# Questions about sound card input and HDMI output



## prattwd (Mar 31, 2014)

So I was able to get the multi channel output from my laptop's HDMI port working fairly easily. I have 2 questions though that I can't seem to find an answer to on the forum:

1. When outputting through hdmi and using the line in on the sound card for the SPL input, do I still need to do a sound card calibration? If so, do I still follow the steps outlined in the help manual or are there some extra considerations?

2. When using hdmi outputs, is it still important to use a timing reference? If so, how would I set that up? Seems like the only thing I could do is set up a reference using the line out and line on the sound card but I'm not sure that really works in this situation.

Thanks for the awesome setup tutorial.


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## Sonnie (Apr 11, 2006)

Hi prattwd... and welcome to the forum.

The thread in which you asked this question was probably not the right thread, hence the delayed response. I have moved it to it's own thread.

Are you referring to plugging the mic or SPL meter into the sound card on your computer? What are you using for your microphone?

The HDMI output won't have anything to do with the sound card input, those are two separate things, so your question is somewhat confusing.

Do you have a desktop or laptop? What is your sound card... what kind of inputs?

Typically we would use a USB mic and no sound card calibration would be needed, but if you are using a USB sound card for a separate mic or SPL meter mic, then you would want to loop it via the REW Help File instructions and generate a calibration file for it.

For HDMI outputs, I am not sure what you are referring to as "timing reference". You would use the HDMI setup tutorial provided by miniDSP and REW will generate the sweep to the appropriate channel you select within REW, based on those instructions. There is nothing more to do other than measure that sweep with your mic. There is no "timing" involved. If it ain't mentioned in the instructions, don't worry about it... no reason to add any confusion to the process, if you know what I mean. :T


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## prattwd (Mar 31, 2014)

Sonnie-

Thanks for the reply, very insightful. I should have been more specific in my post, sorry. I have attached a quick diagram of my setup. This was meant to be a real quick setup put together with things I already have as a proof-of-concept to learn the basics before I invested in upgraded equipment (i.e. a USB mic or sound card).

As you can see, I am using a RS SPL meter plugged into the right channel of my mic input on my sound card. For my output to my AVR, I am using the HDMI port so I can access each speaker in my 7.1 system. My first question was about needing to calibrate my sound card and I think you answered that. Since I am using the input on my sound card to bring in the recorded sound, the answer is "yes". I thought that would be the case but I was a little confused about whether or not when I calibrated the sound card if I also needed to include a loop back from the HDMI output to account for any distortions introduced by that hardware.

The second question was about whether or not I needed a timing reference with my setup. I ask this because it shows up in the non-HDMI setup material you have in your help guide and because when using the ASIO connection, there is a place for the user to select the Timing Reference input and output. As you can see from my drawing, I routed the left channel of my headphone jack to the left channel of my sound card mic input jack and used them as the output/input for the timing reference. I have no idea if this is still necessary with my setup (or even when using a USB mic). The link you provided that shows the HDMI/UMIK-1 setup doesn't really go into this. My setup seems to be working. I can take measurements that seem reasonable. I just want to make sure I am not missing anything.

As an aside, it would be really nice if the user could select multiple HDMI channels to output to. That would allow us to easily test say a sub/main configuration or sub/main/center configuration. Just a suggestion :bigsmile:


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## Sonnie (Apr 11, 2006)

I have not seen too many laptops that work well, but if you do the sound card calibration, it might. I don't think you need to loopback from the headphone out to the mic input.

I am not familiar with the reference settings, but my guess is leave them at the default. 

For running the sweep through multiple channels, just change the driver back from ASIO to Java and it will run through all speakers. You will want to disconnect the ones you do not want the sweep to run through. For movie setups, I generally look at the center plus sub... then for music (if I use Stereo and not Pure Audio) I will look at the front or left speaker plus the sub. :T


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