How Loud is a 15 Watt Tube Amp?
Are you thinking about investing in a 15-watt tube amp but you’re not really sure how loud it’s going to be? Well, you surely aren’t the only one!
A lot of musicians have trouble when deciding if they should get a 15-watt tube amp, mainly due to the confusion of how loud an amplifier can really get.
Is a 15-watt tube amp loud enough to do gigs with? Is it too loud for practicing at home? How can you even tell?
In this article, you’ll learn some of the common misconceptions regarding the “loudness” of an amplifier, how to get a feel for measuring the loudness of an amp, and how loud a 15-watt tube amp is. So let’s get started!
Well…Just How Loud Is A 15-Watt Tube Amp?
The answer is…it depends. Is it even possible to determine amplifier loudness based on its wattage?
When it comes to volume or loudness, it’s pretty common for musicians to consider the wattage or power rating of the amplifier to get an idea of how loud it’s going to be.
Generally speaking, more watts mean louder volume output, so it makes sense for musicians to take wattage into account. In fact, some of them don’t consider any other aspect.
While the amp’s wattage is indeed important to determine the amplifier’s loudness, you should also think about the efficiency and sensitivity of the speaker(s) connected to the amplifier. Here’s a basic breakdown:
Wattage and SPL
First things first, let’s talk about decibels (dB). To put it simply, decibels express loudness. The higher the dB value, the greater the loudness.
However, since dB is a logarithmic unit of measurement, we can’t add numbers or values the way we normally do. For example, 100dB isn’t twice as much as 50dB. It’s actually many times greater.
In the audio world, loudness is referred to as Sound Pressure Level (SPL). If you want to “double” the perceived loudness, you need to achieve around 10dB increase in level.
This means that if one amplifier produces 90dB SPL and another amp generates 100dB SPL, the average listener will perceive the second amplifier to roughly sound as twice as loud.
So, how does this apply to the amp’s wattage?
Let’s assume we got two amplifiers – the first is rated at 10 watts while the second is rated at 20 watts. Obviously, the second amp is double the power of the first amp, but this doesn’t mean it’s twice as loud.
You see, doubling the input power translates into an increase of 3dB SPL, and we already established that to “double” the loudness of a sound, we need an increase of 10dB. So, a 20-watt amp will definitely sound louder than a 10-watt amp, but never as twice as loud.
The same rule goes for higher wattages. A 100-watt amplifier isn’t going to sound two times louder than a 50-watt amp, it’ll just be 3dB louder (given you use the same speakers). A 3dB increase is definitely noticeable, but not the same as doubling the perceived loudness.
Wattage and Speaker Sensitivity
I hope you’re still with me!
I know you just want to know how loud a 15-watt tube amp is, but like I said – it’s a complicated answer!
Speakers include specifications that correspond to their sensitivity and efficiency. Typically, speaker sensitivity is expressed as: 90dB @ 1W/1m.
This means 90dB SPL using 1 watt of power and measured 1 meter away from the speaker. According to the 3dB increase per doubling of the input power, the SPL will go something like this:
1 watt – 90 dB
2 watts – 93 dB
4 watts – 96 dB
8 watts – 99 dB
16 watts – 102 dB
It’s worth mentioning that going above 95 dB can put your hearing at long term risk. The OSHA limits the exposure to 90 dB at 8 hours, with the allowable time cut in half for every 5 dB increase.
Is a 15 Watt Tube Amp Loud Enough to do Gigs with?
Whether it’s a yes or a no depends on a number of factors such as the type of music, the tone you’re going for, the type of gig, the room, and how loud you want to sound in general and in relation to your drummer. Your band’s PA system can also play a big role in this since it’ll do some lifting if it’s good enough.
As we explained above, a 15-watt amp is pretty loud in a normal world setting (I like the Monoprice tube amp and it cranks!). However, being in a band changes things. If you play alongside an acoustic drum set with a 300-watt bass amp, your low-watt guitar amp is likely to get drowned out, especially when dealing with rock or metal drummers.
What if another guitarist in your band uses a 100-watt amp? Should your 15-watt tube amp sit gigs out in such cases?
You may not be willing to let your 15-watt tube amp go, and we can’t blame you. Small amps are definitely easier to carry around, easier to set up, and easier to maintain. So if it sounds good to you, why should you ditch it?
Well, the answer is simple; don’t. Your 15-watt tube amp can be heard perfectly fine if you use a mic and a sound reinforcement system. So if you know you’re going to mic your rig and knowledgeable sound guy is managing you a good monitor system, your 15-watt tube amp can be loud enough to do gigs.
Is a 15 Watt Tube Amp Too Loud for Practicing at Home?
Again, it depends on the setting. One would say that a 15-watt tube amp, with its dB level exceeding 95, is probably far too loud to use at home. It can be uncomfortable for you, your housemates, and your neighbors. It can even pose a potential threat to your hearing over time.
Some would go as far as saying that cranking a 15-watt tube amp to break up a little can peel paint off your wall!
That being said, a 15-watt amp may not be too loud if you run it clean at low volumes, buy an attenuator, install an isolation box, or use special speakers for low-volume listening.
Long story short, a 15-watt tube amp can be loud enough for gigs, and can go even farther when you use a mic and a monitor/sound reinforcement system. As for practicing at home, you can use a 15-watt tube amp’s volume controls to find a sweet spot for whatever room you’re in.
Ultimately, the question of how loud is a 15-watt tube amp really needs you to look at what you’re trying to do with it. Luckily, 15-watt tube amps generally give you enough control of their loudness that there is a strong chance it will match your needs.