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Discussion Starter · #1 ·
I'm trying to measure Thiele Small Parameters with REW. There's a tutorial in the REW support manual.

I cannot find a USB soundcard that has a stereo (TRS) line input/microphone INPUT.
The line inputs are only available on the old school desktop PC's motherboards or on those old PCI Soundblaster cards.
Even my Macbook Pro only has a mono (TS) input.
So I cannot run TSP measurements using a laptop.
I've tried several USB adapters and they don't work.

Anyone here have any luck with this?
 

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Discussion Starter · #3 · (Edited)
In the REW diagram it shows
Output has left and right (TRS)
Input has left and right (TRS)
They omitted the shields for some reason.
also that cable seems incorrect to me. Maybe someone can verify if that wiring diagram is correct.

a mono microphone input does not have left and right it only has +/- (TS)
I’ve spent a week trying every single setting and preference combination with a stereo output and mono input, nothing has worked.

and I found this:

 

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Discussion Starter · #5 · (Edited)
REW Impedance Measurement Guide

Windows 10 laptop (internal sound card did not work for REW impedance measurements)

Ugreen USB Soundcard

REW 5.20.6
 

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Apologies, I thought I replied to this yesterday. Must have forgot to hit “Post.”

The REW diagram shows the soundcard inputs and outputs are unbalanced (TS). I’m not very familiar with REW’s TS Parameters function, but I expect that you need a USB audio interface like the Behringer U-PHORIA UMC22 or similar, not a device like the one you linked.


Regards,
Wayne
 

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Discussion Starter · #7 ·
Apologies, I thought I replied to this yesterday. Must have forgot to hit “Post.”

The REW diagram shows the soundcard inputs and outputs are unbalanced (TS). I’m not very familiar with REW’s TS Parameters function, but I expect that you need a USB audio interface like the Behringer U-PHORIA UMC22 or similar, not a device like the one you linked.


Regards,
Wayne
99% of PC inputs are mono microphone TS inputs, so this double stereo (TRS) requirement should be clearly stated in the guide. a TRS input is called a LINE IN.
Also that diagram is confusing. They are not TS unblanced jacks.
Apparently those oval/ellipse looking things are the common shield contacts. I have never seen a contact illustrated in that manner.
For example :

First the output stage would require the RIGHT (RING) contact connected to the Rsense (IN) together with the input stage LEFT (TIP) .

Then you would connect the output stage SHIELD together with the input stage SHIELD

Then the input stage RIGHT (RING) would connect to the Rsense (OUT) together with the positive speaker lead.

Finally the input stage SHIELD would connect directly to the negative speaker lead.
 

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Also that diagram is confusing. They are not TS unblanced jacks.
Yes, they are unbalanced. Balanced would have three connection points for each jack: Signal (+), signal (-), and shield. As you can see, there are only two connection points for the jacks: The tip is signal (+) and the “oval rings” are the shield, which also carries the signal (-).

Thus, a “RIGHT (RING)” connection does not exist. There are only tip and sleeve connections in the diagram.

a TRS input is called a LINE IN
A line input can be TRS, but that would only be for a specific piece of equipment. A TRS line input is by no means universal, or anything even close to that. As far as I can tell, it would probably only be seen with computer-related equipment. TRS inputs are non-existent on stand-alone audio equipment.

It might be easier to visualize the connections in the diagram as a soundcard that has four RCA jacks - two for input, two for output.

As I noted, and as you’ve discovered (Post #3), your existing device is not going to work because it has a mono input, while the REW diagram shows that a stereo input is required. You need an outboard stereo soundcard.

Regards,
Wayne A. Pflughaupt
 

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As Wayne posted, you do not need a "stereo" audio interface.
You need an interface with 2x inputs and 2x outputs. Each of those I/O is mono.

Anything looking like this will do, no need to spend the big bucks.
Light Product Audio equipment Font Red
 

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Discussion Starter · #10 ·
I used a Vantec 7.1 USB Soundcard

I hooked it up like this (photo attached below)
wired with two stereo TRS adapters to the MAIN SPEAKER (OUTPUT) [TRS] and the LINE IN (INPUT) [TRS]
Seems to be working. It's late so I'll report back tomorrow but it's the first time I've accomplished an Open Calibation and a Short Calibration without any errors.

Thanks guys.
 

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Discussion Starter · #11 ·
They should also include this screenshot in the REW Impedance Mesurement Guide

I'll edit this post if something changes, but so far, these are the correct soundcard Input/Output preferences that correspond with wiring diagram above.
 

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