I am thinking about purchasing headphone. What does this mean?

[Michaelb4]

I am thinking about purchasing headphone. What does this mean?   4.5Vrms maximum,  32 ohm minimum load. I just want to purchase a real nice pair of headphones at normal listening levels. Recommendation appreciated. 
 

Mike

 

 

 

[audiobomber]

Most headphones will show specs for the nominal load in ohms and a power spec, usually stated as SPL/mW. The impedance spec is straightforward; do not buy a headphone with a nominal impedance less that 32 ohms, as this will draw too much current. The voltage spec is more complicated. Go to this Ohm's Law page:

https://ohmslawcalculator.com/ohms-law-calculator

Enter 4.5 in the voltage field and the headphone's nominal resistance spec in the resistance field. When you hit the calculate button, it will show you the power in watts that your amp can push into that load. Convert to mW by multiplying watts x 1000, and compare this number to the headphone's rated sensitivity in SPL/mW. Here are a couple of examples using my headphones:

 

Grado GH4: impedance 32Ω, SPL/mW = 99.8dB

Using the calculator: 4.5V and 32Ω, power = .633W x 1000= 633mW. Doubling the power gives you 3dB greater loudness. In other words, power is way beyond what you need for extremely loud listening with this headphone.

 

Beyerdynamic DT 1990 Pro: Impedance 250Ω, SPL/mW = 102dB

Using the calculator: Power = 0.81W = 810mW. So you would be able to play this headphone well beyond 102dB, too loud for comfort. 

1mW = 102dB

2mW = 105dB

4mW = 108dB

8mW = 111 dB

16mW = 114dB

32mW = 117dB

64mW = 120dB

128mW = 123dB

256mW = 126dB

512mW = 129dB

1024mW = 132dB

So the DT 1990 could go as loud as about 130dB, and you would never want to. 

 

If the above is more that you want to know, you can ask me about any headphone you're considering. Your headphone amp is reasonably powerful, should drive most headphones on the market just fine. 

[Michaelb4]

Thank you- very helpful.