8-inch sub­woofer

InCar Entertainment  - - CONTENTS -

Hertz’s out­stand­ing engi­neers once again prove that small is beau­ti­ful… and can also be ul­tra-pow­er­ful.

Un­sure how to put this del­i­cately, so this is rather bluntly straight to the point; the Hertz Mille range went off the rails there for a year or two. Now as I com­mence but­ton­ing up the flame suit al­low me to place some his­tor­i­cal con­text around such in­con­gru­ous com­ments.

It started around ten years ago when Hertz was be­gin­ning to make se­ri­ous in­roads into the car au­dio mar­ket world­wide. Some au­da­ciously stated Hertz was just a flash in the pan and that its pop­u­lar­ity would promptly dis­ap­pear along with its flam­boy­ant or­ange pack­ag­ing. Not to stand for such in­so­lence Hertz struck back, de­vel­op­ing the Mille range which not only spent the en­su­ing years dec­i­mat­ing its com­pe­ti­tion, but be­came prove pos­i­tive that Hertz was no Johnny-come-lately to the high­end au­dio scene. This friends, is where things started to go a lit­tle pear shaped, as far as this au­thor is con­cerned. The com­pany rested on its lau­rels, re­leas­ing a new range of Mille com­po­nents that, while ac­cept­able, truth be told they were a shadow of their for­mer glo­ri­ous self. The re­sult be­ing that many peo­ple, this writer in­cluded, be­gan howl­ing like wounded ly­can­thrope about it. We fast for­ward to to­day where Hertz, never one to be friv­o­lous and in­deed one that lis­tens to its con­stituents has rec­ti­fied the sit­u­a­tion cre­at­ing a new Mille range. And it’s re­gal enough to bear the leg­endary Mille moniker once again.


To ac­com­pany the Mille com­po­nent speak­ers we re­viewed in is­sue #3-2015, Hertz de­vel­oped a pair of sub­woofers to fill out the bot­tom oc­taves of the Mille range – an 8-inch ML 2000.3 and 10-inch ML 2500.3. We’ve cho­sen the ML 2000.3 for re­view be­cause the Mille driv­ers are in­trin­si­cally sound qual­ity ori­ented, and sys­tems of this na­ture tend to not al­ways re­quire titanic-sized sub­woofers. For ex­am­ple; did you no­tice there’s no 12- or 15-inch vari­ant? How­ever, that said, the ML 2000.3 is no weak­ling, on the con­trary it has more col­lo­quial mus­cle than many other sub­woofers on the mar­ket, in­clud­ing meek im­i­ta­tions thrice its size.

Start­ing at the ki­netic end; the ML 2000.3 fea­tures a 200mm di­aphragm con­structed from a base core of pressed-pulp re­sult­ing in a very nat­u­ral sound. The up­per and lower sides are then sealed and treated with a min­eral pow­der coat­ing which gives ex­cep­tional rigid­ity and ter­rific damp­ing char­ac­ter­is­tics. Just paus­ing on the afore­men­tioned sub­ject; cone pro­file or shape, is some­thing that many read­ers gloss over with­out giv­ing it a sec­ond thought. Cone ge­om­e­try has ad­vanced in leaps and bounds over the years – it’s not just about brute strength. Of course, the abil­ity to re­tain shape un­der duress is most im­por­tant, but the ac­tual phys­i­cal pro­file of the cone is also para­mount

to the dif­fu­sion az­imuth and the pro­jec­tion of the sound for­ward of the driver. Hertz has spent count­less hours get­ting the cone shape of all the Mille driv­ers just right, util­is­ing its trade­mark-reg­is­tered ex­po­nen­tial V de­sign to give su­perb strength and au­ral re­pro­duc­tion. This is not only within the sub­sonic re­gions but also the higher mid­bass re­gions too, to the tune where the ML 2000.3 can sound equally com­pe­tent play­ing the sub­woofer role all the way through to that of a se­ri­ous mid­bass driver – some­thing most sub­woofers can only dream of.

As­sum­ing that you’ll be run­ning it in its in­tended role as a true sub­woofer, you’ll no doubt de­sire some se­ri­ous kick, and this equates to se­ri­ous sus­pen­sion. To that end the top edge is sur­rounded by a bound­ary-free IIR rub­ber sur­round which works in con­junc­tion with the flat non-pro­gres­sive rolled poly­cot­ton spi­der be­neath. These al­low the mo­tor to move freely but with scrupu­lous con­trol, within the dens­est mag­netic fluxes cre­ated by the ex­traor­di­nar­ily large neodymium mag­net which has been op­ti­mized with FEA sim­u­la­tions aplenty and lives within the core of the struc­ture. But the ex­trav­a­gance doesn’t end there. Work­ing with this mag­net is the cen­tral pole which con­tains a large alu­minium short­ing ring and to­gether the mo­tor moves with min­i­mum dis­tor­tion both ra­di­ally and ax­i­ally right out to its 23mm Xmax ex­cur­sion. Now the best mag­net in the world isn’t go­ing to do much with­out be­ing mar­ried up to an im­pres­sive mo­tor within, ergo the for­mer is a whop­ping 100mm item that’s con­structed from TIL, a ma­te­rial made from a fi­bre­glass base which of­fers the strength and weight at­tributes of Polyamide com­po­si­tions but pos­sesses the ther­mal dis- sipa­tion qual­i­ties of al­loys such as alu­minium. The voice coil is a sin­gle 4-ohms multi-layer af­fair, com­pris­ing of twin cop­per-clad alu­minium winds lay­ered one on ei­ther side of the for­mer in such a fash­ion to al­low for uni­form cool­ing of the en­tire coil, to the tune of it be­ing able to han­dle over 700 watts con­tin­u­ously be­fore the cool­ing sys­tem comes into ques­tion.

