Help with REW

[rock68]

I was wandering if anyone could point me to a thread or help me with REW without a BFD device. I just want to graph my sub with a laptop, receiver, and SPL meter if possible. Not sure what connections I need as in adapters and such and how to run through the receiver. Hopefully I don't need an external sound card. Thanks!

[Otto]

Hi rock,

Not sure if you had a chance to read the help files. Here's the link for the REW files, and here's the link for the BFD itself.

You won't need an external sound card if your existing card has a line out and a line in -- but you can't use "mic in" for the input. As long as you have line out and line in, it'll most likely be fine.

Have a look at the help pages and let us know if you have any questions.

Good luck!

[brucek]

Hopefully I don't need an external sound card

I suspect you will need an external soundcard, since most laptops only have a microphone input and REW requires it have a line-in jack.

Take some time and read the setup section in The REW HELP FILES. The connections are shown there.

Generally, you feed the line-out of the soundcard into the AUX or CD input of your receiver, and then you feed an SPL meter (Galaxy CM140 or RadioShack models) into the line-in of the soundcard.

brucek

[Spridle]

I have a Dell Laptop that came with a built-in Crystal WDM souncard. It only has 3.5mm jacks for microphone and headphones (no line-in or line-out jacks). REW works fine for me the Radio Shack meter. I can also use a calibrated microphone with an AudioBuddy preamp/phantom with no problems.

[brucek]

REW works fine for me the Radio Shack meter

Yeah, sometimes you can get away with it. SPL meters output a line level and a microphone input is looking for a very low signal level. Offtimes the mic inputs also provide a +5 volt phantom signal that may be a problem to the SPL meter.

The mic inputs offer very high gain, and as such are quite noisy. They usually suffer from very poor frequency response and so a soundcard calibration can be quite problematic. I don't know that I would trust the response from using a mic input. I would certainly check the impulse response to ensure my signal was sufficiently above the noise, and I would ensure a loopback test of a cable was flat after calibration.

For the price of an external soundcard, I wouldn't attempt a measure with a mic input.......

brucek

[Spridle]

My soundcard calibration is +/- 1dB from 20-20KHz. Also, here is an impulse graph generated from a 20-20KHz sweep of the loudspeakers and measured with a mic connected to the microphne input of the soundcard. Not sure what this graph tells me.

[brucek]

Great, I'm glad it worked out for you. I can't see the graphs too well because they are so small, but I'm sure its fine. Most aren't so lucky using a mic preamp with a line level input.

brucek

[rock68]

Thanks for the input guys. It's going to be slow to get this going but hopefully I'll have time soon. I am trying to get this setup and running on my current setup so I'll be ready when my PB13 comes in. Thanks again!