Can I use just one speaker in a two speaker amp?

Discussion in 'Marshall Amps' started by JCGdes, Oct 1, 2020.

  1. What?

    What? Well-Known Member

    Joined:
    May 17, 2018
    Messages:
    1,286
    Likes Received:
    1,113
    That is generally true, or it used to be. But it isn't absolutely true, depending on how the solid state amp is made. And now with class-d amps out there, who knows. Some solid state amps can be damaged with either no load or too low a load.
     
    Lance Chambers likes this.
  2. marshallmellowed

    marshallmellowed Well-Known Member

    Joined:
    Jun 26, 2009
    Messages:
    4,273
    Likes Received:
    5,946
    What? You'll have to be more specific, as in stating a specific example. Loosely stating something does not make it fact. I personally don't know of a solid state design, no matter what class (A/B, D...), that would be damaged by a no-load condition. Any amp can be damaged if overloaded (too little impedance), unless equipped with overload protection.
     
    Last edited: Oct 1, 2020
    Jethro Rocker likes this.
  3. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

    Joined:
    Mar 11, 2011
    Messages:
    9,220
    Likes Received:
    12,565
    Location:
    Saskatoon, Canada
    Nope I have never heard of a SS amp that can be damaged with no load on it. The nature of the beast.
    No load equals infinite impedance. I also have a D amp that has no issues at all with no load.
     
  4. What?

    What? Well-Known Member

    Joined:
    May 17, 2018
    Messages:
    1,286
    Likes Received:
    1,113
    How I understand it, some of the old solid state hifi amps, p.a. amps, and line amps used output transformers for their solid state designs and could get damaged by running without a load. Search on McIntosh for example. On solid state guitar amps specifically, I don't know of any.
     
  5. marshallmellowed

    marshallmellowed Well-Known Member

    Joined:
    Jun 26, 2009
    Messages:
    4,273
    Likes Received:
    5,946
    As far as I'm concerned, if you don't have specifics, it doesn't exist, and just adds confusion to the discussion, as we're discussing the OP's guitar amp.
     
    Last edited: Oct 2, 2020
  6. Sg-ocaster

    Sg-ocaster Well-Known Member

    Joined:
    Jun 1, 2020
    Messages:
    475
    Likes Received:
    560
    On the one speaker that still works but is sounding weird but still has resistance.....take it out lay it magnet down and carefully and evenly with two hands lightly push the cone in slightly(don't bottom it out)and let it come up by itself.....if it's stuck( it's shot)or if it scraps when you do this you have voice coil rub( fixable by a pro sometimes but not worth it unless it's a valuable vintage speaker)
    As for the two 12 amp.....if they are blown....why not just buy a couple used 12" celestion of the correct impedance and not try to mess with one???
    And another quick test is to touch a 1.5v( aaa aa c d)battery quickly across the speaker terminals and see if it makes a peep sound......sometines ohm meters act up.....make sure it's disconnected from the amp when you do this.
     
    Last edited: Oct 2, 2020
    Jethro Rocker likes this.
  7. Georgiatec

    Georgiatec Well-Known Member VIP Member

    Joined:
    Apr 23, 2010
    Messages:
    5,598
    Likes Received:
    5,114
    Location:
    Looking for something I don't remember what.
    Blowing 3 speakers in two different amps in a short space of time is like lottery winning odds likely.
    I would certainly be looking at amp internal failures or operator error.
     
    John BNY likes this.
  8. SkyMonkey

    SkyMonkey Well-Known Member

    Joined:
    Oct 28, 2018
    Messages:
    3,107
    Likes Received:
    4,094
    Location:
    Location:Location
    I have a 1997 Valvestate VS65R (i.e. SS with one preamp tube) that I ran accidentally without a load briefly.
    It happened when I took the chassis out to change the tube.
    I switched the amp on to test but forgot to connect the speaker.
    There was a curl of smoke and a bad smell.
    As soon as I noticed I switched the amp off.
    Once fully reconnected the amp worked fine.
    I was lucky.
    Not all SS amps are the same.
     
