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IRONMAN 4×4’S BLACK OPS BUILD: PHASE 6

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I enjoy music a lot, more so than most people I know. I grew up playing my dad’s seven-singles on his retro Hammerstein radiogram. It was an FM unit with a turntable. Despite his best efforts to lock the glass covering of the turntable section, I always managed to open it.

When I think back, I realise that my dad (an Afrikaner) had a surprisingly comprehensive collection of 60s Brit Rock; I think my British mom contributed a little. His Valiant had an 8-track tape player − and the likes of Jose Feliciano, Nana Mouskouri, Johnny Mathis, John Denver and The Carpenters still remind me of road trips down to Durban for Christmas.

My own taste in music was enhanced in the 80s, when I got my first portable, double-tape-deck, detachable-speaker boom box. The synth sounds of the 80s from the likes of Depeche Mode, Yazoo, OMD, Alphaville and Yello, along with artists such as Jean-Michel Jarre, Vangelis, Enigma and Mike Oldfield, remain firmly entrenched in my iPod playlists.

When the end of the previous century rolled around, I was properly swept up by Electronic Dance Music (EDM), and I am not ashamed to say that I have many rave parties under my belt. While I was partying like there was no tomorrow, I was always aware of the intricacies of the music that was keeping me on the dance floor till well after sunrise. This exposure to thumping dance music also introduced me to slow, chilled-out versions of the popular dance tracks played in the chill-out lounges at these rave parties. As I write this article, the soothing ambient sounds of Marconi Union are washing around in the background.

I now have a fully-fledged home music studio with top-end equipment and software in which I create electronic musical soundscapes for my own enjoyment. Sometimes these are pumping, trance-like tracks, but most often, they are chilled, ambient pieces of music. It’s a great hobby and a superb anti-stress pastime. I get immense satisfaction from listening to something I’ve created. I am by no means a good musician, and one of my greatest regrets in life is not having taken the trouble to learn how to read music or to play a keyboard.

One of the spin-offs of this hobby is the fact that I have, over the years, developed an ear for a good music system. I have an opinion of what sounds good − and what, despite the best efforts of the hi-fi sales person, does not. Like most 4WD folk, I do a lot of homework before I part with my hard-earned cash. I have a lot of respect for Yamaha amplifiers because of their industry-leading DSP (Digital Sound Processing) circuitry. I am also of the opinion that the English make the best hi-fi loudspeakers. Once you’ve heard a set of Bowers & Wilkins Nautilus loudspeakers, you’ll never be the same!

At this point, you may be wondering what this has to do with our Ironman 4×4 Bush Truck. Since my very first set of wheels, I have always had big sound in my vehicles, and the Bush Truck would be no different. When I look back, I realise that these were loud, brash, inaccurate beginnings that would be quite embarrassing today. A long and steep learning curve has ensured that I now have a finer appreciation of what sounds good in a vehicle. I have become very fussy, and feel a fair amount of displeasure when listening to a good piece of music on a poor sound system.

There are typically three components to most car audio systems.

  1. Head unit: This is the source unit, also referred to as the car radio or, as I prefer, the head unit. This started out as a radio, after which I incorporated a tape player, then a CD player − and, more recently, DVD and media players. Many years ago, I saw an advert for a 7-single record player hanging from the bottom of a car dashboard from the 60s. And to think that I had the gall to complain about CD skipping on one of my early car CD players!
  2. Amplifier: The music from the head unit has to be amplified, and then routed to a speaker for you to be able to hear it. Most often, the amplifier is built into the head unit, as the level of amplification required to power small OE (original equipment) car speakers is not high.
  3. Speakers: The fancy term for a loudspeaker is an electro-acoustic transducer – it converts electrical audio signal into audible sound waves (speech and music). The electrical audio signal moves through the speaker internals, causing a membrane to vibrate and create the sound waves. As humans, we can discern sound waves that range from a low of 20Hz (hertz) to highs of around 20kHz (kilohertz). Car speaker systems thus attempt to cover this range of frequencies − with varying results.

For many years, this was the status quo; and, if you are not a serious audiophile, this may still suffice. My first car audio “system” was a Fisher tape-deck and a pair of Denon 5-inch speakers in the parcel-shelf at the back of my 1600 Ford Cortina. The Cortina was not a fast car, and had to be thrashed most of the time, drowning out the best efforts of the Denons. This led me to discover separate amplification to give it more volume. Trial and error (more error than trial) over the years taught me a lot about how to put together a decent-sounding car hi-fi system, and has now brought me to the stage where I absolutely relish the prospect of a journey in my truck.

