superlux hd681 evo

8/10/2019 Superlux HD681 EVO

1/11

Superlux HD681-EVO an Evolved HD681 ?

The Superlux HD681-EVO is put on the market as an 'upgraded version' o the still availa!le HD681 "red trimming version#$Superlux makes the ollo%ing statement a!out the HD681-EVO&

The best-selling model HD681 is a high quality headset with rich bass,crystal clear high resolution and accurate sound field positioning. owthe new HD681 !"# upgraded $ersion has a completely new, moreslender shape and an impro$ed smoother, more neutral, treble tone.The HD681 !"# easily meets the requirements of stage and studioprofessionals for a high-quality sound in monitoring headphones.

The HD681-EVO is in O %a( reminis)ent o the 'original' HD681version"s#$ The looks are dierent* the )ups are dierent* the pads aredierent* the head!and is dierent* the )a!le is dierent* the sound isdierent *the pri)e is dierent and the driver is dierent$

+n sto)k orm the HD681-EVO is a ver( 'dark' sounding headphone*overl( '%arm' %ith 'at' !ass !ut indeed doesn't have pier)ing highsthat )hara)teri,es the HD681 series$ + think in sto)k orm it ma( !epopular %ith (oung people that listen to a lot o ele)troni) musi)$ e%se)onds o listening %as all it took to realise this is OT an HD681that has EVO-lved or 'improved'to MY earsand it doesn't have mu)ho the soni) .ualities the original HD681 has "ex)ept or having lots o!ass#$ /ersonall( + %ould have given it a )ompletel( dierent t(pe-

num!er simpl( !e)ause it +S a )ompletel( dierent headphone in 00 aspe)ts$There are some similarities though and that is$$ the )a!le is also mi)rophoni) "!ut this )a!le is deta)ha!le like that o the HD668# and thepads are still a !it 'sti)k(' and 's%eat(' ater a %hile* the( are also made o vin(l "thi)k pleather#$ dmittedl( the pads are not exa)tl( thesame$ The EVO pads are !etter looking "stit)hing and mounting method diers# and are also a !it 'soter' to the tou)h and slightl( thi)ker$

The head!and has a thin la(er o ru!!er on the underside %ith 'air illed)ushions' and is a !it more riendl( to olli)all( )hallenged heads "likemine# than the plasti) ones on the HD681-series$ The shin( sura)eortunatel( is nota ingerprint magnet !ut s)rat)hes %ill !e .uite visi!le$ot the greatest asset %hen vie%ing it rom proessional usagestandpoint %here headphones usuall( aren't treated gentl( to sa( theleast$ 0ooks-%ise it seems to !e targeted at mo!ile (ounger people orthe )lassier looking Hi-2i market though$Stevie 3onder and 4e Heale( might a)tuall( like the HD681-EVO as ithas raille markings on it* indi)ating the letter 0 and 5$/eople %ith good e(esight have tore)ognise 0 and 5 !( a ver( small andhardl( visi!le small '5' in a!ro%nishred )ir)le on the inside 7ust!elo% the small head!and s)re%$

The )a!le )on)ept is similar to that o the also %ell kno%n and liked HD668$ +n other %ords a ver( shortpie)e o )a!le is dangling out o the let )up$ +t is a single entr( headphone )a!le and 7ust like %ith themost other Superlux headphones the t%o metal rods that are part o the head!and )onstru)tion are the')onne)ting %ires' to the other driver$ The HD681-EVO )omes %ith %ires o dierent lengths %hi)h )an also !e )onne)ted in seriesmaking an even longer %ire$ !onus o this )onstru)tion is that %hen or some reason the )a!le is pulled upon it simpl( dis)onne)tsinstead o ripping the %hole headphone o (our head or !reaking a )a!le or expensive e.uipment$ /urists* ho%ever* %ill ro%n a!out theseextra )onne)tions as %ell as the EVO not !eing dual entr(* + have no su)h reservations and eel re-)a!ling is onl( needed i (ou %antdierent lengths or a more supple or less mi)rophoni) )a!le* not ever(one %ill agree %ith me there though$

The !ig .uestion is i this headphone is %orth the pri)e$$$$$ %ell that depends$ + (ou are looking or a headphone that sounds neutral anddoesn't need an( modii)ations + %ould suggest the HD668* + (ou %ant a more 'un' headphone %ith a modern look perhaps the HD661"although a !it shrill at times# $ + (ou aren't araid o hot tre!le the HD681 and HD681- )ould make a !etter )hoi)e$ Onl( %hen (ou hatehot tre!le and love ex)essive %armth and pronoun)ed !ass "as in opposed to 'tight' )lean !ass# the EVO is a good )hoi)e$

