30 watt speaker in a cranked 22 watt amp... yes or no?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Think Floyd, Mar 7, 2015.

  1. Think Floyd

    Think Floyd Member

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    I recently bought an Allen Accomplice with a 30 watt Weber Blue Dog Alnico speaker. The amp sounds great, and I did turn it up fairly loud for a few minutes while trying it out (both clean, and dirty with a Barber Burn Unit and the amp set clean). The loud clean and dirty tones were wonderful.

    However, I'm concerned that if I'm in a situation where I'm playing loud for an extended period of time the 30 watt Weber may not be able to handle the cranked Accomplice (22 watts). Common sense tells me that this amp should have a 50 watt (or more) speaker, but I've also heard that some speakers are rated conservatively and can actually handle more wattage than their rating.

    Will I be okay with the 30 watt Blue Dog, or should I replace it? At the moment I'm not jamming with anyone, so the amp won't be cranked at all. Since I'm not in a rush to make a decision, I'll have the chance to get to know the amp better and decide if the Alnico Blue Dog has the tone that I want.
     
  2. Blue Strat

    Blue Strat Member

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    Hard to say for sure. People don't realize that 15 watts of dirty signal can be more dangerous to a speaker than 25 watts of clean signal.
     
  3. mgarrison99

    mgarrison99 Silver Supporting Member

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    Looks like your speaker setup will work without blowing, but will have an overall limited service life based on thermal stress. Excellent tech article on it can be found here, but it basically confirms your gut feel that your speaker should be rated about twice the wattage you're going to be pumping through it. Here's the quote from the article:

    "There is no standard method used by all amp manufacturers when selecting an appropriate speaker power rating. If you want to choose a speaker to last a lifetime, you'll want to choose a speaker that can handle the maximum amount of preamp and power amp overdrive distortion that can possibly be put into it and safely avoid exceeding the speaker's thermal limits. In the case of single speaker setups, this means choosing a speaker rated for at least twice the rated output power of the amp."

    Here's a super-technical explanation:

    https://www.amplifiedparts.com/tech_corner/guitar_speaker_power_handling
     
  4. schmidlin

    schmidlin Member

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    I'm a Weber fan and follow their products closely. The consensus is that they are rated properly, so you should be okay. That said, if things do go south, they will re-cone their speakers for a third of the cost of a non-Weber 12 ($25 +S&H) and at that point you can have them upgrade it to any wattage rating up to 100 watts.
     
  5. Think Floyd

    Think Floyd Member

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    The last time I had an Accomplice, I tried a Celestion Gold in it. It sounded sweet at home, but I just didn't care for it in a "band" situation. This Blue Dog is also an Alnico, but with distortion it sounds better to me than the Gold. However, I have no idea how it will sound in a band mix, and might not get that chance for quite some time.

    Odds are that I'll eventually replace the Weber, since I'd rather be safe than sorry.
     
  6. pdf64

    pdf64 Member

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    Amps are rated on their sine wave output.
    When heavily overdriven, the output will become pretty much a square wave.
    All else being equal, a square wave has 1.414 x the power of a sine wave of the same peak amplitude.
    22 x 1.414 = 31 watts.
    So if the amp is used under continuous overdrive, a 30 watt speaker may not have a long working life.
     
  7. Think Floyd

    Think Floyd Member

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    Thanks for the info everyone.
     
  8. kyoungsteadt

    kyoungsteadt Member

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  9. ripple

    ripple To keep fresh, keep capped & cold. Silver Supporting Member

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    This is one of the reasons I love this place: a knowledgeable pro technician who willingly shares a golden nugget of information for zero personal gain.

    If you pay attention around this place, you can learn things... a lot of things.

    Thank you Pete. You have helped me (and countless others) in amp build/tech threads in the past. I've filed this little factoid away in the old noggin as well.
     
  10. pdf64

    pdf64 Member

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    You're welcome, I'm pleased to have helped!
     
  11. zenas

    zenas Member

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    How often do you get the volume knob past 4 ? I have that same speaker didn't care for it in my BFDR but if I would have liked it I would have ran it.
    Might revisit that speaker now that's it's broken in some in a 65 Bandmaster cab.

    I know on paper my Twin Reverbs should have 200 watts (or more)of speakers in them but they never get anywhere close to putting out all the power Leo built into them. Neither does the BFDR I just can't use that much volume. If I could I'd have EVs, Swamp Thangs or some other 30 pound speaker in them.
     
  12. Scumback Speakers

    Scumback Speakers Gold Supporting Member

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    One of my clients had a G12-65 in a Gibson GA-8 1x12 combo amp. Amp was single ended Class A. 9w clean, 17-18 cranked.

    That speaker lasted 14 months with the amp putting out 17-18w most of the time.
     
