Beyerdynamic DT770 Pro 80 Mod (Pt. II)

Desoldering & Cleaning up the Drivers

To the right, is how the drivers should look once you’ve desoldered the old wires and removed the old solder using a wick. Notice how you can see the tiny little holes for each terminal.

This is where having a temperature controlled soldering station helps quite a bit; the soldering station I have doesn’t give you a true readout on how much wattage is being fed to the iron, but for soldering my interconnects, I usually have it set at about 40% its total power, so about 15watts. For removing the solder, you’re going to want to kick up the juice a little bit to about 25watts; the idea is to get in on each of these fast with the wick, have it suck up the solder and then take a break. It took me about three passes per terminal to remove the solder completely. You don’t want to try to do each one in one pass, as you’ll most likely heat the terminal too much and if you do that: Game Over, you’ll need new drivers.

Modification of the ear cups

The next thing I did was modify the cable opening on the Left Ear Cup so I could fit in the female mini XLR casing. In order for the Redco jack to fit snug, you’ll need a 3/8″ drill bit to modify the original, rectangle-shaped opening. Make sure the small button used to lock/unlock the male jack faces outward, then use a couple of toothpicks to spread in some E6000 glue around the edges and set this aside to dry. It should be ready in about an hour. Once sealed, the jack’s casing is fused to the ear cup.

Now it’s time to wire everything up and solder in the new and improved wires. Below is a comparison between the stock wires (above) and the Canare Star Quad cable I used (there are cotton strands between the shield and the four wires, you don’t need them; I took this comparison picture before cutting the shield and these strands off).

The next step is modifying the inside of the ear cups for dampening. Below is a shot of the original ear cup; I decided that since the material I use is really dense, that I would cover the deepest rectangle depression as well as the smaller inner circle. I did nothing scientific here, I just guessed that this much coverage would dampen the lows just enough; the reason why you’re reading this now is because I think I got lucky and my assumption worked!

Heat up your Glue Gun and if it’s got a “low” setting, use that. This of course, assuming you’re using a similar type of dampening material. If you’re using something else, use an appropriate adhesive.

This is what the ear cups look like after hot gluing in the dampening material.

At this point, I already had painted all of the parts and assembled the cans back together. Below is what the painted and assembled headphones look like, with the ear cup modifications and the casing for the female mini XLR jack glued in place.

Soldering the new wires & connectors

The next step is to make the wire harness and solder the female mini XLR jack. I used some left over cable and used one of the white wires for the shield, which I marked at either end.

Then, I soldered the additional wires needed for the right ear cup and shrink-tubed the joints:

The lower wires are for the left driver, the two twisted wires are for the right driver; the left driver needs the shield, negative and positive wires soldered to the terminals, while the right driver only needs the shield and positive wires soldered. This is the left driver with the new wires soldered in place (from left: white wire=negative, blue=positive, white (marked)=shield).

Before soldering the right driver, I shrink-tubed the wires with both blue and red shrink tubing, just to match the corresponding blue (L) and red (R) details. You want to have enough wire that will allow you to extend the cans all the way without stretching the wires. Shrink tubing is a good insulator as well as protector for your wires, definitely better than the thin insulation of the stock wires.

This is about how much room you want to leave yourself for soldering in the wires to the drivers. I also placed small cable ties inside the ear cups to avoid the wires pulling on the soldered connections as a precaution (not really necessary since there’s plenty of room to stretch the can, but just in case someone or something pulls on the wires at either end, they’ll be extra protected). The wires don’t need to be secured under the headband, they simply tuck inside and then you snap the headband’s buttons, that’s all.

This is a close-up of the cable tie from the inside of the ear cup:

Putting it all back together

After you’ve soldered the drivers, simply tuck in the excess wire into the ear cup, place the foam disc over the drivers and snap the holding rings back in place, then the ear pads; have fun putting these back in place

Building the new cable

The Male Mini XLR connector:

One of the things I like to do after soldering all my connectors is apply some hot glue in between each terminal for added stability and insulation. There’s going to be a little bit of excess glue preventing you from closing the connector with the tiny cover, so if you do this, you’ll also need to cut off the excess glue until you are able to cover the connection with the cover as shown in this pic.

Once soldered (and this goes for the female connector in the left ear cup), slip the soldered connectors into the casings to make sure they fit, then put a little bit of E6000 glue on the connectors and slip into the casings. Let dry and then fill the cavities with hot glue gun (for even more insulation and stability inside the casings).

The Furutech 1/4″ plug:

What is hidden by the cover on the Mini XLR connector above is the fact that I soldered the two blue and white wires to each of the positive and negative terminals on both connectors. This is definitely not a requirement, but many believe that doubling up the wires improves performance. I can’t tell for sure, but I did notice more separation of instruments that isn’t as noticeable when listening to the stock DT 770. I’m certain it’s not a placebo effect either, since I’m able to switch between both sets using a passive switcher that I built.

On the mini XLR end, I added about 4 layers of shrink tubing for strain relief and on the 1/4″ end, I used the coiled strain relief included with the Furutech plug. This was a bit of a challenge since the addition of Techflex made the cable diameter slightly larger, but found that turning the coil counterclockwise while pushing it through did the trick.

In Conclusion:

I’ve put together this two part tutorial about 8 months after I made this modification and I’ve put these cans through a lot of use since then. I definitely am hearing an improvement throughout the entire frequency range and they are not fatiguing to listen to (at moderate volume levels). These have become one of my favorite pair of cans to listen to music on, and I use them also to check my masters. They have not eliminated the use of my Bowers & Wilkins speakers (685 bookshelfs with 608 sub) for checking my masters, but I rarely find the need to make tweaks to my audio work after checking it over these.

I hope you found this useful; if you have any questions regarding this build, feel free to drop me a line.

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