ludoo
1000+ Head-Fier
I recently decided to try and apply the damping knowledge I gathered modding orthodynamic phones, to a pair of AKG K27i which are essentially the same, minus the padded headband, as the JBL 410 or the K414P.
The theory is simple: the phones are too bassy and have too many resonances for two reasons. One, is that the driver has little damping, requires little energy to move, and cannot "brake" quickly on deep notes, the ones who make it reach its maximum excursion. The second reason is the hard surface of the closed cups, which make the sound bounce and reflect.
If you open up the K27i, you can see AKG tried to lessen the first problem by sealing two of the four small holes on the back of the driver that make it breathe, to try some form of air damping (less exit holes, more air pressure, the diaphragm should encounter more resistance when moving). Which is more or less what the previous mod described above does. We will do the same, only in a cleaner way, using felt which is a "proper" acoustically damping material.
Your first job is thus to clean up the back of the driver, and to remove some of the hot glue that seals the driver to the cups.
Your next task is to get two types of felt: a thin, very dense one (thick wool is ok, test its density by blowing air through it with your mouth) to damp the driver holes; and a thicker one to damp the vents (the small holes next to the top of the cups) and the back of the cups. Here you see the felt pieces in place.
The black felt disc on the driver has been glued with Gorilla Glue. Be careful to apply only a minimum quantity of glue and don't go too near the holes, as the glue expands into a hard foam which might cover them. I used a 50 euro cent coin to cut the black disc, and a vise grip to hold it in place while the glue dried.
The felt tightens up the bass considerably, cleaning the other frequencies, balancing the sound and bringing out the details that were previously masked. Another dramatic change in sound is possible with a recable, using Silver Plated Copper instead of the crappy, puny stock cable. If you recable them with SPC, you might want to remove the purple felts as the cable has bright sound, and with the purple felt in place the phones might sound too bright for your tastes.
My pair, modded and recabled.
The theory is simple: the phones are too bassy and have too many resonances for two reasons. One, is that the driver has little damping, requires little energy to move, and cannot "brake" quickly on deep notes, the ones who make it reach its maximum excursion. The second reason is the hard surface of the closed cups, which make the sound bounce and reflect.
If you open up the K27i, you can see AKG tried to lessen the first problem by sealing two of the four small holes on the back of the driver that make it breathe, to try some form of air damping (less exit holes, more air pressure, the diaphragm should encounter more resistance when moving). Which is more or less what the previous mod described above does. We will do the same, only in a cleaner way, using felt which is a "proper" acoustically damping material.
Your first job is thus to clean up the back of the driver, and to remove some of the hot glue that seals the driver to the cups.
Your next task is to get two types of felt: a thin, very dense one (thick wool is ok, test its density by blowing air through it with your mouth) to damp the driver holes; and a thicker one to damp the vents (the small holes next to the top of the cups) and the back of the cups. Here you see the felt pieces in place.
The black felt disc on the driver has been glued with Gorilla Glue. Be careful to apply only a minimum quantity of glue and don't go too near the holes, as the glue expands into a hard foam which might cover them. I used a 50 euro cent coin to cut the black disc, and a vise grip to hold it in place while the glue dried.
The felt tightens up the bass considerably, cleaning the other frequencies, balancing the sound and bringing out the details that were previously masked. Another dramatic change in sound is possible with a recable, using Silver Plated Copper instead of the crappy, puny stock cable. If you recable them with SPC, you might want to remove the purple felts as the cable has bright sound, and with the purple felt in place the phones might sound too bright for your tastes.
My pair, modded and recabled.