  13. otaypanky

    otaypanky Gold Supporting Member

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    I have a Chinese Celestion G12M rated at 25 watts in a Sweet Spot which is listed to be 25 watts with 6L6's or 18 watts with 6V6's.
    I run it with 6L6's and quite often it's up at 3/4 to max on the volume with no issues at all.
    That speakers been in there 3 or 4 years and gotten a lot of use. Sounds great
     
  14. 71strat

    71strat Member

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    Buy a Blown JBL E120. Send it to A Brown Soun for Hemp Recone and never look back.

    I also like the Altec Lansing / Great Plains Audio 417H.

    Great Plains Audio bought all the Original Altec Manufacturing Gear and the Rights to the Altec Brand. They have made them for years.
     
  15. walterw

    walterw Gold Supporting Member

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    or at least they should be!

    do we know this for a fact about traditional fender designs?

    could this be why an old "100w" marshall seems to be so much more powerful than an old "100W" twin, one is really rated at its still-clean limit while the other is rated at the point some distortion has kicked in?
     
    Last edited: Mar 8, 2015
  16. zenas

    zenas Member

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    An E120 that needs a recone is what a hundred bucks? Then the hemp cone is 200 more bucks plus shipping both ways.

    At some point you have to ask yourself if your listen with cubic dallors spent or your ears?

    Try a 50 dallor Weber SigB sometime without thinking about how cheap it is and listen to it. There's two of them in my BFTR now and the two JBLs are out.
     
  17. pdf64

    pdf64 Member

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    For a guide to the power rating of vintage Fender amps, perhaps we can look to their modern re-issues?

    The max sound pressure level created by an amp will be governed by its power output and the efficiency of the speaker array used; a 4x12 can create a mighty sound, and yes, vintage Super Leads seem to put out over 100 watts before clipping.

    I think that Celestion may have a degree of de-rating with regard to their power handling spec, even to the point that of them being suitable for an amp of the same power rating, eg AC30 with 2 x Blues.
    That may not be a good idea with other brands, ie to use speaker (arrays) of similar power rating to the amp.

    As with any component, to get good life, eg accommodate line / component tolerances, it's good practice de-rate key specs by at least 10-20%.
    When combined with the 30% de-rating (1/1.414 = 0.707) required by the sine to square thing, it can be seen why (for overdriven guitar) it can be beneficial to use speaker arrays with twice the power handling capacity of the amp.
     
    Last edited: Mar 8, 2015
  18. 71strat

    71strat Member

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    Weber SigB is a 50 Watt speaker.

    2 x 50 Watt Speakers in an 85- Watt RMS amp ?? No Thanks. Those are like the old time Jensens, Oxfords ect.

    Been there done that back in the 70's with the Real Jensens, Oxfords, Eminence ect. ALL DISASTORS. YMMV.

    The Very First Thing I Do with ANY Speaker is run my amp on 10 or 8 hours straight. With a LOOPER. Though I haven't bought speakers in several years.
    I have a sound proof attic and my neighbors don't care anyway. I also do this with all NOS Tubes I buy.

    I wont but any tube that doesn't have at least a 30-45 day warranty.

    I allow for my tech to have the amp 1 week and then the next 3 weeks I will burn in the tubes at 100% output for 100 hours.

    If they don't last they go back. That is Normal usage for a tube back when they were made.

    I use Mullard 12AX7 Master Series Gold Pin. They were Guranteed from the factory for either 2 Years or 10,000 Hours. 10,080 hours is 59 weeks at 100%.

    They did not Specify at Half Power ect Either. It was 100% for 10000 Hours. If they fail. You get a New 1. The Guarantee was on the box.

    So my 100 Hour Burn in is Nothing. For tubes or Speakers.

    You can buy Blown E120's for 40-60 dollars blown. You can buy great shape E120's for $130-$175. I just like the Hemp Cones.N
    The OP has a NICE AMP. SPEAKERS are the HEART of the AMP. I would never recommend a 50 dollar speaker in a $1800 amp that's new. His may be used but its still a Really Nice Amp that deserves the Best Possible Speaker he can get. Of which I Know Best is OPINION. This is mine.

    And Not saying the JBL is the ALL OUT Absolut Best. There is no Best.

    Also a JBL.. ANY JBL in an Open Back Twin is not the best match either. a 150 Watt E120 is in Reality on ly good for 75 Watts in an Open Back. So even 2 E120's in an 85 Watt RMS amp is Not Optimal.

    Also Many don't know it and WIRE JBL's BACKWARDS.

    On JBL the Red is Negative and Black is Positive. If they are Wired Incorrectly they sound WEAK and Anemic.

    There are 4 Blown E120's right now on Ebay for $39 + $32 Shipping. So $70.

