# headroom



## fredridge (Jan 17, 2007)

I keep hearing how important headroom is, but most responses are about just adding more watts and I keep thinking that it is not just about having lots of whats but an amp with the ability to dig deep and quick.... I finally posted this because foxpro's post about his xetec running out of steam, but it seems to have a lot of watts

We all know that many recordings today take away headroom by make the whole track louder

so here is my question.
Is headroom really more power or is it an amps ability to dig deep.





sorry if I am rambling, just stuff goin through my head


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## drake78 (May 27, 2007)

I would say dynamic head room vs rms. Is the ability of the amp to produce massive peaks in power during peak music passages. Wich then gives the sound illusion that the amp has massive power.


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## drake78 (May 27, 2007)

....


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## drake78 (May 27, 2007)

....


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## durwood (Mar 7, 2007)

What if you want an 88dB speaker to play constantly at 100db? Ignoring other factors such as power compression how much continuous power do you need to reach that level?

Now let's say your music needs to hit a dynamic peak 20dB higher than your continuous 100dB level, how much power will you need to reach that extra level?

What if you were running your amp 100W amp at it's 100W level to reach the 100dB mark but needed to hit 120dB on peaks and the max the power supply could give you is only 200W? Will you reach that 120dB level, or will it clip?


I haven't even gotten into power compression of the speakers, but think about it.

This is why you hear people bridging amps down to 300W for tweeters, 500W for midbass, etc etc. They are not using all that power all the time, only on dynamic peaks, plus hopefully the power supply has even more in reserve, some amps cap it off though.

http://www.diymobileaudio.com/forum/showthread.php?t=18660&highlight=power


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## fredridge (Jan 17, 2007)

durwood nice posts.... and that is really what I am thinking.... but since I don't have the technical skills let me try and equate to an engine, I know it's not the same, but it helps me think

I am driving a 4 cyl car and it takes 1/4 throttle to keep a constant 65 on flat land, I come to the hill, I have more power but at 1/4 throttle I slow down....I am thinking lack of torque

same scenario with a diesel engine... low horsepower, but tons of torque


so car audio
you have a 200 watt amp that runs at 100 watts, you still have power to go, but will it make a difference for those big dynamic hits... will it really play louder and make that big dynamic difference without giving it more gas (volume)

isn't this part of the difference in the Zapco lines the c2k's don't have more watts, but more ability to store those watts and respond to dynamic peaks verses their "lower" lines

not sure if I am making sense


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## durwood (Mar 7, 2007)

yes I think you got it.

Now the more difficult problem...

How loud can your speakers play before you burn them up or destroy them?

You have to set a goal, figure out how loud you need it to play and go from there. Design you power and acoustics around that. What if you can't reach the loudness level you desire with your speakers without burning them up? You must redesign your setup if it will not reach your goals.


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## fredridge (Jan 17, 2007)

So is it better to buy more powerful amps or amps with better headroom?

and is what you are saying, yes and yes , but what can my speakers handle

should we start changing the way we think about headroom


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## azngotskills (Feb 24, 2006)

hmm...great question

Yea for some reason, i "feel" the 50W off my Arc Audio XXK was more powerful than the 100W from a Blaupunkt Velocity...would this fall into amp design, components used, or neither?

So does more power = headroom or are we talking about something else?


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## fredridge (Jan 17, 2007)

exactly.... if you have ever read a Zapco manual they spend the first several pages telling you why their amps "sound" more powerful....

the big question is do we really need higher power amps or amps that can "dig deeper" - sorry not sure how else to describe it.

though I liked my massive audio amp, it's high power seemed to lack depth.... had a lot to do with the rest of the system, but still felt it lacked



azngotskills said:


> hmm...great question
> 
> Yea for some reason, i "feel" the 50W off my Arc Audio XXK was more powerful than the 100W from a Blaupunkt Velocity...would this fall into amp design, components used, or neither?
> 
> So does more power = headroom or are we talking about something else?


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## thehatedguy (May 4, 2007)

Some amps have a certain amount of head room built into them- higher capacitance for the rails, more devices than needed, etc.

It's really for transient/burst power. 

One way to insure headroom is to over build the amp and really underrate the power output...build about an amp that is able to do 300x2 and rate it at 100x2.


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## drake78 (May 27, 2007)

fredridge said:


> So is it better to buy more powerful amps or amps with better headroom?
> 
> and is what you are saying, yes and yes , but what can my speakers handle
> 
> should we start changing the way we think about headroom


What are you worried about.  Are you still running the zuki eleets amps? I haven't used a single highly regarded car amp that's more dynamic sounding.