O )ourse* those reading this arti)le %ill pro!a!l( like to kno% +2 thisheadphone )an !e made to sound a lot more neutral$ The good ne%s is$$$$(es$$$ it )an !e made into an ex)ellent sounding headphone %ith someeort$ 3ith some extra unds spent on it* the modiied HD681-EVO %illgive more expensive headphones a good run or their mone($Superlux headphones are ex)ellent value or mone( an(%a( and )aneasil( )ompete %ith 9:;H more expensive headphones$ Those that liketo read a!out the HD661 as %ell as the HD681 and it's modii)ations )ando so in the arti)le 'HD681.... revisited' and 'Superlux HD-661'$

These arti)les )an !e ound here&http&di(audioheaven$%ordpress$)oms)hemati)sheadphone

On the right* a revamped HD681$ +t has aluminium trimming instead o redplasti) ones*


2/11

Some observations and measurements and analysis

lot has !een said a!out the issue o '!urn in'$ ll + )an sa( a!out it is@having modiied man( HD681 + have ound that some o them sho%edpoor !ass response right out o the !ox that improved in the irst e%minutes and in one )ase even took an hour$ + also ound not all HD681had a similar amount o !ass$ This is not !a)ked up %ith hard a)ts"plots# !ut determined su!7e)tivel( !( means o )omparing !et%een m(o%n "modiied# HD681 and another modiied version$ The irst test to seei large dieren)es o))ur in the irst e% hours is !( measuring theheadphone dire)tl( out o the !ox "magenta tra)e# leaving it un tou)hedon the measurement rig$ 'urn it in' %ith 0O:D !ass heav( musi) or

A hours and dire)tl( ater that measure it again " tur.uoise tra)e# to see ithere are note%orth( )hanges that %ould make me think %ould !e .uiteaudi!le$ + %ould see a tin( dieren)e "max ?$>d# in the lo%est re.uen)(range !ut don't think %ould !e ')learl(' audi!le$ 3aterall plots sho% no)hange as %ell and thus aren't sho%n$

The dieren)es !et%een sto! HD681"red trimming# and sto! HD681-EVOare sho%n !elo%$

=reen tra)eB HD681 "red trimming#5ed tra)eB HD681-EVO "%ith the "elt removed#

2rom 1?H, to 1kH, the( !ehave ver( similar* that part )ould !e the'HD681' in the t(pe num!er HD681-EVO$ !ove that point things start todier* + guess this is the 'EVO' part in HD681-EVO$The pier)ing highs o the original HD681 are )learl( visi!le in the greentra)e$ The( rea)h similar levels as the lo%s so the HD681 sounds !ass(and "pier)ingl(# !right at the same time %ith su!dued mids$The upper mids "rom 1kH, to >kH,# are a good Ad louder in theoriginal HD681 making it sound a 0OT ')learer'$ !ove AkH, the highs othe EVO are a good 1?d soter and less 'ragged'* a real improvement$The lo%er mids and highs make the EVO sound 9:;H darker and less'resh'$ The mids and highs ma( !e 'more !alan)ed' !ut the( are hugel('overpo%ered' !( the massive amount o lo%er mids and lo%s$

3hen )omparing the HD681-EVO %ithout elt and the HD681 one thing is ver( o!vious$ 3hile the HD681 driver looks the same "%hen theoam dis) is removed# the( )ertainl( do not measure nor sound the same or even remotel( similar$ +n some ora it is )laimed that %hen theelt dis) )overing the EVO driver has !een removed the headphone sounds a 0OT !righter and is "almost# indistinguisha!le rom theoriginal HD-681* there!( suggesting the drivers are pro!a!l( the same$ Either 'versions' exist or .ualit( )ontrol is !ad i this %ere true$

ext measurement$$$ #$at does t$e "elt doC lue tra)eB elt removed* green tra)esto)k "elt on driver#$

s expe)ted the elt does ae)t the highs !ut not nearl( enough assome people )laim it does$2rom 6kH, up%ards %e )an see some inluen)e and around 1?kH, theelt seems to dampen the highs !( a good -d$ !ove 1?kH, thedieren)e is %ell over Ad$+ndeed the removal o the elt makes the HD681-EVO sound a !it')learer' and a lot 'airier' !ut the area !et%een 1kH, and AkH, is still agood Ad lo%er than the original HD681 and unae)ted !( the elt$ sseen in the plot a!ove the highs o the original HD681 are a good 1?dlouder %hile the elt removal onl( (ields an in)rease o - d in thesame area$ =ranted that 1?d o the HD681 is argua!l( 3F toomu)h and makes it sound si!ilant or harsh$ ased on measurements%e )an )on)lude* that %hen the elt has !een removed some o thehighs are )learer and it sounds !etter %ithout the elt to most people$

3e )an also )on)lude that the drivers themselves do OT seem to !e the S9E given the a)t that under the same )ir)umstan)es "no eltover the driver !ut oam dis)s in pla)e# the HD681 and HD681-EVO measure very dierent rom 1kH, up%ards$

