Gold

iOS for test and measurement
« on: December 28, 2018, 01:27:28 PM »
I thought I would start a thread on performing audio test and measurement with iOS.  Here are some reasons I like iOS.

1. I don’t have a lot of room on my bench and iPads and iPhones are compact. It also makes a great “to go” setup.
2. iOS is a closed system. If you download an app and it doesn’t work it’s probably a developer problem. I’m not computer savvy so that’s a big plus for me.
3. Once you purchase an app it is available on all supported devices tied to the same account. That way all software is available on any compatible device. Some software is iPad only. One thing that has always bugged me about personal computers is that although it’s possible to run multiple pieces of software simultaneously it often is not practical. Not enough connectivity or the different software doesn’t play nice together. With iOS you just get a new device for a new function.

The main disadvantages as I see than are that iOS devices can be pricey and there are not a lot of software choices.

Since test and measurement is mostly a real time exercise you don’t need a lot of memory. This makes the least expensive model useable. There are also refurbished  older  models for deep discounts.  You can pick up a perfectly useable iPad for less than $150. With the move to USB-C the closed system will open up a little allowing external storage and more peripherals.

I’m in the middle of expanding what I have. I will wait to post some of my experiences with specific software and hardware until after I can do more of a round up.

Anyone else trying to do this?


cyrano

Re: iOS for test and measurement
« Reply #1 on: December 28, 2018, 03:38:52 PM »
I totally agree with that.

The latest ipad I bought, was 30 €. I use it for remote control of Reaper and RME's TotalMix.

But I'd love to use it for measurements.

The only gripe I have with it, is that finding anything through the appstore is next to impossible. And even when you know the name of the app you're looking for (and spell it right) it's happened to me that search shows zero results.

That results in finding apps through Google, but not all apps seem to have a website, so you'll still miss out.

I've dabbled a bit with acoustic measurements, mainly because the iphone is always with me. And the results are useful, even with the built-in mic. With an external mic, it's easy enough to reach a +/- 1 dB accuracy. And that's enough for most measurements I need.

Have a look here:

https://blogs.cdc.gov/niosh-science-blog/2014/04/09/sound-apps/

And here:

http://www.acousticfrontiers.com/2011315free-apple-ios-acoustic-measurement-app-created-by-studio-si-html/

https://itunes.apple.com/us/app/splnfft-noise-meter/id355396114

https://www.studiosixdigital.com/

Why is it people love to believe and hate to know?

Gold

Re: iOS for test and measurement
« Reply #2 on: December 28, 2018, 05:06:44 PM »
Thanks for the links.

I have a StudioSixDigital setup with the iAudiointerface2.  I’m still sorting through it and feel like I should hold off posting a review until after I have some more time with it.

I just ordered. $99 2 in 2 out Presonus USB 2.0 interface.  I’ll try to get that going and see how it goes.  When that gets here I’ll try it with SSD AudioTools and Auria DAW. Auria looks remarkably capable for $25. The pro version adds MIDI and other composition tools so isn’t necessary for work with audio files.

I also want to try out some different methods of networking devices together.


john12ax7

Re: iOS for test and measurement
« Reply #3 on: December 28, 2018, 08:13:00 PM »
I'm not too familiar with iOS,  but REQ Wizard does have a Mac version,  so that might be worth looking into.

On the hardware side, it really depends how accurate you need the measurement to be.  You generally need test gear that exceeds what you are measuring, or a good way to calibrate out the shortcomings.

Gold

Re: iOS for test and measurement
« Reply #4 on: December 28, 2018, 09:25:17 PM »
I'm not too familiar with iOS,  but REQ Wizard does have a Mac version,  so that might be worth looking into.

On the hardware side, it really depends how accurate you need the measurement to be.  You generally need test gear that exceeds what you are measuring, or a good way to calibrate out the shortcomings.

I don’t want a full computer on the test bench. I don’t have space and I would destroy it within a couple of months by physical damage. I tried REW on the Mac a while ago and didn’t like it. Ive been following the update thread and the latest updates are a great improvement. I still don’t want a full computer on the test bench.

I have an AP Portable One but it doesn’t have FFT capability.  I primarily want an iPad setup for FFT.  I’d also like something that is portable for general testing of level, distortion, crosstalk, etc.  The Portable One seemed Portable 25 years ago but isn’t now.

Even a cheap USB interface is close enough for me for noise and distortion. I’m a builder not a designer. I have enough meters to figure out gain structure and levels. Like REW the most comprehensive software  in iOS is geared towards acoustic measurement. Line level audio was an afterthought. Most of the Y axis are calibrated in dB SPL. I’m figuring out how to make the scales easy to read in dBu.

john12ax7

Re: iOS for test and measurement
« Reply #5 on: December 28, 2018, 10:25:33 PM »
I like ARTA as a  measurement tool.  It's  for windows,  but the website suggests it works on Mac and Linux with an emulator.