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## fredridge (Jan 17, 2007)

not worried, just wondering.... every time I see someone talk about how much headroom it is all about how many watts.... and my mind starts working through the stuff above



drake78 said:


> What are you worried about.  Are you still running the zuki eleets amps? I haven't used a single highly regarded car amp that's more dynamic sounding.


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## Kris (May 23, 2006)

thehatedguy said:


> Some amps have a certain amount of head room built into them- higher capacitance for the rails, more devices than needed, etc.
> 
> It's really for transient/burst power.
> 
> One way to insure headroom is to over build the amp and really underrate the power output...build about an amp that is able to do 300x2 and rate it at 100x2.


... or build for XXX watts and rate it at 0.1w  

(sorry, that was just too good to pass up)


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## fredridge (Jan 17, 2007)

ok, good more of what I am thinking..... the first part is what I am thinking it should be, but the second part still takes me back to my gas pedal analogy. wouldn't the volume know need to be higher or is it that because it is not running at full tilt it still has room to respond?



thehatedguy said:


> Some amps have a certain amount of head room built into them- higher capacitance for the rails, more devices than needed, etc.
> 
> It's really for transient/burst power.
> 
> One way to insure headroom is to over build the amp and really underrate the power output...build about an amp that is able to do 300x2 and rate it at 100x2.


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## cvjoint (Mar 10, 2006)

Good topic! I've never really found a straight answer to this. I think this hints at a watt is a watt debates and that's why a lot of folks shy away from tackling it.


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## Abmolech (Nov 2, 2006)

I use live sound as reference material.
While most (rock etc) recordings are compressed, they still can pose a problem for in car reproduction.
I suspect people under rate
1/the back ground noise (70 plus dB), 
2/the effect of power compression (twice the power required), 
3/the use of xmax to obtain this SPL (70 % Bl = twice the power , compared to 100 % BL), 
4/passive crossovers requiring twice the power compared to active, 
5/the fact that the sensitivity is rated at 2 Pi steradians which is rarely obtained with most peoples sad attempt at a baffle.
6/The equal loudness curves


Point
Most people are not in the game. 

I would "fail" a single 6.5 " driver for mid bass, because they cannot reproduce 100 Hz with enough SPL to be useful in a moving vehicle. (unless you want your sub to do this, and then I might have "interesting" discussion about room nodes) 

If your "serious", array's, wave guides, and horns are going to feature in your design plans.

Still I would expect a decent system to be able to play classical and opera, so your criteria may vary. ( Classical can have 70 crest factor)


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## mtnickel (Mar 15, 2005)

as was mentioned, the way modern music is compressed, the average vs peak is not THAT different. In my research i also found something else interesting...some tracks (some Dave Mathew band, etc), the musical peaks of the tweeter signal (high pass 3k 24db) actually still peak to 0db where everything else is mastered...i really found this surprising. Sure the average rms was much lower throughout, but peaks remained as high as the rest of the signal.

I started a thread about how much power to run a while back and brought this up. I almost always heard a "buy as much power as you can afford" and "have you ever heard anyone say, I wish I had less watts".
It's peace of mind really.
But from listening, i can say I did notice a different from the 65 wrms stereo to the 200wrms bridged. When cranking it, it didn't feel like it had the balls behind it like before. Somehow it'd get quieter or lose output. With the 200rms on hand, i felt when i cranked it the amp had everything it required and it was the speaker that started to distort and smell (VC smell). This was a 4 ohm mid for reference. Perhaps as i entered power compression on the lower wattage, i didn't have enough power to overcome it and get louder while also wreaking havoc on the coil. In terms of output though, i'd have been decently happy with only 65wrms. 
I'd say anything around 90 and up is plenty for most 7" (8" midbass would be a different story i'd think).
As for tweeters, they are usually 3db more efficient and regardless of the lower total RMS content, peaks still do exist that need to be played correctly.

see attached:
first is #41...normal looking song and filter @ 3k does yield lower peaks...
then look at Motherfather...although it doesn't peak very often (18 samples), they do get pretty high. Unfortunate that those peaks do happen, because look at the maximum RMS differences: 7db different (looking at 50ms window)...on top of the 3db efficiency difference, you could run a much smaller amp (if you didn't care about those peaked samples).

What do you guys think?


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## mtnickel (Mar 15, 2005)

PS...you can tell which song is clearly more Mainstream mastered. I really enjoy the dynamics and SQ of #41 and the rest of that CD (Crash 1996).


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> Some amps have a certain amount of head room built into them- higher capacitance for the rails, more devices than needed, etc.
> 
> It's really for transient/burst power.
> 
> One way to insure headroom is to over build the amp and really underrate the power output...build about an amp that is able to do 300x2 and rate it at 100x2.


