Confused about this part

beenthere

Joined Apr 20, 2004
15,819
Well, 5.6 uF is an odd value. The 100 volt part is easy enough, though. What does it do?

The electrolytics in my catalogs mostly jump in value from 4.7 to 6.8 uF.
 

Audioguru

Joined Dec 20, 2007
11,248
It is not a polarized electrolytic. It is a non-polar film capacitor that come in all 5% values.

Some people call them Mylar capacitors. I call them metalized plastic film capacitors. In the Orient they are called a "green cap".
 

Thread Starter

cat3rn

Joined Jun 3, 2008
117
Well, 5.6 uF is an odd value. The 100 volt part is easy enough, though. What does it do?

The electrolytics in my catalogs mostly jump in value from 4.7 to 6.8 uF.
It is part of a crossover for an Alpine F1 series car audio speaker system for the mids and highs. Just wondering if it is a cap because it is so large. Might be a couple of years old.
 

Audioguru

Joined Dec 20, 2007
11,248
The coils have inductance that attenuates high frequencies when they are in series with a woofer or a midrange speaker. The inductance can be calculated if you know the frequency and the impedance of the woofer at that frequency.

I think the woofer has the left inductor in series and the 22uF capacitor in parallel.
And the tweeter has the 12uf capacitor in series then the coil to ground then the 5.6uF capacitor in series.
I like the light bulb current-limiter on the right side for the tweeter.
You want the resistance to be as low as is possible so the woofer gets full power.
 

Thread Starter

cat3rn

Joined Jun 3, 2008
117
The coils have inductance that attenuates high frequencies when they are in series with a woofer or a midrange speaker. The inductance can be calculated if you know the frequency and the impedance of the woofer at that frequency.

I think the woofer has the left inductor in series and the 22uF capacitor in parallel.
And the tweeter has the 12uf capacitor in series then the coil to ground then the 5.6uF capacitor in series.
I like the light bulb current-limiter on the right side for the tweeter.
You want the resistance to be as low as is possible so the woofer gets full power.
I am planning to build these crossovers myself. The speakers are Alpine SPX-137R Manual here
http://vault.alpine-usa.com/products/documents/OM_SPX-137R.PDF
I also have the 177r in the rear deck.

What part would you suggest buying from Mouser or Digikey?
 

beenthere

Joined Apr 20, 2004
15,819
From Alpine.

If those are 1 1/4" X 1/4" clips, we used to have a collection of sawed-off potentiometer shafts for blow-proof fuses. All it's gotta do is conduct.
 

thatoneguy

Joined Feb 19, 2009
6,359
I am trying to figure out what type and size of air coil to use.
Are you building another circuit like the one shown in your attachment, using the Alpine crossover for a reference?

I'm confused by "size and type of air coil to use", when the circuit looks complete.

--ETA: Thread was in cache and didn't refresh. The value needs to be calculated for the coils, in uH/mH. The DC resistance (0.5 Ohm/0.4 Ohm) is only relative to the Q of the inductor, and not the actual value.
 

Thread Starter

cat3rn

Joined Jun 3, 2008
117
From Alpine.

If those are 1 1/4" X 1/4" clips, we used to have a collection of sawed-off potentiometer shafts for blow-proof fuses. All it's gotta do is conduct.
I did not think of that I have a few laying around. Thanks

Are you building another circuit like the one shown in your attachment, using the Alpine crossover for a reference?

I'm confused by "size and type of air coil to use", when the circuit looks complete.

--ETA: Thread was in cache and didn't refresh. The value needs to be calculated for the coils, in uH/mH. The DC resistance (0.5 Ohm/0.4 Ohm) is only relative to the Q of the inductor, and not the actual value.
Yes I am trying to duplicate that circuit. How do I find the Q of the coil? I could then put that info on the forum to help with the diagnosis of the circuit.
 

SgtWookie

Joined Jul 17, 2007
22,230
The inductance of the air coils could be replicated fairly closely, if the inside diameter, inside length, and flange diameter of the plastic bobbins were known, along with the gauge of the wire wrapped around it.
 

Audioguru

Joined Dec 20, 2007
11,248
The 5.25" speakers are too small to be woofers and have low sensitivity.
The 6.5" woofer also has low sensitivity.

The crossovers in the manual have the inductances of the coils.
I doubt if you can buy the coils.

Use a power amplifier for each speaker and make an active crossover with opamps (no coils).
 

SgtWookie

Joined Jul 17, 2007
22,230
Hmm, I don't think that standard fuses are 1/4" in diameter. Trying to cram a standard 1/4" pot shaft into the fuseholder/jumper would probably damage them. Seems to me that AWG 4 solid copper wire might be a close match, but I don't know where my spouse hid my digital calipers at the moment, so I can't check. :rolleyes:

Many older pot shafts were made of brass. They would have 4.8 times the resistance of copper. Newer pot shafts seem to be made from aluminum; they're about 1.55 times the resistance of copper, but have a nagging tendency to return to their natural state (bauxite, a white powder) that does not conduct electricity well at all.

The jumpers were gold plated to eliminate the corrosion problem. Internally, they were most probably solid copper.
 

SgtWookie

Joined Jul 17, 2007
22,230
OK, so Audioguru says the inductance of the coils is in the manual; so that unknown is solved.

Next, the AWG size of the wire used in the coils needs to be determined. An inexpensive digital caliper obtained from someplace like Harbor Freight Tools would suffice for the measurement. After that, it's selecting an appropriate bobbin, obtaining the wire, and winding the turns on.
 

thatoneguy

Joined Feb 19, 2009
6,359
Using the "jumpers"/fuses currently set, These values should be close (10%) to the corner frequencies, I am guessing the inductor on the woofer side is a bit smaller to have resistance under 1Ω, or heavier wire than I'm estimating from pictures.:

Scratch these... Had 150uH and 1.5mH, using 20 ga wire (0.8mm). Manual uses 1mm wire - 18ga.
Proper dimensions soon.

Finally, the 1.5Ω/10W Resistor should be mounted above the board about 1/2" for air circulation, the bottom side of the board is discolored due to that resistor overheating.

--ETA: I wish I would have refreshed to see inductor values were known before I did all those calculations. :( Interested to see if I'm even in the same realm, or missed by several octaves.... or a m in place of a 'u'....



-- Manual shows 320uH and 3 inductors, valued from 100 to 320uH. 1mm wire.Inductors: Air Core; 1mm wire (0.2W DCR), 0.7mm (0.3-0.5W DCR)
 
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thatoneguy

Joined Feb 19, 2009
6,359
Correct instructions for inductors from manual (value and wire gauge)

Identical cores, Look like what is shown in your photo: 3/4" inside diameter, 1/2" tall, 18ga Enameled Wire:

0.10mH - 72 turns, 16.5 ft wire, Est Resistance 0.12 Ohms

0.18mH - 95 turns, 23.5 ft wire, Est Resistance 0.16 Ohms

0.25mH - 110 turns, 28 ft of wire, Est Resistance 0.20 Ohms

0.32mH - 123 turns, 32.5 ft of wire, Est Resistance 0.23 Ohms


Again, the 1.5Ω/10W Resistor should be mounted above the board about 1/2" for air circulation, the bottom side of the board is discolored due to that resistor overheating.
 
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