Wednesday, December 26, 2012

Does Your Car’s High Fidelity System Have an Alternator Load Dump Filter?

Common sense dictates that your car’s electrical system never rises above 13.8 volts DC, but is it equipped with an alternator load dump filter nonetheless?

By: Ringo Bones 

It seems like 1992 was only yesterday when “mainstream” electrical and electronic engineers where dumbfounded on why their car audio / car high fidelity system gave up the ghost after only eight months or so. Well, these tenured “mainstream” engineers seems to have failed to research one of the nasties that’s been lurking inside every automotive electrical system called alternator load dump and how it could shorten the lives of solid-state integrated circuit based electronics of a typical car stereo / car hi-fi system. 

An alternator load dump occurs when the load to which a generator is delivering current to is abruptly disconnected, causing a brief but relatively high spike in output voltage from the generator. In a typical car’s alternator-car battery system, this applies to disconnecting the car battery while it is being charged by the alternator. Ever since automotive technicians equipped themselves with electrical measuring equipment, it has been found out that during alternator load dump situations, voltage measurements can be as high as 87 to 120 volts and may take up to 400 milliseconds to go back to 13.8 volts. 

Given that spec sheets of automotive solid-state integrated circuit based power amplifiers - like the AN214 - that operate in the 12-volt DC environment of the car can only handle a power supply voltage spike of only 48 volts for up to 500 milliseconds or so, even a “brief” alternator load dump that more often than not exceeds this voltage is enough to shorten the lives of solid-state integrated circuit based car hi-fi. Is there a solution to protect one’s car hi-fi from the inherently hostile automotive electrical system? 

There are commercially made / ready made alternator load dump filter boxes available out there and due to the prevailing ignorance of a majority of do-it-yourself electronic enthusiasts of what constitutes such filters, they are priced as if they are made of gold by unscrupulous manufacturers. But a reliable alternator load dump filter can easily be made by using unused parts lying around in a typical DIY electronic enthusiast’s electronics workbench. 

A typical alternator load dump filter consists of an inductor-capacitor or L-C filter. Usually a 100 to 300 milliHenry inductor and a 1,000 microfarad 16 volt electrolytic capacitor whose negative terminal is connected to the car’s negative ground. To further save costs, one can even wind his or her own 300 milliHenry inductor using a 30-foot piece of number 20 AWG magnet wire into a ½ - inch plastic bobbin with a ½ - inch E-I silicon steel core to increase its inductance. One can even over-engineer the alternator load dump filter by using a 10,000 microfarad 35 volt capacitor for the L-C filter. This type of filter can also has the benefit of further minimize the hum to inaudibility of an AN214 IC based amplifier connected to a 12-volt full wave center tap power supply plugged into a typical home’s 220-volt 60-Hz ac current. 

Tuesday, December 18, 2012

High Fidelity Versus Public Address Systems: Insurmountable Kultur Kampf?

Even though both can play back recorded music when fed with an audio signal, is there a preexisting insurmountable Kultur Kampf between home high fidelity systems and PA systems?

By: Ringo Bones

It may be down to one’s ears’ aesthetics but almost all audiophiles – even new recruits – have readily perceived the preexisting and insurmountable Kultur Kampf between domestic high fidelity systems and Public Address systems used in high capacity stadium rock concerts. Even though pro audio public address speaker systems manufacturers have yet to manufacture a stadium rock PA system speaker whose sound quality is as beguiling that of a 200 US dollar entry level hi-fi loudspeaker for domestic use, are the two worlds forever destined in a “never the twain shall meet” stand-offish behavior?

My very own “epiphany” on questioning why PA systems never sound as good as well-shorted entry-level budget domestic high fidelity systems may seem oxymoronic to anyone uninitiated to the hi-fi world, but to hi-fi enthusiasts, the truth can be self-evident to one’s own ears. As an amateur heavy metal musician who judge “naturalness” of a heavy metal rock recording via live-in-the-studio standards, I kept on wondering till this day on why live concert PA systems and / or pro audio gear manufacturers had kept on ignoring the sound quality aspect of their PA loudspeaker rigs.