So...looking at my mid, the Seas Excel w22: 
Short term max. power 300 W
Long term max. power 120 W

Would you say there are two ways to ensure max headroom?
1. Buy a 120w rms amp with capacitance and devices that can do 300w (overbuilt, not overrated)
2. Buy any 300w rms amp (a 120w amp underrated with a real spec of 300w rms)

Any output over 300w is useless if my coil can't deliver even in a short burst.


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## mtnickel (Mar 15, 2005)

cvjoint said:


> So...looking at my mid, the Seas Excel w22:
> Short term max. power 300 W
> Long term max. power 120 W
> 
> ...


The general rule i've seen (saw in the pro-audio industry), is to use an amp that does 50% more RMS than the long term handling RMS rating. It seems to be pretty ideal. So 180rms in your case.


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## durwood (Mar 7, 2007)

thehatedguy said:


> Some amps have a certain amount of head room built into them- higher capacitance for the rails, more devices than needed, etc.
> 
> It's really for transient/burst power.
> 
> One way to insure headroom is to over build the amp and really underrate the power output...build about an amp that is able to do 300x2 and rate it at 100x2.


Very true but then again, will anyone know if it's possible that it will do a clean 300x2 instead of it's rated 100x2? That is the basic concept but no good for regular consumers who have no way of knowing that it really is overated. It's too bad we have no real idea what the power supply/output stage can do in terms of peak dynamic power without measuring it. Car audio marketing abused it back in the early days and so now it has become a meaningless or untrustworthy spec in some cases.

As thylanter suggested in another thread, wouldn't it be nice if a database was arranged to show power output of different amps as done by bink in the pro audio world? It woudl sure disolve mystery.



cvjoint said:


> So...looking at my mid, the Seas Excel w22:
> Short term max. power 300 W
> Long term max. power 120 W
> 
> ...


Yep except in option 2 is doesn't really need to be an underated amp capable of more, you jsut need to use the amp in it's linear range (not clipped). Example use a 2 channel 100Wx2 amp brdiged to each driver to get roughly 300W of unclipped power. It all depends on how much you want to trust the amp to deliver clean power in the range you need it. If you can't get the output you desire with a single driver and proper power, as abmolech suggested, better start considering multiple drivers and arrays.

It all depends on your goals you set. Some people don't need that much power or want loud dynamics based on how loud they listen, and some listen to music that has no dynamics to begin with, so it's not so easy to answer sometimes.


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## FoxPro5 (Feb 14, 2006)

I know exactly what you are talking about Fredridge! I thought I was starting to become a little nuts because of the recent theories I've developed with power amplifiers. I've come to this realization after using lots of "powerful" amps over the years.

The very first time was when I tried the MB Quart Q series 4 channel. You know the one that does 250x4 @ 4 (tested to do like 270 something by CA&E)? I put the amp in and level matched it to the previous amp (don't remember what it was, but it didn't do 1/3 that power). First impression: Wow nice and loud, but ****ty. Nice power, very little nuts.

Also tried Zapco Competition. Much different initial impression: Engaging and sweet. Effortless power that could "dig deep."

Kicker SX. Very ballsy and responsive. Seemed I'd never run out of gas.

DLS Ultimate. Loud and the music is alive, but lacked the "heart beat" to really drive it.

ICE Power amps....Eclipse XA, Pioneer Premier, Alpine PDX. The Eclipse could get down, but the power was "thin." The PDX was just loud! Really nothing beyond loudness. No substance. I couldn't move my seat back far enough as the really loud sound anoyed the **** out of me. 

Linear Power: How in the hell do these amps do this? Pure balls that just keeps coming and coming. A 50x2 amp level matched to a highly efficient 150x2. Surely 150x2 wins? No, not even close. 

That's when I came up with my theory: Loud power vs Pure balls power. A working hypothesis based on the most stringent anecdotes and pseudo-science I can muster up.  I like it, so shut up! 

The list of amps goes on and on and I really feel I can place any one within those two groups. Yea it's fantasy and drugs are cool, but it's fun.


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## cvjoint (Mar 10, 2006)

Very good posts guys. I can finally walk out form this thread with a solid realization. 

Unfortunately bridging a 100/4w amp will not do with 8 ohm coils. It seems like 150w/2 bridged would be the only way to achieve 300w/midrange driver = a plethora of 2 channel amps bridged per single driver. 

Another way is to buy a super amp like a zapco c2k and bridge a 4/100w amp to give 200w/midrange and hope the overbuilt factor will get you to 300w/driver. Like you guys mentioned we have to rely on all sorts of market signals for that factor since we don't see it tested. 

IMO
From a pricing perspective it is still cheaper to buy a plethora of good ole class A/B than half the number of super amps. In the end, more $ will give you a more compact amplifier bay (one C2K 4.0x vs. any two 150w/2 average amps).


