Are all say 25w speakers actually 25w?

Discussion in 'Cabinets & Speakers' started by Madfinger, Nov 14, 2019.

  1. Madfinger

    Madfinger Well-Known Member

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    Are they or do some vary due to manufacturing?
    All my life I have been under the impression that if you have a say 20w amp you should at least double the wattage of the speaker/s to be on the safe side. Does that still apply these days or am I just showing my age.
     
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  2. Matthews Guitars

    Matthews Guitars Well-Known Member

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    No, that hasn't changed. Speakers are still typically rated for their ability to handle a signal, usually pink noise, for a certain amount of time. Test time is typically from 2 to 100 hours.

    There is a second power handling spec that applies to short duration peaks, and that is the 1 dB compression point. This is the point at which an increase in drive level is not matched by an increase in speaker output, and the difference is 1 dB. The speaker is lagging behind the increase in input signal level.

    That spec is often found in speakers meant for the high end audio market, and not for speakers we'd use in a typical guitar amp.
     
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  3. Adieu

    Adieu Well-Known Member

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    Modern 20-25w labelled Greenback-types appear to be more than somewhat underrated, since pairs are often bundled with 50-60w amps and quads with 100-120w amps as the factory recommended speaker (EVH 5153 etc)

    That might just be "vanity sizing" labelling, since there doesn't seem to be an epidemic of blown speakers
     
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  4. ampmadscientist

    ampmadscientist Well-Known Member

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    That is correct.
    A 20 watt amp should have (at least) a 40 watt speaker.
    This is for reliability.

    Speakers are rated for clean power.
    Using distortion, a speaker can become quite a bit hotter than normal.
    This is 'why' the rating of the speaker is doubled.
     
  5. SkyMonkey

    SkyMonkey Well-Known Member

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    I often read that manufacturer ratings are conservative.
    So, let's say, a 50W rated speaker can take 60W (no science here, just playing with figures).
    This may be to preserve their reputation.
    If a manufacturing variance is +/- 10% then an exactly rated speaker may or may not be suitable in an amp with the same rating.
    An exactly rated 50W speaker in a 50W amp is on a knife edge of capability, if there is no conservative leeway, and could fail.
    But the speaker said 50W, we all cry, and the manufacturer looks bad.

    And not all amps are the same. Amp rating has variance too.

    No proof of this BTW, but if I made speakers I would rate them conservatively.

    That said. Double the amp rating is probably the best.
    I changed the 75W V-Type in my DSL for a 60W G12CV and have no worries about blowing it with only 1/2 more than the amp rating.
    Depends on what you do with it too. Coils heat up when playing is loud and continuous.
    Full blast for a 2 hour breakneck set = double the rating.
    Me in the Man-Cave for 2 hours intermittent playing at moderate volume = no worries.
    Plus, I run an extension cab containing the original V-Type too (120W total), but I have confidence in the G12CV on its own.
     
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  6. SkyMonkey

    SkyMonkey Well-Known Member

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    This is from the Celestion website:

    Different speaker manufacturers use differing methods to determine power handling. At Celestion, every speaker is rigorously power/longevity tested using an in-house developed noise source. From this test, we find out how much power the speaker is capable of using and how much will destroy the speaker outright. By skilful analysis of the test data, we calculate a suitable power-handling figure.

    The value chosen is low enough so there's little or no risk of damage, but high enough for the speaker to fulfil the application it was designed for. It is NOT an absolute limit above which you must never go, more like a "speed limit" You can exceed the limit if you want, but it's not recommended and if you do, there may be trouble ahead...Generally, you can safely run a 60-watt Celestion speaker at 60 watts and it'll keep going all day long.* Connect it up to 100 watts and it might work for an hour or more before it incinerates. "Over-power" any speaker and it'll work fine for a while; just don't bank on it lasting.

