StratoGrado  Frequency Response and CSD Waterfall Plots

Great bass extension.

The RS1 has peaks at 2k, 5k, and 9k with 5k being the sharpest, and 2k being the broadest. In contrast, the Stratogrado seems to shift the midrange peaks down to 1k and 3.5k. The 9k ridge really sticks out, at least for me when I'm listening. The 3.5k peak does not bother me.

Grado drivers put into semi-closed cups. There's a small hole (not pictured - cut off) in the center of the outside surface of the cup. I think the cups may be stuffed with something inside. The Strato pads must be used to obtain the correct results.

Too bad the bass can't from the these can't be combined with the Koss driver.

Thanks for measuring these, Purrin.

As I contacted Purrin via PM about measuring these I informed him about my objectives with this project, which were as follows:

1) Answering the question if a closed Grado could work (even more so  because it seemed common knowledge it was not possible)
2) Improving the bass extension.
3) Reducing or eliminating the Grado shout.

I ended up with a setup that sounded acceptable to my ears and I thought measurements would certainly tell me if I was on the right track or not. Listining to the headphones I thought I was, but you never know before you actually see the graph.

As for the 9k peak, I did not find it that annoying, maybe because I focussed too much on the bass and midrange.

FYI:

Used drivers: Grado SR80i
Cups: Wood cups RS1 style
Bass vent: 8mm bass vent at the bottom of the cup (damped internally)
Damping:  felt, medium density foam and sheep's wool
Driver damping: Now this is the tricky part. Compared to the Koss driver the Grado driver is a bitch to get working in such a setup. Whereas you just put a Koss driver into the cup and you have a working headphone, you can't just do that with a Grado driver. You literally have to choke it to get it working.

Now if I were Grado, I would use some shiny exotic wood cups, some drivers that have a better response in the higher frequencies, copy the StratoKOSSter pads and apply the StratoGrado damping scheme. Then I would call it the "Grado Revolution" and sell it for USD 1K. And make some dough.

@purrin: If you happen to have time, I would be very thankful if you could try the following and hear/see for yourself if the results changed for the better or worse:

a) putting some foam (like the Koss earpad foam disk) between driver and ear
b) lifting the drivers a bit from inside the cup to increase cup volume
c) changing the damping on the driver back (different variations of felt/paper)





 

Not necessarily. The Grados have more capability for bass extension.


Also, I will follow up on Strat's ideas to tone down the treble with the StratoGrados.

The StratoKOSSter bass is not bad, although the StratoGrados sound fuller and extend even better. Distortion looks better too, also compared to the distortion graphs of other Grados on Innerfidelity.

As for the rest, the Koss drivers are simply more well-behaved and unproblematic. You can simply put a KSC-75 or KSC-35 driver into a foam-damped cup, mount the StratoKOSSter pads, and  you will end up with a nice and decent headphone. If you do that with a Grado driver, you will end up with sonic desaster. You have to gag the driver and teach it a lesson.

When developing the StratoGrados I decided on using SR80i drivers I had lying around, just to see if it could work. I did not want to ruin a more expensive Grado driver (the PS500 drivers with their lack of hf energy could be an option) and burn my wallet.  Let's see if Purrin can measure a positive effect of changes to the setup. Then I might sacrifice Magnum drivers to create a really decent headphone.

Then again, even if the StratoGrados V80i are still imperfect, it is definitely nice to listen to a "Grado" with real bass extension, comfortable leather pads and decent isolation.