Audio Speaker Circuitry Parts

We carry speaker crossover parts from only the most respected manufacturers in the industry; Mills Resistors, Alpha/Goertz Foil Inductors, Reliable Capacitors AudioCap PPMF and PPMF-Theta, and MultiCap PPMFX. We also list the drivers that we use in our own designs. We provide these parts in our kits and completed speakers, or you can order them individually, below. Any of these make great upgrade components. See our Speaker Design system if you are attempting to determine which parts you need for a special speaker project; it can recommend the proper capacitors, inductors and resistors for your system.

If you wish to order only components, please place your order over the web site. If you are ordering many components, or have pre-sales questions, feel free to call us at 503-472-0688, 10 AM - 5 PM Pacific Time, Monday through Friday.

Drivers

Other Hardware

In addition to passive electrical components, we also carry:

• Perforated circuit boards
• Jumper wire
• Woodworking, speaker and crossover board mounting screws
• Nylon standoffs (for crossover boards)
• ABS Pipe for acoustic ports
• Binding posts

Questions about Circuitry Components

Why do the components cost so much? I can get mid-level brand X capacitor/inductor/resistor for half as much elsewhere.
We carry circuitry components only from the most respected companies in the industry; Mills, Alpha, Reliable, etc. These components simply cost more, but if you are taking the time and effort to make top-quality speakers, we think it is worth it to spend a little extra to get the best possible sound. (Besides, even if you use our design system, there is no requirement to purchase your components here from us.) We don't inflate the prices, but we do put a lot of time and effort into making it as easy as possible to order what you need and get the right item on the first try. For these and other reasons, these parts cost a little more than the competition.

Which is better, air or iron core inductors, round wire or foil, and what gauge wire?
For high-fidelity audio applications, the general consensus is that air core coils carrying higher frequencies (~5000Hz+) introduce less distortion than metal core coils. But at lower frequencies it is a matter of some dispute. For the higher inductance values needed at low frequencies, metal core coils have the an advantage of smaller size and lower resistance (and therefore better power handling). The choice of foil or wire coils is also a matter of debate. Some argue that foil coils, like air core coils, introduce less distortion than round wire coils. It isn't clear, however, that this is true when comparing a foil coil to an "equivalent," high quality well-made wire coil. Bigger is not always better (or necessary): All other things being equal, coils with thicker conductor will have less resistance, more power carrying capabilities, more weight, more expense and larger size. Even an 18 gauge coil, well made, handles 300 W, many times the average power rating needed for almost any home system (and 14g can handle as much as 800W!). However, it will have roughly twice the DC resistance of a 14 gauge coil with the same inductance. So if circuit resistance is an issue, the choices are heavier wire (or a metal core).

Okay, how about resistors?
Specialized non-inductive audio resistors have very little inductance relative to their more common cousins. The less inductance, the more 'true' the audio signal will be to the original. Some audio resistors also need to burn off a significant amount of power, usually resistors used in woofer circuits. For these, we generally recommend 10-12W power ratings. Almost all other audio crossover resistors need not be more than 5W except in very unusual circumstances. This site analyzes the power levels likely to go through your crossover and recommends power ratings accordingly. There is no harm in picking a resistor with a power rating greater than is needed, but don't pick one that is smaller unless you have backups (or a fire-extinguisher) handy.

What about speaker cabling and internal hookup wiring
There probably isn't a more contentious subject in speaker making. There are about as many opinions on this as there are audio freaks, but they fall into two general camps: Only the most expensive exotic cables will do, or, just pick some good, heavy wire. Everyone agrees that corroded, faulty wire is bad. Beyond that, the jury is still out (and probably will be in perpetuity).

Capacitors: What style should I use?
Like questions about enclosure material, drivers, inductor and resistor design, the capacitor design and manufacturer is a matter of debate. The general consensus is that, for most applications, metalized polypropylene capacitors, if well made, are excellent for higher capacitance values and lower frequencies, and (more expensive) film and foil capacitors for higher frequencies and lower capacitances. Electrolytics are generally discouraged, but better quality bipolars are sometimes used in lower-end filters or when a very high capacitance is necessary, as in a subwoofer; a $10 bipolar electrolytic is fine for a subwoofer low-pass filter.

How close should my component values be?
Capacitors, resistors and inductors can be custom ordered and made to incredibly-tight tolerances, but for a price (usually a very high one). For example, we can custom order individual custom resistors from Caddock, but they cost as much as $50 each. Within 5% is usually fine. If your real value is off by 10% from the ideal, it might cause problems, especially if this is the case for multiple components. We purchase several of the same item at a time and hand measure and mark them for our use. Sometimes you have to combine two or even three components in series or parallel to get as close as desired to the ideal value, and it will still cost less than a custom part (e.g., 14μF capacitance requires three different AudioCaps PPMF placed in parallel, but this still costs less than a 14μF MultiCap -- more on this, below). It is unlikely that pursuit of 1% or better tolerance is actually useful because other, external factors will drastically affect the sound too.

Should I add fuses or breakers to the circuitry?
If your speakers are being connected to an amplifier capable of driving them beyond their long term peak power limit, then fuses or breakers should be added. Breakers cost less than new drivers.

