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Hertz Mille Pro MPK 165.3 incar speakers REVIEW

Hertz: it’s a technical unit for cycles per second. But it’s also an Italian car audio equipment marque, established 20 years ago this year, and sharing a stable under Elettromedia with Audison.

Here we’re looking at a pair of component speakers from the Hertz Mille range, the Pro MPK 165.3 two-way speaker system — which is about midway up in the Mille range. Below this is a two-way coaxial unit, above is a three-way system (and above that Hertz’s Mille ‘Legend’ offerings). The MPK 165.3 comes in a pack with two tweeters, two bass/midrange drivers, two crossover networks, along with grilles and hardware. The hardware includes both flush and raised mounts for the tweeters.

TALKING PARAMETERS
We’ll look at all these bits individually in a moment, but first I’d like to note some welcome figures provided in the booklet that comes with the speakers. (They are also available in a tech sheet available from the Hertz website.) These are the ‘Electro-Acoustic Parameters’ of the drivers. These are not the standard specifications, such as frequency response and power handling. These are things like the effective diameter of the drivers (usually measured from the mid-point of the roll surround), the free air resonant frequency, and even more obscure parameters going by such names as Qes and Vas and Re. This are the specifications that allow system designers to tune enclosures to provide the best performance for the speakers (sometimes they’re called the Thiele/Small parameters).

That these are provided up front speaks well of Hertz. Whether they’ll be useful is less certain. After all, the opportunities to provide well-designed enclosures in a car are limited, other perhaps than for subwoofers.

The bass/midrange units (model number MP 165.3) are nominally 165mm models
(effective diameter 132mm, if it matters). They feature a 25mm voice coil of pure copper that’s wound on a Polyamide former. This, says Hertz, provides both high power handling and “very low intermodulation distortion of vocals” (I’m not quite sure how). The cone is called an ‘Exponential V-cone’, made of pressed pulp with cotton fibres, and rather than the usual rounded dust cap over its centre, in the middle it tends to recede slightly more sharply into a hollow point. Hertz says that this and its overall shape is geometrically optimised for mid-frequency linearity and dispersion”. There are assorted other features for this driver which Hertz says provide for “improved efficiency”, and “low distortion at high power levels”.

Its electrical resistance is 3.1 ohms. Actual impedance is a frequency-based curve that depends on a number of things, including enclosure design. Nominally the package as a whole is the usual four ohms.

HIGH FREQUENCY SUPPORT
The MP 25.3 tweeters have a 29mm diameter — both effective and nominal — and adopt a soft dome using something called Tetolon fibres. (If you do an internet search for Tetolon, you’ll mostly find links to Hertz and Audison speakers — though it also appears in a 2006 patent for an exciting new kind of bra cup which better maintains its shape after extended wash cycles.)

The tweeter’s voice coil is 25mm in diameter, and is ferrofluid cooled for high power handling. A neodymium magnet is used. Hertz says that a ‘Center Turning Duct’, along with ‘selected’ damping material in the rear chamber, provides for a lower resonant frequency and reduced harmonic distortion, while the faceplate aims to assist ‘high linearity in off-axis installations’.
The DC resistance of the tweeter is 3.9 ohms.

The included crossover has a nominal dividing frequency of 3.5kHz (the 1.2kHz free air resonance of the tweeter is well below that). These are very impressive crossovers, quite heavy and substantial, beyond what I’d expect to see in any similarly priced two-way home high fidelity loudspeaker. The low pass filter to the woofer operates at a gentle 6dB per octave for reduced phase shift, while the high pass to the tweeter features a 12dB per octave slope, the better to protect it from potentially damaging low frequencies.

The crossover uses Hertz-branded components: two hefty coils, three five-watt resistors and a 160V-rated bi-metallised polyester film capacitor, all on a printed circuit board in a
100 x 75 x 30mm ventilated case. A two-position switch sets to the tweeter level to 0dB or +2dB, and the connections for amplifier, tweeter and woofer are all screw clamps, clearly labelled and easily accessible, and capable of accepting good thick cables.

Hertz rates the frequency response of the whole system at 40 to 22,500Hz, and the power handling at up to 220W peak or 110W continuous. The sensitivity is rated at 92dB (presumably for 2.83V input, at one metre).

