Lots of noise

[Tommy D]

When I set the level of the reciever to read 75db at listening position using the RS meter I get about 65db noise ( static and hissing). The sound card is SB Live 24. When I unhook the sound card from the reciever the noise goes away. Tommy D

[brucek]

Is the REW sweep level at -12dB and does your output level showing in the REW output VU meter look correct?

With the soundcard connected to the receiver and REW not transmitting any test signal, is there still static and hiss?

brucek

[Tommy D]

Sweep level is-12db and VU meter looks good. Noise is there with no test signal.

[brucek]

With REW not running and the soundcard simply connected to the receiver, does it make this noise?

With a cheater plug on the computer and monitor, does it still make this noise?

brucek

[salvasol]

If I use my laptop with the power supply I get a hum noise too ...

To avoid that, I run the laptop on batteries when running REW

[thewire]

Same thing here. If I run off the power adapter there is tons of noise. I use pink noise more often when using the adapter because it mask the noise and I can adjust the subwoofers/mic in real-time. My laptop runs off alot of power also. If I don't use the adapter it does not run my graphics card the best (I have read) but the noise does go away with the battery. I toasted a universal car adapter with my laptop that I was told would work by the store. They replaced it with another one. For very complex measurments I don't always have the luxury of noise free testing, unless I take a break while the battery charges.

[Tommy D]

Ok, I unplugged the power supply and it is quiet now but what did I do wrong? This a measurement of the subs.

[brucek]

You forgot to run the Calibrate SPL routine and set it to 75dB after the Check Levels routine.

You also need to use the standard graph limits of:
vertical = 45dB-105dB and horizontal = 15Hz-200Hz.

brucek

[Jailer]

brucek wrote:

You also need to use the standard graph limits of:
vertical = 45dB-105dB and horizontal = 15Hz-200Hz.

brucek

Only been around for about a week, but if I had a nickle for every time you post that............

[Tommy D]

Oops, I guess that's what happens when I work out in the heat all day. Must have fried some brain cells. I'll correct things in the morning before I work outside.

[thewire]

I didn't use the calculate SPL routine on my last post. That is not what I wanted to get at though. Since we have rewired the electical in the HT I now have a hum from the subwoofers when using my laptop battery but not with the AC power adapter. It is now complete silence using the adapter. A 60Hz and the fundamental 120Hz show up in my measurements most of the time still, even though I have checked the ground plugs and they are perfectly fine. Wierd huh?

[Tommy D]

That is wierd. You would expect the opposit, hum with the adaptor. I'll do some more measurements this afternoon.Tom

[Tommy D]

I had troubles posting the graphs on the lap top. The attachment section doesn't show even after signing out and logging back on. Any ideas?

OK, I got everything set up and running. The first graph is the subwoofers responce. The second is with the mains in the mix. Don't know what to think of the dip at 63hz. The xo is set at 80hz in the receiver and xo set max on the sub. Tom

[brucek]

Don't know what to think of the dip at 63hz.

Adjust the phase of the sub..............

brucek

[thewire]

Noise will effect the soundcard calibration, will it not? Will the soundcard calibration effect the waterfall? Should Tommy and I recalibrate the soundcard now?

[thewire]

The calibration for each my adapter and the power cord had shown different waterfall plots so I thought it a good idea.

[Tommy D]

For some reason my lap top decided to drop the attachment section of the reply. I can't attach any graphs with out e-mailing them to my desk top. What's wrong? Tommy

[atledreier]

About the 60-ish dip, that's probably the floor-ceiling node. Try adjusting the height of the listening position/microphone and see if it moves.