I posted this originally on a different thread
here , but reposting it , as a separate thread for visibility and its broader impact.
I need to let out a pet peeve , on the Power calculator, often referred to by many of our AH members..,when someone asks in the forum , what kinda amp or AVR is suitable for my speaker for my room or how much power do I need to drive a speaker etc..Often they get pointed to this
Peak SPL Calculator .
While it does adequately what its intended for (to get the SPL for a given sensitivity , power input at MLP)..., it lacks in many aspects and can infact be misleading if not applied correctly (esp by inexperienced people), I think. Lets look at this closely...,
All it takes as User inputs are Sensitivity , Amp power( the very thing the people are trying to find out! ), distance to MLP, #Speakers and boundary reinforcement and spits out dB SPL at MLP.
1st gap:
To get the required amp power, for a given SPL, you need to keep trying different Watts as input, until you hit the required SPL . The quickest and right way to do this would be to punch in your required SPL and the calculator to spit out the required power ... not the other way around like this calculator does!
There's no way to input the average SPL !
2nd gap:
This calculator implicitly assumes 8 Ohms speaker! What do you do , when your speaker has a 4 ohm nominal impedence ? An inexperienced person may not even realize this and just use the Watts as it is...leading to a gross mistake in power requirement.
To get the right Watts, for a 4 Ohm speaker, you'd have to double the amp power from this calculator
OR
derate the speaker sensitivity by 3 dB to get the watts, at the same implied 8 ohms
3rd gap:
No place to input headroom required to account for peaks in SPL.
You'd have to manually keep adjusting the Amp power ,until you hit your desired headroom (say +20 db)
4th gap:
Doesnt clearly distinguish equivalent RMS Watts and Peak Watts. Again can mislead people, where they can unwantedly double the power again , to get the peak!
There are better Amp power calculators out there...that addresses the above gaps . Maybe we should redirect people to these calculators instead ...
For eg, this one from
Acoustic Frontiers
- Allows you to enter the desired average SPL and get the required Peak & RMS watts in one shot. No need to keep trying different amp watts to find the right one!
- Also allows you to input Speaker's nominal impedence such as 8 or 6 or 4 etc ...to account for all speakers..and not having to play around with power or sensitivity to account for speakers with impedences other than 8 ohms. Automatically adjusts's speakers sensitivity to account for impedence ( He's incorrectly calling Sensitivity as Efficiency ..thats not right..,but that's a different topic!)
- Allows you to enter the desired headroom/peak SPL such as +10, +20, +30 etc.. No need to do any adjust amp watts further to estimate for peak listening levels
- Clearly identifies the Peak and equivalent RMS power required...No confusion and wrong interpretation leading to costly amp mistakes (like buying double of what you really need)!
From my pov , this one
https://myhometheater.homestead.com/splcalculator.html is a little use-less for the amp estimates with different conditions..(not completely useless, just less useful and error prone and can be misleading inexperienced people)...
Ofcourse we dont need these online calculators and go straight with calculations.., but they're useful for most people with a polished UI. The acoustic frontiers one (and there are others as well ) are much more verstatile, flexible and should get the job done, without trial-and-error and further error-prone manual adjustments to get the final numbers.
What do you guys think, can we all switch and redirect future questions to this one instead ?
That'd be my suggestion ( until the audio industry switches to the more appropriate Voltage/Current specs , from the current Power specs)