Kar­dashian at­tributes

See­ing as I’m an in­quis­i­tive soul I thought to look fur­ther into the cool­ing sys­tem and to do this we need to start with the acous­ti­cally trans­par­ent alu­minium frame, so se­lected due to its mag­net­i­cally in­ert and anti-res­o­nant prop­er­ties. The black an­odised bas­ket fea­tures six web fin­gers and built into each of these are the vent­ing in­take holes. These large in­takes feed cool air di­rectly into the voice coil gap just be­low the spi­der and, once within, this ze­phyr flows up and over the voice coil gap be­fore snaking its way into the cen­tre for ex­pul­sion via the 25mm pole vent. It’s not just any pole vent ei­ther – one glance gives con­fir­ma­tion that it’s a der­riere with a phys­iog­nomy ri­valling a Kar­dashian. Con­structed from a sin­gle gar­gan­tuan solid alu­minium block, the back cap is metic­u­lously ma­chined and boasts an ad­di­tional eight air vents with var­i­ous facets to as­sist in air flow. Be­sides en­cas­ing the en­tire mo­tor and mag­net the end cap also ex­tends down to pro­vide for ex­tra sus­pen­sion over­run, giv­ing the sub­woofer a max­i­mum power han­dling abil­ity of over 1400 watts be­fore bot­tom­ing out be­comes of con­cern.

The Hertz logo is proudly dis­played upon the back end while the ter­mi­nals are smarty at­tached to the side. What’s also in­ter­est­ing about the over­all back­end de­sign is that be­cause the voice coil is large, di­a­met­ri­cally speak­ing, it doesn’t have to be overly deep. This means that with a mount­ing depth of only 117mm you can have your cake and eat it too.

When talk­ing smaller sub­woofers and their as­so­ci­ated en­clo­sures many will pose the sup­po­si­tion that these driv­ers only han­dle higher fre­quen­cies, an as­sump­tion which is mis­placed to state the least. More of­ten than not the prob­lem lies with the en­clo­sure be­ing the in­cor­rect vol­ume to re­turn a de­sir­able Q. With this in mind, we set out to model the per­fect en­clo­sure, be­ing aware that Hertz rec­om­mend 10 to 17 litres sealed for op­ti­mum per­for­mance. It’s true that com­pa­nies of­ten un­der­size en­clo­sure rec­om­men­da­tions in or­der to har­bour less war­ranty re­turns be­cause the overly com­pressed air makes it harder to bot­tom the sub­woofer out. How­ever this im­pacts the en­clo­sure Q, of­ten send­ing it well over 1.0 and this is the ac­tual rea­son why many sub­woofers don’t ap­pear to play very low. Hertz in its wis­dom how­ever has recog­nised that be­cause the ML 2000.3 is a se­ri­ous sound qual­ity sub­woofer, it’ll likely lend it­self to an owner which ex­er­cises equal con­sid­er­a­tion in or­der to achieve a per­fect Q. Our mod­el­ling re­turned an en­clo­sure vol­ume of 16.06 litres sealed and Q of 0.707, which is right on par with Hertz’s rec­om­men­da­tion and this vol­ume also of­fers a con­stant group de­lay of 4ms.

As some­one who has sold and in­stalled plenty of Mille sub­woofers in the past, both the good and the not so, it was most cap­ti­vat­ing to see how this new one would stack up. It cer­tainly looks up to the task, easily ri­valling the orig­i­nal Mille sub­woofers and look­ing for all the world like it will pro­duce in spades. In­ter­est­ingly, Hertz does not sup­ply a grille as part of the pack­age but it can be pur­chased as an op­tion.

So how’d she go son­i­cally? Well putting it mildly, it’s one ex­tremely solid lit­tle per­former. In­deed the pri­mary thing that comes across even dur­ing its run­ning-in process is that it’s a strong sub­woofer, with a phys­i­cal pres­ence that com­mands the sound. This could easily be at­trib­uted to the colos­sal mo­tor within, how­ever, re­mem­ber back to what I said about the cone pro­file too. The sub-bass that em­anates from the ML 2000.3 is more than just a lit­tle hearty, es­pe­cially given its de­cep­tively diminu­tive di­men­sions and, thanks to the di­aphragm pro­file, its sound pro­trudes well for­ward of the cone, thus al­low­ing for it to be mated per­fectly with your front stage no mat­ter what the fre­quency. It’s also very ac­cu­rate, with its tran­sient speed and de­cel­er­a­tion rate be­ing su­perb. Of course a lot of this per­tains to the am­pli­fier em­ployed but, that said, you don’t start with rub­bish and end with bril­liance.


When the sec­ond gen­er­a­tion Mille sub­woofers came out they were good, but alas noth­ing com­pared to the orig­i­nal. How­ever, with this latest in­car­na­tion we’ve wit­nessed Hertz mak­ing a com­plete one-eighty, de­vel­op­ing a new sub­woofer range that makes both the pre­vi­ous and even the orig­i­nal look pale in com­par­i­son. Truly ter­rific stuff.

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