9ost people %ith experien)e in modi(ing headphones %ill !e ver( mu)h a%are o the a)t that pads that ma( look the same ma( soundver( dierent* the DTGG? DTII? pads are a good example$ This raises the next .uestion$ re those dieren)es in the 1kH, to ?kH,region )aused !( the dierent pads !e)ause the( do dier in material and depth "or height depending on ho% (ou look at this# C

lue tra)eB EVO pads ""elt removed#orange tra)eB HD681 pads ""elt removed#

s expe)ted there are some dieren)es !ut notin the 1kH, to AkH,region* some dieren)es are seen a!ove 1?kH, !ut )ould also partl( !ea measurement artea)t !e)ause o slightl( dierent positioning$ 3hatdiers mostl( is the lo%s$+t seems the HD681 pads a!sor! some o the energ( !et%een 1?h, andA??H, resulting in slightl( "-d# less !ass$ So a slightl( less 'dark

sound %ith HD681 pads$ The EVO pads thus seem to )ontri!ute a !it tothe massive !ass and '%armth' signature as %ell$ The sharp dip at >kH,"rea)hing -?d# did not )hange %hi)h also seems to )onirm the ideathat the drivers indeed DO dier$ The su!stantial measura!le dieren-)es !et%een the t%o models do not seem to !e )aused !( the pads northe elt and appear to !e mainl( a driver issue$


3/11

%ads& '$at an t$ey do ?

/ersonall( + don't reall( )are mu)h or pleather pads$ The( tend to lake as time goes !( and the( are used intensivel( or 'harden'$ lsothe( eel .uite hot on (our ears and !e)ome .uite s%eat( ater a %hile$ Velour pads have a ni)er eel so it stands to reason to ind out %hatother pads )an !e used and ho% the( inluen)e perorman)e$ s the diameter o the HD681 and HD681-EVO )ups is the same the mosto!vious )hoi)e is to use the ? pads have almost the same diameter and )an 7ust it on there$ 3hile pla(ing %ith dierent pads also thepleather version "S5H-8>?# %as tried$ s these pads %ere on)e !ought or modi(ing 2ostex TA?5/ headphones* + also had some original2ostex pads at m( disposal %hi)h also it* al!eit a !it 'tightl('$

elo% the results o these experiments* !lue tra)eB original HD681-EVO pad* red tra)eis other pad$

!ove& red tra)eB ? pads do something similar as the HD681 pads$tre!le is )onsidera!le less '7agged' and !etter extended$ ass is lo%ered !( d and 1kH, to kH, region is raised !(

d$ Highs are less '7agged' and also slightl( higher in amplitude$Overall the '%armth' is redu)ed !( a!out >d and indeed the EVOsounds !etter !ut still .uite %arm and !ass($ +nterestingl( enoughthe >kH, dip is smaller$ The S5HI>? pads are oval pads and area)tuall( a !it smaller !ut )an !e itted$ 2or some people onl()hanging the pads to S5H-I>? ones ma( all !e that is needed J

!ove& red tra)eB Shure S,H-8*+ pleat$er pads$ !ove& red tra)eB 2ostex 0+,% pleat$er pads$ass levels are a!out the same !ut the mids and highs are e)ause these pads are 9:;H thinner as the original padsraised a!out >d ee)tivel( )reating a similar ee)t as the the drivers are mu)h )loser to the ear* there!( in)reasing theS5H-I>? pads do !ut in a dierent %a($ Some%hat more mids in amplitude$ There is still a irm !ass !ut the slope !et%een'7agged' and %ith more ')larit(' )ompared to the sto)k EVO pads$ 1??H, and >kH, is mu)h less and thus sounds mu)h less %arm$ $Overall the '%armth' is also redu)ed !( a!out >d$ The in)rease o mids !( a good Ad is more than a su!tle )hangeThe( are more V-shaped like the HD681 %hi)h makes it a more 'un' and makes it 9:;H !etter sounding$ dd the a)t that rom 1kH,sounding headphone %hen these pads are used$ The 'su)ked out' to ?kH, the levels are .uite 'lat' makes a %orld o dieren)e$mids still don't make it into a realisti) sounding hi-i headphone$ + (ou do not like to do an( modii)ations that re.uire opening theThe >kH, dip is also smaller* 7ust like %ith using the S5H-I>? pads$ Headphone or tinkering %ith ele)troni) )omponents and are not9a(!e using these pads is all it takes or some people !othered !( thin pleather pads this %ill !e the easiest modii)ation

that makes the HD681-EVO into a mu)h !etter sounding

headphone %ith the smallest amount o eort$

+ (ou ind the HD681-EVO %a( to !ass( and la)king )larit( and mids* all it takes ma( !e to remove the original pads* pull o the elt "onl(glued around the edges# and it the "oval# TA?5/ pads$ little !it o sear)hing on the %e! %ill (ield a e% addresses %here these pads )an !e pur)hased$ +n the 2ostex TA?5/ modii)ation s)enesome people might !e a!le to suppl( (ou %ith a pair o those pads as %ell$


