Amplifier Headroom - does (size) matter?

[mrsrobinson]

While researching amps to upgrade to Crutchfield tells me do not go with an amp with a continuous RMS higher than the speakers continuous RMS, in my case 65 Watts for the 6.5s and 130 for the subwoofer. My own research suggests I should go a little higher, what's called headroom. I tend to agree with my own research, I am not sure why Crutchfield is saying what they say. I also think it makes sense to go a little higher in case I want to change out the speakers in the future.

I'd like to here from the audio gurus on this one.

 

[Skybolt]

My speakers are the same as yours and my amp is 75w RMS. Nothing wrong with that since the 75w RMS is not always being seen by the speakers. The RMS wattage changes with volume level and is a max rating.

 

[ZZ13]

Could be the world record for individual threads on one continuous project.

 

[Wylie_Tunes]

Fisrt and foremost, regardless of a speaker's rating or an amp's rated rms and peak, proper tuning of the complete system is important.

Myth; you will blow a speaker by underpowering it. Many beleive this because they dont understand what actually happens when there is a blown speaker on a low wattage amp, including the built in amp of a head unit. Its not the low wattage that blew the speaker, but rather a erratic wattage the amp produces when its driven into a state clipping/distortion. This is usually the case, because the owner is expecting/wanting more from the system and jams the gain dials/volume to 11.

RMS is measured output under specific conditions. Its like a cruise control speed for a highway. Peak is an unrealistic ouptut, often used by for marketing by the low-rung amp manufactures to make their product look better. You will measure peak mere seconds before the magic smoke appears.

Music is dynamic, so even properly tuned, you will not measure a steady output of the amp's rated RMS. RMS is a tool to help make a good amp to driver paring.

Headroom; Here is my analogy of headroom. Think of a couple cars going down the autobahn. One is a small 4 banger Opal and the other is a big V8 BMW. The Opal (lower wattage amp) is pedal to the medal just to go 200 KPH. Here comes that big BMW that blows past the Opal and goes out of sight, all the while at being about half throttle, with more power in reserve. Which engine is running at a higher RPM? Which is working harder? This is headroom.

Now, does it mean its bad to go with an amp thats right around a speaker's RMS? No.

More later, off to get breakfast.

 

[Wylie_Tunes]

Crutchfield likely steered you away from an amp with an rms rating above the speaker's rms, because they dont want to warranty the DIY installed equipment.

Do I need headroom, and if so, how much? Good question, with no one size fits all answer. Every system can benefit from lots of headroom, but it sometimes does not yield a detectible return on the extra investment of the higher output amp. So it oftem comes down to system goals and budget.

Application; Are the speakers cabin, salon or rear-firing/tower mounted? Does the owner want concert level volume or is this a large open floor center console fitted with quad 300's? Rear firing and tower pods, I always like to have the extra wattage. These speakers are often the hardest pushed on a boat system. So we need the speakers to perfrom to their potential and yield a lot of volume. Salon speakers often do not need a lot of power. Due to the closed and small space, it will not take a lot of volume input to make the system seem loud. cabin speakers can go either way. For the average boat, there are mulitple cabin speakers spread throughout. So we typically dont need a ton of headroom to make the volume level exceptable while underway and on plan. Then there are systems where the owner wants to make it really jam. So to get clean, quality volume, we need that extra wattage headroom.

Signal quality and noise; Think back to the cruise control and autobahn. To keep the signal clean, we need to speaker to reach its potential/desired volume level with the volume dial level lower then max and the amp's gain level as low as possible. Headroom allows for this. With the extra wattage potential, we can supply the speaker with what it can handle without taking our volume dial past 75%. This insures a slean signal. We can get the amp to deliver what the speaker needs, with the amp gain at a lower level v's an amp with a lower wattage potential. As the gain level increases, we run the risk for unwanted noise and a clipped/distorted signal.

With that said, ill take lower wattage thats clean from a quality amplifier over higher wattage from a price-point bargin amp.

 

[mrsrobinson]

Thank you @Wylie_Tunes, this helps, and makes sense.

"How much headroom?" is a question I see when I research this. 2 times seems to be the general answer. Do you agree? I am guessing it's a "it depends" answer.

I don't mind spending a little more money now for headroom and expansion, versus purchasing an amp I later wish I had not.