SPL vs JAX Stereo Tool (AU)
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
SPL
This professional-grade digital sound level meter measures decibels with advanced modes and filters meeting ANSI Type 1 standards. It allows storing, exporting, and calibrating measurements, and can be used with external calibrated microphones for precise results.
- Professional-grade digital sound level meter
- ANSI/IEC Type 1 standards compliant filters and modes
- Store, recall, and export GPS/time-stamped results
- Supports external calibrated microphones
- Adjustable calibration for accuracy
- Internal mic compensation filter
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SPL is a professional-grade digital sound level meter (decibel meter) for your iPad, iPhone or iPod touch. It includes all of the modes, filters, and features that you would expect from a professional ANSI or IEC Sound Level Meter. All filters and averaging modes meet or exceed the criteria for ANSI Type 1 standards or better. SPL is created from the same team who brought you the Audio Toolbox and ATB Plus. Store Results -- Uses the same powerful Save / Recall engine as our premier app, AudioTools. Allows storing GPS and time-stamped results, and exporting them to your computer. You can also use SPL with our calibrated iPhone measurement mic, iTestMic, or iAudioInterface. The screen flips if you turn the phone upside down, so that you can point the built-in iPhone mic directly at the sound source. *** Modes: Slow, Fast, Impulse, Peak, and Leq. *** Filters: A and C weighting, and 10 octave band filters. *** Includes a resettable Max field to track the highest reading. *** Includes a reference field (except in Leq mode) so that you can set a reference level and do seat-to-seat comparisons. The SPL meter can be fully calibrated. It comes preset with the calibration for a typical iPad, iPhone, and iPod Touch. Most iOS devices will be within a few dB of this reading. If you have access, even temporarily, to a calibrated sound level meter, just use the calibration field on the settings scree to match the meter, and you will be accurately calibrated. Also, see our other professional-grade audio apps: AudioTools, our premier suite of professional-caliber audio and acoustics test apps, Speaker Pop, to test speaker polarity, and RTA, a real-time analyzer for the iPhone. And, we have a group of calibrated, accurate measurement microphones, including iTestMic,iTestMic2, and iAudioInterface2, that allows full professional results for Type 1 or Type 2 measurements. This will allow measuring a range from approximately 30 dB SPL to 130 dB SPL. Each mic will include a calibration factor that you will enter into the SPL app for calibrated measurements. This mic will also work with Speaker Pop, our speaker polarity tester, FFT, RTA, ETC, and other acoustical measurement apps in our AudioTools app that is available now. Also, see our iAudioInterface2 system, which supports any pro test and measurement mic. Now includes an iPhone internal mic compensation filter, to cancel out the low-frequency roll-off present in the iPhone and other iOS devices. See our other audio apps, including AudioTools.
JAX Stereo Tool (AU)
This audio processing tool allows users to visually manipulate the stereo image of digital audio. It functions as a mastering effect, enabling real-time adjustment of stereo width and the recovery of mono compatibility. The app includes a correlograph for visual feedback and optimization.
- Visual stereo image manipulation
- Real-time stereo width adjustment
- Mono compatibility recovery
- Integrated correlograph for visual feedback
- Audio Unit (AUv3) plugin format
- System-wide availability
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JAX Stereo Tool is a visual Audio Unit plugin for manipulating the stereo image of digital audio. The distribution app comes with an embedded plug-in (Audio Unit) that is available system-wide when you install the app. You should be able to use it with most supporting host applications. Audio Units are Apple's recommended method for providing shared audio effects for applications and audio editors. You can load the plugin into any host application that supports at least stereophonic audio effect plug-ins (in Audio Unit format - AUv3) with its own user interface. JAX Stereo Tool has its main use as a mastering effect, that allows you to modify the stereo image of your audio by narrowing or widening it in a controlled manner. That is, the stereo output can be continuously adjusted in the basic function of pure mono to very wide stereo. This happens in real time and you can observe the result with the integrated correlograph, controlling and optimizing the audio thanks to this helpful additional visual information. One of the special functions of JAX Stereo Toolis to recover lost mono-compatibility. This technique is conceptually quite simple and effective but somewhat difficult to understand. Please read the manual for further details. The manual is shipped with the app or available on the product website at https://audio.digitster.com
Screenshots
Verdict
The clearest difference is rating: JAX Stereo Tool (AU) at 4.4 against SPL's 3.0. JAX Stereo Tool (AU) also leads on update cadence (every 11 days vs every 6 months) and price ($5.99 vs $8.99). On ads, in-app purchases, monetization model and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
SPL costs $8.99 and JAX Stereo Tool (AU) $5.99 up front. Neither carries in-app purchases, so what you see is what you pay.
JAX Stereo Tool (AU) holds the better App Store score, 4.4 against 3.0. That said, the two scores are not equally well evidenced: JAX Stereo Tool (AU) has 27 ratings behind it against 4, so its average is the more settled of the two. Written reviews point the same way: 68% of SPL's written reviews are positive against 80% of JAX Stereo Tool (AU)'s.
SPL ships an update every 6 months, JAX Stereo Tool (AU) every 11 days. The most recent releases landed on October 15, 2026 and October 12, 2026 respectively.
| Parameter | SPL | JAX Stereo Tool (AU) |
|---|---|---|
| Price | $8.99 | $5.99 — better |
| Rating | 3.0 (4 ratings) | 4.4 (27 ratings) — better |
| Positive reviews | 67.6% of reviews | 80.0% of reviews — better |
| Number of ratings | 4 | 27 — better |
| Update frequency | Every 6 months | Every 11 days — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Paid |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 15.0 | 12.0 — better |
| Further details — not scored | ||
| Size | 29 MB | 10 MB |
| Age rating | 4+ | 4+ |
| Developer | Andrew Smith | Jens Guell |
Customer experience
SPL
JAX Stereo Tool (AU)
In-app purchases
SPL
No in-app purchases
JAX Stereo Tool (AU)
No in-app purchases









