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Creating good quality sound is an art.  There are many things to consider, whether you are building a home system, putting a system in your car, or building your own speaker enclosures.  Even though speaker quality is usually one of the first things considered, paying attention to the smaller things can make a huge difference in the quality of your sound system.  At CHOKES UNLIMITED we design and manufacture inductors (also called coils or choke coils) and custom crossovers.  We distribute these items along with capacitors, resistors and a large selection of installation and do-it-yourself supplies through out the world.

A crossover limits the frequency range that reaches a speaker.  A speaker should not receive a frequency range greater than it's design limits.  By using crossovers you not only increase the quality of your sound dramatically but you also protect your speakers from damage caused by distortion.

There are four types of passive crossovers:  LOW PASS, HIGH PASS, BAND PASS, and NARROW BAND PASS.

LOW PASS crossovers allow low frequencies to pass through and reach the speaker while gradually reducing the power of the higher frequencies and cutting them off.  COILS are used in low pass crossovers because they cut out the higher frequencies.

HIGH PASS crossovers allow the high frequencies to pass and reach the speaker while gradually reducing the power of the lower frequencies, thus cutting them off.   The power reduction increases as the frequencies become lower.  CAPACITORS are used in high pass crossovers because they cut out the low frequencies.

Crossover points or frequencies are changed by using different values of coils and capacitors to achieve the crossover point desired.

BAND PASS crossovers are a combination of the previous.  They only allow a certain band, or range, of frequencies to pass through and cut off frequencies above and below that band.  A band pass is most often used on a mid range speaker where the extreme highs and the extreme lows are cut off so they don't reach that speaker and cause it to distort.

A NARROW BAND PASS crossover should be used when the band of frequencies chosen to reach a speaker is less than a decade apart, that is, if the high crossover frequency is less than 10 times the low frequency.  A narrow band pass has the same function as a normal band pass, however, it is wired very differently and values of the components are different.

6 dB, 12 dB or 18 dB SLOPE
There are different rates for the reduction of power, called SLOPES.  The most common are 6 dB, 12 dB and 18 dB slopes. (dB=decibels)  A 6 dB slope will reduce the power at a rate of 6 decibels per octave starting at the chosen crossover frequency, creating a gradual slope of power reduction.  The 12 dB and 18 dB per octave slopes work the same way except that a 12 dB slope has twice as much reduction per octave as the 6 dB slope and an 18 dB slope has three times the amount of reduction, thus cutting off the unwanted frequencies three times as fast.

We make AIR CORE COILS and 3 types of IRON CORE COILS: Standard Iron Core, Solid Iron Core and Ferrite Bobbin

AIR CORE COILS are popular because of their ability to deliver great clarity, which is especially important at mid to high frequencies.  Coils in these frequency ranges are small and inexpensive and their DCR (Direct Current Resistance) is low.  Low frequency air core coils are more expensive and have higher DCR than iron core coils when both are made using the same size of wire.  It is important to keep the DCR low.  Resistance blocks power.  Higher resistance blocks more power.

IRON CORE COILS are generally used on woofers and sometimes midrange speakers and are popular because of their ability to handle large amounts of power while keeping the DCR low, and their size is much smaller than air core coils of equal inductance.  With coils, size is relative to price.

Our STANDARD IRON CORE COILS handle up to approximately 150 watts.

Our SOLID IRON CORE COILS are used for higher power handling (500 watts or more).

Our FERRITE BOBBIN COILS are smaller than iron core coils, have lower DCR than iron core coils and are able to handle about 50-75 watts of power.  Ferrite is a ceramic material which is like iron power and glue mixed together.  This is molded into the shape of a bobbin.  You must be careful when handling ferrite.  If you drop it on a hard surface, it will shatter like a ceramic coffee cup.

There are three basic types of capacitors used in crossover networks: NON POLARIZED ALUMINUM ELECTROLYTIC, MYLAR (polyester film) and POLYPROPYLENE.  Always use the best capacitor you can afford.  We carry all three types with a 100 volt rating on the electrolytics and a 100-600 volt rating on the Mylar and Polypropylene.  100 volt rating equates to about 300 watts of power handling.

NON POLARIZED ALUMINUM ELECTROLYTIC capacitors are by far the most commonly used in the audio world.  They are generally smaller than Mylar or polypropylene caps and are the most practical to use at low to mid frequencies.  Be sure to use NON POLARIZED (or bipolar) electrolytics, NOT POLARIZED!   There is a difference.

MYLAR capacitors are generally used in the higher frequency ranges because of their ability to deliver a clearer signal.  Clarity is very important in high frequency ranges.  Mylar capacitors cost more than electrolytics.

POLYPROPYLENE capacitors are the best because of their ability to deliver the clearest signal.  They are also the most expensive.  We sell what are generally considered to be the finest polypropylene capacitors in the world.  Polypropylene caps are also generally used for the higher crossover frequencies and we currently stock values which are compatible with mid to high frequencies.  We can also provide you with almost any value of polypropylene cap by special order.

At CHOKES UNLIMITED we manufacture custom crossovers.  Just tell us what you want and we will design it and make it for you.  Our custom crossovers are hard wired on black ABS, for show quality.

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