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Author Topic: Sennheiser HD558 (modded) Frequency Response and CSD Waterfall Plots  (Read 14952 times)

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ultrabike

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Re: Sennheiser HD558 (modded) Frequency Response and CSD Waterfall Plots
« Reply #30 on: October 20, 2013, 07:21:46 PM »
Yes. I tried the latest Audacity using wasapi and no go. This one here is only right channel through Windoze DirectSound, which is the best I can do for now, since I only have one mic currently. For REW I use ASIO.

The 150mVrms file that stv014 used for his results was probably done using the impedance test recording setup. Hopefully I didn't mess up this time.
« Last Edit: October 20, 2013, 08:05:48 PM by ultrabike »
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stv014

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Re: Sennheiser HD558 (modded) Frequency Response and CSD Waterfall Plots
« Reply #31 on: October 21, 2013, 10:38:56 AM »
Graphs created from sweep_44100Hz_HD558_90dBSPL_mic_rightonly_2.flac:

Frequency response (it shows that the bass response is slightly compressed at higher SPL)
THD vs. frequency (includes D2 and D3, the -15 dB plot is dominated by noise)
THD vs. level at 60 Hz and 1 kHz (at low levels it is mostly just noise). 15 kHz is not shown because of the limited bandwidth.
Linearity at 60 Hz and 1 kHz (this again shows how loud bass is compressed). The plots are normalized, so the absolute levels do not matter, and at 60 Hz and low levels noise is significant.

By the way, is 90 dB SPL the level corresponding to 0 dBFS in the test sample, or to -3 dBFS (the level of the first sweep) ?
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ultrabike

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Re: Sennheiser HD558 (modded) Frequency Response and CSD Waterfall Plots
« Reply #32 on: October 22, 2013, 07:12:17 AM »
I believe it was -3 dBFS, but not sure.
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ultrabike

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Re: Sennheiser HD558 (modded) Frequency Response and CSD Waterfall Plots
« Reply #33 on: October 27, 2013, 04:59:02 PM »
Adding calibrated HD558 Impedance curve. Ignore octave smoothing comment.

« Last Edit: October 27, 2013, 06:11:11 PM by ultrabike »
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Tor4

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Re: Sennheiser HD558 (modded) Frequency Response and CSD Waterfall Plots
« Reply #34 on: February 14, 2015, 03:57:37 AM »
Sorry for resurrecting a very old thread...

I currently wrote 2 different articles around HD558:

1) The first one is dealing with HD558 in general + comparing old vs new pads (measurements) + examining pad burn-in effect (measurements): http://headaudio.weebly.com/clanky/ochozene-vs-nove-nausniky-recenze-sennheiser-hd558

2) The second one is focused on modding - I experimented and found out again that ring-shaped felt rules them all!:
http://headaudio.weebly.com/clanky/modifikujeme-sennheiser-hd558

Again, the site is not in english but all the graphs are fully english... And I will be happy to comment here in english if needed (or use Google translator). For now, I will post the most relevant graph I guess:



Green curve is HD558 w/ HD598 mod and a few days old pads. White curve is w/ two felt rings inserted in between driver and plastic dust cover (see images inside the article for better understanding) while gray curve represents three felt rings inserted. Ignore 8.5 kHz dip on the graph and partially the one around 15 kHz as well.

HD558 w/ two felt rings really rocks in terms of neutrality... The headphone just felt neutral from the first second. It also destroys my other headphones here in terms of value (HD201, K712 Pro, HE500). HD558 w/ three felt rings sounds the most clean and grain-free even though it's already on the darker side of neutral which can be felt sometimes. I personally cannot decide which version is better... Both are significantly better than stock and both are the best in their way.

An interesting question to finish off: Driver burn-in vs earpad burn-in - how these two relate to each other, how big their impact is on your new headphones especially during the first days of listening? I would like to test a brand new headphone with a set of older but fully functional pads to get closer to answering this question (as I already tested a brand new set of pads with an old headphone)...


EDIT: One ring, again, does almost nothing... Four rings are impossible to fit inside and would theoretically cause the headphone to sound too dark. And I, again, tested other materials as well... But felt just rocks.

EDIT 2: Forgot to add - measured with SA-31SE (around 1 ohm output impedance).
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