  9. John BNY

    John BNY Well-Known Member Silver Supporting Member

    Joined:
    Jul 13, 2013
    Messages:
    2,080
    Likes Received:
    3,285
    Location:
    New York
    In the years I've been playing at high volume levels, I have never blown a speaker. As others have said, if the OP blew multiple speakers, there likely is a problem with the amp itself.

    Also, my understanding is that mismatching the impedance between the amp and speaker (at least in tube amps) will damage the amp and not the speaker. I've never heard of blowing a speaker from mismatching impedance. Then again, I never mismatch impedance, so I don't have any experience with what potential damage can come from mismatching.
     
    Mitchell Pearrow likes this.
  10. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

    Joined:
    Mar 11, 2011
    Messages:
    9,220
    Likes Received:
    12,565
    Location:
    Saskatoon, Canada
    With SS the issues can occur with running lower than minimum impedance at high levels. There is no matching with SS, higher impedance simply means less volume.
     
  11. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

    Joined:
    Mar 11, 2011
    Messages:
    9,220
    Likes Received:
    12,565
    Location:
    Saskatoon, Canada
    Even though there was smoke I disagree that the issue was running no load. If one did that with a tube amp, odds are slim it would puff smoke right away. If it did, it would not work again when turned on the second time.
    A SS should not puff smoke for that. Dunno what it was,,perhaps something burned on board but it still works?
    Manuals state not to go below 4 ohms. No speaker becomes an infinite load with SS. They do not have an output transformer. Other people with VS100 etc have run them without loads.
     
    SkyMonkey likes this.
  12. SkyMonkey

    SkyMonkey Well-Known Member

    Joined:
    Oct 28, 2018
    Messages:
    3,107
    Likes Received:
    4,094
    Location:
    Location:Location
    I don't have the nous to explain it.
    No load = smoke.
    Load = happy amp.

    It happened immediately, and I switched it off within seconds.

    The VS65R has no minimum load statement in the manual or on the rear.
    I just assume 8 ohms is the minimum load due the the rating of the stock speaker.

    Also I am not willing to repeat the experiment, even in the name of science :noplease:
     
  13. MullardFillmore

    MullardFillmore New Member

    Joined:
    Nov 1, 2012
    Messages:
    21
    Likes Received:
    8
    If you use 1 speaker instead of 2, the wattage must be at least the combined wattage of the original 2 speakers. That’s playing it safe.

    You also need to have the correct impedance. If you had two 8 ohm speakers in parallel then that is 4 ohms. You will need one 4 ohm speaker.

    Technically, if your amp is set to 4 ohms you can use a speaker 4,8or 16 ohms. IOW the speaker must be equal or greater in impedance than what the amp is set to. These types of combinations will sound different due to reflections from the impedance mismatch.
     
  14. Lance Chambers

    Lance Chambers Well-Known Member

    Joined:
    Jun 23, 2019
    Messages:
    1,719
    Likes Received:
    2,747
    Location:
    The Land That Time Forgot
    My GMX1200H modeler amp clearly states not to power on the amp without a speaker load connected.

    :drunk:
     
  15. yafal

    yafal New Member

    Joined:
    Feb 10, 2012
    Messages:
    25
    Likes Received:
    9
    Location:
    Buenos Aires, Argentina
     
  16. Mrmadd

    Mrmadd Active Member

    Joined:
    Jul 29, 2020
    Messages:
    97
    Likes Received:
    154
    You can use a higher ohm load on an amp and not have any problem, ex 8ohm speaker on 4 ohm amp. Not the best thing to do, but you can get away with it.
    MG amps are notorius for pcb manufacturing issues that result in amp failures. These issues are not easy to find if you are not an experienced tech. I am not.
    It may be cheaper and way less issues to roll the dice and go to some place like GC used or Sam Ash used websites and just buy another
    amp. MG amps are kind of a dime a dozen at times.
    I have had a couple go bad, and just turned them into speaker cabs for heads that work. Some have worked out great.
    One thing to note, certain speakers are designed for certain amps and when mixing parts as such, your sound quality may suffer when you create a mis-match.
    Ex. MG 4 hole cabs are best suited for Marshall solid state amps. It is the same with the combos. I guess that is part of Marshall engineering.
    Good luck!
     

Share This Page