec 25, 2011
    Knob position really don't tell you how much power the amp is putting out. Many amps make full power with the knobs around 10 O'Clock, so you may have fed your 400W cab more than 400W. I am not certain but I believe the early SWRs were tuned pretty low and did not tolerate well being driven much above their RMS power rating. Keep in mind this is a pretty old cab so it may have just been time.

    The other issue is speakers are often rated on the thermal rating of the voice coil. A more important rating for bass speakers IMHO is mechanical power handling, and unfortunately not many companies publish this data. The mechanical limits of the cab are determined the drivers Thiele/Small parameters, the volume of the cab, and the dimensions of the port. It will probably surprise you but a cabs mechanical power handling limits below 100hz are often less than it's RMS power handling.

    Here the way a ported cab works. As the driver begins to cut off, the port begins to become resonant and produce sound. The cab is tuned so the driver's cut off and port vibrations sum and produce and extended and relatively flat low end. The vibrations of the port actually help control the excursion of the driver. So excursion will increase as the frequency goes down, and then when the port start operating driver excursion when begin to decrease. Below the port tuning frequency driver excursion increase quickly and output drops off quickly. So you really don't want to ask the speaker to operate very far below it's port tuning frequency. It won't make much sound in this range and it's mechanical power handling is extremely low.


    A high pass filter (HPF) can help because it reduces the amount of power that is fed to the speaker below the port cut off. The other thing you can do is make sure you have enough rig to cover your SPL needs. I think your amp is probably a bit overpowered for a single Goliath I.

    If you use an amp that exceeds the power rating of your speakers, you must use discretion. This means you must avoid hitting the cabs with excessive low end and also avoid turning the amp up too much.

    I uploaded a cab design document for the Eminence 2512. This document came from PartsExpress. Take a look at the graphs labeled Maximum Electric Input Power and Cone Displacement on p. 2, and then reread what I have written. Note this driver is rated for 250W RMS but the tuning notes on p. 1 says "Displacement Limited to 125 Watts; F3 of 64 Hz. Use a steep high pass filterset to 35 Hz to protect your woofer." F3 is the point where frequency response is down 3dB. Fb is the port tuning frequency (44hz for this tuning). The drivers maximum excursion (Xmax) is 4.9mm. Note how driver displacement has reached a minimum at 44hz on the Cone Displacement graph. Also note the significance of 4.9mm on this graph.
     

    Attached Files:

    RSBBass and eriky4003 like this.
  6. bobyoung53

    bobyoung53 Supporting Member

    If only one speaker is making noise there is something wrong with that speaker. Don't use settings to judge how much power it's putting out, just about any amp can put out way more than it's rated power (with distortion) at less than full volume. I use SVT's and they are putting out their full rated power at less than 12 o'clock depending on how much is coming out of the bass, active basses put out a lot more sound than passive basses too. Use your ears not your eyes.
     
    lizardking837 likes this.
  7. bobyoung53

    bobyoung53 Supporting Member

    That means basically that it's getting too much signal from your bass.
     
  8. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    Welcome to TalkBass!!!

    Yeah, it's a confusing world of numbers out there. Honestly, output watt ratings of amp and watt ratings of cabs mean very little in the real world. Just be cause you have a 400W cab and a 300W head that does NOT mean you can crank the head all the way up. You will blow that speaker to bits.

    The best way to determine if your cab is struggling to keep up is using your ears. Forget dial positions and watt ratings.

    I'm a big fan of an HPF (High Pass Filter) as well.
     
    Bboopbennie likes this.
  9. A_maz

    A_maz

    Feb 24, 2020
    Lol thanks I definitely should’ve been on talkbass before it’s literally so helpful. Ok so I’m hearing I was a bad bass player and wasn’t listening as well as I should have been. So what are some tips just to make sure I’m putting a safe amount of power through the cab?

    Also I just checked and the Eden-D410T has a frequency response of 80Hz to 14kHz and my Trickfish head has a bass frequency selector @ 40Hz or 80Hz. To avoid blowing it, should I not put the bass frequency selector at 40Hz and only use 80Hz?
     
  10. Jim Carr

    Jim Carr Dr. Jim

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    I'm a little confused, so bear with a couple of questions.

    Can you send us pics of the cabinet? I would like to verify it is a goliath I.

    Furthermore, Did you use any effects, either pedals or built-in, like distortion, overdrive, synth, octaver, etc.?
     
    Bassdirty likes this.
  11. A_maz

    A_maz

    Feb 24, 2020
    That’s a lot of knowledge and thank you for blessing me. And yeah, I wasn’t sure if it was just the speaker being old or if I was being dumb but sounds like it’s a bit of both. I feel like I absorbed the main idea so I just want to make sure I understand: numbers/knobs are not an accurate reflection of power output, and the lower end frequencies can actually be the death of a bass cab. What HPFs would you recommend I use? And also if my head has emits a bass frequency lower than a cabinets frequency response, will that damage it?
     
