ModBlog: On Power..
We have all been taught, there is no such thing as too much power! That’s not exactly an incorrect statement, but it does imply that we need immense amounts of power for the best sound. Since the first HiFi shop opened, salesmen and marketing departments have been working this angle. How power is defined is key. We really don’t need as much power as we think. Most of the time, we can get away with a lot less…but not always!
Let’s first define terms:
When talking about power, we are referring to Loudness or Sound Pressure Level (SPL), measured in decibels (dB).
Speakers are rated by sensitivity, expressed as:
dB @ 1 watt @ 1 meter.
This simply means, the dB level produced from the speaker with 1W of power, measured at one meter from the speaker.
Example:
A 88dB sensitive speaker: 1 Watt produces 88dB at 1 meter.
Importantly, every time you double power, you only gain 3dB!
For example, for this speaker 1 W = 88dB. Increasing this to 2W = 91dB, 4W = 94dB….to 64W = 106dB! As a point of reference, the normal listening level in a home is 75-85dB average, which means that most of the time, 1-10W will achieve this.
So why do big amps exist at all? Music is dynamic, not static. A well recorded orchestral crescendo can have 20dB peaks above average level. For this reason, headroom is needed and reserve power is desirable. Most of the time, we are only using a fraction of the amount of power an amp can deliver, but during dynamic peaks, an amp’s true power capacity is critical.
Speaker efficiency is a factor. An 87-90dB speaker will provide exceptional performance with an amplifier like the KWA 99 which produces 100W/8 and 200W/4. The first 15W are pure Class A, and current reserves from the 500VA transformer (per channel) mean the playback will be effortless.
Speakers of less sensitivity, in the 84-86dB range, will benefit from more power. In fact, an 84dB speaker will require 4 x the power of a 90dB speaker. At this point, you might want closer to 200W+, especially in larger rooms.
Efficiency is one factor, the type of load is another. A ‘Difficult’ load is one of low impedance or high reactance due to complex crossovers. Many of the bigger high-end speakers from companies like YG Acoustics, Magico and others, present difficult loads and medium-to-low efficiency.
System synergy is everything, and some things work that you wouldn’t expect.
At Capital Audio Fest one year, we made beautiful music with 87dB efficient Fritz Carerra speakers and 8W of 300B SET tube power. In this case, it was more about a benign load, rather than efficiency. The Carerra’s I learned have a very simple first-order crossover and 8W of tube power was enough in a small room. At that same show, we ended up using 150W KWA 150SE SS power amps with a horn speaker…you just never know!
When we face lower efficiencies and difficult loads, the speakers demand CURRENT! Big power amps, like the soon-to-be-released KWA 300 stereo amp, have large transformers and high capacity power supplies. The KWA 300 provides 300W at 8 ohms, over 550W at 4 ohms and nearly 1KW into 2 ohms. This is made possible in part due to its 2KVA power transformer. The monoblock versions of the KWA 300 stereo amp will provide 600W @ 8, 1200W @ 4 and over 2000W into 2 ohms.
An amp like this preserves transient integrity and controls bass drivers with authority.
At a demonstration in Erie CO at TMR (The Music Room), we drove YG Acoustics Summit speakers with a KWA 300 prototype. When the first notes of ‘Queen Mary’ slammed people in the chest, eyes were raised!
The key factor here is that power provides control, not just volume.
OK you say, you just proved the point, more power is better! Yes, to a point. The problem that I have with power ratings, is how salesmen and marketing teams have used ‘power insecurity’ to their advantage:
- The terms Peak Power vs RMS power
- Power rating at 1Khz rather than 20hz – 20Khz
- Power rating at 10% distortion?!
- No mention of low impedance load stability
When you hear an amp rated at 500W/channel, ask how big the power transformer is. If the amp is based on a 250VA power transformer, I can tell you they are lying already. 500VA translates roughly to 500W. VA = Volt-Amperes where Power is defined as Voltage x Current (Amps).
Amps are sold based on rated power. But, design and power supply reserves can make a well designed 100W amp sound more powerful than a 300W amp built to a price point.
Real power is defined by:
- Power supply capacity
- Current Delivery
- Output stage robustness
- Thermal stability
- Low distortion under dynamic load
So…How much power do you really need?
This really depends on speaker sensitivity, impedance behavior and room size.
I would say that for speakers of 92-100dB efficiency, 50W – 100W is more than enough.
For speakers in the most common range of 86 – 90DB, 100W – 200W is ideal.
When you start dropping into lower efficiencies, in big rooms with difficult loads, then 200W – 400W becomes necessary for true authority.
At ModWright we offer something for all speakers:
- The KWA 99 monoblocks at 100W/8 and 200W/4 will drive most speakers exceptionally well.
- The KWH 225i offers more power in an integrated at 225W/CH
- KWA 300 Reference Power amp and Reference Monoblock amps to follow, provide authority, composure and limitless headroom for demanding high-end systems.
Most of the time, you will use 5-20W. This is why ModWright amps are all high-bias Clas A-B, designed to provide the most pure Class A watts in the range where it counts most.
Power is not about loudness, it is about control, composure and truth under dynamic load.
At ModWright, this is what we design our amplifiers for…
If you are interested in how these principles apply to our amplifier designs, you can explore our KWA amplifier series here:
KWA 99 Mosfet Monoblocks
KWH 225i Hybrid Integrated Amplifier
KWA 300 Stereo Power Amplifier coming soon!
Come see it at Axpona 2026 April 15th in Chicago.
RELATED READING:
Tube vs Solid-State Power: What really is the difference?
MOSFET vs BJT: What are the sonic differences and strengths of each?