Gold

Re: iOS for test and measurement
« Reply #6 on: December 28, 2018, 11:10:36 PM »
I have a Windows 7 laptop. I have a Mac Airbook.

I’m not interested in Windows, OSX or Linux. This is for iOS.  iPad and iPhone.

Take a look at this for an idea of what is possible.
https://www.studiosixdigital.com/
« Last Edit: December 28, 2018, 11:19:00 PM by Gold »

john12ax7

Re: iOS for test and measurement
« Reply #7 on: December 28, 2018, 11:26:22 PM »
I’m not interested in Windows, OSX or Linux. This is for iOS.  iPad and iPhone.

Sorry,  completely missed the distinction between iOS and OSX.
« Last Edit: December 29, 2018, 02:34:42 AM by john12ax7 »

rackmonkey

Re: iOS for test and measurement
« Reply #8 on: January 01, 2019, 04:02:25 PM »
one big caution about buying an older iOS device: any newer software you might want to run on it may not be supported on the most recent version of iOS that the older device is capable of running. For example, if you buy an older iPad mini (say, version 2 of that device), the most recent version of iOS you would be able to run would be something like iOS 6.x.x. Look at the minimum OS requirements of a sampling of iPad apps currently in the App Store and you’ll find that many of them will require a minimum version that’s higher than what the device can run. So you’re boxed out of running any of those apps.

Even when the older device can run an iOS version supported by a given app, you’ll find that the app is often buggy when run under older iOS versions. It’s just too much of a testing burden for developers to thoroughly test all supported iOS versions for a given app or app update for them to catch bugs on the older versions. So they tend to concentrate on the newer iOS versions for testing because most iOS users update their devices/OS regularly.

It’s not quite “planned obsolescence”, but the net result is the same.

BT
Whether you think you can or you think you can't, you're probably right.

Gold

Re: iOS for test and measurement
« Reply #9 on: January 01, 2019, 04:23:10 PM »
one big caution about buying an older iOS device: any newer software you might want to run on it may not be supported on the most recent version of iOS that the older device is capable of running.

Good information. I've been learning about some of the ins and outs of iOS and the hardware. It seems like the major dividing line is the 64 bit processor. I have an iPad Air2 so I think I'm good for a while.  At the other end of the spectrum the newest iPad Pro with USB-C might not work with devices that have lightning connectors.

I've gotten much further with this setup. I've spent a lot of time with it over the past week. I'm still working some stuff out and have some questions I'm hoping the developer will answer. So far so good though.

Another thing I learned is that iOS supports 24 input channels but only 2 output channels. I hope that changes soon for more output channels.


rackmonkey

Re: iOS for test and measurement
« Reply #10 on: January 02, 2019, 01:46:55 PM »
Yes, the Air2 should be fine for the foreseeable future.  Keep us posted on your findings.

BT
Whether you think you can or you think you can't, you're probably right.

cyrano

Re: iOS for test and measurement
« Reply #11 on: January 02, 2019, 06:32:46 PM »
Another thing I learned is that iOS supports 24 input channels but only 2 output channels. I hope that changes soon for more output channels.

I'm pretty sure that's not a limit of iOS, but of the software you're using. 
Why is it people love to believe and hate to know?

Gold

Re: iOS for test and measurement
« Reply #12 on: January 02, 2019, 09:16:11 PM »
I'm pretty sure that's not a limit of iOS, but of the software you're using.

I read that on the Auria DAW forum. The post was by a developer in answer to someone who asked why they saw all their interface  inputs but only two outputs.

I don’t have a multichannel interface so I can’t test it. On the Auria website there is a list of interfaces that have been tested. The answer wasn’t “get one that works”.

abbey road d enfer

Re: iOS for test and measurement
« Reply #13 on: January 03, 2019, 11:24:26 AM »
When that gets here I’ll try it with SSD AudioTools and Auria DAW. Auria looks remarkably capable for $25.
Is it for assessment of the global operation, or is Auria capable of doing measurements?
I must admit I am not familiar at all with Apple products (actually rather refractory due to their planned obsolescence policy and the blind devotion of many followers), but I'm ready to cross the Rubicon if it proves a better solution than a PC with RMAA and REW.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

cyrano

Re: iOS for test and measurement
« Reply #14 on: January 03, 2019, 12:03:42 PM »
I read that on the Auria DAW forum. The post was by a developer in answer to someone who asked why they saw all their interface  inputs but only two outputs.

