How to use REW to RTA a recording electrically?

[BenToronto]

Let's say I am listening on a MacBook laptop to YouTube (Moonrise Kingdom) and wonder how low is the big drum or using Quicktime player. How can I patch into the music electrically to do a real-time freq analysis with REW (rather than using a mic)?

In the past, the best method I've found is to plug into the headphone output, then a DAC/ADC back into a USB port. No easy way to listen with that set-up and seems pretty dumb way to do it, but works quite flat and clean with a MacBook, as is easy to verify with an REW sweep.

Can someone please tell me the right way to do the RTA with music playing?

Thanks.

B.

 

[DanDan]

Not sure about the term 'right' or what inputs you have available to you. I have used an iMac in the past to run extensive Frequency, Distortion, Phase, and Noise tests on a big old Radford STA15 Valve Hi Fi power amp.
As you have done treat the headphone output as a Line Out and find a Line In. If your Macbook does not have a jack input switchable to Line In...... you will have to use an interface.

 

[EarlK]

Ben,

There are already abroad range of stand-alone Spectrogram apps that will visualize your choice of audio input .

This one costs ( but looks great ).

3D Spectogram ( by faberacoustical )

 

[BenToronto]

Thanks. Fabulous display. Good apps from Faber (and I was very happy when REW* added a scope similar to Faber's).

But watching the simple FFT frequency plot made by REW dovetails with my info needs really well: "Say, what frequency was that big drum I just heard" or triangle or complex organ note**. And needs just REW that I am fairly good at using.

B.
* to which I do contribute every so often
** quite interesting to see the RTA of music sounds; organ notes show up as a bunch of narrow specific harmonic peaks coming from a specific group of pipes, unlike other instrument peaks that may sway about.

 

[Michael Boeker]

Another way is to use JRiver Media Center as your playback software. It has a built in spectrum analyzer that lets you see what is happening at all times. It also supports VST plugins and you can use more advanced spectrum analyzers such as Voxengo Span.

 

[BenToronto]

But how can I do the RTA with REW, a tool I am experienced at using and that integrates with a lot of other purposes?

OK, I suppose outputting the music using the headphone jack or out and in by USB/DACs is accurate enough for my purposes, but how to audition the music during the RTA with REW?

 

[DanDan]

Some sort of Y lead, the other side of the headphone out, split signal, Mult out we used to call it in the Studio Patchbays.

 

[BenToronto]

Not sure I have the that odd "Y" but might work nicely after digging out my headphones. Thanks.

My ordinary output to speakers is: laptop, USB, coax SPDIF, DSP, 4-gang vc, amps.... so no easy way to re-wire the speakers in there. Unless somebody made a USB "Y". Actually, a USB "Y" is the device I need. Some DACs have multiple audio outputs, like Creative Sound Blasters.

I am content to let this thread drop. I gather there's no software way to set up REW to do what I need. Ought to be - seems pretty evident that folks might want to RTA whatever is streaming (or just stored) from their computer (hint: should be able to mix L and R prior to RTA).

Thanks for helps.

Ben

 

[DanDan]

There are software apps which patch audio from one to the other. I am Mac only but there must be many more for PC.... https://rogueamoeba.com I suspect coax SPDIF can be Y split

 

[BenToronto]

The SPDIF is en-route to my DSP (the wonderful Behringer DCX2496 - a good audio life not possible without it, esp for those who play with REW)... soooo after that split, I'd have to convert coax SPDIF back into USB for REW to chew on.

 

[DanDan]

Perhaps the Behringer also has Analogue outs? Macbook audio is typically quite good, why not just use the onboard mic?

 

[BenToronto]

Yes, REW is geared up to do the RTA on a mic input - just as it (almost) always does, while the streamed/played music is playing. But using a mic in a room is one really lousy way to RTA a music file. Which is why I started this thread.

But it seems a simple matter for REW to access the internal streaming/playing file instead of the internal mic or any of the USB available. Some cogent reason why that is hard for the REW software?

 

[DanDan]

REW is extremely complex at this stage. It has become difficult to fully learn, and to operate properly or fully. Personally I would like to see a slow down or even a 'Lite' version. There are no Programs that I know of that have built in OS interconnectivity. But with the vast amount of streaming during the last year has seen that there are quite a few interconnect options out there. Rogueamoeba, SouceNexus...... ?

 

[sam_adams]

Yes, REW is geared up to do the RTA on a mic input - just as it (almost) always does, while the streamed/played music is playing. But using a mic in a room is one really lousy way to RTA a music file. Which is why I started this thread.

But it seems a simple matter for REW to access the internal streaming/playing file instead of the internal mic or any of the USB available. Some cogent reason why that is hard for the REW software?

The RTA will work with any input selected. Your best results will probably be achieved with a USB interface that has an SPDIF in and out. That way you will keep everything in the digital domain and avoid any analog conversions. The FocusRite Scarlett 8i6 comes to mind. There are probably other USB interfaces that have the same capability. Software solutions from Rogue Amoeba for Mac may also help you solve your issue.

 

[BenToronto]

Aside the intriguing idea of an SPDIF splitter*, the point is not to use an input (that's the big circle I'm trying to avoid). The music is streaming or playing in Quicktime inside the computer. Why can't REW tap into that? Can we please stick with that question. Why can REW only output its own signals and get input only from various jacks and not the internal music signal?

*Of course it does seem weird but not inconceivable to "intercept" the music in the link leading to the coax SPDIF (which has a few other names) going into the DSP box input.

 

[sam_adams]

Aside the intriguing idea of an SPDIF splitter*, the point is not to use an input (that's the big circle I'm trying to avoid). The music is streaming or playing in Quicktime inside the computer. Why can't REW tap into that? Can we please stick with that question. Why can REW only output its own signals and get input only from various jacks and not the internal music signal?

*Of course it does seem weird but not inconceivable to "intercept" the music in the link leading to the coax SPDIF (which has a few other names) going into the DSP box input.

Take a look at LineIn or Audio HiJack on the Rogue Amoeba site and see if either of those apps get you to where you want to be.