Assuming one judge the “naturalness” of the sound of a live heavy metal rock concert using the preexisting sound quality of the Public Address system loudspeakers being used, does this mean that an overdriven 200 US dollar bookshelf hi-fi loudspeakers destined for domestic use is the “natural sound” of a live heavy metal rock concert? You got to be shitting me!

Remember Stereophile magazine editor John Atkinson’s review of the Wilson X-1 Grand SLAMM hi-fi loudspeakers back in the December 1995 issue of Stereophile? Well. One of his statements on that specific review probably brought a sense of relief in me back then that I’m probably not the only one “astonished” by the sound-quality Diaspora between domestic hi-fi and pro-audio live concert PA Systems; According to Atkinson: “The bass guitar…thundered fourth from the (Wilson) speakers’ big Focal woofers in a way I had previously experienced only from live rock.” Not surprisingly, this was inevitably followed by scores of Stereophile subscribers writing in “angry letters” pointing out to John Atkinson the inherently low-fi sound quality of live concert PA systems.

Inevitably, John Atkinson issued a response on subsequent next issues of Stereophile magazine on the matter of the sound quality Kultur Kampf between domestic hi-fi rigs and PA systems that goes: “When you use a PA system to play back recordings, you are involved in a creative act, which is not what the concept of high fidelity is about. However, when recorded faithfully, the big, underdamped roar of a live bass guitar through a PA rig is just as much an authentic acoustic source as any other. It is also one that almost all hi-fi speakers, other than the big Wilsons get wrong in trying to recreate.”

Given that PA systems tend to be 5 to 10 times cheaper than their “proper” domestic high fidelity audio systems when compared in a power output per dollar basis, many had perceived Stereophile magazine editor John Atkinson’s statements about the difference between hi-fi and PA systems as nothing more than being self-serving to the whole hi-fi industry back then. But is it? Well, given that almost all hi-fi enthusiasts -including me – already possess ears that already know that there is indeed really a difference on how domestic hi-fi and the pro-audio PA system world play back music, is just makes me sad on why the two tribes can never see eye to eye when it comes to sound quality. After all, hi-fi enthusiasts go to live rock concerts too, while live concert FOH engineers also buy proper domestic hi-fi rigs.

Thursday, December 13, 2012

Open Baffle Loudspeakers: Best High Fidelity Loudspeakers?

Even though do-it-yourself hi-fi for the home started with open baffle speakers, why is it that mainstream hi-fi loudspeaker designers frown upon the very concept of it?

By: Ringo Bones

D.I.Y. high fidelity loudspeaker design books whose “self-worth” is invested upon the mathematics behind the Thiel-Small Parameters often view open-baffle hi-fi loudspeakers as “a fish out of water” due to their low bass output being 100 times less in comparison to closed-baffle box hi-fi loudspeakers optimized via Thiel-Small Parameter based mathematics. But is this really so?

Believe it or not, home D.I.Y. or do-it-yourself hi-fi as a hobby started a few years or more before the “Golden Age of Stereo” got underway in the mid 1950s. Back then, the home constructors set-up consisted of a 15-inch Tannoy Dual Concentric loudspeaker mounted in an open baffle in the corner of the listening room – or some young hobbyist’s bedroom – driven by a home built zero negative feedback single-ended triode amplifier putting out 3-watts or so. Such open-baffle hi-fi loudspeaker set-up was known for their open and natural midrange qualities that made recorded singers sounds as if they are really singing in front of you. But the higher bass output – probably the inherent “boominess” of closed-boxed loudspeakers commercially designed and manufactured around the Golden Age of Stereo and the advent of Rock n’ Roll Music probably won out in the end, relegating the open-baffle hi-fi loudspeakers by the wayside.

