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The mid bass hump on dynamic headphones

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#1
From reading allot of FR charts I've noticed lots seems to have a mid hump and audible distortion that tube amps have, not sure if its 2nd harmonic. The HD600 is seen as flat or balanced yet it has a 5 db @ 100Hz. Meanwhile a lot of non dynamic based headphones have that hump, The ER4S and LCD are flat from 20 - 1000Hz with really low bass distortion.
 

pozz

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#2
It's a matter of the resonant frequency of dynamic drivers and manufacturer tuning by controlling cup size, spacing and volume. As far as I know there's nothing that prevents closed back dynamics from having a good linear response as long as the seal is good, which unfortunately means that open back dynamics will have an inherent weakness in the low bass.

With planars, and unlike dynamic drivers, the interaction of the magnetic field with the wire set into the diapraghm can drive the entire surface at once if necessary, so bass response is not sacrificed in open back designs.

Edit: The ER4S you mentioned is IIRC a hybrid balanced armature and dynamic driver IEM. The lever-based action of BAs means they will tend to have peaky resonant frequencies and limited range, so are used with multidriver designs with crossovers. Because IEMs are so small its a matter of tuning, gauging insertion depth and driver size, the latter determining whether they will fit in your ear as close to the eardrum as possible, or sit just outside of it.
 
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#3
For a correction the ER4S is a single BA set up its uses a Knowles ED-29689, It has a FR of 20 - 17,000Hz and the peaks are flattened by damping filters. Yes the deep fit of IEM's allow 5 - 8 mm drivers to be as good as there larger brethren. Because i hear more details out of my ER4SR than i did on the Shure SRH1540.
 

pozz

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#4
For a correction the ER4S is a single BA set up its uses a Knowles ED-29689, It has a FR of 20 - 17,000Hz and the peaks are flattened by damping filters. Yes the deep fit of IEM's allow 5 - 8 mm drivers to be as good as there larger brethren. Because i hear more details out of my ER4SR than i did on the Shure SRH1540.
Thanks. Faulty memory:)
 

solderdude

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#5
I measure the HD600 as 'flat' at 100Hz but this is because I apply a correction somewhat similar to Harman.
This makes my measurements of LCD's also be a bit subbass shy.

The ER4SR has about +3 to +5 dB in most plots which makes them sound more 'open' and 'forward'.

So it really depends on who's measurements you look at and how they were made.
 
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#6
I measure the HD600 as 'flat' at 100Hz but this is because I apply a correction somewhat similar to Harman.
This makes my measurements of LCD's also be a bit subbass shy.

The ER4SR has about +3 to +5 dB in most plots which makes them sound more 'open' and 'forward'.

So it really depends on who's measurements you look at and how they were made.
I've noticed that which fuels on forums how the ER4/LCD are bass shy, When the ER4SR has more sub bass than the HD600 under 40Hz.
 

solderdude

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#7
Sub-bass extension is a good thing and audible with certain recordings. It adds to realism somehow.
Most bass notes are between 50 and 200Hz though and a mild roll-off below 60Hz usually doesn't harm the bass.
A steep roll-off does.
Our ears are quite insensitive to lower bass and needs to be kind of loud to hear them.
At certain levels the lower bass suddenly seems to kick in because of this.
As most music is mixed at average levels of 80 to 85dB the tonal balance is 'accurate' only at these levels.
At lower levels (normal headphone listening levels for relaxation and long-haul listening you need to compensate for that when you want the studio experience at lower listening levels. Add to that the lack of tactile feel of the bass and you may even need a bit more compensation.
Correlation between measurements and plots thus also depends on listening SPL and the type of measurement rig and compensations used.
With IEM's there are seal and insertion depth as well as diameter issues and the needed compensation to correlate to measurements.

Some incorporate that in their plots (Harman, Rtings, Sonarworks, me) others do not (SBAF, EARS and some DIY rigs) which makes plots seem different.
 

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