[Review] JBL Tools free app

JBLTools

Must-have app!

Product name: JBLTools app/software
Manufacturer: Harman of Brasil - Brasil
Cost: free download for Android
Reviewer: Lucio Cadeddu - TNT Italy
Reviewed: October, 2021

We all use our smartphones for music listening, via YouTube or the various streaming platforms, but there's more we can do. There's an endless list of - mostly free - apps that we can install for audio/HiFi purposes. Among these, my favourite one is JBLTools, designed by Harman of Brasil, that's the Brazilian Company, which is part of the Harman Group.

This app is 100% free and available on Play Store for Android devices (I've not found it on the Apple Store). JBLTools is mainly a repository for many different tools, it is extremely well made and easy to use, with instructions (in English) and an extremely user-friendly interface. The app offers six different sections (with subsections), we're going to explore in the following: Speaker - Calculations - Polarity Checker - SPL Meter - RTA - Wavelength.

Speaker

This section contains fill-in forms that allow you to calculate the volume of a given box of different shapes: rectangular, cylindrical, prism-shaped vertical, prism-shaped horizontal. Just fill in the blanks and let the app do the maths for you. You can even insert wood thickness and box volume with/without speaker. Just click on calculate and you're done.

Calculations

This section contains six different subsections:

DUCT. It allows you to calculate the size of bass reflex duct(s) (you can chose as many as you wish) just inserting the volume of the box and the desired tuning frequency. The app gives you the diameter and the length of the duct.
TUNING FREQUENCY. This performs the inverse procedure: given the volume of the box and the size of the duct, it reveals the tuning frequency. This is useful if you wish to know at which frequency your loudspeakers are tuned.
SENSITIVITY. This subsection gives you an idea of the SPL (Sound Pressure Level) you should expect when partnering a certain loudspeaker (with given sensitivity) with a certain amplifier, at the desired listening distance. For example, a pair of 90 dB/w/m loudspeakers, partnered with a 50 watts per channel amp, produce an SPL of 103,99 dB at 2 meters of distance. The app also lets you choose how many speakers you are using (normally two, I assume). This is extremely useful because it helps debunking many myths on the required amp power output. With reasonably sensitive loudspeakers, 25-30 watts are more than enough to produce a hardly tolerable (for your neighbourhoods) sound pressure level.
AMPLIFIER. This subsection lets you calculate power and voltage output of your amp on a given speaker impedance.
WAVELENGTH. This subsection lets you calculate the wavelength (i.e. the distance, in the direction of propagation, between repetitions of the waveform) at a certain frequency. For example, a 200 Hz tone has a wavelength of 1.5 meters.
OHM's LAW. This subsection lets you manage the output of the Ohm's Law, which links together voltage, current and resistance (I=V/R). For example, a 100 watts amplifier generates, on an 8 ohm load, a voltage of 28.20 volts and a current of 3.54 amperes.

Polarity checker

This section lets you discover whether your loudspeaker (or your system) respects the correct polarity. This requires an MP3 file that appears to be no longer available on the app website. In any case, you can use any MP3 polarity checker file that can be easily found on the web. The section contains the instructions on how to perform this measurement.

SPL Meter

This section contains a fairly accurate SPL meter, i.e. a tool that measures, with the hep of the mic of your smartphone/tablet, the sound pressure level while you're listening to your system (I do not know if it measures dB or dBA, it is not specified). It is not 100% precise as its precision depends highly on the quality of the microphone, but it still gives a gross estimate. This information is of paramount importance if you wish to avoid spending some extra cash on power you don't really need. The app gives readings of peaks and real time measurement in terms of dB. In a standard living room, it is hard to exceed 90/95 dB peaks. Above this level your neighbourhoods will be calling the police (or knocking at your door/ceiling/walls/floor). It's useful for those who think they need 1000 watts per channel, when they really use 15/20 watts. Do not let your wife/spouse understand how the SPL meter works ;-)

RTA (Real Time Analyzer)

This section shows the frequencies generated by your system, by means of a choreographic dance of blue bars. This is the so called Real Time Analysis or spectrum analysis.

Waveform

This sections does more or less the same as the above, except that it displays the sound in terms of waveform, instead of dividing it into different sections/bars.

Conclusion

For the die-hard DIYer or for the audiophile who wants to better understand certain aspects related to his system, this is the app to have. It is free, it works well and it is extremely easy to use. Things are explained in layman's terms and you do not need a degree in physics to understand how things work. Sometimes, at least on my OnePlus phone, the app crashes, but it can be reopened in a fraction of a second. Too bad it isn't available for iOS.

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