Various people have complained about how crap the bass is on a Sony WM-D6C. I have looked at the schematics of the WM-D6C and conclude that there is a very simple and reversible fix to this issue.

Following on from lowering the bass level response on my AIWA HS-JX505, I've turned my attention to the Sony WM-D6C.

First of all a bit of background and an apology to all those readers who fall asleep regularly at math or physics class.

The fix relies heavily on capacitive reactance theory. This is derived from the formula :

Xc=1/2ΠfC

Xc = Impedance (Ohms)

Π = Mathematical constant Pi (~3.1415926536)

f = frequency (Hertz)

C = capacitance (Farads)

Rearranging the formula to find frequency gives :

f = 1 / (2ΠCXc)

That is theory at least, and if I have tickled your interest in Reactance you can read more about it from here -> http://www.electronics-tutoria...filter/filter_1.html

Anyway back to the WM-D6C. Below is a part of the schematic from the service manual (click on it zoom in).

I have red boxed two components of particular interest. Capacitor C138 (100uF) and resistor R152 (15Ohm). Note : These are both for the left channel, C238 and R252 are the corresponding right channel components that are not shown on the schematic.

What this schematic tells us, is that when we apply the second equation above to calculate the roll off frequency (or the lowest frequency we want to hear), we need to allow for an additional 15Ohm from resistor R152.

So for a standard 16 Ohm pair of headphones what is the roll off frequency with the stock C138 capacitor? Using our second equation above we get the following :

1 / (2 * Π * (16+15) * (100 * 10^-6)) =  51 Hz

For a higher impedance pair of headphones say 32 Ohms :

1 / (2 * Π * (32+15) * (100 * 10^-6)) =  34 Hz

Now if we were to substitute the capacitor with a higher value say 220uF 6.3V :

1 / (2 * Π * (16+15) * (220 * 10^-6)) = 23 Hz

Also for a higher impedance rated pair of headphones say 32 Ohms with the 220uF 6.3V capacitor, this gives :

1 / (2 * Π * (32+15) * (220 * 10^-6)) = 15 Hz

In conclusion, the frequency response of the WM-D6C can be extended lower by increasing the capacitance value of capacitors C138 and C238. This effect can be more pronounced in higher impedance headphones.

Of course it should be noted that if you were to use a pair of 600 Ohm rated Beyerdynamic headphones, then you should not ought to have to perform this mod

Very good information, thanks plop!!

Have you tried the mod yet? I'm interested in hearing about the results...