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How do they reckon "watts"

Discussion in 'Amps and Cabs [BG]' started by Philbiker, Aug 8, 2003.


  1. Philbiker

    Philbiker Pat's the best!

    Dec 28, 2000
    Northern Virginia, USA
    Since I've been using my practice amp almost exclusively for playing the last few years, I almost sold my "big" bass rig amp head over the last couple weeks. I've since reconsidered and decided to keep it, but it got me thinking.

    How the hell do you recon "watts" and why is it so inconsistent? My speaker cabinet is a very early (white label) Eden D210T which is absolutely wonderful sounding.

    My amp is a 1966 Fender Bassman (pic attached).

    Now, I know this thing is supposed to be "50 watts" but I can tell you it is a hell of a lot more powerful and louder than my old Dean Markley "150 watt" combo was. For that matter it's on par with my old Eden Nemesis "200 watt" combo. This sucker is LOUD and CLEAN let me tell you!

    And boy oh boy does it have tone. Tone like you wouldn't believe, thich, rich tone that dreams are made of. Volume won't be as good as lots of modern stuff, but man oh man the tone of this thing is simply unbelievable.

    How come this "50 watt" amp is so friggin' loud?

    [​IMG]
     
  2. Johnny BoomBoom

    Johnny BoomBoom Supporting Member

    Jun 8, 2001
    Glasgow, Scotland
    Not exactly sure how they arrive at a watt value for an amp. Alos not sure each manufacturer is totally consistent in their method of calculation.

    Perhaps your Eden cab is more efficient than the speaker section of the combos you refer to....just guessing!
     
  3. Philbiker

    Philbiker Pat's the best!

    Dec 28, 2000
    Northern Virginia, USA
    I'm fairly sure that it is - good point!
     
  4. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Arriving at wattage is just math. Measure the voltage at the speaker terminals and then calculate:

    watts = volts x volts / impedance.

    50 watts = 14.2 volts x 14.2 volts / 4 ohms

    Why does it sound louder?

    1. More midrange emphasis (ears are most sensitive to mids)

    2. More distortion and compression

    I'm amazed you call it "clean". I have never found a 50 watt Bassman that was clean much above 5 on the volume knob and at gig volumes mine always are grinding a little. Many of them on the bench can barely hit 50 watts with fresh tubes. I had one that clipped at about 40 watts.
     
  5. BruceWane

    BruceWane

    Oct 31, 2002
    Houston, TX
    1)Yes, the Eden is probably more efficient.

    2)Tubes amps can be run into mild clipping without sounding bad. Solid state amps cannot. This effectively gives the tube amp more useable headroom, and thus more volume.

    3)You have to understand the watts versus volume equation. A fairly noticeable increase in volume is about 3db; it takes an increase of 10db for something to be percieved as "twice as loud". For every increase of 3db you have to double your wattage. To achieve a 10db increase you need ten times the power. In other words, let's start at one watt into an average cabinet......

    1 watt = 98db
    2 watts = 101db
    4 watts = 104db
    8 watts = 107db
    16 watts = 110db
    32 watts = 113db
    64 watts = 116db
    128 watts = 119db
    256 watts = 122db
    512 watts = 125db

    ......and so on.

    So you can see where

    1)There's really not that much of a difference between 50 watts and 150 watts and

    2)You can see where a 50 watt tube amp can easily compete with or be louder than a solid state amp of 150 watts.
     
  6. Mcrelly

    Mcrelly

    Jun 16, 2003
    Minnesota, USA
    I think part of the problem is TRUTH IN ADVERTISING. Just the other day I accidentally found a 800 WATT DJ AMP FOR $165!!! and I'm like WOW, I wonder if I could use that on my bass? luckily I searched the forum for other people who have used the PYRAMID amps. allmost everyone said "it's not 800watts average output, it's 800watts peak and more like 175Watts per side." I know that with other specs they'll measure a distortion rating at a specific frequency rather than the whole spectrum or a frequency, say 150hz, where we would likely be hearing problems. its very very easy to "play with the numbers".

    I think a common amp rating trick is to put numbers out without clarifying what they apply to like "500 watts" and that may in reality be an actual measurement, but it could also be at 1.5 ohms, at 1khz frequency, for .85 seconds!

    I'm gonna talk to my dads old electronics technitian friend today and ask him some of these questions. side story, when I first showed him one of my amps, SWR WM-10, he said "why in the world do you need 80watts?", "I KNOW that I can put 10 REAL WATTS into a speaker and you couldn't stand it!" or something like that. I do believe that before the 70's and the stereo and car stereo boom amps were real amps and numbers told it like it was.
     
  7. K-Frog

    K-Frog

    Feb 6, 2002
    Camden, AR, USA
    should you feed it a 1Khz signal and measure just before clipping? Is that the most consistent method used?
     
  8. Philbiker

    Philbiker Pat's the best!

    Dec 28, 2000
    Northern Virginia, USA
    Sure sounded clean to me, but I was playing at or below 5 the whole time. Also, I'm using a passive Jazz Bass, perhaps active basses adversely affect the preamp stage in old amps that were designed for standard passive output.
     
