A5 Pro

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published: Oct-1-2014, updated: Oct-4-2014

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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.
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.


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Philips A5 Pro


The Philips A5 Pro is a closed headphone intended for usage by DJ’s. With some small modifications it makes a quite decent HiFi headphone as well.
It has a lower than usual impedance of 16Ω and can handle 3.5W so they can also be used as small ‘speakers’ hanging around the head without being blown up in the process.

The clamping force is high (its a DJ headphone) but bending the, leather covered, steel headband improved this.
The pads are large enough to fit my ears in BUT larger or people with protruding ears may want a larger inner diameter/depth.
Also the pads are ‘sticky’ and ‘hot’ after some time, it is highly recommended to buy the PCU110 velours pads !

This is one of the very few Philips headphones that has replaceable parts AND 3 different types available.
The headphone cable can be detached and inserted in either the left or right cup.
The cord is also microphonic … alas… and part straight part coiled.  A bit too long for portable usage.
The build quality is excellent and not your typical ‘Philips’ quality so no creaky plastic parts but real aluminium and leather is used looks to be very durable.
Makes it somewhat heavy in weight though.

It has big bass (with the stock pleather pads) but not of the most realistic quality, a bit too much in quantity making it a bit overly bloated/warmish sounding.
For some popular music, however, it sounded ‘decent’ in quantity.
With the velours PCU110 pads the sound is more balanced and could pass for HiFi listening.

Below the frequency response of the A5 Pro with stock pleather pads right, left

a5pro freq
The big bass and ‘hot’ but not extended treble is evident.
The 4kHz ‘dip’ isn’t very audible, I didn’t pick it out on a quick listen. Usually a dip there makes it lacking in clarity but may be ‘masked’ by the small increase around 1.5kHz.

The CSD shows some very short lived resonances in the treble area but I don’t think it is very audible  right, left superimposed.

a5pro csd

To tame the highs I have always found felt in front of the driver often helps (sometimes it doesn’t)
With some 3mm thick synthetic felt over the drivers (and under the pads as well to raise them a bit) worked well in reducing the peak but also increased the bass even more !
Treble improved in quality though. The used felt is blue, but black felt can also be used.

A5Pro close
To reduce the bass I have often find that a simple passive high shelf filter yields good results.
The plot below shows the difference between the stock (R channel) and with felt + simple filter.

mod vs stock a5pro

Below the FR plot of the A5Pro with felt + filter right, left.

a5pro modified
The details of the mods will be published later. I like the sound of it MUCH better and is more HiFi and very similar to that of a stock A5Pro fitted with PCU110 pads.
Even though the FR is a bit sloping towards both extremes it doesn’t appear to lack treble (extension) and subbass.

The PCU110 velours pads alter the sound quite substantially from bass heavy to bass neutral and increase comfort and is also oval so ears have more room inside.
(Left channel only) velours vs original pleather

a5pro l stock vs velours

Below the left and right channel with velours pads, left, right.

a5 pro velours

and to be complete also the CSD left, right:

csd a5pro velour

There is quite a gaping ‘hole’ around 3kHz which makes it less ‘strident’ sounding but is masked because of the ‘peak’ around 1.5kHz which make the voices sound ‘forward’ and ‘jump-out’ more.
Treble quality is much better but could be lowered a bit.
Below some of the same 3mm thick synthetic felt is used in front of the driver.
Left channel only, stock velours, velours + 3mm felt.

a5pro l velours vs velors+felt

I would not recommend the A5Pro in stock form as ‘true HiFi’ headphone (with the stock pleather pads that is).
With the velours pads (PCU110) the SQ is more Hi-Fi and with 2mm thick synthetic felt in front of the driver it has good sonic qualities, comfort and build quality.
One of the better sounding closed headphones.

Still, the high weight, microphonic (and too long) cable, clamping force (bending outwards helps) and the stock pleather pads are things that lower the overall rating.
Stock these may be great for DJ work though.

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