HD570 Symphony

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published: May-22-2021, updated: Dec-13-2021

NO SMOOTHING is applied to the shown plots. Most measurement sites have some smoothing applied which ‘irons flat’ sharp peaks and ‘wiggles’. I do not use smoothing because some info about sound quality is lost when plots are smoothed.

Aside from a small correction of the microphone itself also some correction in the lowest frequencies is applied to the plots to compensate for the perceived loss of bass when using headphones. This is described HERE in more detail.
A ‘horizontal‘ frequency response curve on the shown frequency response plots on this website thus indicates a perceived ‘flat’ tonal signature.

ALL measurements are made with a good SEAL on a flatbed measurement rig.
The shape of your head, bone structure, pad size, pad ‘softness,  (compliance), hair or no hair and or wearing glasses may (drastically) change the frequency response of some headphones, so… your personal experience may differ substantially from these plots.

Frequency response (tonal balance) is the most sound-determining aspect of headphones. A horizontal line shows audible neutral response in the plots on this website. Deviations in different severities at different frequency bands have an effect on the sound character.
The bigger the deviation the stronger the effect.
Below an aid to help determining the sound character of headphones with relation to the frequency response.

 

Sennheiser HD570 Symphony

The Sennheiser HD 570 is an open over-ear headphone. When this headphone came out (1998) it sold for around € 100.-. There was a small line with similar shaped headphones HD500 Fusion, HD575 and the $350.- HD590 prestige.

It comes with a thin 3m detachable cable which has a 3.5mm plug with a push on 6.3mm adapter.
The cable is not microphonic so in quiet passages and silences the cable rubbing against clothes is barely audible in the left cup.

The headband is soft and comfortable and so are the velours pads. When I got this the foam filling inside the headband as completely gone (sticky black stuff remained). Fortunately the headband can be removed and easily re-filled with foam. Also the foam in front of the driver was decayed. The pads still feel firm.
There is enough room for most ears. Height adjustment and tilt of the cups is large enough to suit most head sizes well.
The clamping force is ‘low’ but because of the low weight it won’t move around on the head easily.

The velour pads are exchangeable and all black. The original pads can still be ordered.
One does NOT have to worry about seal being essential for bass reproduction.

The cups can swivel far enough sideways but the vertical tilt is a bit limited. The headband can not be extended over a wide range so it may be difficult to get a good fit with larger heads.

The 3m long cable is connected via a 2.5mm TRS connector into the left cup. It fits snugly in the headphone so won’t be janked out easily by accident. The long cable indicates that this headphone is primarily intended for home/desktop usage. Very low in microphonics and has a 3.5mm plug with a 6.3mm adapter.

With a sensitivity of around 102dB/V the HD570 can not be used directly from a phone and reach high enough levels for normal music listening. To reach impressive levels it needs a bit more voltage than a phone, tablet or USB dongle. This headphone is not very sensitive so requires an amplifier to reach higher listening levels.

Note: I bought this headphone second hand.
The reviewed and filter modified HD570 symphony is up for sale.

specifications:

Type: Over ear, open
Usage: Home, studio
Driver type: dynamic
Pads: replaceable, velours
Collapsible: No
Headphone cup connector: Sennheiser 2.5mm TRS jack
Cable entry: single sided, left cup
Cable: 3m terminated in a 3.5mm TRS jack with a 6.3mm adapter
Driver size: 38mm (36mm membrane)
Inner Pad dimensions: depth = 21mm, Width = 45mm, height = 70mm, egg shaped
Max. power rating: 0.1W
Max. voltage: 2.6Vrms (7.5Vpp)
Max. current: 40mA
Max. S.P.L.: 110 dB
Impedance: 70 Ω (measured)
Efficiency:  90dB @ 1mW
Sensitivity: 102dB @ 1V
Weight: 210 g. (excl. cable)
Clamping force: low (3N)

Subjective sound description:

Bass and mids are on the warm side of neutral. The midrange can have a ‘sharp’ and ‘coarse’ character with certain recordings. Treble quality isn’t top notch either. It is a bit accentuated and lacks finesse.
It sounds like a lower quality HD599.

Measurements:

Below the frequency response of the HD 570 (Left, Right)

The channel matching is excellent, but that’s about all that is good about it alas. At least from a ‘hi-fi’ standpoint.
Bass is not well extended but present and does not feel ‘lacking’ and rolls off very gently below 40Hz. From 100Hz to 2kHz the response is linear and gently sloping (warm signature). At 3kHz there is a +4dB peak which can make voices sound ‘harsh/shrill’. The dip around 5kHz also does not help the sound. Then there is a substantial peak that can easily be lowered with 1 ply of 2- or 3-ply toilet paper. This does not affect the 3kHz peak though.
Lowering the treble peak makes the HD570 sound dull so it may be best to leave it as is to give the headphone a slight U-shape sound. The dips and peaks above 4kHz make the treble coarse and not very detailed.

comparisons

Below a comparative measurement of the HD570 compared to the current and more expensive bigger brother HD599.
Bass extension is the same. From 20Hz to 2kHz the headphones measure the same. Above 2kHz the emphasis at 3kHz, deeper dips and higher peaks make the HD570 sound a bit ‘brighter’ but also less ‘smooth’ and pleasant.

Below the HD570 versus the HD650
The HD570 is a bit ‘warmer’ and has a bit more lows than the HD650 but above 2khz the differences become obvious. There is no contest here. The HD590 may well be closer to the HD650.

