I am playing around with some sweeps tonight because I have a major issue between 40 and 60hz with some hardcore ringing. Is this down to the room or something else. The rest off my sweep is cool. This is with Audyssey EQ only on the receiver. No BFD EQ. The graph has a time length 1000 m/s and its still there.
I am going to do all the measurements off my room tomorrow night but the room is 18 feet 9 inches wide, the subs are located in each corner facing inwards off the room. The LP is 9 feet away from each sub which is the centre off the sofa.
The room is 20 feet long but there is an understairs cupboard at the rear right hand side.
It doesn't seem that the ringing you have is somehow connected with the dimensions of the room. If you carefully observe, the amplitude remains unaffected. I believe it is hum noise from the mains. Do you have any kind of transformer of electrical appliance nearby? Check it out...
The mains socket is behind my left sub and I have a tacima 6 socket conditioner which all my amp, receiver, tv etc... is connected to it. How do I check and what first.
The wierd thing is that it is the same for 100hz and 150hz too.
Since REW takes in-room measurements, it’s noise that apparently is loud enough that it should be audible. If it’s not from the mains, like John said it could be the AC system, your refrigerator or even something from outside the house.
Harry is spot on, that is mains hum (at 50, 100 and 150Hz). If you see any feature in a waterfall that is constant over time it is an interference tone, mains hum is the usual culprit but others can include air conditioning systems or even something like a car outside with its engine running.
It could be a hum loop involving the measurement PC, if it is a laptop try runnning on batteries. Beyond that, try disconnecting items from your receiver to see what helps - you can use the RTA view on REW to see what is happening to the levels at 50/100/150 as you disconnect things. I'd start by disconnecting the Sky HD box.
I looked on my previous graphs form other subs and I never had it before. I put the rta feature on and even when I turn off all the sockets in the room it still shows a massive spike at 50hz. The only thing I have changed since is the EQ.2 hpf, step down voltage transformer and that is it.
John I have disconnected the BFD already as I wasn't using it.
In the RTA window the hum at 50hz is showing at 65db. Yulks. I know zero squit about electrics which is a pain. I may have to get an electrian in to find out what is causing it.
If you disconnect the REW output connection from your laptop is the 50Hz signal still there? If so, it is acoustic noise that the mic/meter is picking up. In that case, switch off the sub and see if the noise is still showing, if it is then the source is outside your system, if it goes away it is a ground loop within the AV system somewhere - the thread on BFD hum has lots of possible causes and cures for that.
When I disconnect the phono from the reciever which goes into the output off the sound card it is still there. When I turn the sub off it is still there.
When I turn the plug off which has the conditioner connected for all AV equipment it is still there. Also when I turn the other plug off it is still there.
So I can only presume it is something outside this room.
The step down voltage convertor is for the EQ.2 hpf I bought from the states. Even when I turn that off at the wall it is still there.
I am using a phono lead which has single lead one end and a red/black the other. When I plug in the red I get the hum. When I plug in the black I don't.
Well, the steady-state signal is gone, so it looks like you had a bad cable. But on the other hand, you shortened the window from 1000 to 300 ms, so it’s hard to tell for sure...
One other thing I have noticed is that when I connect the EQ.2 in the chain I can hear a hum coming through the subs. With it disconnected it goes away. It is a similar hum that I get with the BFD connected.
I will have another look at the BFD hum thread again.
It was a pretty cheap cable to be honest. I am going to buy another cable this weekend and see if that helps. There is still a slight hum there but hopefully the new cable will show that up.
Is there anything that produces audible hum in the room? Do you have any kind of fluorescent lights or electronic dimmers? I believe it is more than obvious that something like that is happening. You can as well check with the RTA module. A spike should be clearly visible at 50Hz....I hope you'll sort this out...
The spike in the RTA was originally 65db which is pretty loud. When I swapped the red lead on the phone lead with the black one it reduced alot but it was marginally still there as you can see in the graph.
No other fluro lights or electrical dimmers in the room. When I connected the BFD when I first got it a year or so ago I noticed a very small hum through the subs but ignored it as it was not audible enough from where I sat. But even then it didn't show up a spike in the waterfall. I get the same hum when the EQ.2 is connected.
I will take some more measurements with a longer decay time to see before and after so you can see how much is still left.
cheers
Graham
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