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Hello,

I just finished building a pair of speakers and I wanted to take a look at the spl spectrum. I installed REW, got a USB-mic with calibration file and started measuring.
When measuring the speakers, I noticed a dip at 500Hz, 4000Hz and around 13-14 kHz. I measured different other speakers in different rooms to find out if it was a fault in my speakers' design or with my measuring setup.
Seems like all the measurements get a dip at those frequencies. I suspect that it has something to do with the sound card from my computer (internal soundcard on laptop).

I read that you can not calibrate internal sound cards and that it isn't even necessary to do so. But I have no explanation other then the soundcard being the culprit. Can I manually calibrate the sound card? I could measure the voltage output from the 3.5mm jack? I already installed a program called Equalizer APO that I could use to boost certain frequencies.

What are your ideas on this?

Kind Regards,
Reinhout
 

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Seems like all the measurements get a dip at those frequencies. I suspect that it has something to do with the sound card from my computer (internal soundcard on laptop).
Hi Reinhout,

This is typical stuff. It’s not the sound card. It’s the room. Take your speakers to a different room and measure them, and the graph won’t look the same.

Regards,
Wayne
 

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Hi Reinhout,

This is typical stuff. It’s not the sound card. It’s the room. Take your speakers to a different room and measure them, and the graph won’t look the same.

Regards,
Wayne
Hello Wayne!
That's what I have thought about..I started in the living room measuring my new speakers. Saw the dips so I measured a Sony system in the living room as well. Went on to my desk (different room) and measured a cheap logitech 2.1 system. And yet again the dips are on the same frequencies. That's why I'm coming to you guys. I don't get it. Different speakers, different rooms, same dips at the same frequencies.
 

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A minor point first: it is best to select the output device, output, input device and input you are using in the REW soundcard preferences rather than leaving them as default. The default device can change as devices are connected and removed so you can end up not using the interface you thought you were using.

The problem you are seeing is probably because you are using two sweeps. You say you are using a USB microphone, so the input device is not the same as the output device. The two devices will have slightly different clock rates, so when REW tries to align the captured data from each of the two sweeps they will usually not align precisely and cause a kind of comb filtering. Use single sweeps and you should see better results. Multiple sweeps are really only applicable when input and output are on the same soundcard or when using devices that have a common master clock.
 
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