    Wasnex likes this.
  12. A_maz

    A_maz

    Feb 24, 2020
    Images attached. And no, I don’t really use effects too often but I would like to know about how they can overwork a speaker. More specifically delay, envelope, and octave(if there is any difference). I have noticed when I plug in my Boss DD-7 that sometimes it makes the sound more nasally but can’t tell if that’s just me.
     

    Attached Files:

    Jim Carr likes this.
  13. A_maz

    A_maz

    Feb 24, 2020
    ALSO: just learned that clipping/distortion is caused by an overdriven amp, and NOT the cabinet being pushed too hard. Or at least that’s my dumb understanding of it. Please clarify if I’m wrong.

    And just to let you know, I also backlined the rig for a house show where two other bands used my bass rig so it could have just been overworked in one night. And this guy with a passive bass cranked the volume knob but I thought it was ok because (as I’m learning on this thread) I’m dumb.
     
    bobyoung53 likes this.
  14. Richard Martin

    Richard Martin Estimator Extraordinaire Supporting Member

    May 13, 2015
    Greenville, NC
    Where are you setting the HI LO switch? Since you have an active bass, the switch should be set to the LO position. An active bass set on the HI position, can create speaker crushing distortion at very low levels.
     
  15. A_maz

    A_maz

    Feb 24, 2020
    It was set on high. I kinda figured that might have been the nail in the coffin.
     
  16. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    From preamp distortion? Why? Unless I'm misunderstanding, if the cab died, it's because of it being asked to performed past its limits due to volume.

    While distortion can raise the RMS power of a signal, it still needs to be at a power level significant enough to cause damage. Distortion isn't a speaker killer, only total power is.
     
    David Jayne likes this.
  17. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    This is wrong. A cabinet that is pushed too hard can absolutely "fart-out".

    However, contrary to popular belief, a speaker being driven past its limits may not always give audible clues that are easy to hear. I know this from personal experience.
     
  18. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    I just read the manual. It's somewhat confusing, but the indicator on this amp in particular seems like it's meant to indicate a signal strength after gain and EQ that will cause the preamp to distort - not just from the instrument or input.

    So any combination of instrument volume/signal entering the input + "gain" gain + EQ gain = the level that the indicator checks for. It says specifically that raising EQ could boost the signal enough to trip the light, in which case the gain can be brought down to balance it out... at least if I'm reading correctly. As I said, the way the manual words it is a bit confusing.
     
  19. Wasnex

    Wasnex

    Dec 25, 2011
    You seem to grasp the concepts I was trying to communicate :thumbsup:.

    If the head produces a lot of power below the cabs pass band it increases the chances that damage will occur due to over excursion. An HPF will attenuate or roll off those super low frequencies.


    Consider an HPF from @fdeck or https://www.broughtonaudio.com/
     
    A_maz likes this.
  20. Jim Carr

    Jim Carr Dr. Jim

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    You are not dumb. You need a little more information and more experience.
    You are lucky, a goliath I is a good sounding 410. It is really the cabinet that started the massive shift to 410 ported bass cabinets some time around 1980 or so. That design still works fine, but has been surpassed, IMHO.

    Distortion comes from a lot of places, but the only kind that harms speakers is that caused by asking them to do what they cannot do. Sending a signal that asks them to move farther than they are designed to move will eventually burn them out, melt glue, or literally tear them up.

    Heat build-up and mechanical over-excursion are both caused simply by playing (generally low frequencies) too loud. Too much power.



    Distortion from your pre-amp (gain), your amp (master volume), an effects pedal, etc. will NOT by themselves harm your speakers.
    The problem is that all those other sources of distortion or extreme signal complexity will make it impossible to tell if your speakers are distorting.

    Speakers usually complain before they fail. They can make ugly sounds that mask the actual pitch. The intended waveform of your instrument is not correctly reproduced, and frequencies that don't belong to a given note obscure what should have been there. Sometimes it is a rattle, sometimes popping, sometimes clicking or even burps, fuzziness, or "farts."

    My advice is as follows:
    1) Get your goliath I fixed. It is a cool cabinet that is rare and worth keeping around in working condition.

    2) Get a newer second cabinet that weighs less and can handle more power. Having the goliath as a back up or rehearsal cab would be good.

    3) Experiment with your new amp head and cabinet. Get to know their limits.

    4) Carefully supervise any use of your gear by others.

    5) Wear hearing protection at all times in a loud music situation.
     
    Last edited: Feb 26, 2020
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    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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