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I've been fooling with stereos for years and always hear the word Headroom.
Scientifically speaking - what is it????
When I have a stereo that is reviewed as having a lot of headroom, it seems to just be a strong top end, mild mids and strong bass. SO it has a good solid top and bottom.
Is this what it really is? Or is it some other measurement like distortion?
charles
Follow Ups:
If the speed of the sound peaks and recover are a major part then would that be a function of the power supplies slew rate?
charles
Here's my way of describing headroom -
For arguments sake, say (for example) the AVERAGE listening level at your main listening position is 85dB. You would require that your amplifier have enough power to be able to drive your speakers to that level without clipping, but .......
....... on well recorded material with lots of dynamic range it wouldn't be unusual for the PEAK level (without you advancing the volume control) to be 20dB higher, for a total of 105dB. You would then require that your amplifier have enough HEADROOM to allow it to drive your speakers that additional 20dB without clipping.
The concept of your system having enough dynamic range to play musical peaks without undue distortion while listening at your max desired volume for the "average" signal. Note average is a mathmatic term here not a description of anyone's musical taste.
Calculate the max SPL you can generate with your system given your amplification, and system gain. Measure the peak level of your music you are playing, the difference between the max SPL and the peaks equals the headroom you have.
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
you would have to measure this in each inmates listening domocile. Sounds like a fun project. Maybe we can get funding????
Stuff appears to be in short supply nowadays :)
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Step back to the broader concept -- music is dynamic. There is the perception of an average volume with some parts that will be softer and others much louder. Live music is what it is, in this regard.
Ideally, if recorded accurately (a very big "if"), you'd want your system to correctly reproduce the whole dynamic range.
All of the aspects mentioned by others can be more important in some systems and less so in others. An amp with a lot of reserve would be a lot more important with a pair of inefficient, current-sucking 4 ohm speakers than with a set of higher impedance, higher efficiency speakers.
And, completely ignoring power amps, headroom is important in the recording studio and from the beginning of the playback source. You don't want the microphone or its preamp overloading, or the average recording levels so close to their maximum that peaks are constantly clipping in the recording or preamp stages. (Of course, sometimes that is the "sound" people want.)
The needed technical aspects of headroom will vary with the details of the equipment involved and its position in the chain, but the concept is pretty simple. When at the desired average sound level, is there enough capacity left in the system to capture or reproduce the peaks without distorting them?
I first heard the term working in sound studios. Remember analog tape machines ? We would record live music at as hot a level as practical, while leaving some "headroom" for crescendo peaks; so as not to overload (saturate) the tape/tape head/electronics synergy.
When choosing a preamp/headamp/phono cartridge combo, we need to consider how the components interact with the rest of our system. If the low ouput moving coil cartridge needs a step-up tranny or headamp, there better be headroom in the preamp to prevent the preamp stage from overloading. Likewise, concerning the preamp output level, we want to be able to drive the amp/speakers to comfortable levels, plus a significant headroom margin to be able to cope with dynamic peaks and/or be able to push the levels to party levels; without distorting. We like headroom.
So, you might be able to reduce all the answers, here and below, to setting up the sound system with enough "reserve" to always prevent overload distortion. Headroom relates to system synergy in a big way...
It is an amp that has more power, but not only more power, more current/amps. A high current amp is one that gets close to, or doubles in power output as resistance doubles. This produces a constant/consistent voltage and takes better command and control of the driver cone, making it move more precisely. With plenty of power to spare ABOVE its normal operating range, - it is not taxed and that translates to what you hear, a more relaxed character.
"Asylums with doors open wide,
Where people had paid to see inside,
For entertainment they watch his body twist
Behind his eyes he says, 'I still exist.'"
...I think of extra amplifier power left to reproduce dynamic peaks in the music.
Usually these higher powered amps are described as "sounding relaxed no matter how hard they are pushed."
