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Archive for October, 2008

George Simon Ohm

Posted by yonni1967 on October 5, 2008

George Simon Ohm (1787-1854)

Georg Simon Ohm was a German physicist born in Erlangen, Bavaria, on March 16, 1787. As a high school teacher, Ohm started his research with the recently invented electrochemical cell, invented by Italian Count Alessandro Volta. Using equipment of his own creation, Ohm determined that the current that flows through a wire is proportional to its cross sectional area and inversely proportional to its length or Ohm’s law.

George Simon Ohm adalah seorang fisikawan jerman yang lahir di Erlangen, Bavaria pada tanggal 16-maret-1787. Dia hanyalah seorang guru SMA yang memulai risetnya saat teknik Electrochemical Cell ditemukan oleh Alessandro Volta dari Italia.

Using the results of his experiments, Georg Simon Ohm was able to define the fundamental relationship between voltage, current, and resistance. These fundamental relationships are of such great importance, that they represent the true beginning of electrical circuit analysis.

Dari hasil eksperimennya George Simon Ohm menemukan hubungan dasar antara Tegangan, Arus dan Resistansi. Hubungan dasar ini menjadi sangat penting dan menjadi cikal bakal semua acuan untuk menganalisa sirkuit listrik sampai masa kini.

Unfortunately, when Ohm published his finding in 1827, his ideas were dismissed by his colleagues. Ohm was forced to resign from his high-school teaching position and he lived in poverty and shame until he accepted a position at Nüremberg in 1833 and although this gave him the title of professor, it was still not the university post for which he had strived all his life.

Sayangnya, pada saat dia mengumumkan penemuan itu di tahun 1827, ide itu dicekal oleh para koleganya. Dengan tidak mengenal putus asa dan rasa malu George tetap mengajar di kelasnya dan hidup dalam tekanan ekonomi sampai akhirnya idenya diterima di Nuremberg pada tahun 1833 hingga mendapat gelar profesor. Yang patut diteladani walau gelarnya tinggi ia tetap bersahaja tidak sok ilmuwan dan terus berjuang sepanjang hayatnya.

Ohm the Genius! the Mozart of Electricity …

Ohm and corrosion monitoring

Ohm’s main interest was current electricity, which had recently been advanced by Alessandro Volta’s invention of the battery. Ohm made only a modest living and as a result his experimental equipment was primitive. Despite this, he made his own metal wire, producing a range of thickness and lengths of remarkable consistent quality. The nine years he spent at the Jesuit’s college, he did considerable experimental research on the nature of electric circuits. He took considerable pains to be brutally accurate with every detail of his work. In 1827, he was able to show from his experiments that there was a simple relationship between resistance, current and voltage.

Ohm’s sangat tertarik menyelidiki arus listrik setelah Alessandro Volta menemukan battery. Dalam penyelidikan itu Ohm mempergunakan alat-alat sederhana dan kuno namun dalam teknik pembuatanya ia memperhatikan kualitas secara presisi seperti kawat metal buatannya. Setelah menghabiskan pendidikannya di perguruan tinggi Jesuit’s, Ohm lebih amat sangat teliti dalam semua pekerjaannya. Pada tahun 1827 barulah ia berani mempertunjukan hubungan sederhana antara resistance, arus dan tegangan.

Ohm’s law stated that the amount of steady current through a material is directly proportional to the voltage across the material, for some fixed temperature:

Ohms menyatakan bahwa arus yang mengalir melalui suatu bahan adalah sepadan dengan tegangan yang melintasi bahan itu. Dinyatakan dalam rumus yang terkenal :

I = V/R

Ohm had discovered the distribution of electromotive force in an electrical circuit, and had established a definite relationship connecting resistance, electromotive force and current strength.

Kemudian Ohms menemukan distribusi dari gaya elektromotif dalam rangkaian listrik yang menentukan hubungan pasti terhadap rangkaian resistance, gaya electromotive dan kuat arusnya.

Ohm was afraid that the purely experimental basis of his work would undermine the importance of his discovery. He tried to state his law theoretically but his rambling mathematically proofs made him an object of ridicule. In the years that followed, Ohm lived in poverty, tutoring privately in Berlin. He would receive no credit for his findings until he was made director of the Polytechnic School of Nüremberg in 1833. In 1841, the Royal Society in London recognized the significance of his discovery and awarded him the Copley medal. The following year, they admitted him as a member. In 1849, just 5 years before his death, Ohm’s lifelong dream was realized when he was given a professorship of Experimental Physics at the University of Munich. On July 7th,1854 he passed away in Munich, at the age of 65.

