Technik: Using Apple Pro Speakers with a class-d amplifier
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This guide shows you how to revive the Apple Pro Speakers – but without a Griffin iFire or similar. You will need a standard audio amplifier. There are great sounding, small class-d amps, so you can also deploy the speakers on your desktop.
- Autor: rafael
- Geschätzte Zeit: 20 Minuten
- Schwierigkeitsgrad: Schwierig
The Apple Pro Speakers (made by harman kardon) are a great piece of technology. They were specially designed for the iMac G4 and the Power Mac G4 MDD (mirrored door drives) series. Those computers had a special connector which supplied both – an audio signal and power – to the speakers.
There are some guides which explain how to connect the speakers using a 3.5 mm jack, but this will never be a real solution as these speakers need to be driven by a real amp – and not the line-out of a computer or other audio device.
As Griffin iFire converters are expensive and hard to get, this guide relies on a class-d amp, which means that you can revive the speakers for about 40 US dollars.
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- Audio amplifier, Recommended: class-d / class-t, at least 15 watts per channel, 4-8 ohm
Schritt 1 — Using Apple Pro Speakers with a class-d amplifier ¶
This image shows the complete setup with which you will end up. With a little bit of work you can soon enjoy the clear sound of true harman kardon speakers.
Please note: This guide will destroy the original cable/connector which is used to connect the Apple Pro Speakers to an iMac, Power Mac or the Griffin iFire.
Please also note that – as with every electronical repair or modification guide – you alone are responsible for your own health and the health of others. Also be aware that you alone are responsible for any damaged electronic equipment.
Schritt 2 ¶
Cut each of the speaker cables. To get the maximum length you can cut the cables near the white "knob" which merges the two cables.
Schritt 3 ¶
Remove the outer insulation on each speaker cable. Remove up to two inch of isolation. You can use a scissor or a wire stripper. Be ultra careful not to damage or cut the inner wires.
Two wires are inside each speaker cable.
Schritt 4 ¶
Now also remove the insulation of the small inner wires. Again be careful not to cut the cables as they are very small.
Schritt 5 ¶
You should end up with something like this.
Schritt 6 ¶
Now you will need to find out the proper polarity of the speakers, i.e. which cable is negative (-) and which is positive (+).
Unfortunately – at the time where I did this conversion – I did not photograph the cable colors. But there is an easy trick to find out the polarity:
In this image you see two banana plugs and a AA battery. Just imagine these are two stripped wires from one of the speaker cables.
Schritt 7 ¶
Now connect one wire to the negative terminal (-) and the other to the positive terminal (+) of the AA battery.
If the speaker cone bulges out (left image), you've got the proper polarity. You now know that the wire on the positive terminal of the AA battery is your "+" wire, i.e. it will connect with the "+" output of your amp.
If the speaker cone moves in (right image), the polarity is reversed. You now know that the wire on the negative terminal of the AA battery would be your "+" wire, i.e. it will connect with the "+" output of your amp.
Schritt 8 ¶
Now solder an extension cable to each of the stripped wires. If you want you can use a red wire for positive (+) and a black wire for negative (-) so you can easily connect the speakers with the amp later.
Schritt 9 ¶
Finally insulate the wires properly. Use shrinking tube and/or electrical tape.
If you like you can also use shrinking tube on the previously insulated wires, so you end up with a single cable (per speaker) again.
Schritt 10 ¶
Now strip the extension cables of each speaker. You are now ready to connect the speakers to your amp.
If you like you can use banana plugs with the stripped cables (like seen in the image).
Schritt 11 ¶
You are almost done. Now properly connect the speaker cables/banana plugs with your amp. Connect your Mac or PC or some other audio device with the amp and enjoy your old new Apple Pro Speakers.
Please note that the Apple Pro Speakers don't sound too loud, but that's by design. Still, their sound is very clean and detailed (on a class-d amp).