What is headroom?

Damned if I know. I just like to use the word as much as I can.

Maybe this is right, maybe not.

Headroom refers to the difference (in dB) between the nominal input level in an audio system and the maximum level before clipping (distortion) occurs. 

In layman's terms, your system has particular electronic specs, and there is a certain sound amplitude level at the input (the front end) that the system most efficiently handles. That's the "nominal level". If the signal is too hot (i.e. it's turned up to high), it will overdrive the electronics and you will get distortion. Headroom is the difference (usually in decibels, or standardized measurements of amplitude) between the "special level that your system works best with" and the point at which distortion occurs.

The benefit of having high headroom is that if you have a really dynamic sound source (for example, if your sound goes from really quiet to really loud really quickly), you can run your quietest sounds closer to this "nominal level" without worrying about your loudest sounds overdriving your equipment and getting distorted. Obviously you don't want distortion, but you might be wondering, "Why wouldn't I just accept a system with low headroom and turn down my levels to avoid distortion?" The answer is that your system makes its own noise, and this noise comes through the outputs with your signal. The louder your signal is relative to this noise, the cleaner your output signal. Thus a system with high headroom can be run hotter on quiet sound sources--allowing for this cleaner signal--and ALSO be able to avoid distortion.

Another benefit is that, even though you should want to maintain your signal close to the nominal level at all times, you have more room to boost the signal in the system on the front end before distorting on the back end. That is, you will lose quality if you use your headroom as "room to amplify more", but at least you have that option of always getting a little louder. I guess you could say "it goes to 11".

I stole that off the interwebtubbiethingy

Jonbouy


With one exception, with Bapu it means how many unposted posts there are available in his head.

Forumized.

Back in the day, it meant that little room behind the stage.


Randy

I thought it was the name of the basket (or bucket) used to catch the severed bit on the Guillutine.

Nice job bapu.

Now... see my other post.


best,
mike

Used loosely...how much room you have before you "hit the ceiling".

I think the easiest way to understand headroom is too understand that it's value is determined within context of a specific interconnection.

For example; let's say you have an A.R.T. preamp and it is rated at Maximum Output Level +27dBu.

The first thing to consider is that this is not a complete specification. Well it could be true that the maximum output level is 27dBu. The specification we want to know about is the maximum output below some threshold of distortion.

So let's assume that the spec above means 27dBu before square wave clipping and that distortions sets in at some progressive rate below that level.


For the list below let's assume we are talking about the balanced output that ART describes as having 27dBu output. In other words... let's not worry about connections adapters or whatever.

1) If you take that device and send the output to device that expects a +4dBu nominal level than you have 23dBu headroom at the preamp.

2) If you take that device and send the output to a old professional reel to reel recorder and push the tape deck hard... you may end up with only 10dBu headroom at the preamp.

3) If you take the device and send it to a home stereo input that expects -10dBv you will have close to 35dBu headroom at the preamp.


So it's basically exactly what bapu said... but it's important to appreciate how the available headroom is relative to the situation.


best regards,
mike

bapu


What does that guy Gulliver have to do with it.

Oh I get it. He had mucho headroom above the Lillipudlians.

Those tiny people from Lillipool?

Headroom = fudge room.

SteveStrummerUK


 
 
 
    

THIS!!!!!!!

I thought it was a woman's big mouth.

The main reason to appreciate headroom... is that what ever the spec is... there is still distortion occurring below that so you may want to know where you are operating along that progression of quality.

Understanding headroom is really helpful when you try to predict how prosumer gear may interface with pro gear.

For example you may have a device that is listed as +4dBu nominal output... but it may only have a +10dBu max. The fact that there is only 6dBu headroom should alert you to the idea that the +4dBu spec is probably wishful thinking and you'll find that it may be rather distorted at "+4"... especially if compared to the distortion of some other "+4" device that is rated at 30dBu max before clipping.


That is one reason a spec like "Maximum Output Level +27dBu" is inconsiderate.

Is That 27dBu at onset of clipping on the peak?

Is that 27dBu at some mild level of distortion? With a actual max output being higher than 27dBu?

Is that 27dBu at full saturation with a square wave so that the RMS of the output is absolutely maxed out and not a bit more voltage can be made?



A number like 27d Bu max output is very impressive... so impressive that a curious engineer will demand further clarification.


The point is that any pertinent headroom info is not really a consideration of sound you don't hear. A consideration of headroom offers insights regarding the character of the sound that you will hear.



I hope that is helpful.


best regards,
mike

I visited you with Google maps last night.

Thousand Oaks seems like the best place near LA... how'd you get so smart?


(I was actually checking out Trestles the surf spot south of LA when I saw Thousand Oaks and said ah hah.)