Hampir-hampir ia ragu bahwa hasi teori dasarnya gugur dan menjadi bahan olok-olokan karena selama itu kemiskinan selalu menderanya hingga ia tetap mengajar secara privat di Berlin. Karena itulah hasil penemuannya tidak pernah mendapat simpati dan pengakuan sampai pada akhirnya menjadi pucuk pimpinan di sekolah polyteknik Nuremberg pada tahun 1833. Di tahun 1849, lima tahun sebelum wafat, mimpi panjangnya menjadi kenyataan saat menjadi guru besar di Experimental Physics, the University of Munich. Ohm wafat di usia 65 tahun, tepatnya 7-Juli-1854.

This belated recognition was welcome but there remains the question of why someone who today is a household name for his important contribution struggled for so long to gain acknowledgement. This may have no simple explanation but rather be the result of a number of different contributory factors. One factor may have been the inwardness of Ohm’s character while another was certainly his mathematical approach to topics which at that time were studied in his country a non-mathematical way. There was undoubtedly also personal disputes with the men in power which did Ohm no good at all. He certainly did not find favor with Johannes Schultz who was an influential figure in the ministry of education in Berlin, and with Georg Friedrich Pohl, a professor of physics in that city.

Pengakuan teori ohm terlambat namun kematiannya membekaskan pertanyaan : mengapa perjuangan panjang beliau sangat berat dan panjang untuk mendapat pengakuan setelah kematiannya, padahal penemuan (yang dianggap) sepele itu ikut ambil bagian terbesar dalam peralatan rumah tangga kita?. Ini membutuhkan penjelasan panjang dan banyak penyebab. Salah satu faktornya mungkin pembahasan teorinya dengan pendekatan matematis yang rumit sedangkan latar belakang sekolahnya dianggap tidak mendukung apa yang digagaskannya. Pada saat itu banyak orang meragukan bahwa teorinya hanya bualan semata!. Pada saat itu sayangnya ia tidak mengenal kebaikan hati orang yang berpengaruh seperti Johannes Schultz sebagai menteri pendidikan di Berlin dan Friedrich Pohl, seorang professor fisika di kotanya.

Electricity was not the only topic on which Ohm undertook research, and not the only topic in which he ended up in controversy. In 1843 he stated the fundamental principle of physiological acoustics, concerned with the way in which one hears combination tones. However the assumptions which he made in his mathematical derivation were not totally justified and this resulted in a bitter dispute with the physicist August Seebeck. He succeeded in discrediting Ohm’s hypothesis and Ohm had to acknowledge his error.

Padahal bidang kelistrikan bukanlah topic utama Ohm dalam semua risetnya dan bukanlah perjalanan kontroversi satu-satunya dalam penemuannya. Di tahun 1843 bahkan ia menyatakan prinsip dasar psikologi akustik yang menyelidiki respon pendengaran manusia terhadap kombinasi nada. Lagi-lagi dengan asumsi bahwa Ohm bukan Ilmuwan dan pakar matematika handal, ia menuai hinaan yang menyakitkan dari fisikawan August Seebeck, dalam perdebatan, Seebeck telah berhasil meruntuhkan hipotesa Ohm salah besar!. He..he…he…dia keliru besar.

Pesan dan kesan : bahwa tidak semua penemuan besar lahir dari disiplin bidang keilmuan yang sama. Perjuangan yang panjang dengan kesabaran dan disiplin tinggi dapat mencapai hasil yang bermanfaat bagi umat manusia. Jangan pernah meremehkan pendapat orang lain karena latar belakangnya atau kemiskinannya.

Salam : Yonni.

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Power Amplifier tutorial

Posted by yonni1967 on October 2, 2008

Understanding amplifier power ratings

(pemahaman rating power amplifier)

There are different methods for measuring the power ratings for amplifiers and speakers. And different measuring methods give different values so it is vital to understand the difference between theosedifferent power ratings to be able to make at least some comaparision between different power ratings. This article is collection of information posted to rec.audio.tech newsgroup at July 1996. The information is compiled from Usenet newsgroup rec.audio.pro articles written by Norbert Hahn, Dick Pierce and Earl K.

