Audio connectors
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Tru Components Cinch connector with screw connection
My experiment with 45-year-old active speakers
Do active speakers from the early 80s still work? If so, how do they sound? I took a trip down memory lane.
The Philips speakers remind me of my childhood. They were in my childhood living room in the 80s and 90s, connected to a Pioneer SX-550. Having already snapped up the receiver, I find myself dragging the speakers into my apartment. I want to see if they still work and if so, what they sound like.
These are active speakers. The Philips AH 586 MFBs were developed back in the 1970s and sold from 1978. As was common at the time, they were manufactured in Europe, in this case in Belgium. MFB stands for «Motional Feedback», a technology developed by Philips, way ahead of its time. An accelerometer in the speaker measures the movements of the woofer and compares them with the input signal. This allows the speakers to correct distortions and reproduce very low frequencies. According to the specs, down to 30 hertz.
Longevity test passed
Both speakers have a power cable and only run when plugged in. The only ports they have are RCA sockets. One RCA cable leads from the source to one speaker, a second from there to the other speaker.
When I first switch the system on, only one of the speakers turns on – strangely enough, the one that’s only indirectly connected to the source via the other speaker. After switching it off and on again, it works.
A couple of minutes later, the speaker which initially refused to work starts to crackle and buzz. And doesn’t sound good otherwise either. Again, this problem disappears after an on/off manoeuvre. It reappears later, but after using it regularly it gradually resolves itself.
The speakers are roughly 45 years old and have a lot of electronics in them. Each speaker has two amplifiers – one for the tweeter and one for the bass/midrange driver. Many of the capacitors are probably at the end of their lifespan. Pretty amazing then that these things even run.
How good do they sound now?
I remember these speakers sounding good. But what does that mean? I was a kid, I had hardly anything to compare it to, and I also had a CD player at the time, so everything sounded better anyway.
My first impression is that it sounds nice, unobtrusive and unspectacular. Treble emphasised, with weak bass. But after a while I realise I’m not using the speakers properly.
On the back of the speaker, there’s a rotary knob for the input signal strength. This changes the impedance. So I could adjust the volume here, but I’d be better off doing that at the source. At the quietest level, the impedance is too high for the weak signal from my smartphone. That’s why the basses are weak.
One speaker crackles loudly when I turn the knob. I suspect the potentiometer’s broken. However, the adjustment works and the bass now sounds more powerful.
Hidden behind the fabric cover are three toggle switches that correct the bass frequencies depending on whether the speaker’s positioned on the floor, in front of a wall or to the side of a wall. You can just about hear the correction, as these speakers aren’t prone to strong bass reflections anyway.
Connected to the receiver
The lowest four levels of the rotary knob are intended for connecting to an amplifier. My father had connected the speakers to a Pioneer receiver at the time. But how? The outputs for the speakers use normal speaker cables, i.e. open wires. I can only connect the line-out of the amplifier with the RCA cable. Firstly, the signal is no stronger than with my smartphone, and secondly, the controls for lows, bass, balance and volume don’t work. There must be another way.
I can’t find a cable in our range that has RCA plugs at one end and open wires at the other. My attempt at making something myself fails because the wires of the cut cable are so thin. Finally, it works with special RCA plugs which I can screw normal speaker cables onto.
What can I say? It sounds great. Still quite high-pitched, but with enough power in the bass. At least for my taste. They’re actually capable of reproducing 30 hertz, but only quietly. Perhaps they’d sound even better if they were new. All in all, I’m impressed by what was already possible back then.
David Lee
Senior Editor
David.Lee@digitecgalaxus.chMy interest in IT and writing landed me in tech journalism early on (2000). I want to know how we can use technology without being used. Outside of the office, I’m a keen musician who makes up for lacking talent with excessive enthusiasm.
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