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## FoxPro5 (Feb 14, 2006)

BTW, if you listen to an iPod in your car all you need is Rampage amps or their equivalent, because your music is just going to loud and flat anyway. 

Beethoven "Choral" Fantasy, Telearc 1993. Classical opera recording with nice dynamic range. Avg recording level is -21 dB.


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## thylantyr (Jan 21, 2008)

> I keep hearing how important headroom is, but most responses are about just adding more watts and I keep thinking that it is not just about having lots of watts but an amp with the ability to dig deep and quick.... I finally posted this because foxpro's post about his xetec running out of steam, but it seems to have a lot of watts


How do you know the Xetec is running out of steam?
How do you know the Xetec has a lot of watts?

Unless you test the amp, you don't know.




> so here is my question.
> Is headroom really more power or is it an amps ability to dig deep.


I see headroom as two parts.

1. The clipping headroom determined by rail voltage
and amplfier losses. 

2. The burst power of an amplifier determined by the
amplifier's ability to hold rail voltage high and not sag
under load. Extra capacitors do a great job at high
frequency bursts, but the effects dimish quickly as you
lower the test frequency. 

Example: My favorite general purpose amplifier for
home audio is really a pro audio amplifier, PLX3402.
Rated for 3400w @ 1khz, but not rated for that high
power at 20hz.

I tested this amp at 2kw using the rms test method @ 20hz with 110VAC input. It can do more if I feed it 120VAC,
but I had AC line losses I couldn't control.

Later, someone burst tested this amp using 50mS bursts.
Results.

PLX3402 [bridged mode]; 
20hz = 2704W 
50hz = 2916W 
200hz = 3136W 
1khz = 4900W 
5khz = 5184W 
10khz = 5476W 
20khz = 5775W 


I got 2kw rms @ 20hz, the amp burped at 2.7kw @ 20hz,
but did 5.7kw @ 20khz.

This is typical for any SMPS amplifier design including car
audio amps because they are also SMPS.

The amount of rail capacitance used in these PLX's are
pretty low, there is room for improvement. In theory,
that amp could burp 16kw at high frequency if there is
enough capacitance.


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## durwood (Mar 7, 2007)

Headroom?










nope










Almost there...

















MAX HEADROOM!


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## thylantyr (Jan 21, 2008)

People in any audio industry grossly underestimate how
much power a driver can handle a burst. If you can control
the excursion to prevent mechanical damage to the driver,
then the thermal issue on a burst is easy.

I drive sixteen 4" 5 watt mids in an array with a bridged
PLX3402, tested betwen 2.7kw - 5kw on a burst, the
driver's band pass is 65hz - 1700hz. I run the system
to clipping. The array power handling is sixteen x 5w = 80 watts. [technically, array power handling is higher, but
I don't know the math, lol].. But anyways, those are cheap
drivers that cost 49 cents during a Partexpress buyout.

I have used the Seas Excel W22 with a bridged 600w
home amp on the test bench bandpassed and it worked
well. If I really push it hard playing heavy music the driver
started to smoke a bit. Other drivers I used in a similar
test did far better handing the power. I would have no
hestitation driving them with a 500w/ch amp.


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## thylantyr (Jan 21, 2008)

durwood said:


> Headroom?


I use the ceiling example to explain 'clipping headroom'


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## durwood (Mar 7, 2007)

durwood said:


>


That's a good one for uncontrolled and everything goes to hell clipping 

That's what happens when my A/D/S PH/PQ series amps clip.LOL


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## FoxPro5 (Feb 14, 2006)

So what's the sense of investing in amp power with adequate dynamic headroom, oodles of power, etc when your music is the weakest link?

The loudness war is one thing, but then add to that compression with "lossless" encoders. For example, here's a very recent recording that sounds pretty good to many these days: Alicia Key's "No One". The sound of the music isn't in question, it's the nature of the audio signal produced by it that is.

This particular track is off an XRCD copy of her album, of all things. It was riped into iTunes using Apple's Lossless encoder and then burned to audio CD with iTunes. It was scanned by Sound Forge directly from that CD. Again, an XRCD original. 

Since I don't have the original copy of the album, I can't scan it and compare...but effects of doing this to your music are right here for your eyes to see. This is a graphical representation of what your system will play in your car. 

First scan of "No One." Everywhere you see blue is where there is music. Notice the "wall" of sound. 










Scan with the statistics in the lower right hand corner. The avg level of the track is -9.7 dB. Contrast this to an uncompressed RnB track from the 1980's which might have an avg RMS of about -18 dB (give or take a dB or two). That's roughly a 10 dB difference. Using an A weighted scale, the Keys track would sound twice as loud. Lots of noise, no dynamics.....lots of loud, flat sound and certainly no headroom. 