Below the HD559 versus the well known DT990-250
The DT990 also has an emphasis in the lows (U shaped sound) but is a bit higher.
The treble peak of the DT990 is well known and is even higher than that of the HD570 but is ‘smoother’ and more detailed.

Below the HD559 versus the also well known DT880-250 Edition
The HD570 has more emphasis in the lows. The 3kHz peak is not present in the DT880. While the treble of the DT880 is elevated the peaks and dips are much smaller making the DT880 sound much smoother yet highly detailed.

Below the HD559 versus the Amiron home
The Amiron Home has much more lows/warmth and even higher treble. It is very V-shaped but here too the treble is still higher quality.

Phase response

Below the phase response of the HD570
Gentle sloping phase is not audible. Above 4kHz the phase changing within a narrow frequency band is more problematic.

output resistance / damping-factor

As this is a dynamic headphone the frequency response can be amplifier output resistance dependent when certain higher output resistance amplifiers are used.
Instead of showing impedance plots, which are hard to ‘read’ when it comes to assessing the tonal balance change in the real world, the HD559 is measured via a few different resistance outputs (0.2Ω, 10Ω, 33Ω and 120Ω). On a higher output resistance amplifier the output level will be lower of course due to voltage division. To compensate for this the amplifier is cranked up to the same level (8.2dB for 120Ω at 1kHz in this case). This way the plots are overlaid and it is easier to see how the tonal balance changes. Output resistances between the mentioned resistance values will result in tonal changes between those traces.

The tonal balance hardly changes when the HD570 is connected to a higher output resistance amplifier. The resonance frequency is around 100Hz resulting in a just very slightly warmer sound.

Seal can be an issue with closed-back headphones but is usually less of a problem for open headphones. Breaking the seal (improper fit on the head) usually means a loss of (sub)bass. Perfect seal, seal broken with a thick arm pair of glasses and seal substantially broken by slightly lifting the bottom of the pads which can occur when not properly seated.

The HD570 is quite insensitive to a seal breach.

Below the distortion measurements of the HD570 (Right channel).

The plot above shows the level differences between the signal (upper trace around 90dB SPL) and the harmonics. Most people prefer to see percentages instead of level differences so below the exact same plot except ‘normalised’ to the actual signal and level differences given in percentages.

Distortion levels in the lowest frequencies are 2^nd harmonic above 100Hz distortion drops below 1% which is kind of high. Also the 2^nd harmonic distortion is still a bit high up to 1kHz. The distortion around 4.5kHz reaches over 1% but is a bit ‘misleading’ because of the dip there. Still around 1% in that range is potentially audible.
The actual 2^nd harmonic distortion above 1kHz may well be lower than 0.2% . A shortcoming of my measurement rig.

Below the CSD (waterfall) plot of the HD570 . (Left and Right are overlaid)

No big red flags here. Only around 13kHz a clear resonance can be seen but is not worryingly ‘long’

Below the Group Delay plot for the HD570

There is some  pad bounce  at 70Hz. At just above 6kHz the resonance is visible. The ‘grass’ between 1 and 3kHz also shows up in the spectrum plot below.

A different plot is the spectrum plot. This basically is a CSD (Waterfall) plot but viewed from above where the level differences are colour coded instead of being in the vertical axis. Also the frequency range of the spectrum plot is wider (from 100Hz instead of 500Hz). The time span is also bigger in the spectrum plots and expired time is shown from below to top where in the CSD the time is shown from rear to front.

Below the spectrum plot of the HD570 (Right channel)

The plot shows short lingering in the lows, no obvious problems in the higher frequencies.

Step response

Below the step response plot which, when the sound is balanced and well extended should show a rise to around 0dB, (indicating fast driver response) and should be slightly sloping downwards indicating bass extension.
The lack of deep bass extension is visible as the horizontal trace drops quickly after 2ms. The ragged and elevated part in the first 500μs shows the sharp and coarse highs are dominant over the mids and lows.

reducing the treble

To reduce the treble (but not the 3kHz peak) a single ply of a 2- or 3-ply piece of toilet paper can be used.
The pads need to be removed as well as the foam (which probably needs replacement anyway).
Below the HD570 driver (the HD575 and HD590 have a different driver closer to that of the current HD6** range).
On the right side the driver with a single ply on top of the driver.
On top of that an AKG K240 foam disc is placed and the pads are pressed on again.
Below measurements with 1 layer and 2 layers pulled apart from 3-layer(ply) toilet paper vs stock.

The treble can easily be lowered with simple passive means. Alas the 3kHz peak is the most annoying part.
This was addressed with a passive filter. Below 2-ply + filter vs original HD570

Also with these modifications the treble is not refined and a bit coarse, just not as sharp sounding.

square-wave and impulse response

Below 40Hz and 440Hz square-waves and 100μs impulse response of the modified HD570, stimulus (and target) and measured response.

Conclusion

The HD570 is 20 year old headphone with a different ‘form’ than most other headphones (oval or round cups).
Only 4 of these similar shaped designs were made. Most likely this hasn’t caught on with the general public.
The HD500 and HD570 were not aimed at the audiophile crowd. The HD575 and HD590 might be more suited for serious listening.
These headphones are too insensitive to be used with portable gear. Also not really suited to listen to popular music.
For Classical music the sound signature isn’t really bad but there are, and were around 2000 as well, better headphones around.
A warmish but ‘sharp’ and ‘coarse’ sound signature. I haven’t seen the drivers that were used in this headphone in later models either. I guess the sales numbers were a bit disappointing.

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