    (* Extreme use can break a speaker at lower-than-rated power levels. For example a sustained drop-tuned Metalcore pummelling through vintage-type speakers would almost certainly cause damage.)

    https://celestion.com/speakerworld/guitartech/9/37/Power_Handling:_All_you_need_to_know!/
     
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  7. SkyMonkey

    SkyMonkey Well-Known Member

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    From the Eminence website:

    The power rating on our speakers is simply a maximum thermal limit. If you ensure your amp is rated lower than the speaker you are considering, the speaker’s power rating is not an issue (this only applies to guitar speakers). Plus, it is not very practical to apply 150 watts to a single, say 12”, speaker. While a particular guitar speaker may be able to handle 150 watts thermally, the result may not be very musical. So, you might ask, why Eminence does not rate their guitar speakers based on how they will sound? Well, we do not know if the amp you are using is bass heavy or high gain, if the cabinet is sealed, ported, open, or if your guitar has humbuckers or single coils, or etc., etc. In other words, there are just too many variables, so we must cover all the bases and let you know what the speaker can take at an extreme.

    https://www.eminence.com/under-powering-a-guitar-speaker/
     
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  8. Ken Underwood

    Ken Underwood Well-Known Member VIP Member

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    As long as they say either RMS or Peak, it makes a whole lot of difference knowing and appreciating which one is which.
     
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  9. SkyMonkey

    SkyMonkey Well-Known Member

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    On Peak and RMS (Root Mean Square)
    Again, from Eminence:

    Eminence uses an industry standard method (EIA 426A) for establishing power ratings. A speaker is tested in free-air with a continuous noise signal with a 6dB crest factor. This continuous average power rating (or “watts” rating) is basically a thermal limit. Eminence does not associate a watts rating with “RMS.” RMS pertains to voltage or current, but “RMS watts” is an erroneous term. The music program rating is always twice the continuous rating. It is a higher rating because music has many peaks and dips and is not as abusive as a continuous signal. This is a good rating to select amplifier power for proper headroom in a pro audio application. Eminence does not publish a peak rating, but we accept it as four times the continuous rating. Peak is higher because the shorter duration of a burst of sound is less abusive than a music signal or a continuous signal.

    https://www.eminence.com/understanding-loudspeaker-power-ratings/
     
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  10. GIBSON67

    GIBSON67 Well-Known Member

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    Celestions are definitely conservatively rated, but then so are Marshalls!
     
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  11. Ken Underwood

    Ken Underwood Well-Known Member VIP Member

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    As long as the average Muso, said with total respect, understands what has been said here today then there should not be any confusion.
    You can read about it but does anyone understand it.
     
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  12. Sacalait

    Sacalait Well-Known Member

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    I think it's the guy from Warehouse Speakers who shows up now and again on this forum and states pretty much the same: you should double the speaker power rating to be safe with a Marshall amp. (Maybe any amp). But I did recently fry the voice coil on a Celestion Greenback 25 watt speaker with my SV20. So you should use some caution.
     
  13. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Not all speakers are created equally. There may be slight anomalies that cannot be heard but which may rear their ugly head when the speaker is pushed hard.

    And as Eminence wisely stated above about users:
    "Well, we do not know if the amp you are using is bass heavy or high gain, if the cabinet is sealed, ported, open, or if your guitar has humbuckers or single coils, or etc., etc. In other words, there are just too many variables, so we must cover all the bases and let you know what the speaker can take at an extreme."
     
  14. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    How was the guitar, amplifier and any other equipment set?

    Also refer to above post.
     
  15. Scumback Speakers

    Scumback Speakers Well-Known Member Sponsor

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    One of my first amp clients got a Celestion G12-65 for his combo amp. The amp was a dual 6V6 single ended Class A design. It was measured at 10.8 w clean (vol @ 3), 19 w cranked (vol @ 7). He used a boost pedal, wah, and some other fx. That G12-65 lasted 14 months with the amp.

    He moved to a pre rola G12H30 55hz 30w speaker. That speaker lasts to this day.

    The magnet size/weight helps dissipate some of the heat in the voice coil area, acting like a heat sink. The bigger the magnet, the more heat it can handle.

    While most guitarists like the 35 oz ceramic magnet for tone (M75, G12M), they don't dissipate as much heat as a heavier magnet.

    The only way around that is to have more speakers to split the signal so they don't get as hot, and wind up melting the voice coil. The higher the fuzz/boost settings, the more heat the signal becomes and sends a square wave to the speaker, which is the ultimate heat generator.

    And now you know why Hendrix used a full stack with his Marshall 100w, fuzz, univibe, wah. He used to turn the control all the way up on the amp, then kick the fx in. His old Plexis were putting out 115-120w clean, and 200w cranked, plus the pedal boosts. It's no surprise why he blew so many speakers.
     

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