Sennheiser HD535 headphones upgrade

[Fatmarley]

I bought some cheap Sennheiser HD535 off eBay for £20, replaced the pads for a pair of Premium ear pads (also off ebay)

Plugged them in to my S.M.S.L sAp II headphone amp, and was quite disappointed, they have a shouty upper midrange and the treble is very OTT. This is compared to my Sennheiser PX100 II.

I don't have a proper headphone measuring rig, but I knew the problem was around 2khz for the shouty upper mids, so I took a measurement by holding the microphone against the middle of the driver to see if it would reveal anything.

This is the Harman curve, and is supposedly what most people prefer.

And this is what I got with my rather unprofessional measurement.

It looks like it roughly follows the Harman curve at the highest frequencies, but sounds bad IMO. I've heard that some people don't like the Harman curve, because it has too much bass, and a shouty upper mid, and I can see why. I'd imagine you'd need a tight seal to get accurate low frequency measurements, but luckily that's not where the problem is.

I put the measurement into LspCAD and designed a low pass filter to drop the highs, followed by a notch filter to remove the 1 to 3khz shouty upper midrange.

Here's the before and after measurement. Red is obviously the standard headphones and blue is with the filter:

To my ears they sound better than the PX100 II, and interestingly, I sold my Sennheiser HD650 because I was enjoying my PX100 II more (It may well of been worn pads that was the problem with the HD650s though)
After living with the upgraded HD535, the PX100 II sound thick and boomy in the lower frequencies, and have less clarity in the upper end.

Here's the circuit diagram:

And here's the filter. It's a bit of a mess because I tried quite a lot of circuits before settling on this. My model in LspCAD didn't match the actual frequency response, so it took a few attempts to get it right.

I can give a parts list if anyone's interested?

 

[neonixcool]

Good day
Excellent work dear
But maybe you need change headphone amplifier or change headphones to HD600 or HD650?

I buy HD535 about 3 month ago and I listen him about two days also I listen HD650 and HD535 have more bass and little low details with HD650
Also my friend buy HD535 too and he said like you about high midrange ) maybe HD535 all different )

 

[Fatmarley]

Good day
Excellent work dear
But maybe you need change headphone amplifier or change headphones to HD600 or HD650?

I buy HD535 about 3 month ago and I listen him about two days also I listen HD650 and HD535 have more bass and little low details with HD650
Also my friend buy HD535 too and he said like you about high midrange ) maybe HD535 all different )

It could be the amp, or DAC I suppose. I'm tempted to try something else, but wouldn't want to spend much because I don't listen that seriously. Maybe the iFi Audio ZEN DAC V2 would be worth a try.

If I was going to buy some better headphones, I'd be tempted to try the Sennheiser HD560s and notch or low pass the peaky treble. https://diyaudioheaven.wordpress.com/headphones/measurements/brands-s-se/hd-560s/ - It looks like they have good low frequency extension compared to the 600/650.

Maybe the HD535 are all different. I read some good reviews before buying them, so was a bit surprised by what I heard - http://www.audioreview.com/product/headphones-home-audio/headphones/sennheiser/hd535.html

 

[Fatmarley]

Not sure if anyone's interested, but I think this mod makes a nice improvement to the sound. There's a bit more bass and more fine detail. It also sounds smoother in the treble. I've also adjusted the filter. If anyone's interested (looks unlikely), I will upload a circuit diagram if asked.

It just 9mm thick wool felt, cut in a 15mm wide x 150mm long strip.

And measurements here: Red is with the wool felt, Blue is with nothing.

 

[Fatmarley]

I just want to add that I think the reason why this mod worked was because of the pleather pads. They are obviously solid and will cause reflections. Velour type pads probably wouldn't benefit from this mod.

 

[ToTo Man]

@Fatmarley , I don't wish to offend but your mod looks like something that would be served up on an I'm A Celeb eating challenge, hair intact!

 

[ToTo Man]

diyaudioheaven is an informational goldmine but I wouldn't take his, or anyone else's measurements (including mine!) as gospel. I've long argued that there are significant intersample variations in headphone models and that you really need to measure several of them and do an average to ameliorate potential outliers. E.g. his measurements suggest that in terms of bass extension HD58X > HD650 > HD600 > HD660S. However, as you can see in my measurements of all four models, my HD600 > my HD650. My dad's HD600 on the other hand less bass and more treble than my HD600. I really need to get a better measuring rig as it's incredibly difficult to get a consistent seal over the overly-firm and oversized pinnae of the miniDSP EARS, but my ears verify what my measurements are telling me.

 

[Fatmarley]

@Fatmarley , I don't wish to offend but your mod looks like something that would be served up on an I'm A Celeb eating challenge, hair intact!

Yes, they aren't great to look at, but It's all about the sound (Also, I've brushed off the stray hairs now )

 

[Fatmarley]

diyaudioheaven is an informational goldmine but I wouldn't take his, or anyone else's measurements (including mine!) as gospel. I've long argued that there are significant intersample variations in headphone models and that you really need to measure several of them and do an average to ameliorate potential outliers. E.g. his measurements suggest that in terms of bass extension HD58X > HD650 > HD600 > HD660S. However, as you can see in my measurements of all four models, my HD600 > my HD650. My dad's HD600 on the other hand less bass and more treble than my HD600. I really need to get a better measuring rig as it's incredibly difficult to get a consistent seal over the overly-firm and oversized pinnae of the miniDSP EARS, but my ears verify what my measurements are telling me.

