MDR-MA900 Mods and Resistor Removal

Did a couple small tweaks to my MA900.

1. Removed the fabric in the back of the cups.

2. Removed the fabric directly behind driver. Just have to be very careful nothing gets in there. Stock grill even without fabric cover should prevent all but the smallest dust particles from getting in, so keep these bagged up when not in use. Or you could mix, only remove either the fabric in back of cups or directly behind driver for some level of protection.

3. In front of driver, there is a small open hole in all those layers of foam and fabric. I put a single layer, 1/8" circle of open-cell foam there. You might be able to squeeze in more front damping for further tuning.

Next up, did the resistor mod that is pretty common on the F1 and MA900. My amps don't seem to affect the frequency response of the MA900 without the resistor network, so might as well take them out for shits and giggles. (Next up will be a full recable...some day.) I scraped the epoxy off the driver leads and moved the + cable to that spot. Removed resistors. Left ground where it was. I'll attach a modified copy of a diagram I found online.

Subjective thoughts:

- That small piece of foam and removal of the interior fabrics smooths out and balances the treble out better. Less bright sounding overall.

- Cleaner, smoother, more natural sounding overall. Typical audiophile improvements.

- Slightly better staging and air.

- Bass is largely unchanged.

- I have a thing for being able to see the drivers in open headphones. Looks cool.

- No idea if the resistor removals really did anything subjectively. That's what I get for not doing things one at a time and testing. Oh well. Regardless, the less things I need in the signal path, the better.

Quick Measurements

MA900 Stock:



MA900 Modded (If the response was a linear line from 500Hz to that 9.5KHz spot, that might sound pretty good. Alternatively, maybe just lop off the top of that 1-1.5KHz spot and 3-4KHz spot, but otherwise this sounds easier to listen to and more balanced to me now.):



MA900 CSD Stock:



MA900 CSD Modded:



Impulse response stock (take with grain of salt):



IR modded (EAT YOUR SALT!):



Crappy diagram I lifted from a website and modified to fit what I did. Right side is even simpler.

 

Resistor mod may or may not have made a difference. Really comes down to the amp you use it with post-mod.

Oh look, a comment about number of components in the signal path, yet I like the cheap and pricey series stepped attenuators in my arsenal. Have to eat my words I guess.

 

Pretty sure I posted a review of it on the site that you can reference.

 

The PCB is pretty easy to figure out and wire shit up to your heart's content once you have the diagram. Wiring directly to each amp would be the tough part, necessitating drilling a hole in one cup. Again, I'd stress you make sure your amps will deliver the sound you want if you do the resistor mod. (Impedance stuff)

I think sticking a bit of foam right in front of that open spot in front of the driver does the most to smooth things out and provide a slightly more accurate stage. Removing material behind the driver gives the slightest extra oomph and air. The SMD resistors should be fairly transparent in the grand scheme of things.