Ada beberapa cara berbeda untuk mengukur nilai power amplifier dan speaker. Cara pengukuran ini memberikan pandangan sangat berbeda dan penting untuk memahami perbedaan antara theosedifferent power rating yang membuat perbedaan comparision power rating. Artikel ini koleksi dari posting rec.audio.tech newsgroup pada bulan Juli 1996. Informasi di-compile dari Usenet newsgroup rec.audio.pro dan ditulis oleh Norbert Hahn, Dick pierce dan Earl K.

RMS power

(Apa sih RMS itu ?)

To make it short, an RMS power value is directly related to perceivable energy (acoustical, heat, light – or what else applies).

Arti harfiahnya ialah : RMS adalah suatu nilai tenaga (power) yang secara langsung dihubungkan dengan energi yang dapat dipahami (akustik, panas, cahaya atau sejenisnya).

“RMS” is really a rather meaningless figure, when measuring power. R.M.S. is useful for measuring the “power-producing equivalent” voltage. Thus 10 Volts RMS will produce the same power into a given impedance that 10 Volts DC would produce (onto a resistance) Any waveform of 10 V R.M.S.will produce the same power into that impedance. This is because it’s the root of the mean of all the average squared voltages to which Norbert Hahn referred in the prior post. It is if little meaning to compute the mean of squares of all the power values in a wave.

” RMS” sebenarnya suatu figur yang tidak penting saat mengukur power. R.M.S. bermanfaat untuk mengukur ” powerproducing (yang sepadan)” dengan voltase. Dengan umpan 10 VOLT RMS akan menghasilkan sama ke dalam impedansi yang ditentukan dan akan menghasilkan 10 VOLT DC ( dalam resistansi) semua bentuk gelombang apapun dari 10 V R.M.S. Ini adalah musabab akar dari semua rata-rata dalam tegangan seperti yang direferensikan oleh Norbert Hahn di postingnya. Pemahaman ini lebih sedikit dibanding perhitungan mean of square ( nilai akar rata-rata) pada segala nilai dan bentuk gelombang.

RMS, when applied to power measurements, has come to mean “sine-wave power.” A 100 Watt “RMS” amplifier can produce a 100 Watt sine-wave into its load. With music, the total actual power would be less. With a square-wave, it would be more.

RMS, saat pengukuran power mempunyai arti ” sine-wave power“. Amplifier 100 Watt ” RMS” berarti menghasilkan tenaga 100 Watt sine-wave ke dalam bebannya. Dengan dibebani musik, total power nyatanya, ternyata berkurang. Dengan mengumpanii square-wave maka akan lebih meningkat. Mengapa demikian?.

DIN power

The DIN 45000 defines different methods to measure power, depending on the device under test. Well, this is what I remember from reading the DIN some 25 years ago.

For home applicances there are three different numbers for power: Continous power, Peak power and power bandwidth; the latter does not apply for speakers.

DIN 45000 menggambarkan metoda lain untuk mengukur power, tergantung alat testernya, ini yang harus diingat saat mempelajari DIN yang berlaku 25 tahun lampau.

Untuk peralatan rumah tangga ada tiga perbedaan pokok tentang normalisasi power yaitu : continous power, Peak Power dan power bandwidth. Yang terakhir tidak diaplikasikan pada speaker.

Power measurement of an amp requires that the amp is properly terminated by Ohmic resistances of nominal value both at input and output. The continous power is measured when the amp is supplied by its normal power supply. It must then be able to deliver the rated power at 1 kHz for at least 10 minutes while the maximum THD does not exceed 1 %. To measure the peak power the normal power supply is replaced by a regulated power supply and the time for delivering the power is reduced. Thus, higher values for peak power are obtained. You may skip measuring the peak power by simply multiplying the continuous power by 1.1.

Pengukuran amplifier memerlukan nilai hambatan Ohmic dari nilai nominal kedua- masukan dan keluaran. Continous power diukur ketika amp disuplai oleh normal power supply. Kemudian bisa mengirim power rating power 1 kHz sedikitnya 10 menit saat maksimum THD tidak melebihi 1%. Untuk mengukur daya puncak power yang normal digantikan oleh penggunaan power supply yang terserap olehnya. Seperti itulah nilai tertinggi untuk daya puncak dapat diperoleh. Kita boleh mengabaikan pengukuran daya puncak dengan hanya mengalikan continous power dengan perkalian : 1×1.

