[onetrack97]

I'm just getting started but can't get past this problem. I've got a drop out/notch at 90 Hz. This was a nearfield mic placement, two different audio systems.

It's not the receiver or speaker because I duplicated this with a a different powered speaker connected directly to the laptop. I'm using the UMIK-1 USB microphone and have linked the calibration txt file.

It's not the microphone because I can go into the REW generator mode and I can hear the drop out on the speaker when I adjust the frequency up through 90 Hz.

So, it's either something to do with the computer setup (Dell running Win 7) or something that I have set wrong in REW.

Any ideas on this?

Thanks,
Scott

 

[AudiocRaver]

Looks a lot like floor bounce, the speaker is about 3 feet up, the sound bouncing off of the floor takes about 6 ms to get back to the mic and you get a cancellation at 90 Hz. Looks like.

 

[onetrack97]

I don't think it's acoustic, but something in software.

I can hear it out of the speaker when I sweep or set generator to 90 Hz. The sound level drops by 20 dB.
Tried with two systems, different electronics, different speakers, one an amplified monitor connected directly to the laptop.
Speaker on carpeted floor.
Microphone less than one foot from speaker.

It's like there is a notch filter turned on somewhere.

 

[AudiocRaver]

I don't think it's acoustic, but something in software.

I can hear it out of the speaker when I sweep or set generator to 90 Hz. The sound level drops by 20 dB.
Tried with two systems, different electronics, different speakers, one an amplified monitor connected directly to the laptop.
Speaker on carpeted floor.
Microphone less than one foot from speaker.

It's like there is a notch filter turned on somewhere.

Another possibility is that the monitor path of the sound card is turned on. The delayed path would also cause a cancellation that could look like that.

 

[onetrack97]

I don't see anything related to "monitor" in the sound card properties but I will play with some of the settings tomorrow.

Are there any settings in REW that would be related to sound card issues?

Thanks

 

[AudiocRaver]

It also could be:

• Two drivers with a 90 Hz crossover, like a sub and the main speaker
• Closely spaced
• Out of phase
• At 90 Hz, they cancel, giving the 20 dB notcoh

 

[onetrack97]

Wow, you definitely know your Audio.

In this case, it was the computer. Dell laptop had a driver call Realtek. I went into that control panel and turned it all off.

Thanks,
Scott

 

[AudiocRaver]

Glad you got it figured out.