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what is headroom?

Discussion in 'Amps and Cabs [BG]' started by lo-end, Oct 15, 2001.


  1. lo-end

    lo-end

    Jun 15, 2001
    PA
    could someone explain to me what headroom is, in layman's terms? I already know how ohms work, like you have 2 8 ohm cabs and it makes 4 ohms. I think this has something to do with headroom but I'm not really sure what it is... :confused:

    Maybe Joris could help? :D
     
  2. BigBohn

    BigBohn

    Sep 29, 2001
    WPB, Florida
    simply, no technical jargon here, its when you don't have to turn your volume all the way up to get high volume, and thus less hum, cleaner tone, whatever way you want to define it. i have lots of headroom on my rig because the poweramp is 1500watts and the cab can take 1200 watts. i only put the volume onto 4 and get very high volume at a lower output of wattage into the cab, rather than a smaller wattage poweramp putting its full power load into a cab. just got for more wattage at any costs, even thought it might not make your rig louder, it will give you more headroom, which is the essentail item every bassist wants, as you know.

    more wattage equals less hum, which is headroom, just don't overload your cab then you might blow it up.
     
  3. What bigboner said is right, except the part about hum. That's kind of unrelated to headroom. You can have a 1Watt amp that has less hum than a 100 Watt amp, or a 100 Watt amp that has less hum than a 1 Watt amp. The hum level depends on how well designed everything is.

    But like he said, it's like having a huge engine in your car. A Ferrari has more headroom than a Volkswagen (at least as far as power is concerned.) But you only use all that extra power when you take off really fast. Both cars use about the same amount of power when driving at equal speeds, but when you push the gas pedal on a Ferrari, you can really take off fast because it has more reserve power. That's the analogy for headroom.

    Chris
     
  4. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    <b>headroom</b>

    A term related to dynamic range, used to express in dB, the level between the typical operating level and the maximum operating level (onset of clipping). For example, a nominal +4 dBu system that clips at +20 dBu has 16 dB of headroom. Because it is a pure ratio, there are no units or reference-level associated with headroom -- just "dB." Therefore (and a point of confusion for many) headroom expressed in dB accurately refers to both voltage and power. Which means our example has 16 dB of voltage headroom, as well as 16 dB of power headroom. It's not obvious, but it's true. (The math is left to the reader.)

    taken from the Rane audio faq
     
  5. Bigbohners and Throbbinnuts......hmmm, what's going on here?:p :D Just kidding guys. Good answers above, I'd just like to add that having lots of headroom enables your amp to accurately reproduce the dynamics of your playing. More headroom means better response for transients thus better dynamic range, because the amp doesn't limit or distort on the loudest peaks.
     
  6. lo-end

    lo-end

    Jun 15, 2001
    PA
    but I assume that there are diminishing returns with headroom. for example, the difference in a 1500 watt poweramp and a 2500 watt poweramp.
     
  7. Agreed on what Spaceghost ;) said.

    Headroom is overrated. I regularly use a 50 Watt tube amp cranked just to the onset of distortion. The natural compression is good for the lo-fi creamy fat bottom sound. Like Noel Redding on old Hendrix tunes. :D Thick and rich like ........... something that's really thick and rich.

    Chris
     
  8. Luis Fabara

    Luis Fabara

    Aug 13, 2000
    Ecuador (South America)
    Audio Pro - Ecuador
    Headroom is different on a Tube amp.
    When a solid state clips it sounds like "·$%·"$%

    But a Tube amp starts to sound GROOOOOWL,
    It is different.
     
  9. I should have qualified that by saying: "unless you want the natural compression and sweet overdrive that you get from hitting a tube power amp hard." I'm rather fond of that in my bass rig, but I don't want it on my PA. Of course, 50-odd 000 watts of tube power would take up the whole venue and be able to heat a small city....:D. The fact that tube amps sound good when pushed a bit beyond their linear range is also part of the reason why a 300 watt tube amp sounds as loud or louder than virtually any solid state amp. Solid state power amps sound terrible when pushed much beyond their linear range.
     
  10. Hategear

    Hategear Workin' hard at hardly workin'.