That's interesting. Measuring headphones isn't very easy at all, and apparently pad wear can make a huge difference to the measurements as well. I only really use measurements to see the relative differences, and then my ears to adjust the frequency response to taste. It's trying to get that fine line between over-excitement and dull just right. I'm pretty pleased with how they sound now.

I can't really do much to boost the low frequencies, apart from either using a huge inductor or maybe an extra lining of wool felt would help (I will try out of curiosity). Although they don't have the bass of my PX100 II, they do sound more accurate in the lows, so I'm not sure if any improvements can be had anyway.

 

[ToTo Man]

That's interesting. Measuring headphones isn't very easy at all, and apparently pad wear can make a huge difference to the measurements as well. I only really use measurements to see the relative differences, and then my ears to adjust the frequency response to taste. It's trying to get that fine line between over-excitement and dull just right. I'm pretty pleased with how they sound now.

I can't really do much to boost the low frequencies, apart from either using a huge inductor or maybe an extra lining of wool felt would help (I will try out of curiosity). Although they don't have the bass of my PX100 II, they do sound more accurate in the lows, so I'm not sure if any improvements can be had anyway.

Pad wear does indeed make a difference. Worn pads puts the driver closer to the ear and the result is usually a more forward midrange and upper bass and a less spacious / more claustrophobic-sounding presentation. Trouble is pad wear happens so slowly you don't really notice the sound of your headphones changing over time. However, when you replace a set of well-worn pads with fresh ones it's like the proverbial veil being lifted!

What measurement rig are you using? The preferred method on SBAF is a flat-plate coupler as this achieves measurements closest to those of loudspeakers and provides usable CSD data. Sadly I lack the DIY skills to put one of these together so I plumped for the miniDSP EARS. The EARS comes with HPN and HEQ compensation curves to 'remove' the effects of the pinnae, concha bowl and ear canal, but when making comparisons between different headphones I prefer to just look at the raw measurements (I use my HD600 as a benchmark).

 

[Fatmarley]

Pad wear does indeed make a difference. Worn pads puts the driver closer to the ear and the result is usually a more forward midrange and upper bass and a less spacious / more claustrophobic-sounding presentation. Trouble is pad wear happens so slowly you don't really notice the sound of your headphones changing over time. However, when you replace a set of well-worn pads with fresh ones it's like the proverbial veil being lifted!

I'm sure that's why I ended up preferring my much cheaper PX100 II over HD650s. I guess I should have replaced the pads, rather than sell them

What measurement rig are you using? The preferred method on SBAF is a flat-plate coupler as this achieves measurements closest to those of loudspeakers and provides usable CSD data. Sadly I lack the DIY skills to put one of these together so I plumped for the miniDSP EARS. The EARS comes with HPN and HEQ compensation curves to 'remove' the effects of the pinnae, concha bowl and ear canal, but when making comparisons between different headphones I prefer to just look at the raw measurements (I use my HD600 as a benchmark).

I've never attempted or even been interested in measuring headphones until I bought these HD535s. When I first listened to them, I thought they were terrible, with a shouty upper mid and bright treble, so just out of curiosity, I held the mic against the centre of the driver and took a measurement. I know it's far from an accurate way of measuring them, but it's been good enough to design a filter, and with a bit of experimenting, I'm very pleased with the results. Before all that I did try all sorts of wool felt and foam in stuff in front of the driver, but it was always 2 steps forward, 1 step back.

I may have a look into a diy measuring rig, because I'm curious to see how they measure compared to other headphones. Googling SBAF flat-plate coupler now...

 

[a.palfreyman]

Yes, from what I've read about the subject, it's down to standing waves etc and pinae shape. Wouldnt surprise me if different rigs give wildly different results as I notice a small change in the FR even with moving the cups back or forward a little. How about getting your ears laser scanned and 3d printed No idea in what though as surely the 'hardness' of the material will affect FR.

 

[Puggie]

MANY years ago as a student I decided to make some binaural recordings for a piece of coursework. Without any proper gear or excessive amounts of common sense i used the Panasonic WM-61a capsules with the linkwitz lab mods, and put them on some old thin headphone cables. Doubled the cable back and covered the mic body and cable with heashrink so the cable came out in the same direction as the mic pointed... Then popped these in my ears, into the canal as far as I though 'sensible' and hooked them up to a laptop and USB recording box to make my binaural recording rig. This was shockingly effective for the little outlay it cost from memory and I have no idea how repeatable it would be, but it could be a cheap way try and take some measurements? Alternatively for over ear headphones, do you need the pinea to do comparative measurements, would a simple hard domed surface for the ear pad to seal on with a mic element in the middle work? Ikea blanda bowl with a hole drilled in to take a beringer ecm8000 or similar cheap measurement mic.

Anyone know if there is a decent replacement for the old Panasonic mic capsule?

Also I believe you can do 3d scans with the latest iPhone and an app of some description.

 

[Fatmarley]

Knowing what I know about measuring loudspeakers, reflections from boundaries are what cause the most problems. To achieve accurate measurements of a typical loudspeaker, you need to keep it as far away from boundaries as possible (and gate out reflections). The boundaries in a headphone are only 2 to 3" at most, and the wavelength at 3" equals 4500hz. But the driver is only about 20mm from your head/ear/microphone, so maybe reflections don't matter that much?
I still wonder if it would be more accurate to have the microphone pushed through some 2" open-cell, acoustic foam, rather than a hard surface? That should help reduce reflections bouncing around inside the headphones, and I would have thought it would give a more accurate measurement (at the very highest frequencies, at least).

 

[Puggie]

Melamine foam washing up sponges could be a cheap option to test.