Before we delve into the Bush Truck sound system, here are some fundamentals of car audio that I have garnered over time.

  1. Cheap equipment is fine if you just need music in your car to stop you from singing to yourself.
  2. Expensive systems, when done correctly, are superb. Worth the money? If you have it, yes.
  3. A high fidelity system can be put together for a reasonable budget using quality components and a professional installation, provided that the components are carefully matched and that the system is properly calibrated.
  4. If the head unit is poor quality, good speakers are not going to make it sound better. Good speakers will merely amplify the poor quality of the source.
  5. A good head unit will, in many cases, make average OE speakers sound okay.
  6. Good installation is vital for a good result. The best equipment will sound rubbish if the install is done badly.
  7. One of the biggest mistakes that I see being made, is trying to enhance the standard sound system in a vehicle by fitting bigger speakers to the original head unit. To drive bigger speakers, you need power. If there is not enough power to properly move the speaker woofer, the result is distortion.

My wish list

I discussed my intended Bush Truck sound-upgrade with my long-time audiophile mate, Tyrone Hanna from AutoVenture. He recently became an Ironman 4×4 Platinum dealer, but has had a sound shop for as long as I can remember. I have spent a fair amount of money over the years with Tyrone on mostly good-quality gear, and this was going to be no exception. I have a preference for Alpine head units, as I view them in the same light as Yamaha when it comes to my perceived sound quality. Because of the importance of component matching, I have stuck to Alpine amplifiers to complement the Alpine head units, and I have been pretty happy. I have always considered Alpine to be a pretty good Japanese electronics company, but must admit that I have never been overly-impressed by their loudspeakers. As you can tell, I have dabbled with many brands over the years.

Early on, I used mostly Pioneer and Kenwood, as these were decent brands on a budget. Later on, I tried Hertz, MTX, Lanzar, MB Quart and JL Audio. My sub-woofers have always been mounted in proper sub-woofer enclosures, but the Pioneer subs never lasted very long. At some stage, I happened upon Boston Acoustics sub-woofers, which were awesome. The last speakers in my FJ Cruiser were by Focal, a French audiophile company that specialises in high-end speakers. I was mightily impressed and convinced that this would be the way to go again.

From the outset, it became very clear that I could not replace the OE head unit in the Ranger unless I wanted to lose all the functionality built into the Ford SYNC 3 system. In many cases, this can be a problem because of the average quality of the signal coming from the head unit, as well as the aforementioned bass compression. According to Tyrone, however, the head unit in the Wildtrak is pretty good, and can comfortably be used as a good source unit. The only drawback would be that this OE head unit does not feature low-level signal outputs for connecting to an external power amplifier. We would have to use the high-level speaker outputs of the head unit to send signal to the amplifier. With the head unit staying stock, I was now free to look at other brands, and could match the brand of the amplifier and speaker – which would be a first for me.

At this point, Tyrone suggested that we look at Rockford Fosgate. This had truly been one of the last brands on my mind. I had come across a couple of Rockford systems over the years, and my overwhelming impression had been that Rockford are SPL kings first and foremost. SPL is sound-pressure level, or the loudness of the system. High SPL levels will guarantee you a trophy at your local SPL Sound Off competition, but clarity and music enjoyment are not high on the priority-list there. I also found that the higher frequencies sounded too harsh for my liking. That was not what I was looking for.

However, Tyrone insisted that there was another facet to the Rockford Fosgate offering that was well worth a look. I listened to the Rockford system in his Hilux, and it didn’t sound as bad as I’d believed it would. After much discussion, and with the proviso that the Rockford gear would come out if I was not satisfied, we proceeded to spec a system for the Bush Truck.

The stock speaker mounting locations in the Wildtrak are round, 6.75-inch apertures in the front and rear doors, and 1-inch tweeter mounts in the small triangular quarter-panel above the front door panels. As it is a double-cab bakkie, there is no space for a big, double bandpass subwoofer-enclosure for the rear. With this install, I was looking for high-quality listening first and foremost. I wanted a sound stage accurate enough so that if I closed my eyes, I would hear the musicians playing on stage right in front of me. I wanted a good measure of mid-bass response, because I listen to a wide variety of music covering a vast period of music-recording technology. Compared to the latest offering by Yello, an early 80’s Depeche Mode recording has very little in the way of low frequency bass. The recording levels of older music are also most often quite a bit lower than the norm today. Bass definition down low was an absolute requirement, as I definitely like a bit of low-end back massage when the music has it.