Performance
While in practice you will be equalising the speakers for your car and your seat, I did some of my listening without EQ to try to get at the ‘core’ sound of the system. Two things became quickly clear: these speakers sound better and better the louder they are played. And, as a result, they’re going to be perfectly happy if the EQ involves a bit of bass boost, as one suspects it will.

The reason they sounded better as the volume was advanced was that it lifted up
the bass. Jumping ahead, I’ll relate now the measurements made at the end of my time with these speakers (I was keen to see what more objective metrics might have to say). In my test rig their output was a little recessed below a peak at around 150Hz, and I suspect it was hitting a resonance in my environment around there, for the output fell away by around seven decibels below that, then maintained that new level down to 55Hz. Even below that point the roll-off was gentle, with the specified 40Hz bottom-end only down a further 6dB. Note, this was not in a custom box, designed to tune the bass performance to an optimum. If you were to do that, the whole bass end could be flatter.

I should also mention the top-end measured performance. The output was maintained by the tweeter out beyond 22kHz without diminution. Obviously that well and truly covers all treble available from CD, and far beyond that from the likes of an MP3 (did you know that most MP3 tracks are low-pass filtered at 16kHz?).

Your use of the tweeter +2dB setting on the crossover will depend very much on your tweeter positioning and subsequent EQ. Without EQ I preferred the 0dB setting for what sounded to me like a smoother tonal balance.

In addition to the tone, the dynamics were excellent, and the volume levels available were plenty. Indeed, after a time of listening in their natural state, I bumped up the bass level by around six decibels, and that added good body to the bass guitar. I was listening to AC/DC’s ‘Back in Black’ at that point, and the bass grind resulting from a bit of bass enhancement added enormously to the music, without adding any noticeable distortion. The speakers could simply take the power and make use of it. With that boost I was able to play the music a little more quietly while retaining its sense of energy.

Brian Johnson’s voice was delivered with excellent clarity. Even at the 0dB setting for the tweeter, the cymbals were very slightly forward in the mix, although not irritatingly so. The important thing is that all the frequencies are there and undistorted.

Moving to Beyonce’s ‘Lemonade’, the lady’s voice was beautifully rendered, with all the clarity you could need for coherence and understanding of the lyrics, and an absence of wobbles in the upper frequencies that can with some systems make speakers sound tiring. The boost on the bass was again welcome. Of course the very deep stuff — a lot of this album verges on the infrasonic — was absent, but enough of the 40 to 60 hertz region was delivered to give a good sense of the bass underpinnings, and the synth kick drum on Hold It was powerful enough to produce a visceral impact. Use of a subwoofer will, of course, take up the strain.

Something a little different perhaps? How about Kiri Te Kanawa singing É Strano, Ah, Forsè Lui from Verdi’s ‘La Traviata’. Sopranos and car speakers often don’t mix at all well, but that wasn’t the case here. Her power was evident, yet the voice was delivered smoothly and sweetly. There was no high frequency resonance of the kind to which cheap speakers are susceptible; in other words, there was no wincing, even at the climax. The backing orchestra was also well delivered, and there was even a reasonable delivery of the ‘air’ in the recording, the reverberations and space around the instruments and the vocalist.

CONCLUSION
Fine sound, good styling, a quality crossover — I really enjoyed the Hertz Mille Pro MPK 165.3 speaker system. When I discovered that they were priced at just under $500 for the set, they turned out to offer excellent value for money as well.

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HERTZ MILLE PRO MPK 165.3 TWO-WAY COMPONENT SPEAKERS
Cost: $499

+ Very good sound quality
+ High quality crossover
+ Good value for money

– Best if EQ’d for a little bass boost

TYPE: 2 way component speakers
NOMINAL SIZE: 165mm (bass/midrange); 29mm (tweeter)
POWER: 220W peak; 110W continuous
SENSITIVITY: 92dB
NOMINAL IMPEDANCE: 220W peak; 110W continuous
CROSSOVER: 3.5kHz
RESPONSE: 40 to 22,500 hertz
WEIGHT: 1.07kg (Bass/midrange); 70 grams (Tweeter)

Contact: Clarion Australia on 03 8558 1115
Web: www.hertzaudiovideo.com