My last pair were from 2005-06. Owned for 7 year with numerous pads, amps and dacs.
Absolutely, I'm open to all possibilities. My impressions are based on memory and experience - not science. But just like we think we know exactly how our favorite album/song sounds before we play it on different equipment. I know as much as anything how my original 650's sounded.
To try and be more exact with the changes; no one could ever claim that the 650's didn't have rolled off treble at the top. Now there is a peak right at the top. It's not in the upper mids like say AKG or Grado. The treble now emphasises the very highest frequencies ever so slightly to follow on from the upper mids. The older 650's simply did not do this, no matter what amp or dac used. I mainly use vintage amps these days and my prefered amp is a vintage NAD that has quite a low impedance curve but loads of power. Very natural (slightly warm) sounding amp and it also was my prefered amp with the hd800. I also own a couple of headphone amps and the new 650's sound brighter on these.
Remember- I'm not saying these are bright headphones, only there is no roll off anymore and they sound faster, clearer and more resolving. Because my earlier 650's were bought so long ago the changes may have happened sometime after my earlier model was bought. Or they may have been tweaking them over a period of time.
I have a pair from late 2012 and the ones I got about 3 months ago, I hear no difference between the two. I bought the second pair because I liked them so well did not want to lose out if they broke. Now about to receive hd700 tonight so maybe I will like them more, at least enough to let one pair go. We shall see. Sennheiser made no change to the drivers, since the silver as opposed to black drivers, the newer pads are stiffer and there in lies the difference. Check out this link about pad thickness and you may understand the difference...
https://diyaudioheaven.wordpress.com
/headphones/measurements/brands-s-se/......
HD650 pads
The measurements of the headphone above are made with a
black driver +
old type pads.
Most likely the old pads once were a bit stiffer and the foam inside will be somewhat decayed/softened over time.
The
newer pads indeed sound
‘brighter‘ and ‘
clearer‘ and relatively the old pads sound ‘darker’ or ‘warmer’ with less clarity/treble presence.
I was curious what caused the differences as side by side they looked very similar in height.
The
old pad = 30mm high, the
new pad 32mm, the colour of the new pad is darker and the velours of the newer pads feel less ‘soft’ to the skin.
The new pads also come with new foam inlays.
The new pads have the
product code: 050635. They are suited for HD545 / HD565 / HD580 / HD600 /
HD650 / HDI850.
Time for some measurements to show the
differences between the 2 pads (right channel only).
The measurements are done with the same test-voltages from a low output R amplifier and the same driver/channel.
The
old pad has a good 2dB more presence below 1000Hz and is also a bit louder in SPL. The amount of treble (> 4kHz) is about the same level.
The
new pad is more balanced and the ‘warmer’ signature is gone. More towards the HD580 / HD600 signature.
What isn’t very obvious when wearing these is the fact that the old pads
compress a lot more than the newer (less compliant) ones.
When placed on the test rig this became quite evident though.
Quite possible the older pads may create a slightly better seal on some heads (depending on bone structure) as well.
Using the older pads the drivers are thus much
closer to the
ears which results in a slightly higher
SPL below 1kHz.
To check if the pad
thickness is indeed the only parameter that changed I pressed the
new pads against the rig to the same driver-rig distance as the
old pads did by themselves. Below the result of this small test.
This test shows that the newer pads do not have any different absorbtion or other acoustical effects and the differences in sound signature and SPL between the two pads is now the same. They sound equally ‘warm’ under these conditions.
What became quite obvious is that while the old and new pads differ only slightly in height when laying flat on the table (30mm vs 32mm) as shown in the picture above, but the pads
compress in a
substantially different way when being pressed against the skull with the
same clamping force.
Below 2 pictures of both pads with 1kg weight on top of them. Roughly equating to about
10 Newton force which is a bit north of firm pressure but it shows the differences better.
With 10N on the entire surface of the pads the total height of the pads was reduced from 30mm to
20mm. Considering the mounting plate was also included (which is 5mm) the actual pad thickness reduced from 25mm to 15mm a 40% reduction.
Below a picture of the new pads with the exact same weight pressing on it. With 10N on the entire surface of the pads the total height of the pads was only reduced from 32mm to
27mm. Considering the mounting plate was also included (which is 5mm) the actual pad thickness reduced from 27mm to 22mm a 20% reduction.
The question of course is whether or not the old pads had been (much) stiffer when new which is quite likely as the foam inside the pads deteriorates over the years.
If that’s indeed the case then the sonic signature must have become ‘warmer’ over the years without me really noticing it….
Amplifier output resistance effect
Due to the
impedance characteristics of the HD650 the headphone changes its sonic signature slightly when fed from either a low output R amplifier (0.1Ω) or a higher output R amplifier (120Ω). Because of the relatively high impedance of the headphone (around 300Ω) the effect isn’t nearly as dramatic as it can be on lower impedance headphones. Below a plot of the HD650 (with new pads) when driven from a
0.1Ω amplifier and a
120Ω output amplifier (Ember prototype was used).
As can be seen the
mid bass is increased by about
+1dB and the upper
treble by about
+0.5dB.
The SPL was level matched at 1kHz to compensate for the level differences caused by voltage division. The CSD showed no differences other than the small level differences.