The install

The chosen equipment for this install was never going to achieve this with conviction by itself. This one called for something rather special, which is another first for me. For this install, we were going to sound-deaden the cabin of the Ranger to eliminate unwanted sounds from the exterior, and keep the music inside the cabin.

Before we begin, we have to go bare!

I thus stripped out the entire cabin of the Ranger down to bare metal. Roof, floor, doors, rear panels… every square inch of the interior was stripped of all panels, linings and carpeting. I then proceeded to apply around 70kg of Silent Coat sound-deadening mat to every possible piece of exposed metal panel inside the cab. The doors feature a double layer of the mat – on the inside of the outer skin of the doors, as well as on the inner skin which holds the speakers and the door panels. This job took five days to complete, and I am happy to report that I didn’t break a single panel clip. I have rarely come across such an extensive sound-deadening exercise, and the end result is nothing short of astounding. At 120 km/h, the Ranger is whisper-quiet inside, and elicits comment from just about everybody who is allowed into the passenger seat. This also means that the sound system does not have to be overly loud to compensate for vehicle noise.

Sound deadening mats installed.

I also wanted what is referred to as a “stealth” install for this system, with no cutting of panels, or big exposed speakers, or speaker grilles. The Rockford speakers (barring the sub-woofer) would thus have to fit into the stock speaker-mounts behind the original door panels. I also did not want to install multiple amplifiers, as to power these amplifiers with the Ford’s original alternator and battery system would present an additional challenge. I wanted a single five-channel amplifier with enough power to drive not only the four 6.75-inch door speakers and the pair of 1-inch tweeters up front, but also a single sub-woofer in a narrow enclosure behind the rear seat.

Rockford Fosgate have three distinct levels of product, known as Prime, Punch and Power. Power is their top-of-the-range line for when budget is not a consideration. Brett Farquharson, MD of Rockford Fosgate SA, has this in his Wildtrak Ranger − and it is undoubtedly some of the best sound I’ve ever heard in a vehicle. Sadly, my budget was nowhere near that level, so I looked at the Punch range. This range would necessitate the installation of multiple amplifiers, which I was not keen on. So I looked at their Prime range more seriously.

Despite the fact this is an entry-level offering, it is definitely not entry level when compared to other products on the market. The Prime range features most of the high-end technology that Rockford bestows on just about all their products − and I now have the following Rockford gear in the Bush Truck:

Front speakers:

Rockford Fosgate Prime R1675-S. These are a 2-way component, or split system, that features a 6.75-inch mid-range driver for the door and a separate 1-inch tweeter for the upper quarter panel. The crossover circuit is integrated into the speakers and splits the signal frequency at 4500Hz. The tweeters, therefore, only play sounds above 4500Hz. These are the speakers that will be creating the overall sound in the vehicle, as well as determining the accuracy of the sound stage. The fact that the tweeters are separate from the mid-drivers and are mounted higher up towards the front of the vehicle contributes to this.

The stock front speakers.

These speakers can handle 40 Watts of continuous power, with 80 Watts at a peak. They have a rated sensitivity of 89dB. This is an indication of the speaker-loudness when playing a 1-Watt signal measured at 1 metre away from the speaker in an Anechoic chamber − a room that is designed to absorb sound reflections completely, in order to enable accurate measurements of sound sources. They have a frequency response of 55Hz to 20kHz, although it is not ideal for such a small speaker to be playing much below 125Hz.

Rear speakers:

Rockford Fosgate Prime R1675X2. These are 2-way or coaxial speakers. They also feature a 6.75-inch mid-range driver with a 0.5-inch tweeter mounted in the centre of the woofer. These rear speakers are there merely to add a bit of rear fill and enhance the depth of the sound stage. They should preferably not play too much of the higher frequencies and contribute more to the mid- to lower-mid frequencies. The mounting position of the tweeter is thus of little importance in this application. Using these up-front would hamper attempts to create an accurate sound stage because the tweeter is so low.

Rear speakers.

These speakers can handle 45 Watts of continuous power with 90 Watts at a peak. They have a rated sensitivity of 91dB, a bit louder than the fronts. They have a frequency response of 52Hz to 20kHz. They are a little louder and can play a little deeper than the fronts. It is thus important to calibrate these correctly to complement the primary sound coming from the front speakers, and not spoil the staging.

Subwoofer:

Rockford Fosgate Prime R2SD2-10. The sub-woofer membrane has to move a lot of air, and in high-output sub-woofers, the woofer movement or “extension” can be several centimetres. This calls for deep speaker baskets with large-diameter woofers. Because of the very limited space behind the back rest of the rear bench-seat, a very special narrow sub-woofer enclosure had to be built. The Rockford R2SD2-10 sub-woofer is specifically designed for such a small, narrow enclosure: it has a very shallow design, and when seen from the side, is less than half as deep as a conventional sub-woofer.

