Double Bass What does extra headroom sound like?

[pskelly]

I have been reading the threads about matching amps with speakers and I think I understand how speaker SPL, not amp wattage, is the important factor as far as perceived loudness in the room goes, but there are lots posters who also say they like to have "extra headroom" because they like the resulting sound better, which is the most important thing.

If I understand right headroom is having your amp able to provide more watts than your cabs can take advantage of if you just go by the numbers. Could anybody say what it is about having the extra headroom they like in a live situation?

Thanks for any help.
Pete

 

[drurb]

I have been reading the threads about matching amps with speakers and I think I understand how speaker SPL, not amp wattage, is the important factor as far as perceived loudness in the room goes, but there are lots posters who also say they like to have "extra headroom" because they like the resulting sound better, which is the most important thing.

If I understand right headroom is having your amp able to provide more watts than your cabs can take advantage of if you just go by the numbers. Could anybody say what it is about having the extra headroom they like in a live situation?

Thanks for any help.
Pete

Allow me to clear up a few things. SPL, not watts, is important because it is the acoustic power radiating from the cabinet that is important and not the wattage, per se, of the amp that drives the cabinet. Of course, more acoustic power generally leads to greater loudness but loudness is a psychological quantity. I am not picking on you when I point out that "perceived loudness" is actually a redundant phrase. Loudness always refers to a perception.

Headroom does not refer to having more watts than can be taken advantage of by your cabinets. Rather, headroom, in this context, refers to the amount by which an amplifier can exceed its continuous wattage rating during short bursts. It is actually a technical specification. Suppose you have an amplifier rated at 300 watts continuous. Headroom refers to the amount by which the amplifier can cleanly exceed that specification for a very short time. If you have 3 dB of headroom, that means that, for a short period, the amp can hit 600 watts. This usually translates into the amp being able to handle transients that come along without clipping. Thus, it can "sound better."

If only things were that simple! Instrument-gear manufacturers are, shall we say, less than completely truthful when it comes to these specifications. Here's how it is supposed to and how it DOES work in the hi-fi world. An amplifier is rated in terms of the amount of RMS power it can deliver continuously over a specified bandwidth (range of frequencies) and at a specified maximum amount of distortion and noise. These specs are now standardized as a result of governmental controls imposed in the early '70s when consumers were being taken in by false claims.

Headroom is measured by hitting the amplifier with 20 cycles of a 1-kHz tone burst (that's 20 ms) and measuring the power that can be delivered before the amplifier exceeds its distortion specification.

Many design choices for the power amp circuitry affect the amount of headroom that can be achieved. Now, everything is different in the musical amplifier world. First of all, the wattage specifications are hardly standardized and the headroom specs, if you ever get them, are not all that reliable. Suppose an amp is built that can deliver 300 watts continuously but, because of its particular design, can hardly put out more even for short bursts. You might say that's an amp with little headroom and you'd be right. The manufacturer, however, may choose to spec that amp as a 150-watt amp that has 3-dB of headroom! Would a manufacturer do that? Probably not, because a company would rather advertise the amp as being a 300 watt amp (which would be legitimate) and forget the headroom.

Because of the vagaries of specifications in the musical instrument amplifier world, my own approach has been to buy an amp with a power rating (which, I hope, is truly a continuous power rating), that matches the maximum power handling of the speaker cabinet (hoping I can trust that as well).

Look [Invalid or Expired Link Removed]-- especially at the very last paragraph.

 

[Bruce Lindfield]

... but there are lots posters who also say they like to have "extra headroom" because they like the resulting sound better, which is the most important thing.

Could anybody say what it is about having the extra headroom they like in a live situation?

Well - in general I think most Double Bass players are looking for amplification that just makes the sound of their bass louder - as faithful a reproduction, as possible.

As you push amplifiers to their limit, they start to distort and this is exactly what you don't want with DB, as you might as well them be playing BG - where a lot of players actually favour distortion!!

So if you have more heardoom, there is less chance of distortion and you have a better chance of clearer sound reproduction!

 

[drurb]

Well - in general I think most Double Bass players are looking for amplification that just makes the sound of their bass louder - as faithful a reproduction, as possible.

As you push amplifiers to their limit, they start to distort and this is exactly what you don't want with DB, as you might as well them be playing BG - where a lot of players actually favour distortion!!

So if you have more heardoom, there is less chance of distortion and you have a better chance of clearer sound reproduction!

