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Originally Posted by Radio Wrangler
That is a complicated circuit with several time constants close enough together to interact, so a normal manual calculation is either going to be a very involved full analysis, or the usual bode-plot approximations are going to give errors about as big as the amounts of shaping in the midband.
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You're right; it is complex. Certainly, I wouldn't want to produce a complete analysis of the whole circuit by hand, but here, we just had to approximate the difference between 2 components fitted and not fitted, and it only took 30 seconds to come up with a ballpark figure for the change at 10kHz...
My back-of-the-envelope approximation was crude: just using a bit of Ohm's law and making a few assumptions allowed me to simplify the circuit and get to a point where I could see a worst-case change of about 2dB. Refining the simplifications - or running a simulation or real test - altered that figure by only a small amount. Often, the rough answer is close enough, providing you were lucky with your assumptions...
But it gets
really interesting when you consider the turnover frequencies of the capacitors. It doesn't take long to realise that they are turning over in the sub-1kHz region, just as the plots show. So it's not about the HF after all
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I was never a fan of Grundig, they seemed to do too much messing around. I suppose a bit like the Bose radios of their day, although without that level of marketing bull. Oh crikey! That's torn it... I've mentioned the B-word!
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Generally, Grundig did a good job with the equalisation on the smaller sets, but larger sets like the Yacht Boy seem to suffer from over-blown bass (presumably that was their "house style" - perhaps to help sell the large radios over the smaller ones?).
But "fixing" the N210 was easy - and worthwhile, given how ubiquitous they are. I've lost count of the number of discussions about Yacht Boy Bass we've had on this forum alone, so it's good to have some objective measurements on record, along with some options for those who wish to experiment
As for Bose: Buy Other Sound Equipment