Rear subwoofer.

The R2SD2-10 is 10 inches in diameter, which sounds a bit small by sub-woofer standards. The sub is mounted in a custom-made enclosure which features a port on the side. Power-handling is rated at 200 Watts continuous power, and 400 Watts at peak power. The volume of the subwoofer enclosure is accurately determined to ensure a powerful bass response from this relatively small sub in a small enclosure. This sub-woofer has a rated frequency response of between 40Hz and 250Hz.

Amplifier:

Rockford Fosgate Prime R600X5 Power Amplifier. This amp has five output channels to drive the five speaker locations of this install. The four channels to drive the front and rear speakers are stereo, and feature power outputs of 50 Watts per channel continuous power. The fifth channel is mono, and drives the sub-woofer. There is typically no stereo staging for sub-bass sound. This channel is rated at 200 Watts continuous power. The power output of these five channels closely matches the rated power-handling of the various speakers.

The amplifier was installed under the driver’s seat, which is pretty central in the vehicle cabin. The speaker output wires of the head unit were rerouted down the centre of the vehicle to the amplifier. The Rockford amplifier can accept high-level speaker signal directly from the head unit. A slight hiccup was the absence of a switch-on signal from the head unit. Aftermarket head units that feature low-level outputs for connecting to external power amplifiers also have a switch-on wire that is run to the amp to switch it on when the head unit is turned on. With no such wire on the Ford, we had to use a small module that senses signal on the head-unit output speaker wires, and then switches the amp on. The power wire for the amp is run directly from the battery along the shortest-possible route to the amplifier, but (if possible) should not be close to any part of the vehicle wiring loom. This wire is as thick as my middle finger and features a fuse right at the positive terminal of the battery. The negative (or ground) wire for the amp is earthed to the body of the truck, as close to the amp as possible.

New high-quality speaker wires were now run from the high power outputs of the amplifier to the speakers. It is very important to ensure that the correct +/- polarity is maintained with all speaker connections. If not, the speakers will be “out of phase” and opposing speakers will cancel out each other’s signal, causing a loss of definition and performance. The sub-woofer enclosure is custom-made to fit behind the backrest of the rear bench seat. It is bolted into place to ensure that it has a sturdy base. An unmounted enclosure can resonate and move around, potentially resulting in a loss of bass power as well. For the front and rear door speakers, a couple of trim rings cut from MDF board were required because of the added mounting depth of these units. These trim rings were simply mounted between the speakers and the OE speaker sockets, so no big drama. The tweeters from the front splits fitted perfectly into the housing for the OE tweeters, and when the interior of the vehicle was re-assembled, there was absolutely no indication of anything ominous lurking behind the volume button.

Calibration

With the install done, there was one very important step remaining – system calibration. (I have always done this by ear in the past, with what I thought were pretty good result. How wrong I was.) I’d had this system in my Ranger for a while, and I’d been pretty happy with the results. It was louder than I needed, sounded better than most − and for the money, was pretty impressive. However, it did lack a bit of mid-bass definition, and the sound stage was okay, at best.

I recently visited Rockford Fosgate SA HQ, and listened to MD Brett’s system. As stated, my mind was blown. He then jumped into my truck, and I could see that he was less than impressed. Not because it sounded so much poorer than his top-end system, but because he insisted that it should sound heaps better. So I returned to JHB, and looked up another mate in the business, Zoltan Nemeth. Zoltan is a long-time Rockford Fosgate fundi, having worked for them for a number of years. He has now set up his own shop in Woodmead, and has the correct gear to do a proper calibration.

There are four steps in Zoltan’s check of a system.

The first step is to check that all the speakers are correctly wired, and in phase. A test-CD plays a test tone through all of the speakers while a phase-meter (held close to the speaker) checks for errors.

The second step is to determine the maximum volume-setting on the head unit before it starts to send distorted signal to the amp. This is done by connecting an SMD DD-1 distortion-detection module to the input signal from the head unit at the amp. A test CD is played on the head unit, and the speaker wires are disconnected. The head unit volume is turned up until the instrument starts to detect distortion. (I am happy to report that the Ford OE head unit is very decent for stock unit, and at volume-setting 30, which is full volume, there is no distortion from the test signal used to check this. Distortion at this point may not always be heard, but will damage speakers. We were off to a good start.)

