This started from
this thread.
I Thought we'd start a thread to compare the Frequency Response of different receivers/pre-amps.
Method: Basically its taking the Mic out of the loop and connecting the preamp outputs of your receiver to the inputs of your soundcard.
There are 2 ways we need to connect so we can get the measurements we are after.
1) RED line = this is for the full spectrum sweep and Mains when crossover is engaged
2) GREEN line = this is for testing what is actually getting to the sub when crossover is engaged
Note: do not connect both at the same time
Thanks to Brucek for the graph
There are 3 measurements that we can look at
1) Full spectrum sweep 2Hz -->20kHz]
2) Mains with the crossover engaged
3) Subwoofer with crossover engaged
A couple of things I did to keep things simple.
On the receiver
1) Set volume trims to 0.0
2) Set main volume to 0.0
3) Do not adjust volumes between readings(this will keep a reference for comparing)
On REW
1) Under 'Settings' Make sure No Mic calibration file is loaded
2) Under 'Settings' create a soundcard calibration file (include all cables you will use in the loop) load the file and run a sweep and make sure you get a dead flat line.
3) Under 'Measure', set measuring level(dB FS) to -10
4) Under 'Measure', set the End Freq(Hz) to 24,000
5) After the full spectrum sweep, set the 'Trace Offset'(under 'Trace Adjustments) so that the line around 1kHz is as close as possable to 0db on the graph(I had to use -84.8) This value will need to be input to the other measurements, do not change this number even if the other graphs don't line up with 0db(remember we measured at the same level so these differences are due to the crossover being in chain of processing) You can click the 'Add offset to Data' button if you like.
6) Under 'Graph Limits', set to:
Top = 12
Bottom = -12
Left = 2
Right = 20,000
7) After measurements and adjustments are taken click on the 'All Measured' tab and your ready to post
When posting add the Receiver/Pre-amp model information.
You can zoom into the graph to find -1db and -3db points.
You should end up with something like my next post.
Any suggestions are welcome,
Cheers