For the most part, I agree. What you need is sufficient power such that the amplifier does not clip. That, however, may also be achieved by an amplifier that has little to no headroom (as headroom is defined) but that can deliver sufficient power continuously. In such a case, you would not be pushing it near its limit but would have plenty of reserve power to amplify transients without clipping. AFAIK, in the case of most musical instrument amplifiers, you can't really count on having available any more power than what is specified as the (hopefully continuous) wattage rating. That is, the dynamic headroom usually is quite small.

 

[pskelly]

Thanks drurb; as usual you have cleared up a lot.

I guess then I need to back up one step and ask, What do people mean when they say they like the sound they get when they have "extra headroom?"

Do you mean in the strictly correct sense as the ability to tolerate the transient tone burst or do you just mean something like, "With a given DB, volume and EQ settings, cabinet, cords, room, bandmates, etc, I like the sound of an amp rated at 800 watts continuous better than one rated at 400 continuous."

I am just guessing it is the latter and am wondering what the benefit is to what you hear.

 

[Bruce Lindfield]

No distortion!

 

[drurb]

No distortion!

Bruce is right on the money. A more powerful amp does not, all other things being equal, sound better. If you have sufficient power to avoid clipping and distortion, it sounds better! It matters not whether you are using an amp with little headroom but plenty of continuous power or of less continuous power but enough headroom to get you through the transients. If you can reproduce them properly, the sound will not suffer.

Usually, it is more economical and efficient to have an amp that supplies adequate continuous power but that has decent headroom to get you through the short-lived peaks. If you had to buy an amp that can continuously the supply the power needed for those peaks, it will usually cost far more and often be heavier. What you'd be doing in that case is letting it cruise along most of the time well below its maximum available output and using that capability only in the short term. If you need to walk most of the time and only need to run quickly over short distances, you probably wouldn't want to carry around the muscles required to do it continuously.

 

[Chris Fitzgerald]

I guess then I need to back up one step and ask, What do people mean when they say they like the sound they get when they have "extra headroom?"

When I use that term, I mean that the amp has lots of power to spare and never sounds as though it is "straining" to play at whatever volume is going on. A good analogy would be to liken an amp with headroom to a car with a manual transmission going 70 mph on the interstate in 5th gear - the RPMs would still be pretty relaxed. An amp without sufficient headroom would be like the same car going the same speed, but with the transmission in 4th (or worse, 3rd) gear...the car is still going 70, but the equipment is revving like crazy and working much harder.

 

[drurb]

When I use that term, I mean that the amp has lots of power to spare and never sounds as though it is "straining" to play at whatever volume is going on. A good analogy would be to liken an amp with headroom to a car with a manual transmission going 70 mph on the interstate in 5th gear - the RPMs would still be pretty relaxed. An amp without sufficient headroom would be like the same car going the same speed, but with the transmission in 4th (or worse, 3rd) gear...the car is still going 70, but the equipment is revving like crazy and working much harder.

Chris, I see what you mean. Your car in 5th gear is like gaining headroom by buying a 300-watt amp and letting it "cruise" because most of the time you only need 150. In such a situation, it's more economical and efficient to by an amp that can only supply 150-watts on a continuous basis but which has 3-dB of headroom so that it can hit 300 watts for short bursts. To continue the car analogy, its like the old hot-rods from the fifties where, for short bursts, you'd fire nitro into the cylinder. Doing that would give you a rush of horsepower but you sure couldn't do that continuously.

 

[flatback]

When I use that term, I mean that the amp has lots of power to spare and never sounds as though it is "straining" to play at whatever volume is going on. A good analogy would be to liken an amp with headroom to a car with a manual transmission going 70 mph on the interstate in 5th gear - the RPMs would still be pretty relaxed. An amp without sufficient headroom would be like the same car going the same speed, but with the transmission in 4th (or worse, 3rd) gear...the car is still going 70, but the equipment is revving like crazy and working much harder.

yea like he said. And like a car in third going 70 you can feel the strain. I had a WW 100M that I loved the sound of...as long as I didn't have to push it. If you pushed it even before it distorted, it sounded strained, the sound changed form a purr to a huff and puff. When you have enough headroom the character of the sound still may change if you get really lound (because of the pick up and other factors) but the amp sounds unstressed. Seems to me (at least with my amp set up Focus III ) that I get more dynamic range too. The soft notes dont get swallowed and the loud ones dont distort, rather they all "feel" good and well balanced in their range...