The power bandwidth is defined as the bw for which 1/2 of the rated continous power can be obtained.

Actually, DIN 45 500, CNF 97-330, EIA RS-426 and the encompassing IEC 268-5 specify not pink noise, but pink noise filtered by a filter that provides sinificant attenuation in the low and high frequency region of the spectrum to more closely model the long-term spectral distribution of music. Pink noise itself does not accomplish this

Power bandwitdh digambarkan sebagai bw di mana 1/2 dari rating continous power dapat diperoleh.

Sebenarnya , DIN 45 500, CNF 97-330, EIA RS-426 yang mencakup IEC 268-5 tidak menspesifikasikan bising merah muda (Pink noise), tetapi bising merah muda yang disaring oleh suatu penekanan penyaringan yang sinificant di daerah frekwensi tinggi dari rendah dari spektrum kepada mode long term spectral distribusi musik. Pink noise sendiri tidak memenuhi kriteria ini

PMPO (Peak Music Power)

So called “music power”. This power figure tells the power which the amplifier can maximally supply in some conditions. PMPO rating gives the highest measuring value, but this info is quite useless, because there is no exact standard how PMPO power should be measured.

Sekarang lagi trend orang menyebut : ” music power “. Sebenarnya figure ‘power’ tersebut berusaha menjelaskan pada kondisi yang mana amplifier dapat secara maksimal menyediakan sumber tenaga. Rating PMPO maksudnya memberi nilai pengukuran maksimum, tetapi informasi ini sebenarnya tidak relevan sebab tidak ada standard yang tepat bagaimana power PMPO terukur.

The reason for this power rating was to show the max capability of equippment for recreating strong musical tansients like kettle drums and the like. Similar thing (music power rating) was used in the sixties, and I think it assumed a square wave that swung the whole supply range of the output stage. This alone gives them a factor of two over a clean sine wave note.

Alasan power rating maksimum ini adalah hanya menunjukkan kemampuan maximum equipment untuk melukiskan kekuatan transient dalam hal musical seperti dentuman perkusi Drums yang digunakan sejak tahun 60 an. Asumsinya adalah ada sebuah gelombang persegi yang mengayun pada jangkah suplai terhadap tingkatan output yang memberikan satu factor terhadap dua sinyal over pada sebuah gelombang sinus bersih yang lewat.

But the ugliest thing they did was to assume that the high power lasted such a short period of time that the power supply caps would hold the voltages steady without any drooping. In the real world, an under powered PS could be hidden by this ruse and the PMPO might be a factor of 10 or more higher than what could be sustained on a nice instrumental performance.

Tetapi hal paling buruk bagi asumsi ini adalah bahwa kualitas high power seperti layaknya perioda pendek kemampuan power suplly untuk menahan stabilitas tegangan tanpa adanya droping diabaikan. Pada kenyataannya penampilan PSU untuk mengatasi masalah perhitungan PMPO ini harus memperhitungkan factor 10 tiap power rating ditingkatkan volumenya yang tentunya mempengaruhi penampilan kualitas musik.

Forget what adverts say about peak power or other “power terms” because they are not standardized and anyway comparable between equipments. Just look for “RMS continuous Power” or other reliable power rating (like DIN power).

Maka dari itu mari kita lupakan perdebatan sengit tentang terminologyPeak power’ (istilah itu hanya salah kaprah dan umum) yang sebenarnya tidak ada standarisasi yang cocok diterapkan di banyak equipment. Kita hanya mereferensikan “RMS continous power” atau badan standarisasi yang dapat dipercaya seperti DIN power.

Speaker power ratings

The nominal power for speakers is defined quite differently: The continous power is measured by pink noise rather than a sinousoidal signal and it is applied for 24 hours. Bandwidth of the noise is as required/specified by the speaker. Thus the nominal power is applicable to both a single chassis/driver and complete box.

Perhitungan nominal power untuk speaker dapat dijelaskan dengan jalan: Continous power diukur dengan generator pink noise berbanding dengan sinyal sinus yang diaplikasikan selama 24 jam penuh. Lebar bidang noise harus sesuai dengan spesifikasi speaker. Kemudian nilai nominal powernya dapat dilaksanakan dengan driver dan desain boxnya.

And the THD is not the limiting factor: It is replaced by the term that the speaker should by no means be damaged. Rhe requirement is that the speaker meet the manufacturers performance sapecification after the power cycle.