    You can also buy Alnico K Series JBLs for $150. With Original Cones all day.

    Ive been using JBLs and Altec Lansing since 1972.

    I got tired of blowing CTS, Jensen, Oxford, Eminence and several others back in the early-mid 70's when I was 1st experimenting with electric guitars and amps.

    They came standard in Many amps then and I Blew ALL OF THEM. I had a 12 inch Jensen last 2 weeks in my Kustom 50. The previous owner had it for 3 years.

    He never dimed it. I did. It lasted 2 weeks. No pedals either.

    I think Eminence is the ONLY Old Time Manufacturer of that type of speaker that has actually gotten Better in Modern Times.

    I like Emi. Some of them. Especially the Limited Edition that come in Hi Tone Amps and the Eric Johnson Speaker.

    Ted Weber even said the Greatest Sounding 12 inch guitar speaker Ever Made is the JBL D120F, but I didn't recommend that speaker because they are all but Impossible to find with Original Cone.

    I also have 8 x 12 of D120F's that came in my 1970 Sunn Coliseum Lead. It came factory Original with JBL D120F's. In 72-73 Sun had JBL change the Codes to D120S.

    Celestion Sure Hasn't made any speakers that compare to the Pulsonic Cones they used to make.

    I also have some Original Pulsonic Cone Celestion G12M's. 25 watt 75hz Pulsonic cones from 72

    I have Altec Lansing Gauss, Fane Cresendos. Electrovoice 12M's and 10M's. Not the Modern 12L''s.


    But for me I like JBL, Altec, Fane Cresendos. Im not big on most other brands. I also use 4 x 12 G12M's for 38 Watts. That as close too 2 times the RMS that I use. Everything else is 7-10 Times RMS.

    I also Never saw a Price Limitation..

    Weight and Price for me are NEVER a CONSIDERATION Unless stated by OP asking a question. I also want 0 Speaker Distortion and generally use 2 x 1 x 12 JBL E120's Minimum with a 38 Watt amp. So I have 300 Watts RMS worth of Speakers for a 38 Watt amp. MINIMUM.

    But theres No Way I would use 2 x 50 Watt Speakers for an 85 Watt amp unless I never pushed it.
    For me if a speaker cant take FULL OUTPUT for 8 Hours Straight with Drive Pedal Ect.. ITS USELESS. No Exceptions.

    Also Im Not saying these are Bad Speakers either. Its just most of the time they are Not used in the Proper Application and to me 2 x 50 Watt Speakers in an 85 Watt Amp is Not the Proper Application.. YMMV.

    I also still have All of my Altecs and JBLs from the Early -Mid 70's and have Never Blown 1 of them.

    Also the E120 has 103db 1/w x 1/m and gives me Huge Clean Headroom.
     
  19. Think Floyd

    Think Floyd Member

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    I was just playing today, and after spending some more time with the amp I've decided to replace the Blue Dog. I didn't care for it too much at lower volume, and that will be the majority of my playing.

    Since I will be looking for a new speaker, I'll just play it safe and go for at least a 50 watt rating.

    Thanks to all who posted!
     
  20. J M Fahey

    J M Fahey Member

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    Sorry, a squarewave has 1.4142 times the voltage of a sine wave of the same peak amplitude.
    Please recheck your source, it's easy to take one for the other.

    It will have twice the power. (because it's V*V/Z =1.4142*1.4142=2X)

    Then how come the speaker does not blow in seconds or minutes with 2X22W=44 W cranked?

    3 reasons:

    1) most tube amps are "optimistic" ( to put it mildly) , that amp will have 22W with a waveform already distorted (10% distortion in a guitar amp is considered "clean", go figure), with a real Hi Fi clean one maybe not more than 16 or 18W ... that helps.

    2) power comes from a power supply.
    Maybe it feeds enough to get 22W "clean" or thereabouts, in no way it will feed easily what's needed for 44W ... +V voltage will drop, screen voltage will drop even more (that's a big power brake) , even PI will clip tryingb to drive the power tubes, so a guitar tube amp in practice never delivers 2X clean power .... but that's not a Math result, rather a real world supply one.
    Even more limited if the supply has a tube rectifier.

    3) waveform rarely is a perfect squarewave .

    That explains why 2 x 15W Vox Blue survive a cranked AC30 or 4 Greenbacks manage a 100W head .

    Now you do the same with a honestly rated SS amp and you fry the voice coils in a jiffy, SS does not have that much power limiting and supplies in general are much stiffer .... and they have no screens, plus SS easily clips into perfect squarewave .

    In the link mentioned:
    https://www.amplifiedparts.com/tech_corner/guitar_speaker_power_handling
    it also clearly states:
    Yet as I mentioned , speakers are somewhat protected by the usually "just enough" power supply .
     

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