  9. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    getting warmer
    He's right becasue it would sound like a fart.

    Seriously, it depends on so many factors other than just the wattage rating that a statement like this is just vague. What signal is being amplified to 10W? Through what speaker? I can tell you Celine Dion at 10W through a horn tweeter right next to your ear is pretty harsh.
     
  10. Mcrelly

    Mcrelly

    Jun 16, 2003
    Minnesota, USA
    wow, you must really like Celine! :p

    no, seriously my dads friend has been in electronic for over 50 years and I believe what he was trying to say is what Philbiker is experiencing. 50 "no BullS***" watts! if we could all have that we wouldn't need our 800watt swrs or 2000w yamaha's.

    Phil, see if you can find out how much that amp cost in 1966 and what its inflated price would be today? just curious. or post the exact model number and rating.
     
  11. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Alexandria,VA
    Owner/Retailer: Jive Sound
    Electrical power is measured in watts. A light bulb, a microwave oven, and an electrical generator can be desscribed in watts yet none of these are audio devices.
    Sound volume is not measured in watts. No one has ever had a noise ordinance violation because they had too many watts. No hearing protection device will say how many watts it will protect you from. Loudness is measured in decibels.
    What the amp and speaker do with the available watts (power) results in decibels (sound). Since amps and speakers can vary in how they use power, there will be a variance in volume regardless of the available amount of watts.
     
  12. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Wrong, clipping causes COMPRESSION which gives you more volume. You don't have any headroom left if the amp is clipping.
     
  13. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    getting warmer
    Doesn't everyone? ;)

    But there are plenty of vintage "true" ~50W amps that can be had for cheap on ebay. Just do a search for Dukane for example and see the amazing array of tube machines available at low cost.

    A watt is a specific unit of measure which hasn't changed over time. If someone publishes RMS wattage figures they are referring to a specific thing. The question is was it measured at a specific frequency? How much distortion?

    What has changed is what people expect from a bass rig. If you're happy with the overdriven compressed "warm" or "farty" tone of vintage lower wattage rigs, then yeah, the modern 900 watters will seem like overkill. On the other hand if you want something to give you quick transients for slapping and full frequncy response at high volumes, the vintage rigs won't cut it.
     
  14. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Actually the ideal way is to measure at ALL frequencies of interest (like 20 Hz to 20KHz) as many tube amps like a Bassman can't push as much power into the lowwe frequencies due to limitations of the transformers. As a bass player you care more about the full range of the amp than just the output at 1KHz.
     
  15. A watt is a watt is a watt. It's just an instantaneous measure calculated from the voltage on an amp's output and the resultant current developed at a certain impedance. This is not open to interpretation or debate.

    If you have two amps of any kind and you set them up to amplify a test tone to a certain voltage within each amp's linear range, if the load impedances are the same, each load will draw the same current and therefore dissipate the same amount of power.
    Most amp manufacturers derive power specs from a similar process. They drive the amp into a static load with a test-tone to a specified level of distortion (usually <1%). This is all well and good, but it doesn't tell the whole story. Speakers are not static loads, they are reactive loads.
    (i.e. impedance varies with frequency). Some amp designs are better able to drive reactive loads than others. It usually comes down to power supply design. This is a large part of the reason that some amps are louder than other similarly rated ones. The other reasons have been mentioned previously.

    Basically, the crux of this is that there isn't a standardized set of tests and specs for manufacturers to use, so some of them tend to use the ones that put the best spin on their products. It's not bogus watts that are the problem it's non-stanardized tests and tests that don't take real-world loads into account.
     
  16. Philbiker

    Philbiker Pat's the best!

    Dec 28, 2000
    Northern Virginia, USA
    Have you ever heard a vintage amp like mine through a modern cabinet like my Eden D210T? The adjectives you've written here are not exactly what come to mind.
     
  17. 1 Watt = 1 Joule / 1 second... forget the electronics, if you know how many watts any system dissipates as sound energy, you know exactly how loud it is. That's the most meaningful power measure I can think of for any amp (well, maybe total power consumption as well).

    Pathetically, if you give any company two measure of power to market, one meaningful and one high, they almost always go for high. Bah.

    IMO a system of rating amps which states maximum distortion free sound power averaged over 10 seconds, run into a standardised rig with actual speakers would put everything into extremely clear perspective.

    Hmm.. actually, the guys who like power tube distortion might not go for that.
     
  18. If you are referring to the system as including the speaker, then you also have to know the pattern that the speaker emits into the room. This is because loudness is a measure of power per unit area, so it does depend on the mechanics of the loudspeaker and the amount of power that it converts into sound. I am not too sure how much this can vary from cabinet to cabinet, that is something more for BGavin or Joris, I think.

    Geoff
     
  19. K-Frog

    K-Frog

    Feb 6, 2002
    Camden, AR, USA
    It's all good stuff, but you guys are making my head hurt...........
     
  20. Mcrelly

    Mcrelly

    Jun 16, 2003
    Minnesota, USA
    mine too! <shielding eyes from numbers and formulas>

    <unsubscribe> :p