The maximum power is defined for woofers and boxes only. It is measured by applying sinusoidal signals of 250 Hz and lower such that the speaker is neither damaged nor produces unwanted output.

THD tidak membatasi limiting factor dengan terminology bahwa sampai dimana kesanggupan speaker menampung daya dan tidak sampai rusak. Tentu harus dipelajari spesifikasi pabrik pembuat speaker sebelum pengujian.

The AES/ANSI spec provides for two power measurements: thermal power, as you describe above, and excursion limiting, which is determined by either the hard mechanical limits afforded by the suspension, or the difference between the length of the voice coil and the length of the magnetic gap.

Spec. AES/ANSI telah mengembangkan dua tolok ukur pengukuran cermat lain : Thermal power seperti yang disebutkan di atas dan pembatasanya dimana ada pendekatan hal lain seperti (melihat dulu) mekanikal speaker pada kelenturan suspensi speaker atau jarak antara voice coil dan jarak celah magnet speaker.

Other amplifier specifications

Speaker impedance the amplifier is designed to drive

Many amps manufactured these days are rated only for 8-ohm-and-above loads, and not for 4-ohm loads. This is done largely as a cost savings by the manufacturer. Amps which are capable of driving 4-ohm loads to the same output voltage require heftier power supplies, heatsinks, and (often) output-stage transistors: they’ll be delivering twice as much current into the load, and will be dissipating roughly twice as much heat within their output stages.

Kini banyak pembuat amplifier menyediakan rating beban speaker sebesar 8 ohms dan bukannya 4 ohms. Maksud dari semua ini adalah dengan alasan menghemat daya power suplly dan keping pendingin pada transistor akhir dimana semakin besar dayanya semakin besar pula disipasi daya yang terhambur pada finalnya.

If a manufacturer chooses to quote a power rating at 4 ohms in their advertising, the amp must be capable of delivering this much power after a ‘warmup’ period of operation at 1/3 power (which level actually dissipates _more_ heat in the output stage than full-power operation).

Jika ada pabrikan mengklaim power buatanya berating sanggup mengatasi beban pada 4 ohms, amplifier buatannya harus mampu mensuplai banyak tenaga selama “warm up” period untuk pengoperasian pada 1/3 tenaga yang mana dilevel itu sudah banyak pemborosan daya yang memancar sebagai panas selama pengoperasian penuh!. Kesimpulanya beban impedansi 4 ohm bukan alasan untuk mendongkrak performance amplifier.

In order to save money during manufacture, manufacturers often use skimpier power supplies, heatsinks, and output stages – and as a result, the amps may have a 4-ohm power rating which is _less_ than the 8-ohm rating. This is somewhat embarrassing for the manufacturer to advertise – and, so, they often do not quote a 4-ohm power rating at all, and state that the amp is designed to be used only with loads of 8 ohms or above.

Untuk mengatasi hal itu dibutuhkan desain yang menelan biaya mahal. Pembuat amplifier biasanya mengatasinya dengan “skimpier” power supply, keping pendingin lebih tebal dan lapis multi final pada outputnya dibanding desain 8 ohms. Padahal desain-desain itu lebih aman beroperasi pada beban 8 ohm ke atas.

With many such amplifiers, you can drive a 4-ohm load safely, as long as you don’t try to drive it too hard. If you drive a low-Z load to too high a volume, one of several things may happen: the amp may begin to “clip” (sounds very harsh and distorted, may damage the tweeters), or may overheat and shut itself down, or may overheat and burn up (all the magic blue smoke leaks out).

Memang ada beberapa amplifier yang aman beroperasi pada beban 4 ohm, hanya harus diingat jangan terlampau keras memperkosanya dengan volume tinggi dan dengan dentuman bass yang menggebu-gebu!. Ingat! Akan terjadi “clipping” yaitu suara tersendat atau cacat dan dapat membakar coil tweeter dalam sekejab!. Bahaya yang lain yaitu terjadi kebakaran dan pijaran api biru pada peralatan.

Methods for making 4 ohm speaker to appear as 8 ohm

cara membikin speaker 4 ohm menjadi 8 ohm

  • Wire a 4-ohm power resistor (10-20 watt) in series with each 4-ohm speaker. This makes the system to be appear as 8 ohm load and is inexpensive. The cons are that the resistor wastes power, may cause frequency response go bad because speakers do not have constant resistance with frequency. When you play at high volumes the resistor may get hot and burn thing or itself.

