Hello, and Happy Holidays... Edit* Edit * Edit** I am updating this Loaner to the 650 Headphones. . This a "next generation" Loaner for my "proof-of-concept" design for the HD6xx, but maximum performance was attained with the 650. The first test, an old HD580 was used to simulate a 650. But the loaner and focus will be the 650. This is probably the most cost-effective headphone mod, out of all of the units I've worked on. **Redacted due to sounding wrong. I'll Just say it will impress. This is a real improvement, with the percieved observations being: * improved elevated trebles, * increased details, * more vivid & clear presentation, * Adjustable bass * sub-bass slam. Technical improvements are: *Cleaner CSD *Faster CSD decay *Better impuse measurement * Better distortion measurements * More linear frequency response * More extended frequency response * Average 3db elevation in trebles area *Bass frequency response extended PIC Measurements: FR: Sub-bass is up to 7db increased (for impact) Trebles up from 3-5db Upper mids also up for liveliness. Impulse: Bottom peak less dip & second peak smaller. Subdued (more controled) throughout 100-300us range. CSD: Faster decay slices. Decay all less than 1ms from 2k up. Way cleaner mids & low mids area. The headphone looks stock from first look, as it retains the stock foam, yet has more improved trebles than stock. I am currently in a predicament, as this has always been just a hobby for me, and I have no real intention to mod, what would amount to literally untold amount of HD650s out there. I do not even have the time I would like to tinker and make inventions. So I consider the design to be more of an intellectual property, to be sold off to someone who lives/loves the industry, or wants to stop the impending doom of **redacted**.. Let's just say it's competition. About the mod: This design alters the driver performance, not just clean it up, which I do have a technical explanation and visual images for (intellectual property). Looks decieving with no apparent visual changes untill you look closely. The mod consists of using custom ordered driver modding parts, new mold material, new mold shape, new damping, and an ability for me to adjust the bass level (before I send out), without inhibiting dynamics. No past methods of rear damping or front (cut hole in front) methods used, so this is very far from a normal mod. Pics: ********* Requirements: This is not a SBAF sanctioned loaner tour. The purpose of this loaner is simply to showcase a performance increase. As such, for those who are interested, they would accept to follow these rules, and any more is open to suggestions... ** have some type of measurement rig, OR reference to same or other similar or more expensive headphones. ** Participation is limited to members at "Friend" level and Contributors. (Ultimately, selections are made at my discretion.) ** Do NOT Take apart, or make any modifications.. The top membrane needs to be there for sub-bass tuning. I post pics, so there really is no need to open. Full visual disclosure posted above. ** Please keep unit in condition recieved. ** Once members list is up, I must be included in PMs, about the tracking number to next participant. This is to keep track of the tour's current progress at all times. No Addresses posted in thread. ** Please post when you receive the item, and send it to next member. **The loaner period should be about a week from when you receive the headphones. Due to holiday season, non-punctuality is understandable. Any sooner or later, just notify in thread. Shipping will be: CONUS only, with possible exceptions (apologies to non-CONUS friends) The package must be shipped FedEx or UPS ONLY (NO postal service) and insured for at least $50, with signature required. By choosing to participate in this loaner, you agree to abide by these rules and to cover costs for loss or damage, and deal with shipping insurance. Also take & save pics upon delivery for the item condition. As an incentive and appreciation to those who participate, the headphones will be offered for sale to loaners first, at end of this Loaner tour. If demand is high, I also have materials for completion of a few more units. Impressions & observations are welcome, but preferably in the hd650 impressions thread, to keep this one clean and focused on the shipping. https://www.superbestaudiofriends.o...sennheiser-hd650-love-appreciation-thread.44/ Tour order: TBA.