Surprisingly almost out of nowhere, the 1990s came and the “Western World’s” single-ended triode amplifier revival, which again resurrected the charmed qualities of the open-baffle speakers. Given the “irresistible” mid-band qualities of open baffle speakers, why do mainstream hi-fi loudspeaker manufacturers view open-baffle hi-fi loudspeakers – bass volume aside - with such a “low opinion”?

Sadly, despite rigorous scrutiny of every annual convention of the Audio Engineering Society, adherents of the closed box design parameters based on the white papers of A.N. Thiel and Richard Small are not quite entirely truthful in telling the D.I.Y. hi-fi hobbyists about the shortcomings of closed-box hi-fi loudspeakers – ported or not. The cabinet that is placed around the rear of a “conventional” closed-box hi-fi loudspeaker drive unit to contain back radiation – and to boost low frequency bass response below 100-Hz or so – imposes a low-frequency limit upon bass reproduction. More often than not, closed-box hi-fi loudspeakers’ low frequency limits just roll-off too high or too early to allow low notes of properly recorded bass-based musical instruments like acoustic upright double bass and full-sized pipe organs to be played properly with convincing fidelity in a typical listening room.

Closed-box loudspeakers also compromises perceived bass quality by making it sound lumpy, boomy, uneven or just dry and anemic in comparison to the recorded acoustical music event. The panel resonance enclosing the rear of a typical closed-box hi-fi loudspeaker also adds mid-band coloration that makes singers’ voices sound “electronic”, whilst box echoes add whoomph, chestiness and a megaphone effect. Add in the cost of the woodwork, its weight and volume and you have a severely bad idea staring you in the face.

And believe it or not, it gets worse. In my years of actual usage of conventional closed-box hi-fi loudspeakers, the least understood but perhaps the most significant drawback of the closed-box hi-fi loudspeaker: it is a monopole (while open-baffle hi-fi loudspeakers are dipoles in its sound radiation) that cannot be properly matched into an enclosed space – i.e. your listening room / bedroom / hobby-room in other words. All that pulling and pushing of closed box hi-fi loudspeakers in the left and right corner of your listening room to get good – or just maybe “bearable” – bass performance from them is down to this property.

Believe it or not – according to first-hand acclaim to seasoned hi-fi hobbyists – the best hi-fi loudspeaker of all time to them is the Quad ESL-63 Electrostatic, which not surprisingly, is an open-baffle design. So does the naturalness and vocal qualities of the Quad ESL-63 be transferred to the “inherently uncouth” dynamic magnetic coil loudspeakers? In a word, yes, if you mount one in an open baffle and use zero negative feedback single-ended triode amplifier designs to drive them.       

Friday, December 7, 2012

Was Stereophonic Recording Invented During World War II?

Given the widely published assumption of the subject at hand, does anyone ever wonder how many audiophiles know that stereo recording was actually introduced during the height of World War II?

By: Ringo Bones

Contrary to popular belief, stereophonic or stereo recording wasn’t introduced or even invented during the mid 1950s during the beginnings of the “Golden Age of Stereo”, but in actuality, during the “dark days of World War II – in Nazi era Germany of all places! Given that – from a historical perspective – war intends to initiate the strongest impetus of progress in scientific and technological developments, the how’s and why’s of the development of stereophonic recording / stereophonic sound in Nazi era Germany seems to elude the interests of tenured historians until a few years after the fall of the Berlin Wall.

The Haus des Rundfunks (Broadcast House) in Berlin, which later became known as Das Berlin Funkhaus, the radio station building of the Reichs-Rundfunk Gessellschaft or RRG when Adolf Hitler got elected as Chancellor of Germany - that was inaugurated back in 1931 was the first ever building in Europe specifically designed for recording and broadcasting. Part of the structure was then devoted to the Grosser Senesaal – a large hall from which symphony orchestra concerts frequently were transmitted live. By 1942, after some years of development by the Reichs-Rundfunk-Gessellschaft (RRG) technicians, the AEG/Magnetophon R22 magnetic tape recorder for recording and broadcasting was pressed into service.

