Hertz Mille Pro Car Speakers – What makes speakers sound good in a car?

Hertz Mille Pro Car Speakers – What makes speakers sound good in a car?

Hertz Mille Pro speakers are gaining popularity and a reputation for providing unbelievable sound for the price but what makes them such great performers? Below we point toward some of the key design features that put these diamond performers at the top of the pile when it comes to value for money!

Introduced to the UK at the beginning of 2016, the Mille Pro’s took on the unenviable task of replacing Hertz High Energy which had gained a deservedly huge reputation throughout their time in the market. However, there are few similarities other than the key price points and so direct comparison would not be appropriate. Unlike many facelift products released by companies as a portfolio “refreshening exercise” Hertz began with a blank piece of paper (or an empty HDD). Unencumbered by the need to clone the sound of the High Energy range, designers were able to radically rethink their approach to speaker design at these critical price points. The range is comprehensive to say the least with a range of component and coaxial full range systems latterly joined by a pair of 10″ subwoofers.

Considering the essential requirement for a speaker, it is hard for the layperson to imagine what can be done to improve performance. In the case of the Mille Pro range, there was a requirement to provide speakers capable of extracting the best possible performance from specifically Hertz HCP and HDP amplifiers. It was decided to aim for an impedance of 3 Ohms rather than the usual 4 Ohms. This immediately gains better efficiency as the load on the amplifier output is less. As an analogy, it is like taking a handful of potatoes out of a 5Kg bag. The amount of effort required to lift it is less! It si beyond the scope of this blog to explain specifically how this is achieved and anyway, I would have to ask someone but I would think it has something to do with the diameter and conductivity of the wire used in the voice coil but don’t quote me on that one! As a result, Mille Pro speakers have a quoted impedance of 3 Ohms which both HCP and HDP amplifiers are perfectly happy to work with (worth checking that the amplifier you are planning to use is just as happy!). Once we have managed to extract more power from the amplifier it is important that the speakers are able to handle that power. There is a physical limit to power handling in a speaker which is governed by the backward and forward motion available before the rear edge of the voice coil bangs into the speaker base plate in one direction and leaves its moorings in the other – known as excursion. To this end, Mille Pro has been mechanically designed to provide ±4.5mm of cone movement. The length of the voice coil has to be lengthened in order to maintain control over this entire movement and an over-sized magnet employed. What is referred to as a “Boundary Free Surround” is employed. This looks like an oversized rolled surround of days gone by and minimises any forces trying to return the V-profiled cone back to its resting point ensuring as much linearity as possible to avoid sonic degradation at high excursions. As ever, Hertz employ its patented V-Cone to maximise the dispersion characteristic of the finished product which compensates for off-axis listening positions.

Hertz Mille Pro tweeters have also received the benefit of a new approach and now contain a foam dampener in the void behind the 25mm tetelon dome to avoid distortion from back waves . The voice coil is also 25mm, which improves linearity enormously. One of the key features however, is the centre tuning duct which helps to lower the resonant frequency and therefore the lowest frequencies the tweeter can handle. This helps to set a lower crossover point placing the sound stage higher – particularly important in a car where tweeters will hardly ever be mounted at ear height.

The passive crossovers provided as standard are constructed using components which offer huge margins in terms of voltage and current rating. This is to avoid saturation at high listening levels again aiding with linearity. Linearity is a particular problem when using passive crossover which is why most FOUR MASTERS will try to steer customers toward running speakers actively. However, I have heard these speaker run passively and the crossovers do a very competent job.

If your vehicle is fitted with coaxial speakers as standard then never fear The technologies listed above all feature in the design of Hertz Mille Pro coaxial speakers. There is no need to be “sniffy” about coaxial speakers. many fine home hi-fi speakers run coaxials. The proximity of high and mid frequency drivers can have a very beneficial affect on coherent sonic performance. In a vehicle, the positive effects can be sometimes compromised by mounting positions. Once again Hertz addresses these issues by adopting an acoustic lens which helps to provide better dispersion.

It is vital when selecting new speakers for your car that you are able to receive a good demonstration so that you know what to expect when you collect your car. I can write all day about how good Hertz Mille Pro car speakers sound but, the proof of the pudding is in your own ears, so I urge you to head in down to your local FOUR MASTER and have a listen. Don’t forget to take some of your own music with you but please, no MP3!!!


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