As you can see in the picture above, this is a bit of what the "box opening" looks like when you buy either one of these "Reference Class" Sennheiser headphones.
Much has already been said about the headphones being measured today. The Sennheiser HD650 was originally released back in 2003. Of interest historically, there was a fire in the Ireland factory back in 2004 so there probably are not many older pre-fire HD650's floating out there. Tyll Hertsens' article about the Sennheiser HD580/600/650 is a great summary and SolderDude has a ton of stuff on the HD650 on DIY-Audio-Heaven. SBAF has this "compendium" on the HD650 which I think covers everything... and more! Oh yeah, even NwAvGuy got one of these back in 2011.
Likewise, you already no doubt would have read about the Sennheiser HD800 over the years. These came out in 2009, sporting the large 56mm "ring radiator" driver (vs. 42mm transducer of the HD650). The HD800 has since been revised with the HD800S in 2016 (here's Tyll's take with mods discussions). Multiple reviews on Head-Fi. The HD800S sounds very similar to the HD800 to me.
For this post, let's look at measurements comparing the two and I'll put in my 2¢ on the sonic differences as I hear them.
The Sennheiser HD650 (built ~2010-2012)
My friend linnrd bought this headphone back in 2013 used and was able to lend them to me for a listen. Peeking behind the metal grille in the image above, we see that this is not the oldest version based on the color of the driver surrounding material which is silverish/white rather than the pre-2010 version that would have been all black (based on a comment here). So based on this, unless there is a more precise way to find manufacturing date using the serial number (1409XX), this specific headphone was "Made In Ireland" at some point likely between 2010-2012. (I've sent an E-mail to Sennheiser with the serial number, will update if they send me more info.)
Knowing the age of these headphones appears to be important because over time, reportedly there have been changes to the tonality of these headphones.
The 2-pin cable connectors to the ear pieces are easy to remove and replace. I'm somewhat envious of how inexpensive balanced cables are for these HD650 headphones as opposed to the significantly higher price for HD800's (even generics)!
They feel quite comfortable and light (260gm without cable) when worn but that's variable depending on one's head shape and size of course. Clamping force is stronger than the HD800. I measured these with the stock pads on, and while many years old I don't think the headphones have been used too much and the pads look to be in good shape, are clean, have maintained "springyness", and with no noticeable wear/tear of the velour material.
Here are the core measurement results:
That looks good. Relatively smooth shape and the peaks are achieved by 0.75ms.
The Sennheiser HD800 (2010)
|BTW: Notice the 3 bumps over the ear cup for tactile confirmation of the left side (Braille for "L"). The HD650 also has 3 bumps over the top of the left ear piece.|
Subjective comparison & Summary of HD650 vs. HD800
|BTW: Notice the size of the HD800 ear piece and how it's wider, covering the screws that hold the miniDSP (H)EARS silicone piece in place.|
|Another look at the Sennheiser headphones and ear pads... Stock velour pads of the HD650 and Accessory House Hybrid Sheepskin/Protein Leather for the HD800.|
2. Apply EQ: A simple +6dB, 7kHz peak with a broad Q2 will restore most of the treble dip for the Sennheiser HD650 measured here. I've tried this myself and I like the result. Make sure you apply some headroom to avoid clipping.
3. Research and look for mods that could brighten up the headphones. Check this out to start.
|Ran the CrystalDiskMark right after I used Macrium Reflect to clone the OS over.|