    Apr 6, 2001
    Appleton, Swissconsin
    I disagree. The gasoline in the cars' gas tanks is stored power and I'm pretty sure a 12-cylinder Ferrari uses more fuel than my girlfriend's 2.0L, 4-cylinder Jetta. But I see what you were getting at. ;)
     
  11. MikeyD

    MikeyD

    Sep 9, 2000
    You don't really mean that, do you, Space? I'm sure a 3000-watt SS amp would be quite capable of drowning out a 300-watt tube amp. Maybe you meant "...solid state amp of the same continuous power rating." No?
    - Mike
     
  12. Ok. I'll give that a caveat.... I was mainly referring to commercially available bass amps, not mega powerful PA amps. But here's the skinny, based on comparisons I've actually done. My 300 watt SVT easily drowns out the SVT 4PRO, advertised as 1600 watts, the SWR Bass 750, my buddy's PV 8.5 C in bridge mode. With the same cabinet attached (SWR Goliath III). Another friend's WT 400/410XLT pales in comparison. So, either these amp manufacturers are grossly misrepresenting their output power or the tube amp can produce a greater apparent volume. Now, this is at the expense of a little audible overdrive from the SVT, but it sounds good (I like it, anyway:p). Note, I'm not bashing any of the amps I mentioned, hell, I like all of them (except the Peavey). And of course, by no account, is volume the most important thing in an amp. In short, a 3000W QSC (for example) on a 30A mains would probably be louder than the SVT (cleaner for sure), but I'd have to check it to make sure :D. Maybe I'll do that, I do have access to a lot of MX3000s.....
    cheers,

    Mark;)
     
  13. MikeyD

    MikeyD

    Sep 9, 2000
    Thanks for the explanation, Space "ghost"! ;) I vaguely recall your saying something about hot-rodding your SVT. I may be mistaken though. Maybe it was something that you wanted the earlier version of it. What would be really cool is if you were to hook up a 'scope to that beast and record both the voltage and current (the in-phase parts) for various volumes, from clean to overdriven. In other words, actually do the proverbial road test on it. Maybe the 300-watt rating is at lowest distortion (say 1% THD), but the characteristic of the output tubes is that the distortion increases very gradually with power, so maybe you're up to 400 watts by the time you have 5%, 500 watts at 10%, etc. Something like that. It would be really cool to get a curve of the RMS output power vs. distortion. But you might have to borrow some good test equipment to do so. We're all depending on you! ;)

    I don't have experience with the SVT 4PRO, but I note that some of their ad copy claims 1600 watts, while others claim 1200. I seriously doubt the 1600-watt figure. And I've read a lot of dudes say it is very overstated anyway.

    - Mike
     
  14. I have access to test equipment at school....Maybe if I get 5 minutes when I don't have an assignment due or a test or a lab, I'll do the test thing. Anyway, it's 2:45 AM here and I just spent 3.5 hrs on ONE stats problem....bloody Raiffa's urns:confused: . Bed calls,
    cheers,

    Mark

    PS. 4Pro, I suspect has "very" optimistic ratings.;)
     
  15. Headroom = power reserve

    Couldn't be more simple.
     
  16. Joris hit it on the head.

    As for the gas tank size comment by Hategear, that's ENERGY reserve, not power reserve. ;) The only comparison in bass amps to that gas tank thing would be using a car battery to power an amp, versus using a 9-volt battery to power the same amp.

    Now that's how I get picky on my analogies. :D

    Chris
     
  17. So, what you guys are saying is: the 300watt SVT will put out more power at times, but at the expense of an increase in distortion, which is less offensive than a SS amp?
    I have a Vintage, recapped & retubed SVT on the way. I am hoping that it will do the trick (Volume wise). I'm using a D-210xlt and a D410xlt Eden cabs.(8ohms).
    My curreny power is an Eden WT100 (450 per side at 4 ohms) (? at 8 ohms) But I'm craving the all tube sound.

    I also don't want a real mushy sound either. I know it won't be as tight sounding as the SS, but hoping the tradeoff will be better tone.
     
  18. It's how high the ceiling is in a given room so you can stack so many cabs over your head. The higher the ceiling, the more headroom, more cabs, more power.

    Power reserve it is.
     
  19. Hategear

    Hategear Workin' hard at hardly workin'.

    Apr 6, 2001
    Appleton, Swissconsin
    Isn't stored energy stored power? ;)