Me too. Back in the day, some of the review rags used to make a big deal of what they called "dynamic headroom". Supposedly a measurement of how well an amp could reproduce transients without clipping. I guess I was too naive then to realize that what they were really describing was how good the designer was at covering up for an anemically built power supply.
Well, for guitar amps (and maybe hi-fi) it's the way the amp handles transients. Does it compress the tone or have the "headroom" to give it full faithful reproduction? Both have their place in the recording studio.
Power available for *very* short bursts to handle sudden peaks. The term used to be used a lot back in the 80s and 90s to sell cheap receivers and some mid-fi gear(Carver). I haven't heard it used in a long time.
Jack
Edits: 06/26/12
I could be wrong, but 'headroom' would appear to be the difference between continuous RMS power and 'peak' or short-term power. This is for amps. Probably expressed in db, you'd find that 3db 'headroom' was 2x the power.
I'm sure a similar idea could be applied to speakers which might not like high, continueous power but would be perfectly happy at lower average levels with higher peak demand.
As applied to an entire system? Maybe they're talking about the dynmic range from softest to loudest passages and the ability to reproduce the loudest without distortion.
Too much is never enough
has to do with amplifiers. The more 'headroom' the more the amp tends towards class B operation. IOW, class A amps have 0 db of headroom.
The spec is intended to make amps that are not class A look better. But the truth is the higher numbers don't translate to better audio quality.
I'm not sure about that::
The PASS XA30.5 is measured at 30x2 'a' watts. It also goes about 3x that and is than firmly a/b.
I don't know if you'd call that 'headroom' or specsmanship...??
Too much is never enough
What you are talking about with the Pass is not headroom. It is simply the amount of 'A' power as opposed to 'AB' power.
The idea with headroom is that the amp can make more power than rated for a brief period of time. So it favors amplifiers with weak power supplies and class AB or B operation.
Yes, charging caps for bursts is easier than full-time high current supply neede for 'a' operation.
I did note the headroom idea in my first reply::
However, don't count out a/b just yet. My favorite example would be back to the Pass amps.
The xa30.5 and the x150.5 are very similar. I don't know how 'under the skin' this goes, but they each weigh about 75lb.....and are both offered as integrated amps. I suspect the major difference is in bias PS and how that is managed.
The 'a' amp? Stereophile got about 100 a side while the 150 was honestly rated. Remember me at Christmas.
Now, a question for 'ya.
My 'd' amp is rated at 250rms, yet that is for 60 seconds. the FTC rating is much lower.
Now, do you call that headroom or specsmanship or ??? The amp uses B&O modules with included SMPS.
I'd also think that unless you were simply a fan of 'a' amps, that listening and intended use would be one of the arbiters of amp choice. I know I never tap the RMS part of my amp, regardless of how it's rated. I may use 20 RMS and allow for a 10x peak factor. Easy for the amp and it never warms. (4 ohm panels)
Too much is never enough
The 60-second rating is specs-man-ship, not actual headroom as it was originally defined.
In a class D amplifier heat is the main issue as often they don't have much for a heatsink. The idea is the output devices spend no time in the linear region so they don't make much heat. It works fine unless you play organ pedal tones at high volume- extended high power tones can heat up the output and possibly drain the supply.
60 sec rating IS heat related. Even figuring 83% plug to speaker efficiency, that leaves something around 75 watts of heat.....quite a bit....A human emits about 100 watts worth, if I'm remembering correctly.
For the Big kilowatt module? Time limit is 30 seconds.
Both per B&O datasheets.
Heat is, of course, the enemy. Which is why some people will do a first pass judgement of amplifier quality by using a scale. PS and Heatsink, of course.
I don't know that my amp has a capacitor larger than my thumb and therefore doesn't store enough energy to drain. Being a smps, the tranformer is also small, gaining from the high frequency at which it operates.
One day I'll put my Killawatt meter on the amp, crank it up and see how much juice it DOES draw, when I'm pushing it. At the same time, I'll look for PowerFactor which is something neither of us has touched upon as yet. I don't know if that is germain to the headroom issue, however.
::
Too much is never enough
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