4/11

Driver properties

So ar %e have !een looking at one driver onl( to make )omparisons and see %hat )hanged !ut headphones have drivers and the( haveto 'mat)h'$ oth sides have to pla( e.uall( loud at ea)h re.uen)($ Even %ith more expensive headphones there )an !e )onsidera!ledieren)es !et%een !oth drivers that ma( rea)h several d's$

On the let the 25 plot o the let and right driver o a sto)kHD681-EVO "so %ith elt over the driver# in one plot$lue tra)eis 2e"tdriver* 5ed tra)eis ,i3$tdriver$

s this %asn't a revie% sample that )ould have !een sele)ted toperorm !est !ut %as !ought in a store %e )an assume this is a

representative sample o %hat has !een put on the market$Driver mat)hing seems ex)ellent$ The dieren)es a!ove 1?kH,should not %eigh too heav( as the( )ould ver( %ell !e )aused !(slightl( dierent positions on the test rig as %ell$

Some headphones have %ildl( var(ing impedan)es indi)atingresonan)es$ 3hen the impedan)e rises a a)tor t%o or more andthe headphone is driven rom an ampliier that has a high outputresistan)e these headphones )an sound a lot dierent$ This is

explained in the arti)le 'resistance, impedance and other issues%ound on&http&di(audioheaven$%ordpress$)omtutorialsarti)les$3e )anmeasure the impedan)e !ut %ould have to )al)ulate the ee)t it has on the sound$ +t is thus easier to measure the ee)t dierent output

resistan)es have on the HD681-EVO rom an ampliier "/ro7e)t Em!er# in settings "?$1and 1?#$

lue tra)eB ?$1output 5, greenish tra)eB 1?output 5

+t seems there is ver( little inluen)e in the re.uen)( response

aside rom the 1d drop in S/0 %hi)h %as )ompensated or$The plot %as )ompensated in amplitude so it is easier to see%hat happens in the re.uen)( domain$ t the point %here the lines deviate there is some inluen)e and this generall( points toresonan)es$ 2or the higher re.uen)ies the deviation is not)aused !( resonan)es !ut rather !( a rising impedan)e )aused!( the indu)tan)e o the voi)e )oil$The deviation at the main resonan)e point "around A?H,# is onl(!oosted a!out ?$Ad indi)ating the impedan)e has not risenmu)h at that point$ 3e )an also see a VE5F small deviationaround 8??H,* kH, and AkH, indi)ating resonan)es$ !ove1?kH, the indu)tan)e o the voi)e-)oil makes the impedan)e riseand thus starts to deviate$ The original HD681 sho%s similar!ehaviour regarding a )hange in 25$ The drop in overall S/0*

ho%ever* )an easil( invoke the eeling the sound )hanges)onsidera!l( %hile in realit( the real )hange isn't that !ig$

O )ourse re.uen)( range !ehaviour doesn't tell the %hole stor( and the most eared*and on 1?)onsidered 'ruined'* damping a)tor

might sho% itsel more in ;SD "%aterall# plots as these plots sho% ho% the sound de)a(s over time %hen the sound is suddenl( muted$

!ove ?$1 ampliier %aterall plot 1msdiv A??H, to kH, !ove1? ampliier %aterall plot 1msdiv A??H, to kH,

elo% ?$1 ampliier %aterall plot 1?msdiv ?H, to kH, elo%1? ampliier %aterall plot 1?msdiv ?H, to kH,

s )an !e seen the HD681-EVO does not !ehave ver( dierent on vastl( dierent output resistan)es$ This +S a ver( good thing !e)ausethe ele)troni) ilter that is going to !e dis)ussed on page 6 uses resistors in this range$

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5/11

4oam5 'ool5 "elt and pad t'ea!s

9ost people that have un or take pride in modi(ing headphones pla( around %ith elt* oam* !itumen* %ool* glassro)k %ool* )otton orother damping materials$ +t is* ho%ever* .uite dii)ult to determine "and a!ove all reprodu)e# the same ee)t %hen these mods areperormed !( others as dierent densities o materials )an have a prooundl( dierent ee)t$ 3hile it is possi!le to do some t%eaks !( ear%hat one reall( needs is a %a( to measure %hat is !eing done$ lso it is ver( hard to )ompare a !eore and ater mod )omparison as morethan 7ust a ph(si)al )hange has o))urred in the passed time rame and auditive memor( isn't %hat + %ould )all a relia!le thing$

The ee)t o the mm thi)k and dense elt dis) that is glued in ront othe driver has !een dis)ussed on page !ut as a reminder it is sho%non the let$lue tra)eB elt dis) removed$

=reen tra)eB elt dis) in pla)e "sto! ondition#

The elt dis) starts to %ork a!ove AkH, and ilters more the higher there.uen)( is$3hen a headphone is )onsidered to sound ver( 'detailed' %e oten see arise in the AkH, to 1?kH, region$ +n a lot o )ases %e also see a drop-oa!ove 1?kH, ater su)h a peak$This is onl( per)eived as sounding 'detailed' !ut is a ake orm o it'detail'$ Onl( %hen the range rom AkH, to 18kH, runs reasona!l('smooth' and isn't raised %e )an hear true details$ This isn't somethingthat all headphones do %ell* in a)t most roll o !eore 18kH,$

