Hiccups on REW when manual sinewave testing.

[Chrisbee]

Hi

Yesterday I thought I would try and find the boarded floor's resonant frequency in my listening room. It's fun on films to feel the floor melting beneath our chairs. I thought I might find a way to make the IB do this by modifying the response with the the BFD.

The 16-46 was connected to the SB Live! soundcard Front socket and calibrated in REW to avoid overloading. I started from zero gain on the Bash because I'm careful about these things.

I set output in REW to -15 from -6 (once calibrated) to reduce level some more. At -6 I found the SVS was hypersensitive to gain on the plate amp. The siightest touch of the gain control and the poor sub made horrible noises on the pink noise calibration!

I set REW to Manual Test and Frequency Follows Cursor.

Then I took my wireless mouse to the listening position and started playing with frequency. Luckily I could still see my computer screen and the large digital readout in REW was very useful.

But I kept getting small hiccups from the subwoofer. It seemed to be almost frequency independant but occured more often at lower frequencies. I quickly dismissed bottoming out with a quick touch of the driver surround. The cone was hardly moving at these levels and I knew it could often move 5-8 times further on programme material.

So? What was happening here? What caused the strange intermittent "bock" noise? The gain control was at about 9 o'clock on the sub's plate amp and SPLs were only around 70-75dB uncorrected.

I never did find the floor resonance. Probably due to lack of adequate SPLs. The hiccups made me nervous about pushing levels any higher.

Thankfully the sub still behaves quite normally on music with no sign of the hiccups.

[JohnM]

Worth making certain the soundcard settings are not allowing any of the input to get fed back to the output and causing a feedback loop. Also wireless cards/devices can sometimes cause interference on the soundcard outputs generating glitches in the signals.

[Chrisbee]

Thankyou John.

I was using the standard settings on the SB Live! for REW.

Do you think the wireless mouse might have been responsible?

It made no difference whether I was close to the Logitech receiver or 10 feet from it.

[JohnM]

Possibly - the only similar problem I've seen is with my desktop PC, which has glitches on its audio output caused by the wireless card - I have to disable my wireless card to get clean audio.

[Chrisbee]

Thanks John.