Scan with the clip indicator set to 0 dB. Any part of the track that hits the "celing" here will be detected and identified. Usually Sound Forge numbers each clip, and it did in this case but it stopped after about 100!  










As you can see, nearly every peak is cut off. Up close it looks like this:


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## thylantyr (Jan 21, 2008)

*So what's the sense of investing in amp power with adequate dynamic headroom, oodles of power, etc when your music is the weakest link? *

Four PLX3402 + this.









This is my entry level line array. I don't even have interest
in playing CD audio anymore. There is a bigger reward
when you combine audio + video. When I play the DVD
concerts [compressed audio], it is very sweet. There is 
something sweet when you can see the performance plus
hear high SPL, high dynamic music. When I watch movies,
the dynamic range is crazy. I'll set the volume just loud
enough to hear good voice, then when an event happens,
people in the room start yelling 'turn that sh~t' down!!!
... They think I'm turning the volume knob higher, but I'm
not... 

Can it get better? sure, but even with a crippled source
like this, the perception can still be uber great.

Line array - higher SPL, higher power handling, higher sensitivity, big sound stage.
Bridged proamps - higher headroom

From a speaker and amp point of view, it's done. Just get a better source, that's
easy.


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## cvjoint (Mar 10, 2006)

thylantyr said:


> People in any audio industry grossly underestimate how
> much power a driver can handle a burst. If you can control
> the excursion to prevent mechanical damage to the driver,
> then the thermal issue on a burst is easy.
> ...


That is the underlying mechanism for building my setup! I use large drivers bandpassed high so that there is almost no way to max out the suspension. The W22 in question is highpassed at 200hz 24db, the W26 at 63hz 12db. Then...then I feed them lots of power.

I always had the itch to throw more than the 150w that I have on each mid. Unfortunately my trunk cannot take a ninth amp at this time 

I would love to display some of the House music I listen to on the Adobe Audition if you guys can read the headroom for me.


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## thylantyr (Jan 21, 2008)

cvjoint said:


> That is the underlying mechanism for building my setup! I use large drivers bandpassed high so that there is almost no way to max out the suspension. The W22 in question is highpassed at 200hz 24db, the W26 at 63hz 12db. Then...then I feed them lots of power.
> 
> I always had the itch to throw more than the 150w that I have on each mid. Unfortunately my trunk cannot take a ninth amp at this time
> 
> I would love to display some of the House music I listen to on the Adobe Audition if you guys can read the headroom for me.


If you like 'full range' audio and you are maxing out your
car install, then move into crazy home audio. You will be
surprised at how much easier it can get. You can get into
higher SPL designs, use pro audio gear to shave costs
vs. buying expensive home audio gear.

Finish the car, move to home audio madness


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## cvjoint (Mar 10, 2006)

thylantyr said:


> This is my entry level line array.


Sweet dynamite! I use those Dayton planars (?) for my rear passengers, I love them. 

It is most annoying to me when my roommates oscillate the volume according to the dynamics of the movie material. When I watch, neighbors come last 

Edit: btw you have no headroom between those things and the ceiling.


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## 6APPEAL (Apr 5, 2007)

FoxPro5 said:


> Linear Power: How in the hell do these amps do this? Pure balls that just keeps coming and coming. A 50x2 amp level matched to a highly efficient 150x2. Surely 150x2 wins? No, not even close.


Love my LP's for that reason. I've sat with Ray numerous times while he power tested amps. Blows me away how some manufactures rate their equipment, complete BS. When you watch it on an O-scope you see the "real" numbers. Back to back A-B comparisons of LP and Brand X measuring watts, output voltage, rail voltage and listening test. Heck, Ray has even done A-B comparisons of my modded LP's verus a stock LP to let me see and hear the differences.
John


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## cvjoint (Mar 10, 2006)

I popped in a few songs in Adobe audition:

Modern day pop: avg. rms -9db, heavy clipping
Trance: -10db, heavy clipping

House: -15db, 0db peaks, minimal to no clipping
My best selection Sasha, Infected Mushroom -20db, -1db peaks, no clipping
Emma test CD -22db, -1.5db peaks, no clipping

One thing is certain, the older the songs the more likely they will have more headroom and no clipping, even for the same artist. It's a tough new world for audiophiles.


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## drake78 (May 27, 2007)

I like this thread. It gives me some new light in terms of head room. I also wanted to add that that certain hard to drive drivers. Will also impact how dynamic the sound will be. Some drivers sound more dynamic than others by nature/design.


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## fredridge (Jan 17, 2007)

great thread guys, very productive and positive and what I was looking for when asked the questions.



foxpro5..... this is what I have been thinking too....ability to dig deep.



