Speaker box design - loudness

When we are designing an enclosure it is crucial to understand that speakers come in different loudness levels for a given level of input, this is referred to as sensitivity and something that is not understood because people buy into marketing hype or just don't understand and make a novice mistake and buy into power handling which is less important then what you might realize but does play a critical part of the end result.

Speaker A is a 12" rated at 1000 watts and is 8 ohms - our sensitivity is 80dB typical of a car woofer in half space

Speaker B is a 12" rated at 100 watts and is 8 ohms - our sensitivity is 95dB typical of a PA woofer in half space

You can see as we double the power from our amplifier in this example we are increasing our overall loudness by roughly 3dB for both speakers, speaker "A" remains softer than speaker "B" because it has a higher level of efficiency.

Now I'm not going to show you the log formula but rather show it to you in this way as its easier to "see" to understand, this is a crude way to understand but it should nudge you along enough to picking a better speaker going forward.

Our question is this - how many times must we double our watts from speaker A to match speaker B?

So our target is 95dB and we starting out at 80dB so lets kick it off!

80dB @1 watt // 83dB @2 watt // 86dB @4 watt // 89@8 watts // 92dB @16 watt // 95dB @32 watts - this means Speaker A needs 32 watts to be as loud as speaker B, this is a very large difference in power or to be more precise we the difference is 187.87%

You can just how important sensitivity is when comparing 2 speakers, buying on Watts can be a newbro's mistake because it looks like a logical choice at first

In short speaker "A" would need more than 8000 watts to match the loudness level of our speaker "A" with a 256 watts being applied, this is because we have 15 decibels more loudness right from the start. 

So we can deduce that in general car audio drivers are softer per watt, home audio drivers are a bit louder as they need to play in a larger environment with our PA speakers in general being the loudest. 

When considering a speaker to brake the ice consider how loud the speaker must play and secondly look at how many Watts you need to get to that loudness level, a cheap Pa 18" will require less watts often enough to be loud in a room vs a car audio driver that requires tons of power to get to the same level.

To conclude, we should see all types or categories of speakers as speakers but know that the difference between these products are to meet an application. Loudness is not purely based on power handling rather its the relations between sensitivity and potential power.

Our next topic we will look into efficiency, this will further help define just how loud our box design will be relative to sensitivity / frequency and power handling.