Do you know everything you should about your speakers?
Maybe you know the model number and power requirements, but do you know the coverage angle and forward aspect ratio?
How long will it take you to find this information in the field? How many people will wait while you look it up?
I spend a lot of time on every show getting to know all of the speakers I’ll be using. I want to be as informed as possible for quick decision making on site. It’s frustrating and embarrassing to take my phone and try to look up some facts that my colleagues on site may not even understand or think is important.
For a lot of people, the answer to this problem is an app like the PA Bible. My problem with this solution is that you are still spending precious time getting your phone out to go through a database. At least it’s faster than Googling around for the data sheet, but it still takes time.
What if every speaker came with all of the most important information printed on itself, like the tag in your shirt with care and washing instructions? Except this tag would include:
- Angle, order, forward aspect ratio, and lateral aspect ratio for both vertical and horizontal coverage.
- Voltage, current, and resistance.
- Operating frequency range.
- Peak SPL and class.
- Spectral divider (crossover) specification.
- Impedance and power handling capability for each driver.
Now multiply that list by every speaker in your inventory and it’s a lot of information to try to memorize.
But do we really need to know all of this? Will it help us in the field? Let’s look at some example questions we might need to answer.
Where do I put my speakers?
For speaker placement decisions I rely heavily on forward aspect ratio (FAR) and lateral aspect ratio (LAR). FAR will tell me how well my current design matches the audience. LAR will help me space my front-fills for a solid unity line across the front row.
To calculate the FAR and LAR for your speakers use the following math, which you can find on my aiming triangles business card:
- FAR = 1 / sin (coverage angle / 2)
- LAR = 2 / FAR
Where do I cross over my speakers?
The speaker manufacturer will include information in their documentation about how to combine match pairs of speakers. If you are combining two un-matched speakers, their operating range is important to know so you can expect a big area of overlap or a gap.
How many speakers can I put on a circuit?
To answer this question you’ll need to know the rating of your circuit and each of the speakers you want to put on it. The circuit will be rated in amps so if your speaker only has information in watts, you’ll need to do some quick math. Another reason to get that information ahead of time.
Where do I set the limiter for these speakers?
The more separate components you combine in the chain, the more complicated the calculation. I have little experience in this area, but I know that you’ll need to know about the power handling and resistance of every driver in every box you plan to use.
How many speakers do I need in my delay towers?
If you are using unmatched speaker models between main and delay, you’ll need to know the power scaling relationship. Look up Peak SPL on the data sheet.
As you can see, there’s a lot of information we need to know about our speakers. With enough time in pre-production we can gather all the information and make a spreadsheet, but what about when you just show up in the field and are handed a pile of speakers?
Have you ever seen a sound engineer stop to look up the data sheet for every one? I haven’t. And you can’t expect anyone to know every spec of every loudspeaker.
What about a label on every speaker with the most important details that will help us with quick decision making in the field?
It might look like this.
And I might make them.
So what do you think. Would this be useful to you?
I understand the concepts of FAR and LAR but what does order mean?
Also, do you think indicating the weight would be interesting? For example: my name is… and I weigh…..
Nathan Lively says
omg, that’s brilliant. Yes, we should add weight.
Order is from Bob McCarthy’s book. Just search for speaker order.