FoxPro5 said:


> That's when I came up with my theory: Loud power vs Pure balls power.
> .


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## FoxPro5 (Feb 14, 2006)

fredridge said:


> great thread guys, very productive and positive and what I was looking for when asked the questions.
> 
> 
> 
> foxpro5..... this is what I have been thinking too....ability to dig deep.


Yea it's totally borderline psychoacoustics and I'm not so ignorant to think my mind is playing tricks on me, but it sure _seems_ to me that some amps have greater capabilities to get down and dirty as apposed to just being able to put out loud watts. 

I really have no particular brand loyalty, nor do I give two ****s if the amp has "sound quality" but if the amp cannot beat the living snot out of these expensive drivers I have, then I'm instantly board.  

IME, you cannot tune in a more dynamic response into a system. It just has to be able to relax and flow effortlessly. Having "Pure Balls" amps is one of the key ingredients, because loudness without substance is annoying and agitating.

A good example would be a veteran opera singer vs a weaker, untrained opera singer. They might both be able to sing as loud, but the veteran can pinch up his butt cheeks and blast powerful sound out using his diaphragm; while the weak singer just kind of yells from the back of his throat.


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## fredridge (Jan 17, 2007)

agreed, only difference is I think this issue is part of the "sound quality". it can reproduce what is being played... an amps job is to amplify what is being played... if the song is digging deep the amp should be able to do the same.

this also relates back to the compression issue in music....some amps don't need to dig deep, just play loud


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## FoxPro5 (Feb 14, 2006)

cvjoint said:


> One thing is certain, the older the songs the more likely they will have more headroom and no clipping, even for the same artist. It's a tough new world for audiophiles.


_Undertow_, Tool (1993)
Sylvia Massy, Producer
"Sober"
RMS: -17.5 dB
First clip at -6 dB; heavy clipping at -30 dB 










_10,000 Days_, Tool (2006)
Joe Barresi, Engineer; Bob Ludwig, Mastering
"Vicarious"
RMS: -10.8 dB
First clip at -1.5 dB; heavy clipping at -30 dB










10,000 Days is really a pretty clean album, but like everything else it's just so ****ing loud! As evidence by Undertow, there's no reason to make it that hot. I want my 13 years and my dynamics back, guys. Enough with the monitor gain already. You don't have to be an audiophile to appreciate this.


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## thylantyr (Jan 21, 2008)

Here's the waveform for Slayer.


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## cvjoint (Mar 10, 2006)

Can't believe the later call themselves engineers, more like butchers. 

When old folk comment on contemporary music sounding all the same you can't help but take the blow. I've stumbled upon some songs that clip into the thousands of samples, plain ludicrous.


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## thylantyr (Jan 21, 2008)

_What did you say sonny?_


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## aboof (Jul 6, 2008)

FoxPro5 said:


> So what's the sense of investing in amp power with adequate dynamic headroom, oodles of power, etc when your music is the weakest link?
> 
> The loudness war is one thing, but then add to that compression with "lossless" encoders. For example, here's a very recent recording that sounds pretty good to many these days: Alicia Key's "No One". The sound of the music isn't in question, it's the nature of the audio signal produced by it that is.
> 
> ...


This post made me curious, so I did a quick test. I long ago ripped my entire collection to mp3, and I almost exclusively listen to the mp3s, whether at home or in the car. I grabbed the first CD I found lying around, Sonic Youth - A Thousand Leaves, and used the first song on the album.

Here is a piece of the original waveform, extracted directly from the CD into Sound Forge:










Here is the same piece of the waveform, from my mp3:










Here are the statistics for the whole song, from the CD:










Here are the statistics for the whole song, from the mp3:










I would have to guess that either the original CD of the Alicia Keys album had those problems to begin with, or that iTunes is awful for ripping, and was maybe doing some horrible normalization or something. Neither would surprise me.

My CD was ripped using EAC and LAME, with --aps. I don't remember if this is the exact guide I used, but this should be at least as good:

http://www.fryth.com/eacfaq/

I do not believe there's anything inherently wrong with using digital files as a source, if you take care to rip and encode properly. Note that this isn't even lossless, though I believe that music ripped and encoded to mp3 with similar tools and methods has passed several audiophile double-blind A/B tests.

Neither song had any clipping whatsoever.


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## 14642 (May 19, 2008)

Data compression is NOT dynamic range compression.


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## aboof (Jul 6, 2008)

Andy Wehmeyer said:


> Data compression is NOT dynamic range compression.