Sound quality wise, the AEG/Magnetophon R22 magnetic tape recorder for recording and broadcasting was an audio engineering tour-de-force during its day because during the height of World War II, the Allies thought the Nazis had successfully developed a very high speed aircraft because live broadcasts of Adolf Hitler speaking in Berlin were followed a short time later by similar broadcasts from Hamburg and Munich. Given the excellent sound fidelity – at the time – of the magnetic tape recorder used by Nazi era broadcasters at the time, the Allies were not aware – until after World War II – that they were hearing magnetic tape recordings of Adolf Hitler’s speeches – one’s at the time totally indistinguishable from live radio broadcasts.

By 1943, one of the Reichs-Rundfunk-Gessellschaft (RRG) technicians by the name of Helmut Krüger, regularly made magnetic tape recordings of symphony orchestra concerts from the Great Hall in the Berlin Broadcast House a then newly upgraded AEG magnetic tape recorder that ran at (77-cm/sec.)  in which high frequency premagnetization or a.c. bias, then recently patented by its inventor – Walter Weber, was used – affording far better performance compared to contemporary recording machines. Imagine – back in 1943 – a magnetic tape recorder with a frequency response of 50-Hz to 10,000-Hz with a dynamic range of 60-dB and a harmonic distortion of 1.5%. An audio engineering feat that American broadcasting and recording engineering firms were only able to replicate – let alone exceed – at the start of the 1950s.
The two-channel recording head upgrade to one of the AEG/Magnetophon R22 magnetic tape recorder for recording and broadcasting for the RRG was the very impetus that made Helmut Krüger “experiment” and test out his own ideas on stereophonic sound. Although, the two-channel recording heads were originally intended to reduce harmonic distortion in monophonic taping sessions by recording two channels in push-pull.

Ironically, Krüger’s “unauthorized” experimental pioneering stereophonic audio recordings were – for all intents and purposes – actually bootleg recordings! This became so because during regular monophonic with the orchestras, Krüger ran separate signal cables from his microphones and directed them to a small input console with four potentiometers and thence to his “modified” AEG stereo recorder set up in an isolated room in the Broadcast House.

Believe it or not, Krüger was using a spaced-array mike pickup – where one mike is placed to the left of the conductor, another to the right, and a third in the center – which Krüger fed to the left and right channels of the recorder. The mikes were 2 meters in front of the orchestra and 1 meter above the conductor’s head. This set-up, with slight variations, was used by Bob Fine in his Mercury recordings, by Bert Whyte in his Everest recordings during the Golden Age of Stereo of the 1950s – and even Jack Renner frequently used it until today in his Telarc recordings.

According to surviving records, by the end of World War II, Krüger had made between 200 and 300 stereophonic tape recordings – which were stored in a bunker in the Broadcast House and in several other locations. Sadly, when the Stalin-era Soviet troops occupied Berlin took shelter in the Broadcast House, almost all of the tapes there where either lost or destroyed. Of all the stereo tapes recorded by Krüger, only five of which are known to have survived and it wasn’t until 1993 during the 94th AES convention which was held in the first time in post-Cold War era Berlin were mere “civilian” audiophiles had the chance to hear the pioneering tapes first hand with their own two ears. Some had even to wait a few months later when Krüger’s pioneering stereo tape recordings were transferred to CD.

After hearing CD transfers - mastered via an early 1990s version of Sony’s Super Bit Mapping technique - of Krüger’s pioneering stereo tape recordings back in 1995. The residual tape hiss is only slightly louder than those of 1950s era stereo analog tape recordings of orchestral concerts form the mid 1950s. But what fascinated me most was their warmth and pristine tone that 1980s era fully digital recordings of Classical Music orchestras still fails to capture – even during the mid 1990s! The very first Classical Music orchestral recordings may have been made in various places during the mid 1950s at the start of the Golden Age of Stereo – but Helmut Krüger truly deserve the credit for pioneering stereophonic tape recording during the dark days of World War II.