Step three is to adjust the gain levels of the amplifier. This is done by setting the volume on the head unit to somewhere close to, but below, max volume. We chose level 22. Modern recordings would be pretty darn loud at this level, and older recordings would have some headroom to be turned up to compensate for low recording levels. At this level of 22, the gain controls on the amp are now turned up until the DD-1 starts to show distortion from the power amp output channels. The gains are then turned down a touch for a margin of safety. The signal used for these two tests for the door speakers is a 1kHz signal. 1kH is the frequency which human hearing is most sensitive to. Babies cry at around this frequency, and females are thus more sensitive to this frequency. (I thought back to when my young Michael was a baby, and I can tell you that I am pretty sensitive to that frequency, too.) The rear-door speaker gain is then turned down a touch, as we do not want them as loud as the front speakers. The subwoofer channel goes through the same calibration, but the test frequency is at 40Hz, which is the tuned frequency for this specific subwoofer, in this specific enclosure.

COSTS

Prime R1675-S Front Splits: R1 610

Prime R1675X2 Rear Co-Axials: R865

Prime R2SD2-10 Subwoofer: R1 640

Prime R600X5 Amplifier: R6 895

Total for Rockford equipment: R11 010

Subwoofer Enclosure: R1 650

Audiophile Wiring kit: R1 000

Door speaker spacers: R500

Total for fitment gear: R3 150

Labour to install system: R2 000

Total cost of system installed: R16 160

Silent Coat Sound Deadening: R4 500

Labour to sound-deaden cabin: R12 000

Total cost of sound deadening installed: R16 500

Total cost of Bush Truck Sound upgrade: R32 660

Now that we have the output levels of the head unit and the amplifier calibrated, the fourth and last step is to set the active crossover points of the amplifier. The crossover limits the frequency range sent to a speaker. The crossover for the front tweeters is managed by a passive crossover circuit in the wire between the mid-range driver and the tweeter of the front splits. The rear co-axials have a similar setup for that little tweeter mounted in the speaker. The signal from the amplifier to these speakers is still a full signal. We do not want the door speakers playing low down sub-bass frequencies, as we have a dedicated sub for this. Trying to play low bass through these speakers will use a lot of power, and we want to use the 50 Watts of power that we have per channel for these speakers to be used efficiently for the mid-bass to high-end frequencies. For this calibration, we use an SMD CC-1 crossover calibration module. It is also connected to the amplifier output channels. A signal is played from the test CD at the frequency at which you want to cross over. When you are adjusting the crossover control on the amplifier, the CC-1 indicates when the crossover point has been reached. The same is now done for the sub-woofer.

On the Bush Truck, we elected to set the crossover point for the four door-speakers to 100Hz. The frequencies below this are cut off at a rate of 12dB per octave − this is merely an indication of the steepness of the crossover graph. It has resulted in a strong mid-bass punch from the speakers, without distortion or over-driving them. The sub-woofer crossover works in reverse. The crossover point was set at 80Hz, and anything above 80Hz is cut off at the same rate as the four stereo channels. The subwoofer thus tapers off as you move into the mid-bass frequencies and blends beautifully with the mid-bass of the door speakers as they start picking up towards 100Hz.

Conclusion

My system now sounds closer to the system in Brett’s truck, and I can sense similarities − albeit at a different level. I have come away from this with an overall feeling of astonishment and great satisfaction. For an entry-level system, I have yet to hear anything close. I think you would have to spend a heap more cash to get much of an improvement on this system. The amplifier has an added bonus in the form of a small rotary control that adjusts the Punch EQ of the sub-woofer separately. I can feed more bass in for older recordings, and I can take some away from newer bass-heavy ones. Before the calibration, I was seriously considering adding a digital sound-processor to enhance the shortcomings of the uncalibrated system, but I no longer need to do this. The sound stage is perfect, and the sub-bass sounds like it is coming from under my feet.

There is, of course, one major downside to this system. It clearly shows up low-quality MP3 encoded recordings. The quality of music recordings is measured in bit rate, or the amount of data per second. CDs have a bit rate of 1411 kbps or 1411000 bits of data per second. Stereo music has a sample rate of 44.1kHz with a bit depth of 16 bits per sample over 2 (stereo) channels. This gives you the resultant bit rate of 44100Hz x 16 bits x 2 channels = 1411200 bits/second or 1411.2 kbps. MP3s may be encoded down to 128kbps, which is a lot less. You probably won’t be able to tell the difference on your iPod through a set of earbud speakers, but on the Rockford system, I can now hear the difference, especially at higher volume levels. I am going to have to re-encode all of my CDs to a higher quality format such as FLAC. C’est La Vie!
By Mic van Zyl

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