 

[drurb]

Okay, I'll try again. What is being described above is the result of having sufficient amplifier power, per se. It is not necessarily a benefit of headroom. Headroom refers to the amount in dB by which an amplifier can exceed its continuous power rating for short bursts. If you were to buy an amplifier that can supply much more continuous power than you need, the benefits described above will accrue even if that amplifier has virtually no headroom. In such a case, you would be creating effective headroom by hardly using that amplifier's capabilities most of the time. Headroom is being confused with simply having sufficient power.

 

[flatback]

Okay, I'll try again. What is being described above is the result of having sufficient amplifier power, per se. It is not necessarily a benefit of headroom. Headroom refers to the amount in dB by which an amplifier can exceed its continuous power rating for short bursts. If you were to buy an amplifier that can supply much more continuous power than you need, the benefits described above will accrue even if that amplifier has virtually no headroom. In such a case, you would be creating effective headroom by hardly using that amplifier's capabilities most of the time. Headroom is being confused with simply having sufficient power.

Dude mon...I dont think you have any headroom left (its filled up with all dem brains)
just kidding, thanks for the clarification.

 

[seamonkey]

Problem with a "headroom" specs is there's no time duration given. It could be a 10th of a second or 10 seconds.

If I need 600w for short bursts of time, I'd rather buy 600w than a lower wattage amp that claims to have headroom. This is creating what I think most people refer to as "headroom" - just a higher power amp than you normally need.

It probably matters more for double bass because players want to haul small light cabinets that need more wattage to produce a goal SPL level.

 

[drurb]

Problem with a "headroom" specs is there's no time duration given. It could be a 10th of a second or 10 seconds.

If I need 600w for short bursts of time, I'd rather buy 600w than a lower wattage amp that claims to have headroom. This is creating what I think most people refer to as "headroom" - just a higher power amp than you normally need.

It probably matters more for double bass because players want to haul small light cabinets that need more wattage to produce a goal SPL level.

Well, if you look at my post above, you will see that there is a duration that goes along with the headroom spec. Specifically, it is 20 ms of a 1 kHz sine wave. There was some discussion within the AES (Audio Engineering Society) of increasing that duration to around 200 ms as that is more realistic in terms of musical peaks. I agree with you, as I said in that first post as well, that the safest thing is to buy all the power you need and not rely on headroom when it comes to musical instrument amps. Yes, in essence, you create your own.

 

[bopeuph]

Wow. I think I'm getting more confused than I was before.

I just want to be able to play my basses to sound the best they can, and have the right equipment. I never thought I'd have to think so much about all this. I just think if I want something new, I think I'll either call a friend and ask if it's what I want, or post here and ask. This seems like something that will take years to understand, anyway.

Nick

 

[Son of Bovril]

When people say they like the sound of having extra headroom, they mean they like it that when they dig in on their bass/play harder, that the amp doesn't distort so their playing literally results in a louder more powerful version of their normal sound. Ie. it affords them greater dynamics in their playing without being limited by the power of the amplifier...

in simple terms: have a bigger bass rig than you need so that if you do need to push it a bit harder the rig can handle it without distorting/changing the sound.

 

[Ric Vice]

Son of Bovril,
This thread hasn't been active since 2007, just thought you ought to know that. It's a very good thread, primarily because Les came on to it and gave us all the scoop. I'm not sure I ever read it the first time, so thanks for re introducing it. Good Information

Ric

 

[BassGen]

Quite an old thread that came back to life eh? To heck with specs. I'd simple it up like this.

Headroom exists in both the amp and the speaker cabs. If both have sufficient power handling in both that you never have to "turn it up to 11" (Spinal Tap reference in case anybody doesn't catch it) then you should not be getting into ranges where either the amp or speakers will distort. Hence, better sound.

I have a large and powerful rig. I've only once needed to go beyond 40% on the main volume. It always sounds clean and good. In my case, "headroom" means that I could play a much larger venue with a louder band and I've got plenty of clean power to spare.

Please feel free to return to your highly technical discussion now.

 

[NoiseNinja]

What is maxing out the amp then?

 

[Ric Vice]

I just thought I'd point out that you are over on the Double Bass side of Talkbass Forums. A DB with a piezo pickup would definitely start to feedback way before it reached the limits of most newer Micro Amps. I have a couple of Walter Woods amps a MI-400-8 and a WW Electroacoustic Ultra. I've rarely ever gotten those amps any where near their potential out put with an acoustic instrument.

Ric