LAB­O­RA­TORY TEST RE­PORT

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The fre­quency re­sponse of the Dy­nau­dio 60, as mea­sured by Newport Test Labs, was ex­tremely flat, very ex­tended and ex­cep­tion­ally well-bal­anced across the au­dio spec­trum, with per­haps just a very slight roll-off at the ex­treme high end of the au­dio spec­trum, and a rather steeper roll-off that only oc­curs 1kHz above the ac­cepted higher limit of hu­man hearing (20kHz).

The fre­quency re­sponse trace shown in Graph 1 shows the Con­tour 60’s re­sponse as ex­tend­ing from 28Hz to 22kHz ±3dB, which is not only ex­cel­lent, but also pos­si­bly one of the first times Newport Test Labs’ mea­sure­ment has been al­most ex­actly the same as that of the man­u­fac­turer. I say ‘al­most’ be­cause Dy­nau­dio spec­i­fies the fre­quency re­sponse of the Con­tour 80 as ex­tend­ing from 28Hz to 23kHz ±3dB—so with an ex­tra 1kHz ex­ten­sion—but that in­crease in ex­ten­sion is so mi­nor that it’s re­ally to all in­tents and pur­poses the same re­sponse. (Such small dif­fer­ences could be due to model vari­a­tions, mea­sure­ment con­di­tions… many rea­sons.)

Read­ers should note that the graph shown is ac­tu­ally the re­sult of two sep­a­rate mea­sure­ments that have been spliced to­gether us­ing post-pro­cess­ing. Below 800Hz, the trace is the av­er­aged re­sult of nine in­di­vid­ual sweeps mea­sured at a dis­tance of three me­tres. The trace above 800Hz was mea­sured at a dis­tance of one me­tre, di­rectly on-axis with the tweeter,

and us­ing a gated test sig­nal that re­turns the same re­sponse that would be re­turned if the speak­ers were mea­sured in an ane­choic cham­ber. The res­o­lu­tion of this gated tech­nique is ex­tremely high, so it shows dips and peaks in the re­sponse that would not only be in­audi­ble to the ear, but would also not be shown on a trace mea­sured us­ing the less-pre­cise im­pulse mea­sure­ment tech­niques that are so com­mon in the in­dus­try (used be­cause they’re cheap, and be­cause they make mea­sure­ments so fast that less time is re­quired to make them).

Graph 2 shows the high-fre­quency re­sponse of the Dy­nau­dio Con­tour 80 in even-more de­tail, but this time also shows the dif­fer­ence in fre­quency re­sponse be­tween us­ing the speak­ers with the grilles on (red trace) and with the grilles off (black trace). You can see that the two re­sponses are al­most iden­ti­cal, but that with the grille on there are very small dips at 7kHz and 9kHz that are not present when the grille is re­moved—plus the re­sponse above 15kHz rolls off just a lit­tle ear­lier with the grille fit­ted than when it isn’t. I think Dy­nau­dio has done an ex­cel­lent job with the acous­tic trans­parency of the grilles and I would rec­om­mend leav­ing them in place, even for crit­i­cal lis­ten­ing ses­sions, not least be­cause I do not be­lieve the dif­fer­ences shown would be au­di­ble.

Low fre­quency per­for­mance (mea­sured us­ing si­nus wave­forms and stan­dard near-field tech­niques) is shown in Graph 3. You can see that the out­put of the two ports is quite dif­fer­ent, mean­ing that you could ex­pect quite sub­stan­tial dif­fer­ences in sound if you block, say, the up­per port, rather than the lower port (and vice versa). The dif­fer­ence in the high-fre­quency out­put be­tween the lower of the two bass driv­ers and the up­per driver seems to sug­gest that Dy­nau­dio is run­ning the up­per driver a lit­tle ‘hot­ter’ than the lower one, but I think the slight ad­di­tional high-fre­quency ex­ten­sion is sim­ply a re­sult of the dif­fer­ent rear load­ing caused by the dif­fer­ent driver po­si­tion in the cab­i­net. You can see that without bungs, the driv­ers roll-off quite steeply below 50Hz to a min­ima at 28Hz, with the ports tak­ing over the bass du­ties. With both ports blocked, the bass driv­ers still roll off below 50Hz, but the slope be­comes far more shal­low (shown in Graph 4)… just as you’d ex­pect of this align­ment.

The dif­fer­ent align­ments (ports blocked vs. ports open) also af­fects the im­ped­ance of the speak­ers of course, and you can see the clas­sic ‘bass re­flex’ im­ped­ance curve in the black trace on Graph 5, which ex­hibits the two ex­pected low fre­quency peaks (one at 45Hz, the other at 15Hz) whereas when the bungs are in­serted—so the cab­i­net is es­sen­tially sealed—you can see the clas­sic ‘in­fi­nite baf­fle’ im­ped­ance curve ap­pear (the red trace).

Both im­ped­ance traces con­verge at around 70Hz, with the peak at 110Hz sug­gest­ing that Dy­nau­dio is us­ing the cross­over net­work to do some re­sponse com­pen­sa­tion to match the re­sponse of the midrange driver (which kicks in at 220Hz and is the rea­son for the dip in the im­ped­ance at 200Hz). As you can see, the speak­ers will present a load of mostly around 8Ω to any driv­ing am­pli­fier, but that dive in the im­ped­ance at 200Hz down close to 3Ω means that Dy­nau­dio has to clas­sify the Con­tour 80 as ‘nom­i­nally 4Ω’ un­der IEC reg­u­la­tions… which it does, as you’ll see if you look at Dy­nau­dio’s own spec­i­fi­ca­tions.

While you’re look­ing at those spec­i­fi­ca­tions, you’ll prob­a­bly no­tice that Dy­nau­dio rates the Con­tour 60’s sen­si­tiv­ity at 88dBSPL. Newport Test Labs’ mea­sure­ment for sen­si­tiv­ity came within a whisker of this fig­ure, with the lab­o­ra­tory record­ing a fig­ure of 87dBSPL at one me­tre for a 2.83Veq in­put un­der its stan­dard test con­di­tions. This is ac­tu­ally a very good re­sult, be­cause Newport Test Labs uses a more strin­gent method to mea­sure loud­speaker’s sen­si­tiv­ity than most man­u­fac­tur­ers, so al­most al­ways comes up with fig­ures lower than the man­u­fac­turer’s own spec­i­fi­ca­tions… of­ten con­sid­er­ably lower, so a dif­fer­ence of a mere 1dB is a mere bagatelle. At ei­ther 87dBSPL (or 88dB) ef­fi­ciency, the Con­tour 80s will not de­mand an overly-pow­er­ful am­pli­fier in or­der for them to per­form at their best.

That the Dy­nau­dio’s Con­tour 80s are su­perbly de­signed and en­gi­neer­ing was proved in ev­ery one of the many tests per­formed on them by Newport Test Labs: A su­pe­rior de­sign in ev­ery sense of that word. Steve Hold­ing

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