Need help capture EQ Curve

[jriper03]

Hey guys/gals I have an old Philips mini Hi-fi system that I want to capture the EQ curves from. The reason is because the original speakers sound great with the "DSP" applied to them but when I run the speakers through a regular amp they sound not great. The audio processing board uses a TDA7437 which uses an I^2C buss for commands to set the the Bass Mid, and Treb levels. What is the best way to do this ? Read the digital signal and get the Bass Mid and Treb level commands, or tap the output line level signal coming out of the audio processing board? And then what How do I inject a signal and see what is happening to it in terms of EQ?
Links
https://www.google.com/url?sa=t&rct...e-Manual.pdf&usg=AOvVaw2l4WvtwncByukmTfOb0xDk


TDA7437 PROCESSOR Datasheet pdf - AUDIO PROCESSOR. Equivalent, Catalog


Any info would be a great help

Thanks

Julian A Ayala

 

[MarcelvdG]

Play a test CD with pure tones with different frequencies and equal levels and measure the signal at the loudspeaker terminals, if you have the equipment to do so? It's not really a DSP but a digitally-controlled analog filter, but maybe that's why you used quotation marks.

You could also try to reverse engineer the board by checking what filter components are used and looking up in the TDA7437 datasheet what those do.

 

[jriper03]

Yes thats exactly why I put DSP in quotes LOL. I appreciate the response. Yes I had some things in mind like Using REW and do an input sweep, but instead of using a Mic input I use a line level input, but Im not sure of the details. Also looking at the schematic I think you are right I am not sure that tapping the output pins from the TDA7437 will help me.

 

[jriper03]

Yes thats why I put DSP in quotes LOL

 

[AllenB]

That's right. Run a tone sweep through it. Measure the output. Do it all at line level but watch your levels as you don't want to introduce non-linearity or noise. You may also want to have an absolute reference between takes, unless this is just one curve you're doing.

 

[jriper03]

Ok so I was able to get a curve from the line level, I tapped into the signal right before it gets to the power amp See example. Now how do I use REW to generate an equalization curve for lets say a mini-DSP. Im not trying to correct this curve I want to mimic it.

 

[MarcelvdG]

No idea, as I never used REW. It looks similar to a second-order high-pass at 60 Hz with a Q of about 3 cascaded with a shelving filter centred around 2 kHz that lifts the treble about 3 dB.

 

[JMFahey]

Matches what could be expected to "improve" a speaker cabinet.

 

[jriper03]

Thanks for your input Marcel, and JMF.