I don’t have a multichannel interface so I can’t test it. On the Auria website there is a list of interfaces that have been tested. The answer wasn’t “get one that works”.

I've never tried it, but I have USB channel restrictions in my head. USB2 is restricted to 54 I/O total, iOS brings that down to 30. Since you can only have 24 inputs, that leaves (at least) 6 outputs.

These are channel number restrictions for RME devices, based on hardware restrictions. If you need more channels, you need to use Firewire, Thunderbolt, AVB, or Dante.

I'm familiar with Core audio on MacOS, which doesn't have restrictions and I believe Core audio on iOS is largely the same, but the hardware is the resctriction, as fi USB2 is less performant.

Maybe an old post on the Auria forum?

I've read on the audiobus forum that their devs promised to have multi output available "soon". Whatever that may mean. And that was a post from november `18.
Why is it people love to believe and hate to know?

Gold

Re: iOS for test and measurement
« Reply #15 on: January 03, 2019, 12:21:12 PM »
Is it for assessment of the global operation, or is Auria capable of doing measurements?

but I'm ready to cross the Rubicon if it proves a better solution than a PC with RMAA and REW.

Auria is a DAW. I plan on using that for audio playback.

I’m using AudioTools by StudioSixDigital for measurement. It has a single channel of a stripped down version of Smaart and another  FFT module. The software is designed for location acoustic measurement and has a lot of other fancy stuff for that.

From reading the REW thread it looks like it has come a long way from when I tested it. It seems more capable than AudioTools for line level measurements . The Y axis in AudioTools is in dB SPL and there is no way to change that.

The main advantage to iOS is its portability and ability to set up discrete devices to take measurements running the same software without having to have another liscence for each version.  Apple policy is that all software is available on all devices registered to the same account.

I think iOS has the potential to host a great bench measurement system. IOS is more like button per function and you don’t need to take up bench space with a laptop.  Or keyboard and monitor.

I think there is a business opportunity here to make a great software /hardware combination  for bench measurement. It’s a lot easier to drag an iPad behind a rack than a PC.
« Last Edit: January 03, 2019, 12:38:13 PM by Gold »

Gold

Re: iOS for test and measurement
« Reply #16 on: January 03, 2019, 12:28:24 PM »

I'm familiar with Core audio on MacOS, which doesn't have restrictions and I believe Core audio on iOS is largely the same, but the hardware is the resctriction, as fi USB2 is less performant.

Maybe an old post on the Auria forum?

Could be. I was only passing along what I read from what seemed like a reliable source.

Gold

Re: iOS for test and measurement
« Reply #17 on: January 03, 2019, 11:44:03 PM »
One capability of AudioTools is it can have multiple devices communicate over WiFi . You can have multiple microphones set up in a hall and have all the plots on a single screen.  Without running any cables. This would be great for testing large digital or line level systems.

Gold

Re: iOS for test and measurement
« Reply #18 on: January 05, 2019, 05:49:38 PM »
Here's a round up of where I am with this. The software for FFT is designed for a calibrated microphone input. The Y axis is in dB SPL. The iAudioInterface2 has two TRS jacks. One is input and the other is output. They can be configured for balanced mono or unbalanced stereo. There is an output level pot on the interface.

In the setup page it is possible to set a line level reference level. Unfortunately once you are inside the FFT module or the single channel Smaart module you can't use the calibrated level. You have to figure out the gain structure and adjust accordingly. That's not very measurement friendly especially since the output pot is touchy and can be easily bumped.

I don't have a lot of experience with FFT measurement so I'll refrain from evaluation the features of the FFT module and the Smaart module. They seem fairly full featured to me. I don't think that's an issue.

I wrote the developer last week with some questions and a couple of suggestions to make it more line level friendly. I got no response. I guess he has no interest in making it line level friendly. I think that's a shame because it doesn't seem like it would take too much tweaking to get it there. All the ingredients seem to be there. With a little reaaranging it could be great.

That motivated me to ask a couple people I know who could get a project like this going or know people who could. Much to my surprise they both thought it was an excellent idea. If I had money I'd finance the development because I truly believe that the first one there with a good iPad measurement system will have a nice little business on their hands.

The $99 audio interface I ordered isn't here yet. When I ordered it, it said "in stock". After I checked out it said "on order for manufacturer". Bastards. So I can't try the cheap interface.

The FFT module in AudioTools is either $15 or $25. I can't remember. If you have a USB 2.0 compliant interface and an iPad or iPhone it won't break the bank to try it.

In conclusion I'd say this isn't ready for easy line level FFT measurements.


 

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