The elt apparentl( also removes a lot o 'energ(' a!ove 1?kH, %hile the driver itsel still produ)es this$ 5emoving the elt thus not onl( litsthe highs "a!ove AkH,# !ut also extends the re.uen)( range$ !ove 1?kH, %e get in the area that deines the 'air' around instruments andgives that realisti) 'shimmer' to )ertain instruments$ Headphones that are %ell extended anddo not sho% a ver( 'ragged' top end in theirre.uen)( plot usuall( sound ver( detailed and air(* %hile headphones that drop o a!ove 1?kH, ma( still sound detailed "espe)iall( %henthe A-1?kH, region is raised a !it# !ut la)ks 'air'$ 5emoving the elt %ill (ield more "ake# details !ut also !rings orth the 'air' it la)ked$

So ar the ee)t o the elt$ Ho%ever* in ront o that elt there also is aoam dis) %ith )loth on it$ O )ourse this too has an ee)t !ut not asdramati) as that material is a lot thinner and less dense$On the let it a plot that sho%s %hat the oam dis) exa)tl( does$5ed tra)eB'it$out"oamdis)*=reen tra)eB'it$ "oamdis)$+t onl( seems to inluen)e the area !et%een 6kH, and 1kH, and !( 7usta e% d$ +n order to get the ')riti)al' area !et%een AkH, and 1?kH, a !itlo%er the oam should thus not !e removed* other%ise some shrillnessor si!ilan)e ma( !e the result$The plot on the let is %ith the elt removed and an ele)troni) ilter isused$ + )an thus highl( re)ommend to leave the oam dis) in pla)e$

2or those that like to !ut damping materials like %ool or )otton et)$ +n)ups to address !ass issues the plot on the let sho%s the ee)t oadded %ool in the ')ham!er' dire)tl( !ehind the driver$ +n this )ase realsheep %ool %as used and the densit( %as rather high so a !it )rammedin there$ lue tra)eB'it$out%ool* magenta tra)eB'it$%oolThe ee)t is not su!tle and the lo%est re.uen)ies are ae)ted most$!out -Ad around >?H, dropping to d near 1??H,$!ove ??H, the ee)t is as good as gone$The dieren)es seen in the highs are not )aused !( the %ool !ut !(slightl( dierent positioning o the headphone %hi)h oten )auses small)hanges in that re.uen)( area$

The measurements on the let are made %ith an ele)troni) ilter andShure S5H-I>? velours pads$dding %ool !ehind the driver does not ae)t the entire area that needsto !e addressed "?H, to 1kH,# so )annot !e used to o!tain a 'lat're.uen)( response !( itsel %ithout using the ele)troni) ilter$ +t )an !e

used to remove the small peak around A?H,$ /ersonall( + don't mind that small peak as >?H, is 'su!%ooer' territor( and mu)h lo%er thana)tual !ass notes* so adds some 'un' in the headphone$ Slight damping is advisa!le and have applied some in this version$

/ads have !een dis)ussed on page alread( and sho%s that the sto)k pads exhi!it more '7agged' !ehaviour in the* rather )riti)al* area!et%een AkH, and ?kH,$ e)ause o this velours pads "!oth ? pads# sho% a %orth( in)rease in sound.ualit( regarding the highs$ Extension* smoothness and detail retrieval have improved noti)ea!l($

elo%& red tra)eB ? pad* !lue tra)eB sto)k pad elo%& red tra)eB S5H-I>? pad* !lue tra)eB sto)k pad

A


6/11

0$e eletroni "ilter a tunable solution

Even though the TA?5/ pad modii)ation is simple and ee)tive in )reating a 9:;H !etter sounding headphone it also has a e%do%nsides$ These pads are a!out times thinner than the original pads %hi)h means someone %ith more protruding or sensitive pinnaema( experien)e some dis)omort %hen the ears tou)h the driver en)losure$ nother do%nside "to me# is the( are pleather pads and thusalso get s%eat( and 'sti)k(' on %armer da(s$ 9( preeren)e lies in thi)ker velour pads$ The most o!vious )hoi)e %ould !e the ? pads :T these have less !ass )ompared to the original pads$ 3hen these pads are used theilter should !e altered a))ordingl($ This also means that %hen a ilter or the S5H-I>? pads is itted and the original pads are used (ou %ill!e experien)ing a!out d more lo%s* as i (ou turned up the '!ass' )ontrol a e% not)hes on an old ashioned ampliier$

