First equalization and having trouble.. anyone help please

[thewire]

Can anyone make since of this video? It is a measurement on the SPL meter with C-weighting fast set to 70. The filters being used. The sweep is seen in the background of DVE and the Bass management sweep of the subwoofers. Does it look like there is a peak or it normal.

[thewire]

Looking again the meter was not shown in the video because it is flashing out of range. It flashes 80 from the 44Hz area all the way to 58Hz or higher then levels out.

[thewire]

The video does not help so maybe this will. Here is a measurement of my soundcard with the C-Weighting unchecked and no calc file next to a -20dB FS pink noise with the settings that I used to measure the subwoofers. It is a loop back of my right channel



Here is the -20dB FS measurement sweep with the same settings. Please tell me this doesn't look right.

[JohnM]

You can't really use a measurement sweep with an RTA plot, especially not when using averaging. Better off using the Pink Periodic Noise signal in the REW signal generator. You can set averages to None when using the Pink PN signal.

[thewire]

So the dip is a coincidence? Let me ask this then because I want to be sure things are normal and it is not my computer. Maybe you could tell me what sounds wrong and what may be the cause please? When I use the RTA mode my mouse is really slow and stuttering. It crashes my computer occasionally if I run other programs at the same time. Loud ticking noises are coming from the subwoofer when it is plugged into the computer as loud as 64dB or more. When I run sweeps is the progress bar supposed to look smooth? It does not. I have some money to get a new computer now (thanks to loosing my receiver) and if my computer really is giving me problems, it is more a reason to look into a new one.

[thewire]

Here are some computer pics. If I install my motherboard it will access out of date resources and cause my computer to have conflicts with Windows SP2.

[thewire]

Here is the pink pn you requested to clear up my previous post and some sine waves for your inspection.



Edit: Sorry forgot to turn off averaging for the pink pn. New graph with no settings for the pink pn.

[JohnM]

Those plots look fine, but you should change the mode from Spectrum to RTA 1/24th octave, the Pink PN line should then come out horizontal on a loopback.

The RTA mode is quite demanding for the processor as it is constantly analysing the data from the soundcard. You can reduce the load by using a smaller FFT length, but that will reduce the frequency resolution correspondingly.

When using any audio measurement software it is best not to run any other programs, for the software to work correctly there must be no gaps in the generated or captured audio, programs running on your PC can sometimes place heavy demands on the PC resources and leave it without enough time to process the audio data to and from the soundcard, which will cause invalid measurements.

Audio analysis also tends to use a lot of memory as it must generate and process large signals, If you were thinking about changing anything about your PC the first change I would recommend is more RAM. If you end up getting a new PC and it runs Windows Vista make sure it has 2GB of RAM.

[thewire]

Use 1/24, alright. That should help. You are correct that it is to much on my computer. Just running my media player listening to the RT Info Podcast, browsing the web and leaving Photoshop open sets my computer at around 25% usage. I don't run many when I measure but I almost always have had my browser running during testing. I will try without that being open in the future for more accuracy. Thank you for the tip also on the computer.

[thewire]

After I placed the next two subwoofers in the other corner things went wrong again. The low sounds were not that audible but the room was rumbling and the door was flexing out of control. The mid bass sounding like murrroooo-ka-thump. I decided to try like the instructions said in the manual and place one at the center wall midpoint, one each of the left and right midpoint, and I shut off one. That gave me response from 25Hz up with a few dips. One was about 4dB bellow from 40Hz to 50Hz but it was very smooth looking one. I turned back on the corner sub again and the 25Hz area went up and so did the dip. The subwoofers are not positioned perfect for the test and I did not touch the volume on any except the corner sub with the non THX amp for which is pointing at 2:00.

I used a -30dB sweep and the wave volume was so low I got error messages. It said something like 25dB low. I had setup the SPL meter using DVE again. It will take a long time to setup so I thought I would ask if this looks good to continue? There is currently a little bit of ringing around 50Hz but the subs are sort of hanging off some stands and the center is about 4 feet close.

Other ideas - I could also try the sub in the back corner also. Placing one on the back wall center midpoint will fix that 40Hz-50Hz dip also probably and might not require the 2.5dB boost and the 1dB one also. I would require a longer cable to place it there permanently and at the very least a new one to measure.