I can't find a capacitor/inductor/resistor with the exact value I seek.
Perfect capacitors, inductors and resistors exist only in the imagination; in the real world they vary quite a bit. For example, capacitor and inductor actual values may be as much as 10% away from the labeled value. The resistors we carry are within 5%. Component values are also a function of the frequency, power and environment. You have four options:

1. The Easy Way Out: Pick the closest value, hopefully within 10%, from a quality line. This is 'good-enough' for most, and is as good or better than many consumer speakers. But for the sake of argument, let's assume that you are buying a capacitor and the actual component is 10% off. What difference will this make? In a simple crossover circuit with a target crossover frequency of 3500Hz, the desired capacitance value is 5.68µF. This is a difficult capacitor to find -- in fact, we don't know of any that are made (stock). Both 5 and 6µF are readily available. The 5µF, because it is a +/- 10% tolerance, might actually be anywhere between 4.5 and 5.5µF. The 6 could be anywhere from 5.4 and 6.6µF. You won't know with certainty until you purchase the capacitor, receive it and, if you have the tools, measure it. Assuming it is the worst situation -- you purchased a 5µF and received 4.5µF -- this increases the mathematical (and effective) crossover point for the tweeter from 3500Hz to 4400Hz, or about 1/3rd of an octave. It might seem like a big shift, but chances are that the casual listener wouldn't even notice, and you probably wouldn't know it or think to blame anything on it (rightly or not) unless you had personally measured the capacitor prior to installation and done the math. If it shifted the other way, it might begin to run up against the tweeter's resonant frequency if you are already playing it too close. But if the whole world is really stacked against you, perhaps the woofer's filter shifts the other way, from 3500Hz down to maybe 2600Hz. This combination of random but entirely possible events would result in a notable depression of volume in a frequency range to which the ear is quite sensitive (if everything went just the opposite, sounds from 3000-4000 Hz may seem annoyingly loud, making it difficult to hear and understand lower frequency sounds). The chances of this happening just this way or to this extent are relatively small, but it is possible. And this points out a key difference between consumer and custom speakers -- individual component selection and measurement.
2. Feelin' finicky: Purchase several of the same component, measure and mark them, then use the one closest to your desired value. This requires a good DMM and LCR meter, maybe even a signal generator if you want to be thorough. Of course, this could make your crossovers cost several times more than anticipated, but if the left-overs eventually get used, this could be the best 'middle-ground' between precision, performance and price.
3. Obsessive: Do #2, but couple it with a high precision, high quality component to arrive at the desired value. As long as we are measuring things, the most time consuming, expensive, but accurate and beneficial method (short of having components custom made) is to purchase several same-value capacitors, measure and label them, and pick the one closest but a little less than your desired value. Retain on hand a variety of small value but high quality capacitors; perhaps .1, .22, .47, .68, .82 and 1µF. Polystyrene and tin, for example. Even if these are off by 10%, the effect is so small as to be negligible. Place one of these in parallel with your larger capacitor to bring your actual total capacitance up to the desired value. This would give you the desired high capacitance (and relative economy) found only in the metallized polypropylene line, plus some of the incredible audio characteristics of polystyrene film and tin foil. This is usually suitable for capacitors only. It is probably overkill for resistors and difficult to manage with inductors due to magnetic coupling.
4. Manic: #2 + #3 + 'Break in' the capacitors first for 48 hours, then measure their capacitance while they are being excited at the desired crossover frequency.
5. Money is no object: Combine hand picked and measured top quality film and foil capacitors to arrive at the desired value. For low capacitance values, this won't break the bank, but for high values or multiple enclosures, you may need a second mortgage.

Whatever you decide, we measure all of our components here. If you order from us, we will attempt to send you a part that is as close as possible to your desired value.

Aren't Mills Resistors available in 1% tolerance?
They are actually available in 5%, 1%, .5%, .25%, .1% and even tighter tolerances (for a price). We order the 5% tolerance because (1) it is usually close enough for most DIY projects, and (2) we hand measure, mark and select all of our pieces anyway. Custom designs often call for odd values just off of the typical E24 or integer values. For example, we order 7.5 ohms, an E24 series value. Due to its 5% spread, we can us pieces from the order for anything from 7.1 though 7.9, which covers the 7.3 we need for our normal designs. If we ordered 1% resistors, we'd have to order and inventory many more line items -- maybe four or five to cover the same 7.1 - 7.9 -- and each one would cost much more.

What about premade crossovers and crossover boards?
Use them if you like. We make our own crossovers from scratch. Well, we do buy the capacitors, resistors and most inductors. We cut a 1/4 inch thick piece of plywood to fit inside our enclosure, then layout and wire the crossover directly on the ply. The ply gets installed in the enclosure on top of thick foam, held in place by at least four screws.

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Arpeggio Music and Sound, 805 NW Alder St, McMinnville, OR, USA. 97128
Telephone 503-472-0688; FAX 503-434-5803; Hours 10 AM - 5 PM Pacific Time, Monday through Friday
Visits by appointment only.