Yeah, and I don't think FoxPro thought that either, since he was talking about Apple Lossless files, but it seemed like maybe he was suggesting that the process of ripping and encoding, even losslessly, could result in the kind of nastiness shown on that Alicia Keys album. And I'm sure it can, but not if you do it right, even with a lossy codec. I don't know what an "XRCD" is supposed to get you, but my bet would be that the original CD was just that messed up, since not even a proper normalization would do that to a clean original, and I don't use iTunes for ripping or encoding, but it's hard to imagine that it'd do something that extreme to a good original unless it were configured really badly or something.


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## Izay123 (Jun 9, 2009)

I really locked into the post about following the pro audio recommendations about power (for example EAW recommends designers use amps that put out 150-200% of the speaker's RMS rating). 

Can we reasonably conclude that a similar rule of thumb should be followed in car audio? 

For instance, if someone drives a pair of reputable components (let's say Boston's PRO60SE) rated at 125w RMS with a quality amp (Let's say Boston's GT-24) rated at about 2x200, they should reasonably expect to obtain the best dynamics that their speaker could produce --or close to it, with today's music :-( , correct?


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## gijoe (Mar 25, 2008)

Since this old thread got bumped, my opinion of headroom is this:

An amp is already capable of delivering peaks of power significantly higher than it's RMS rating, for short bursts. The only time it would be beneficial to have ton's of power is when your amp is already operating at high levels. I think at these volume levels it would be very difficult to hear whether or not the peaks clip. This is assuming you aren't running a very low powered amp at it's limit. With a decent amp, at reasonable volumes, the peak power that the amp is capable of will take the brunt of the peaks. The clipping that may happen won't destroy the speakers unless this volume is kept up for sustained periods of time.

That said, it doesn't hurt to have the extra power. The extra power can help reach good volumes without clipping the peaks and maintain the dynamics of the recording. But, I don't think that 300 watts to tweeters and 500 watts to mids is ever necessary. I like to have some extra power to work with, but for me the big advantage to running powerful amps is that if they are kept well below their RMS ratings, they will run cooler and theoretically last longer.

The Zuki i run is about 130 watts per channel and I don't feel that I've ever pushed my ID OEM mids to a point where I felt I was missing out on dynamics because my amp was running out of steam.


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## MarkZ (Dec 5, 2005)

aboof said:


> This post made me curious, so I did a quick test. I long ago ripped my entire collection to mp3, and I almost exclusively listen to the mp3s, whether at home or in the car. I grabbed the first CD I found lying around, Sonic Youth - A Thousand Leaves, and used the first song on the album.


Good album. What's the first song? Sunday? If so, that track has a little bit of dynamic compression, so I'm not sure if it's a great example to use for audio quality tests.

Use Sonic Nurse instead. It's recorded near perfectly, IMO. 

PS - Before Andy jumps on me, yeah I know that dynamics compression ain't the same as file size compression.


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## t3sn4f2 (Jan 3, 2007)

I'm starting to think that an amp rated 150 watts into 4 ohms with an 8 ohms non high efficiency driver is the best all around worry free combination. 75+ watts continuously, peaks within the max range of the driver, and you don't have to worry about turning the head unit volume too high and clipping the amp because the increased average power to the coil from clipping should still be within the average power range of the 6dB crest factor noise signal that the driver was rated with. 

It would be a worry free combination since the amps output would act as a compression DSP no matter what is done at the various devices up stream (ie too much EQ, highly compressed track, etc.)

It would not give the best performance but at least you would not have to worry about someone turning the volume to max on the low passage of a dynamic track in order to hear it, resulting in a blown speaker when the peaks hit. Or always having to be conscious of not doing the same thing yourself.


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## VP Electricity (Apr 11, 2009)

gijoe said:


> An amp is already capable of delivering peaks of power significantly higher than it's RMS rating, for short bursts.


No, it's not neccesarily. This thread doesn't seem to address the differences in stiffly-regulated vs loosely-regulated power supplies and the effect of the PS architecture upon dynamic headroom. 

An old PPI, or an Xtant, or a JL slash, have zero headroom - but will make rated power down to 11V. 

Most amps are loosely-regulated, and will make rated power only at 14.4V, and have headroom for short boosts above rated power IF the voltage on the VBAT input holds. For this reason, I suspect that most amps which have headroom on paper don't really demonstrate this capability in most installs, since I suspect the voltage sags and output drops quickly. 



gijoe said:


> The only time it would be beneficial to have ton's of power is when your amp is already operating at high levels. I think at these volume levels it would be very difficult to hear whether or not the peaks clip.


Also incorrect. It is most useful when listening to music with frequent soft passages - which do not come near to clipping any part of the signal chain - and occasional dynamic bursts which would clip the amp (and be very obvious). The classic example is classical music recorded in a concert hall. You need a good noise floor and good dynamic range to listen to many classical recordings. Pop music is much closer to a test tone than classical music is, and does not have significant dynamic range requirements. 

Now if you don't listen to classical, it may not apply to you.


