Soundcard and Cable lengths for SPL and AVR

**thsmith** · **09-25-08, 11:14 AM**

I am thinking of putting my laptop in another room which would mean my cable from the sound card to RS SPL meter would be 25' and from the Soundcard to the AVR is 16'.

Any concerns with these cable lengths ?

**zrzrzrzr** · **09-25-08, 11:18 AM**

I used a 25' cable to connect my SPL to my HTPC. . . But I also came up with inconsistent graphs. hahaha. I'm sure its more my fault than the cable.

**weverb** · **09-25-08, 11:22 AM**

Tracy,

How many threads are you going to start? lol....I use a 36' rca from my desktop to my mic/receiver. Should not be a problem.

**thsmith** · **09-25-08, 11:26 AM**

Yeah, sorry about that, I guess I am giddy with joy having found REW. Sounds like I should be ok with the lenth of cables.

If nothing else this post may prevent someone else asking as I did do a search and did not find the answer.

No new post until tonight, I promise

**weverb** · **09-25-08, 11:34 AM**

I should edit that to threads not posts. Post away with questions.

**Anthony** · **09-25-08, 12:15 PM**

You will get signal losses, but as long as it doesn't pick up any serious noise (power line hum for one) you should be fine.

I would use the long cable in place for your loopback measurement to calibrate the sound card. That way some of the signal losses will be included in your calibration file.

**thsmith** · **09-25-08, 12:41 PM**

Had not thought of using the 25' for loop back, thanks

**Anthony** · **09-25-08, 12:50 PM**

Ideally, your signal losses will be constant through the frequency band, but there is always a chance that whatever cable you use will attenuate more at the high frequencies than down low. Obviously better cable quality mitigates this, but usually we're stuck with what we have handy

You can also get into impedance problems with the microphone preamp of the SPL meter. The extra cable adds extra resistance and that can make it harder for the microphone to "drive" the input of the sound card. However, I doubt this will matter much for straight measurements. It will probably add some distortion, though.

But 25' isn't much. I've done runs of RCA over 50' with no ill effects. And video, which is much more succeptable to interference, signal loss, and impedance problems -- those can go over 50' without too many problems. As I said earlier, though, make sure to keep them away from power cords and other electronic devices (like don't drape it over a mini-fridge).

good luck and post some graphs when you have some results.

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