  • Pasang resistor 4 ohm 10-20 watt seri dengan coil speaker. Resistor ini sebagai ballast tapi resikonya memotong bandwidth. Respon frekuensinya jelek dan jangan pasang volume keras-keras karena resistor ini akan terbakar.

  • Using 4 ohm to 8 ohm matching transformer will not waste much power, but the transformer will be heavy, expensive and hard to find. Transformer has also problems in playing back lowest frequencies (saturation causes distortion in high levels) and in higher frequencies the inductance in the transformer will cause phase shifts.

  • Memakai trafo penyesuai jauh lebih baik hanya ukurannya menjadi berat dan mahal. Resiko yang lain adalah respon pada frekuensi rendah terjadi saturasi yang menyebabkan distorsi. Pada frekuensi tinggi induktansi trafo menyebabkan pergeseran fasa.

  • You can wire two 4-ohm speakers in series if you have two identical speakers. Problem is that if the speakers are not identical type the frequency response and power distributin will be uneven.

  • Cara yang lebih baik lagi adalah menyeri dua buah speaker yang identik. Hanya saja “identik” disini sangat sukar ditemukan walau sama persis secara fisik, harus betul-betul eksak dan absolute.

  • Most “8-ohm” amplifiers can drive a 4-ohm or 6-ohm load as long as you don’t try to get full power out of the amp (if you do, it may overheat and shut down).

  • Banyak amplifier 8 ohm dapat beroperasi baik pada 4 atau 6 ohm selama anda suka, namun ingat sekali lagi jangan diperkosa beroperasi penuh pada volume tinggi jika tidak ingin terbakar!.

  • Buy yourself a decent power amplifier whose output stage and power supply are capable of handling a real honest low-impedance load. Good amplifier will be expensive but gives best sound quality and reliabity.

  • Solusi terakhir jika anda pengidam power ukuran besar; belilah amplifier desain khusus dengan rating power yang sanggup beroperasi pada impedans rendah (tapi mahal dan sulit dapatnya), dijamin memang akan memberikan performa bagus dan memuaskan.

Dampling factor

The output impedance of an amp should be extremely low. If it’s .8 Ohms, then an 8-Ohm speaker has a damping factor of 10. If it’s .08, then the amplifier provides a damping factor of 100, etc. Don’t confuse the actual output (source) impedance with the load impedance that is recommended for the amp (4-Ohms, 8-Ohms, etc).

Impedansi keluaran amplifier bisa jadi rendah sekali. Jika amplifier 8 ohm diumpankan pada speaker 8 ohm memiliki damping factor 10, jika .08 ohm maka dampling faktornya 100 dan seterusnya. Jangan dicampur adukkan antara actual output (sumber) impedansi dengan beban impedansi yang direkomendasikan amplifier 4 ohm, 8 ohm dan seterusnya.

The idea is that if the speaker is 8 Ohms, and the amplifier has a source impedance of .08 Ohms, then the amplifier “damps” the motion of the cone by a “factor” of 100. In reality, the true damping that the cone “sees” is determined by many things, part of which is the damping limitation imposed by the resistance of the voice coil, usually around 5 Ohms or so for an 8-Ohm speaker. You can see that if the speaker has 5 Ohms of resistance, the internal (source) impedance of the amplifier (.08 Ohms for a damping factor of only 100) doesn’t add much to the total resistance in the voice coil circuit, hence has very little effect on total damping. So any modest change in the amplifier damping factor correlates to virtually no change in total damping.

Idealnya speaker 8 ohm itu diumpankan pada sumber impedansi amplifier .08 ohm dimana terjadi peredaman gerakan konus speaker berdasarkan atas factor 100. pada kenyataannya peredaman konus terlihat dalam beberapa hal : misalnya batas resistansi koil speaker, biasanya sekitar 5 ohm atau lebih untuk speaker 8 ohm. Coba anda ukur dengan multi tester harga tahanannya pasti sekitar 5 ohm! Ingat : untuk .08 ohm factor damping nya hanya 100!. Maka dari itu jangan menambahkan harga total resistansi koil suara.

