HD650 KISS Mod (Keep It Simple Stupid) MATERIALS LIST Dynamat Extreme Creatology Adhesive Foam Foam disc (included with HD650, 3 per side after peeling them) TOOLS NEEDED Needle nose pliers Scissors House keys (use to prop open the grills from the side) This is going to be my definitive HD650 mod guide. Yes, there is already a dedicated HD650 mod thread here: http://www.superbestaudiofriends.org/index.php?threads/sennheiser-hd650-love-appreciation-thread.44/ And an index to the mod variations and forks here: http://www.superbestaudiofriends.or...ve-appreciation-thread.44/page-63#post-100789 The reason I am doing this because I have gone through it all and distilled the knowledge to something SIMPLE while finally reaching all of the the goals I originally set out to achieve. I love making things simple and cutting out all unnecessary BS. This mod addresses a minor side-effect of the original set of mods with the spider and back damping foam removed: a slight increase of a few db in the mid-bass. I don’t really find this slight increase in bass necessary. In fact, I kind of wanted to reduce it to HD600 levels. In essence, I wanted an HD600, but without the HD600s minor emphasis around 2-3kHz (which seems to drive @Hands crazy), and with the HD650's more refined character. Frequency Response Differences: Stock, older HD650 mod, KISS mod Note that differences are exaggerated with compressed Y-axis. GREY = STOCK ORANGE = HD650 original mods with front damping removed, rear damping removed, spider removed, an damping material applied on magnet GREEN = KISS mod HD650 Finally, the removal of the spider secure the foam (and magnet) down might result in the magnet falling off. It turns out that depending upon temperature or related atmospheric conditions, the magnet can actually fall out of the housing. This mod works with the friction fit and makes sure the magnet stays on. I originally thought the magnet might have been glued in and that the removal of the spider wouldn’t affect anything, but it turns out I was wrong. Be sure to press the two Dynamat side-strips covering the magnet / housing down with some minor pressure for a secure fit. Here is a picture of the KISS mod. The red Xs mark all the items that are UNNECESSARY or have a minimal affect. I would not bother with them. Out of all of the tweaks, the biggest improvement to the HD650 will be the application of dampening materials to the magnet. Only the application of the Dynamat / Creatology sandwich on the locations marked in the green Ys are necessary. I also DO NOT perform the quarter mod as I did not find it necessary running this out of the Jotunheim. Note that I am no longer using a donut on the magnet, but instead two large strips. This is for two reasons: 1) Keeping the cuts simple; 2) Making sure the magnet stays on the frame. The Creatology layer of the sandwich with the Dynamat Extreme is not necessary. It was done for two reasons: 1) Cosmetics; 2) Ease of marking and cutting through the Dynamat and its sticky gunk. The Creatology Foam part of the sandwich tends to help clean up the gunk on the scissors. One of the foam discs is folded in half into a crescent shape and applied directly on top of the magnet cover the hole. I used dabs of the Dynamat gunk to secure it in place (alternatively super glue might work). Be sure to lightly press a part of the foam (about 1/2 mm of it) into the hole of the magnet. It doesn't need to be perfect, but the foam does need to be flush / very slightly inside the hole. DO NOT get any gunk into the magnet hole and have it fall onto the driver membrane. Make sure the Dynamat does not cover any part of this hole. The driver really needs to breath, otherwise you will end up with something sounding like a Grado. Here are some additional notes for this mod.