The next .uestion %ould !e to ask (oursel i (ou %ant 'reeren)e grade' lo%s* in other %ords a))urate !ass !ut onl( a))urate at higherlistening levels* or a more 'un' t(pe o !ass$ One has to realise that pere)tl( lat reprodu)tion ma( sound dull and !oring %ith lots o)ommer)ial musi) as that is intended to !e pla(ed on speakers or '%arm' headphones$ 3ell re)orded musi)* ho%ever* %ill sound ver(good on a 'lat' headphone$ 3hen (ou %ant more 'speaker alike' sound reprodu)tion the ?H, region should !e a!out >d )ompared to1kH, so !asi)all( !e a !it tilted do%n%ards to 1kH, $ 2rom 1kH, on%ards 'lat' is )onsidered !( most to give a detailed sound$ Those thatlike a ver( mello% sound %ill most likel( preer slo%l( do%n%ards sloping highs that have dropped a!out d around 16kH,$

2or this reason it %ould !e ni)e i the ilter )ould !e ad7usted to have dierent !ass responses$ +t %ould also !e ni)e i the highs )an !ead7usted independentl( as %ell to suit (our taste$ 2ortunatel( the HD681-EVO isn't responding in a !ad %a( to resistors !eing added inseries %ith the driver and this opens up possi!ilities$ nother ver( ortunate )ir)umstan)e is the a)t that rom 1??H, to 1kH, the )urve issloping do%n%ards in a 'linear' %a($ This is a 0OT easier to )ompensate as %hen this slope %asn't as gradual$e)ause o these assets o the HD681-EVO a simple (et ver( versatile ilter )an !e )onstru)ted %ith 7ust > )omponents$

The s)hemati) is ver( simple and !asi)all( )onsists o separatese)tions$ 51 and ;1 orm the lo% ilter se)tion$ 5 and 01 orm the high

ilter se)tion$ The )apa)itor has a value o 1?2 and must !e o the non-

polar"or bi-polar# t(pe$ 2ilm t(pe )apa)itors %ill !e rather !ig in si,e !ut(ou )an also use !i-polar ele)trol(ti) t(pes$ minimum voltage rating oAV should !e used$ These t(pe o )apa)itors ma( !e dii)ult to o!tain$There is* ho%ever* a tri)k so polarele)trol(ti) )apa)itors )an !e used$Tantalum )apa)itors )an 7O0!e used this %a($ T%o polar )apa)itors* thathave to !e dou!le the value o the )apa)itor it repla)es* must !e)onne)ted in anti-series$ This means )onne)t the o !oth )apa)itorstogether and the '' )onne)tions no% orm the !i-polar )apa)itor assho%n !elo%$

+n this )ase x 2AV polar ele)trol(ti) )apa)itors %ill !e)ome an 112AV !ipolar )apa)itor %hi)h is )lose enough to repla)e the

1?2$ O )ourse 2AV or 2A?V )an also !e used$

51 and 5 )an !e small si,ed resistors* po%er rating )an !e an(thing !et%een ?$>3 K 13$

5esistor 51 determine ho% 9:;H lo%s are iltered$ The ee)t o a e%dierent pra)ti)al values is sho%n on the let$

9agentatra)e B ?

Fello%tra)e B

5edtra)e B

luetra)e B 68

=reentra)e B 1??

Fou )an sele)t the amount o '!ass' and '%armth' (ou %ill need$ This %illdepend on the used pads$

2or ?sto)k EVO pads 6is optimal i (ou %ant a 'lat' sound$

2or ?sto)k EVO pads is optimal i (ou %ant a 'un' sound$

2or S5H-I>? pads *9is optimal i (ou %ant a 'lat' sound$

2or S5H-I>? pads

is optimal i (ou %ant a 'un' sound$

The ilter se)tion that )ontrols the highs )onsists o 01 and 5$ The elt pads have to !e removed or this tri)k to %ork$ This %ill also extendthe higher re.uen)ies and make instruments sound more 'air('$

01 B 1mH* it's resistan)e should not !e higher than $Aand must !e

a!le to handle 1A?m$ 9ind the ph(si)al si,e %hen ordering as lo%resistan)e t(pes )an !e huge in ph(si)al si,e$e)ause the highs don't need to !e lo%ered that mu)h smaller steps)an !e made$ On the let the ee)t o a e% resistor values is sho%n$

luetra)e B ?

Fello%tra)e B 1?

Orangetra)e B

=reen tra)e B

Values a!ove I%on't ae)t the ilter a)tion an( more$2or those that don't like highs %ill do 7ust ine$

2or those that %ant a !it o extra 'sparkle' 1Ato might !e !etter$

6


7/11


8/11


9/11

/ull o the part that %as )onne)ted to thehead!and$9ake sure the %ires do not get )aught in its hole%hile removing it$

ote the paper ilter on the let$ +t ma( !e stu)kinside the removed head!and part or ma( still lie ontop o the driver$

Do not orget to put it !a)k %hen reassem!ling the

headphone$ The ee)t it has on the sound has not!een resear)hed !ut 7ust like damping material hasan inluen)e the paper %ill most likel( also havesome inluen)e on the !ass response$

