AVR or pre-pro + amp? How to tell
Should you upgrade from an audio video receiver (AVR) to an audio video pre-amplifier/processor (pre-pro) and amplifier separates? Sometimes the answer is obvious. If you own 4 Ohm speakers, then go ahead. If you regularly experience an AVR thermal shutdown event, then also yes. If you’re a good neighbor living in an apartment, then no. If you’re socioeconomically challenged, then also no.
For everyone else, the reasonable answer is “it depends”. The average AVR outputs 60 to 100W RMS/channel into 8 Ohm. Yet it’s easy to forget that most music listening (if you value your hearing) is below 1 Watt of power per channel. Loudspeaker in-room sensitivity comes in the form of “__ dB/1 Watt @ 1 meter”, usually in marketing friendly in-room rather than anechoic measurements. 1 W is enough to rival a quiet gas lawn mower for loudness.
There’s lot of reasons to be skeptical of mass market AVR and receiver power ratings. With packaging and power supply constraints, manufacturers are reluctant to provide true power figures. But if the marketing states “100W/ch RMS into 2 channels, all channels driven”, you can be reasonably certain your 7.x.4 channel AVR has 200W total to draw from with no headroom. If you listen to stereo, that gives you a respectable 100W/ch. But across 11 powered channels, there’s 18W/ch available on average from the pool (200W / 11 channels). I’m not the only person who’s reached this conclusion:
https://www.axiomaudio.com/blog/how-to-buy-receiverDedicated amplifiers tend to state their designed power reserves/dynamic headroom, and so we treat their peak or dynamic power output differently. So an amplifier that’s only rated at 125W/ch but has 3000W of dynamic headroom due to a pricey and bulky 60,000 microFarad stiffening capacitor means there’s 1500W/ch available in stereo mode, or 375W/ch over 8 channels (3000W / 8).
So what are those peaks? Your typical iOS or Android sound meter app does a better job of recording peak rather than average levels, so have a listen to a demanding music or movie track at your intended listening volume, and let’s see if a hypothetical 18W/ch AVR is capable of performing without clipping for someone seated 3 meters away.
First, there’s a 6 dB drop in loudness for every doubling in seating distance away from the loudspeaker. (Source and calculator:
https://www.omnicalculator.com/physics/distance-attenuation) So for the most common seating positions:
2 meters = -6 dB
3 m = -9.5 dB
4 m = -12 dB
5 m = -14 dB
6 m = -15.5 dB
8 m = -18 dB
Every 3 dB rise in audio volume requires a doubling in amplifier power. So if you standardize on 1 W providing __ dB of volume, then:
+3 dB = 2 W
+6 dB = 4 W
+9 dB = 8 W
+12 dB = 16 W
+15 dB = 32 W
+18 dB = 64 W
+21 dB = 128 W
+24 dB = 256 W
+27 dB = 512 W
+30 dB = 1024 W
Let’s use some real world speakers to see what output we can get from 18 W/channel (rounded down to 16 W for convenience)
Model/ In-room sensitivity @ 1W/ Max RMS / Max dynamic / Peak SPL @ 3 m @ 16 W (-9.5 dB + 12 dB = +2.5 dB)
—————————————
M2: 89 dB / 150W / 600W / 91.5 dB
M3: 90 dB / 200W / 800W / 92.5 dB
M5HP: 91 dB / 300W / 1200W / 93.5 dB
M60: 92 dB / 250W / 1000W / 94.5 dB
M80 (4 Ohm): 94 dB / 400W / 1600W / 96.5 dB
M100 (4 Ohm): 92 dB / 600W / 2400W / 94.5 dB
So if you listen below these peak levels, an AVR is fine.
Disclaimers
- Surround channels rarely need the power demands of the front channels.
- AVR’s benefit from assignable crossovers and powered subwoofers to play louder, so this analogy is not perfect. But AV pre-pro’s share the same advantages.
- We’re ignoring other room gain considerations such as corner loading, wall-reinforcement, and multiple loudspeakers.
- Hearing loss is cumulative. Before you turn it up, maybe enable your loudness/Fletcher-Munson switch and see if that doesn’t provide a better listening experience.
- You might not actually want dynamic range. If you have it, try enabling audio compression (a.k.a. night mode) to reduce the differential between the softest and loudest audio passages. You might actually prefer that.
- You can’t tell from specifications what the threshold is before you can hear loudspeaker thermal compression artifacts. For my Angstrom speakers with 4 and 5 inch drivers but rated 60W, those tonal artifacts start long before 1 W is pumped into them.
- You’ll want to downsize your lifestyle one day. So don’t assume supersizing is always the answer.
Conclusion
I personally never listen to music or movies that peak above 85 dB, so I’m fine with my bottom feeder AVR. But if you like it loud, then consider this another toolkit for deciding what’s best for your needs.
Better and more thorough explanations can be found here:
https://www.axiomaudio.com/blog/powerhttps://www.axiomaudio.com/blog/sound-distortion/https://www.axiomaudio.com/1000-amplifier