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## gijoe (Mar 25, 2008)

VP Electricity said:


> No, it's not neccesarily. This thread doesn't seem to address the differences in stiffly-regulated vs loosely-regulated power supplies and the effect of the PS architecture upon dynamic headroom.
> 
> An old PPI, or an Xtant, or a JL slash, have zero headroom - but will make rated power down to 11V.
> 
> ...


You make valid points, I just think for the average person having 500 watts available to a midbass driver is a bit excessive. I think for someone who is competing, having the extra power might give them a slight improvement, which could potentially be the difference between winning and losing. But for your average listener, who likes modern music and actually drives their car, a good 100x4 amp is going to plenty.

If you have the money to put that kind of power to your speakers, go for it, it can't hurt. I just want to separate the assumption that it's necessary to have 2-3 times the rated power available for a speaker. There are plenty of people who run reasonably low powered amps and have plenty of volume and clarity. I just don't want new people thinking that they absolutely have to have a ton of power in order to have good dynamics.


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## VP Electricity (Apr 11, 2009)

Perhaps the term "headroom" is being used when a better, or more accurate, term might be "power reserve" or "reserve power". Headroom has a specific meaning in audio, and we don't seem to be talking about that. 

NAD was the first company in home audio I remember talking up dynamic headroom, and it was in order to let a lower-power amp sound like a bigger amp. This was determined in listening tests... but it was off 120V mains and was certainly not tested with Sir Mix-A-Lot.


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## MarkZ (Dec 5, 2005)

VP,
But what are they talking about with headroom, exactly? Are they simply talking about the power supply's ability to stabilize the rails? Or is there something in the switcher that's actually boosting the voltage during transients? That would seem like a weird approach to me...


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## VP Electricity (Apr 11, 2009)

I wasn't paying too much attention at the time, but there is some info from this article::



> _
> 
> The FTC rated power, intended to be an amplifier primary rating, concerns maximum continuous power. There is a secondary power rating, the* IHF "Dynamic Headroom," which is the ratio between the maximum power the amplifier can put out for a burst just 20ms long, and the continuous power*. An amplifier that can deliver 200W for 20ms but 50W continuously will have a dynamic headroom of 6dB. In combination with the FTC rating, this secondary rating is supposed to indicate how loud an amplifier will play into a specified load. (This, of course, is a resistor, not a loudspeaker, which is another whole can of worms.)
> 
> ...


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## MarkZ (Dec 5, 2005)

VP Electricity said:


> I wasn't paying too much attention at the time, but there is some info from this article::


That just means they're class G, right? Only...a crappy class G that can't stay on the upper rail for very long. Or a smart class G, depending on how you look at it.


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## VP Electricity (Apr 11, 2009)

Based on lower cost and better performance per dollar, I would go with smarter. 

This post is interesting:

_



'Commutation' was Bob Carver's nomeclature for a rail switching design. I believe he coined this term for the diode on the lower rails, also refered to as an ORing diode (as it allows the output stage to use power from either the lower, or the higher supply, as needed). These diodes switch, or commutate as needed. The fast switching, soft recovery types, or newer high voltage Schottky type are best here.

The theoretical class B efficiency is 78.8%, a three rail design like the M1.0 is 87% (after Pol HSU). When you consider bias in a class AB design, 60% is more in line. Pol HSU found that the rail switcher showed even higher efficiency driving reactive loads vs resistive.

At full power, class G and H are slightly less efficient than class AB. However, the majority of the time we are not at full power.
Worst case for the class AB would be at about 50% voltage out, where the rail switchers are king.

Most Carver are three rail designs, most Crest are two rail designs. AB International has an interesting two-and-a-half rail design. Instead of a third set of transformer windings, associated rectifiers, and filter caps, they use 0V as a rail in class H. No improvement on a resistive load line, but much better into a reactive load line, and a reduction in the Vce required for the outputs.

IMO class G sounds better than class H. One example of this is the QSC MX2000, a 1KW per channel design. The original was class G, the 'A' version class 'H'. The original sounds better, and the used market value is higher for that very reason. 

Why do any class H?

Cost, it is much lower for class H.

The later Carver M1.0 is an interesting hybrid, being class G on the lower rail, and class H on the higher rail. Good sonics at a reasonable cost.

Click to expand...

_


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## MarkZ (Dec 5, 2005)

Weird. I think my dad has the M1.0. I'll have to check it out next time I'm back that way.


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## antikryst (Feb 26, 2011)

so how would you know that you are running out of supposed headroom? thinking of adding a dedicated sub amp so i could bridge my front set on my current 4 channel amp. this is my first car setup and I'm thinking about it.

but.... i would really hate it if it didn't make any difference after spending for another amp.


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