)lose-up o the )onne)tion !oard "/;# o the driver$The %hite and red %ires %ill have to !e removed$O72Ysolder the pads indi)ated !( the orange arro%s$

7EVE,tou)h "or solder# the pads in the !lue )ir)le* these are the pads %here theextremel( thin %ires rom the driver itsel are )onne)ted to and these %ires are VE5Fragile and easil( damaged J

:e"oreun-soldering these %ires )areull( 'lit' ea)h %ire rom the plasti) pins in thepurple )ir)le$ The( are sort-o 'glued' %ith a kind o sti)k( material$ The %ires )an !epulled slo'ly and gentl($ 9ake S:5E (ou do 7O0pull too hard or (ou %ill risk tearing o the pads rom the small )onne)tion /;$5epairing this %on't !e eas( so reall( take (our time* dose the amount o pulling or)e on these %ires and )losel( o!serve %hat'shappening$

On)e the %ires are ree "pi)ture on the let# !oth %ires )an !e un-soldered$ Do OT heat these padsto long or use 1?? 3att soldering irons or soldering guns as the solderpads ma( )ome o rom the/; material

9ake the t%o individual ilter se)tions asin the example sho%n on the right$

1mH indu)tor "01# and Iresistor

"5# are soldered together$The resistor si,e is S2516 "6$ mm !od(length#$

s + did not have a 1?2 !ipolar )apa)itor ";1# at hand + made )reated !(

soldering x 21??V in anti-series " o !oth )aps )onne)ted together and

!oth legs are )onne)ted to a 68S2516 si,ed resistor "51#$ 3hen using a

single 1?2 !ipolar )apa)itor simpl( solder 51 to its pins similar to ho% 01 is soldered to 5$ + reommendvalues !et%een and

s the ilter se)tions are in series it doesn't reall( matter i the( are )onne)ted together and then tied to one )onne)tion o the driver O5

that ea)h se)tion is )onne)ted to either side o the driver's )onne)tion$ This tri)k )annot !e done in an extension )ord as in that )ord onl(the signal %ires ma( have the )omplete ilter se)tion in series and the )ommon %ire must OT have parts in its path$

The small )onne)tion /; has a e% unused pads o %hi)h %eare going to use the !iggest one "on the let in this pi)ture#$Solder one side o the ;151 to the unused pad and solder thered %ire to that same point "in the red s.uare#$ This %ill ensurethe ilter )apa)itor is held irml( in pla)e$ The other part o theilter has to !e soldered onto the pad %here the red %ire %asremoved rom earlier$ This is the pad in the !lue )ir)le$

e sure 7O0to tou)h the pads next to the one in the !lue )ir)leas this %ill almost )ertainl( destroy t$e driver J

The )apa)itors )an !e ixed to the magnet %ith some hot-meldglue* sili)one kit or glue$

Solder the %ires .ui)kl($ Don't heat the pads or too long or the(%ill deta)h themselves rom the /; material$

I


10/11

The +ndu)torresistor )om!ination "01*5# needs to !e)onne)ted to the pad "in the tur.uoise )ir)le# %here the %hite%ire %as removed rom$

Solder the %hite %ire to one end o the 01*5 ilter se)tion$Solder the other part o that ilter se)tion onto the pad in sho%nin the tur.uoise )ir)le$

Se)ure the indu)tor %ith some hot-meld glue or sili)one kit tothe side as ar a%a( as possi!le rom the driver's magnet$

5oute the red and %hite %ires through thehole %ith the protruding rim on it$

+n )ase (ou %ant the lo%est part "?H, to 1??H,# o the re.uen)(

range lo%ered a !it more (ou )an add some %ool in the driver)ompartment$ The ee)t o this is dis)ussed on page A and as areminder sho%n !elo%$ The tur.uoise tra)e is %ith ver( densel(pa)ked %ool* the !lue tra)eis %ithout an( %ool$9ake sure to use the exat same amounto %ool on !oth drivers J

/la)e the paper ilter as sho%n on the let and )areull( align the )up holder "the holesmust !e aligned# and push it !a)k in pla)e$

9ount it on the head!and assem!l( and tighten the s)re%$

5esolder the %ires exa)tl( like the( %ere )onne)ted !eore$ +solate the !lue %ire* thatis )onne)ted to the red %ire rom the driver assem!l(* %ith some shrink tu!ing orisolation tape$ Tu)k all the %iring ni)el( inside the !oundaries o the head!and part so

the plasti) panel )an )lose )orre)tl( and doesn't )at)h or mutilate an( o these %ires%hile putting it !a)k together$

O!serve ho% the head!and tensioning me)hanism %orks and make sure ever(thingslides reel( in its proper position and ever(thing aligns pere)tl($

9ake sure the plasti) side-panel )at)hes onto the hooks "highlighted in the pi)ture onthe right# o the driver assem!l( and pull it up%ards to%ards the head!and$ The )hrometop plate "sho%n !elo% in red# has an indent and the side-panel must !e aligned so italls into a small slot in the side-panel$ /ress ever(thing together till it snaps shut$9ount the small s)re% that holds the side-panel$

5epeat the pro)ess or the )up on the right side$ 9ake sure tonote the %ire orientation rom the driver assem!l( to the rods$

+ these %ires are a))identall( s%apped (ou %ill get a %eird u,,(stereo image$

1?


