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What (Which) Is Headroom?

Discussion in 'Amps and Cabs [BG]' started by Sanctum, Mar 24, 2003.


  1. I've always understood headroom to mean more amp power than cab power. But then ......

    Lets say I'm pushing a 350 watt amp into a 700 watt cab, and am playing a small club, and only need to turn the amp up to 5 - I still can get more volume if I need, but I don't need it. Isnt this headroom?

    Or I have an amp thats bridged to 1200 watts into the same 700 watt cab, same club (or even bigger) and I only need the volume on 3. I still have room to go, although more. But arent both of these examples "headroom?"

    So is headroom just an arbitrary term that means "you can still get louder if you need to"?
     
  2. Nick man

    Nick man

    Apr 7, 2002
    Tampa Bay
    I think headroom is more about handling peaks in playing easily than just being able to turn the knob higher. Either way you are talking about headroom.

    Peace
    Nick
     
  3. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Forget the cabs. Headroom refers to your amp only. It means having power in reserve. Your amp may be 400w but you will very rarely get it pushing 400w while playing normally. You may only be drawing 150w most of the time, so you've got plenty of headroom for that occasional note that you hit harder or, as you point out, turning up.

    But if you're amp is a 150w amp and you're drawing 150w while playing normally, the amp will do it but you're out of headroom.

    I believe the rules are different for Tube amps so I won't go there.
     
  4. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    No, watts are watts. You either drive the amp hard enough so the peaks are distorted or you don't. Tubes have nothing to do with it.

    Things that affect headroom:

    1. compression...the more you use, the less headroom you need because your dynamic range is reduced.

    2. EQ...extreme boosts can kill your headroom. Every 3 dB of boost means you need double the amp power. Most amps (and even basses iwth active EQ) can do 15 dB boosts. That means you'd need 32 times the power (ouch).
     
  5. This subject has been the source of some outstanding debates on this forum. However, in my experience, RMS is RMS meaning a 200 watt SS is the same as 200 watts tube. The difference comes when you drive a tube amp beyond its RMS rating. This distorted power is usable, musical and often desirable where as SS amps sort of hit a brick wall when then go beyond their rated power. I think this might be what Petebass is talking about in terms of headroom. A 200 watt tube amp has more usable, though be it distorted, headroom than a 200 watt SS amp. (here it comes)
     
  6. Well I didnt really want to start that debate again, as I've read it in other threads.

    Part of my ruminations came up will thinking about Edens 800 head - 2x400 watts - and thinking "well if optimal headroom REALLY means more amp power than cab power, why would a company make a 2x400 watt head and 700 (or 1100) watt cabs?"

    I know people on here have diverse opinions (heh) and I'm very happy with my rig (especially now, I just got my 410XLT yesterday) and cant imagine needing any more power/volume than I can currently produce. And I dont even run my QSC bridged. Seems a lot of people seek stadium volume rigs with no real need for that much volume.........

    As an aside (or maybe its on topic), we get a LOT of praise from local soundmen because our stage levels are reasonable, and they can pull a good mix of us through the house system. They alwasy seem shocked because we are a thrash metal band and understand that we dont need to be on "11". The fans comment on it too, how we sounded better than the other bands (SOUND, not necessarily talent :p) .... anyhow, I've seen other bands with their amps cranked SO LOUD on stage that it sounds like crap, and the soundguy cant pull any kind of mix through the house.

    In conclusion .... I find I have plenty of "headroom" to get louder if needed, but in most small clubs with a good PA I end up turning down sometimes to allow for a good mix overall. Thank you. :)
     
  7. You can throw a lot of money around trying to accomplish "Headroom" and really never sound much better. You said it all when you said that you were loud enough. You are lucky if you play in places that have the PA and Sound techs. that can get a good mix with bass. My experience with sound men is as best spotty.
     
  8. The secret is the DI on my Navigator :)
     
  9. Headroom has nothing to do with cabinets as such. The most basic definition I can think of is that it's the difference between the current operating point of an amp and it's maximum power. For example, if you have a 1000W amp but you're only using 100W on average, you have 10dB of headroom. This will be the same irrespective of cabinet power handling. Now, you can get more headroom with a particular amp by using a cab with higher sensitivity. Say you have a cabinet with a sensitivity of 100dB/1W/1M and you need all of your 1000W to get the volume you need out of it, meaning that you have no headroom left in the amp. If you swap that cab for one with a sensitivity of 110dB, you'll get the same volume only using 100W, thus leaving you with 10dB of headroom.
     
  10. stevekim

    stevekim

    Feb 11, 2000
    los angeles, ca
    great post, mark! very succinct and to the point.


     
  11. Fuzzbass

    Fuzzbass P5 with overdrive Supporting Member

    Right... thanks for the reminder that cabinet sensitivity and impedance have an effect on headroom.
     
  12. Thanks guys :D,
    and bump.....
     
  13. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Distorted headroom ????? :rolleyes:

    If the amp is clipping, it is out of headroom.
    Period. That's it.

    It has absolutely nothing to do with the "my distorted tube amp sounds louder" phenomenon.
     
  14. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Yep Greybeard has read my intentions correctly. I was saying that SS amps usually sound crap when they hit their limit but tube amps dont. So headroom is probably more important to those of us who use SS.

    Oh and if you find a speaker with 110db efficiency rating, let me know. I'll take 100....
     
  15. There are lots of speakers with sensitivities in that range, they just aren't bass guitar speakers..... Lots of high end PA cabs are that efficient.
    :D
     
  16. Lockout

    Lockout

    Dec 24, 2002
    Illinois
    SWR's 6x10 Goliath Senior is the only bass cab I know of with an efficiency rating of 110db, now that's one freakin' efficient cab :D
     
  17. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    yeah but a 6x10 is closer to 2 cabs than 1 imo. The more speakers, the more dB.

    What's this got to do with headroom? :)
     
  18. Lockout

    Lockout

    Dec 24, 2002
    Illinois
    Nothing :)

    You guys got on the topic of efficient cabs and I just thought I'd add to it :D
     
  19. Fuzzbass

    Fuzzbass P5 with overdrive Supporting Member

    It's too often said/implied that a 300w tube amp will have more headroom than a 300w SS amp. As mentioned, headroom is equivalent for those.

    That said: Greybeard was correct in his first post when he explained how a tube amp will have more *apparent* headroom than a SS amp.

    Just to clarify, it isn't just because tube distortion is more musical than SS distortion. It's also because tube amps clip more gradually. Both amps listed above will begin to distort at the same point, but the SS distortion will be noticable at a lower volume level (true for most of us, anyway), so the tube amp will *appear* to be louder.