A speaker designer shoots for a certain damping (same as 1/Q) to achieve a certain desired type of low-frequency rolloff. The assumption is that the source impedance of the amplifier is 0 Ohms. If the source impedance is .08 Ohms (damping factor of 100), very little error is introduced into the system. Higher damping factors are getting into diminishing returns in terms of the total damping. In practice we want a certain, relatively low damping figure for the whole speaker system, (1.414 for a maximally flat bass response).

Pendesain speaker menetapkan damping sebagai 1/Q untuk untuk menggambarkan type dari roll-off frekuensi rendah dengan anggapan bahwa sumber impedansi amplifier adalah 0 ohm. Jika sumber impedansi .08 ohm dan faktornya 100 akan terjadi sedikit error pada system. Damping factor yang terlalu tinggi akan mengurangi harga terhadap total dampening faktornya. Dalam prakteknya kita selalu mengidamkan suara merdu bass flat respon secara maksimal.

What is amplifier “bridging” or “monoblocking”?

When you’re told a stereo power amplifier can be bridged, that means that it has a provision (by some internal or external switch or jumper) to use its two channels together to make one mono amplifier with 3 to 4 times the power of each channel. This is also called “Monoblocking” and “Mono Bridging”.

Jika anda bilang : stereo amplifier dapat dijembatankan sebanyak 3 atau 4 lapis per chanel bersama maka hal itu lazim disebut sebagai “mono blocking” atau “mono bridging”

Bridging typical HIFI amplifier involves connecting one side of the speaker to the output of one channel and the other side of the speaker to the output of the other channel. The channels are then configured to deliver the same output signal, but with one output the inverse of the other. The beauty of bridging is that it can apply twice the voltage to the speaker. Since power is equal to voltage squared divided by speaker impedance, combining two amplifiers into one can give four (not two) times the power.

Tipikalnya adalah menggabungkan dua buah amplifier per chanel sekaligus pada satu speaker. Dua buah amplifier itu mengirimkan sinyal bersama tapi lain fasanya/saling menjungkir. Akal-akalan itu memang dapat diperoleh dua kali lipat tegangan pada satu speaker. Awalnya anggapanya diperoleh harga tegangan 4 kali lipat!

In practice, you don’t always get 4 times as much power. This is because driving bridging makes one 8 ohm speaker appear like two 4 ohm speakers, one per channel. In other words, when you bridge, you get twice the voltage on the speaker, so the speakers draw twice the current from the amp.

Sekali lagi dijelaskan disini penggabungan 2 buah amplifier menghasilkan dua kali tegangan dan arus pada speaker bukan 4 kali!. Logikanya pengendalian speaker 8 ohm akan ditampilkan sebagai 4 ohm speaker. Jadi akan mendongkrak daya.

Another interesting consequence of bridging is that the amplifier damping factor is cut in half when you bridge. Generally, if you use an 8 ohm speaker, and the amplifier is a good amp for driving 4 ohm speakers, it will behave well bridging.

Jika anda tertarik menggunakan metoda ini konsekwensinya damping factor akan memotong setengah gelombang sinyal. Jadi harus diperhatikan : metoda ini bagus jika : anda pasang speaker 8 ohm dengan desain amplifier khusus bridge 4 ohm speaker.

Also consider amplifier output protection. Amps with simple power supply rail fusing are best for bridging. Amps that rely on output current limiting circuits to limit output current are likely to activate prematurely in bridge mode, and virtually every current limit circuit adds significant distortion when it kicks in. Remember bridging makes an 8 ohm load look like 4 ohms, a 4 ohm load look like 2 ohms, etc.

Pergunakanlah pengaman speaker karena masalah metoda ini pada pembatasan arus sirkuit terhadap arus keluaran dan pembatasan sirkuit arus semu yang ikut andil dalam hal distorsi bila konus terdorong sinyal. Ingat! Metoda ini membuat beban 8 ohm terlihat sebagai 4 ohm, 4 ohm terlihat sebagai 2 ohm dan seterusnya.

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Operating system

Posted by yonni1967 on October 2, 2008

Bagi teman-teman pelajar, mahasiswa dan umum yang mengikuti program study dan pendalaman materi Operating System dapat mendown load file berikut ini yaitu mengenai sistim operasi : Windows, Unix dan Linux dalam versi format PDF.

For students and publics who’s concerning program in Operating System easy download this following items of the file operation systems lecture notes like : Windows, Unix and Linux in PDF format.

sisitem-operasi

linux

komputer1

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