11/11

0$e "inal result

ll these modii)ations have one goal and that is to o!tain a mu)h 'latter' and a))urate re.uen)( response that is more true to the a)tualre)ording$3hen (ou are o the opinion the HD681-EVO sounds pere)t as is and (ou like the overl( %arm sound signature %ith huge !ass (ou neednot !other doing all these modii)ations* 7ust en7o( it as it is$ +* like me* (ou eel the headphone needs some improvements + )an highl(re)ommend the des)ri!ed modii)ations$

+ (ou %ould onl( like the !ass to !e slightl( less than all (ou need is a lot o dampening %ool !ehind the driver or onl( the ;151 se)tion

and use 1?2 %ith or 51$ + (ou eel the highs are good as it is leave the elt in pla)e$ + (ou like to spi)e up the highs slightl( simpl(

remove the elt dis)$

Ho%ever i (ou %ant this headphone to !e)ome a ar more a))urate headphone andor tune it to (our taste the )omplete ilter in anextension )ord %ith the resistors repla)ed !( small linear potentiometers or trimmer potentiometers$ 3hen (ou have set it to (ourpreeren)e (ou )an repla)e the potentiometers !( ixed value resistors and leave it in an extension )ord or mount it inside the )ups$

+ ound the values or 51 B 68* 5 B Iand 01 B 1mH to give the

'lattest' sound$ The headphone %ent rom 'dark' to 'a))urate'*a total transormation o the sound$

2or a more 'un' headphone + re)ommend 51 B -A6* 5 B 1?-

and 01 B 1mH

The sound also )hanges slightl( %ith dierent pads $+ ound the Shure S5HI>? pads to !e the most )omorta!le and !estsounding option* )losel( ollo%ed !( the ? pads and

some dampening %ool in the rear o the driver "!lue tra)e# )ompared tothe sto)k "orange tra)e# version$

plot o !oth )hannels o the end result "ilter* S5HI>? pads and some%ool#$ Some ver( slight im!alan)e !et%een 0and 5drivers !elo% ??H,is visi!le !ut !elo% audi!le dete)tion$ This )ould !e 'tuned' a little !( eithervar(ing the value o 51 or )hanging the amount o damping materials$ +nthis )ase the im!alan)e is )aused !( !oth drivers having some%hatdierent amounts o %ool$

The sound o this headphone is ver( '!alan)ed' and ma( not !e liked !(

ever( one$ 2or this reason + re)ommend to pla( %ith ilter values in orderto ind the sound that suits (our taste$

s %ith ever(thing in lie ea)h upside has a do%nside$ On page > it )an !e seen that dierent output resistan)es o ampliiers have little tono ee)t on ho% this headphone sounds$ 3+TH the ilter* ho%ever* a dierent output resistan)e %ill have a pronoun)ed ee)t on the soundas the ilter a)tion is "partl(# undone$

+n order to make the headphone perorm as in the re.uen)( plot a!ove the output resistan)e o the ampliier must !e lo% "NA )$

9ost modern ampliiers and porta!le e.uipment all in this output resistan)e range !( the %a($

2or those using ampliiers %ith dierent output resistan)e settings this dependen)( provides a un 'tuning' possi!ilit($The higher the output resistan)e o the used ampliier the more V shaped the modiied HD681-EVO !e)omes$

The tur.uoise tra)eis taken %ith the output resistan)e o the ampliier "in

this )ase the 'pro7e)t Em!er'# in 1?setting$ The orange tra)eis taken in

?$1setting$ The Asetting is not sho%n !ut alls exa)tl( !et%een these

tra)es$This plot is made %ith the sto! pads$

3ith the ilter and dierent output resistan)e settings this headphone )an!e made to sound either a))urate* a !it more un and to have a !ig* !ut notover%helming* !ass !( a simple sele)tion o another output resistan)e$

2or those interested in the ampliier designs used "all %ith sele)ta!le output resistan)e# and the original HD681 as %ell as the HD661modii)ations these )an !e ound in the links !elo%&

HD681* HD681-EVO and HD661 modii)ations& http&di(audioheaven$%ordpress$)oms)hemati)sheadphone"s)roll some%hat do%n#/ro7e)t Sunrise-++* Hori,on* Starlight and Em!er ampliiers&http&di(audioheaven$%ordpress$)oms)hemati)sampliier"s)roll do%n a !it#

5emark* )omments* dis)ussions and more !a)kground inormation )an !e ound on this orum& http&di(ah$!oards$netin the HD681-EVOthread$ + )an !e )onta)ted on this orum as %ell in )ase it is needed$

Solderdude* Sept ?1
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