Hi,
some weeks ago an old friend gave me a speaker set as shown here, top picture: http://grundig.pytalhost.com/1969-70/46.jpg
The subwoofer contains two identical speakers, one per channel, both cubes consist of six midrange/tweeter drivers. Also included in the sub are two 6dB/octave crossover networks with DIN terminals for the cubes.
These sets were made by German manufacturer Grundig from 1969 to 1973, mine actually was made in 1971.
Despite the promising claims in the contemporary ads, and in contrary to my own experience with Grundig speakers of that aera in general, the sound isn't amazing at all. The cubes are too present, not to say obtrusive. So I decided to open the subwoofer and have a close look at the crossovers. There were two EI cored inductors and, believe it or not, two polarized (!) 100µF/35Vdc electrolytics!!
Does one have any clue why Grundig decided to do this no-go? Why did it work anyhow? Could the reason for the unpleasant sound result from these probably worn-out electrolytics? I've heard these speakers at my friend's parents' home when they were new, but can't remember any harsh sound at all.
I think I'm going to replace the capacitors anyway, but have to chose: Do I opt for new non-polar electrolytics, or for foil capacitors that were desigend as motor running caps, cost ten times as much as the 'lytics and are very bulky, leading to an urge to place the crossovers outside the subwoofer enclosure?
Best regards!
some weeks ago an old friend gave me a speaker set as shown here, top picture: http://grundig.pytalhost.com/1969-70/46.jpg
The subwoofer contains two identical speakers, one per channel, both cubes consist of six midrange/tweeter drivers. Also included in the sub are two 6dB/octave crossover networks with DIN terminals for the cubes.
These sets were made by German manufacturer Grundig from 1969 to 1973, mine actually was made in 1971.
Despite the promising claims in the contemporary ads, and in contrary to my own experience with Grundig speakers of that aera in general, the sound isn't amazing at all. The cubes are too present, not to say obtrusive. So I decided to open the subwoofer and have a close look at the crossovers. There were two EI cored inductors and, believe it or not, two polarized (!) 100µF/35Vdc electrolytics!!
Does one have any clue why Grundig decided to do this no-go? Why did it work anyhow? Could the reason for the unpleasant sound result from these probably worn-out electrolytics? I've heard these speakers at my friend's parents' home when they were new, but can't remember any harsh sound at all.
I think I'm going to replace the capacitors anyway, but have to chose: Do I opt for new non-polar electrolytics, or for foil capacitors that were desigend as motor running caps, cost ten times as much as the 'lytics and are very bulky, leading to an urge to place the crossovers outside the subwoofer enclosure?
Best regards!
Hi, i have two caps of nearly same size from a Heco Soundmaster 35 before me, one "Roe 100uF/35V- Elko glatt" and one "NIGG(?) Elyt 16uF 70/80V bipolar". The former one was used in the lowpass. So what? Regarding the 100u/35- one, compare this old 10cm^3 part to a modern 1cm^3 one. Size matters. Your friends may have had a lot of stuffing in their cave, and you were captured by fresh hifi experience, so you did not hear an edge, but your criticals now hear the sats ringing at their 333Hz fundamental and their "Hochtonschleuder" behaviour, as Fosti put it.
Hi kay!
Chances are that:
- The caps are back to back, making a non-polar equivalent of 1/4 the total capacitance. So:
--| |-- + +--| |---
or the opposite:
+--| |----| |--+
If these were 100 uF caps, you could replace them with a single non-polar 50uF.
However, the ESR was very high. You must measure this before replacing, especially in shunt (parallel to the driver) or you can really affect the impedance and sound in a negative way.
Best,
E
Chances are that:
- The caps are back to back, making a non-polar equivalent of 1/4 the total capacitance. So:
--| |-- + +--| |---
or the opposite:
+--| |----| |--+
If these were 100 uF caps, you could replace them with a single non-polar 50uF.
However, the ESR was very high. You must measure this before replacing, especially in shunt (parallel to the driver) or you can really affect the impedance and sound in a negative way.
Best,
E
+1
Grundig were basically radio people and they probably use mostly if not all polar caps in their radios due to the many DC signals. So, to make a loudspeaker crossover work and pass an AC signal with their inventory of polar caps, they did what Erik described. That's my theory.
Now I need to see a pic of the crossover. A polarized cap will not pass an AC signal and thus, you'll have no treble.
Hey, i rather not be the speaker under your hands, doctor! A polarized cap just needs a DC voltage bracketing AC in order to work as specified. If DC is missing, it blows up or may indeed have hi AC resistance, but this model is sized nearly like a bipolar cap and prolly works (prolly, because i never tried it but just removed it and put it into my passive-X-over caps bin).
When I first started in this, the first speakers I built around 1970 used drivers from a German company named Isophon. They were also OEM suppliers for Grundig and liked to use electrolytics in their crossovers. I would not be surprised if these were sourced from them. I would probably replace the caps with 3 16uf caps or 2 24uf caps in parallel.
Just a slight correction to an above post, two capacitors of the same capacitance value placed in series will provide an overall capacitance value equal to 1/2 of one of those placed in series. 50 uf as stated is indeed correct as is the principle, but the working voltage of the combination is still only 35 volts. Electrolytic capacitors whether polarized or non-polarized must have a low ESR when used at high signal levels otherwise excessive heating will occur within the component, particularly if the capacitor is small in size as modern ones are. A 50 uF non-polar with 100v (working volts) would be a better and cheap replacement for each channel's high pass cap.
C.M
C.M
I'm writing it the third time: There ain't no two back-to-back electrolytics in the high pass section of each channel's x-over, there is just a single polarized 100µF one. That's what is really puzzling me.
Do the math: 100µF fits well to the stated x-over frequency of 400 Hz @ 4 ohms.
Best regards!
Do the math: 100µF fits well to the stated x-over frequency of 400 Hz @ 4 ohms.
Best regards!
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I think I know what is meant. In the 1980ies the long-gone German DIY electronics magazine ELRAD published an OpAmp based audio preamplifier, whose output caps consisted of two back-to-back 1000µF polarized electrolytics. Their negative sides were tied together and returned to the negative supply rail via a resistor of several hundreds of kOhms. The output was returned to gnd by a second resistor. Thus, both electrolytics were biased at 15Vdc. Both 'lytics were bypassed by several foil caps, which used to be en vogue in those days.
Best regards!
Best regards!
Caps in series doubles the voltage.
He could connect two 200uf caps negative sides together and use it. The caps could be 50v a piece and he'd be good for 100w.
Well, unipolar electrolytics don't instantly blow up as soon as the slightest bit of voltage in the wrong polarity is applied. They can take a few volts of AC swing. My wife always uses unipolar electrolytics (I believe in the 220uF range) as output coupling caps in the oscillator circuits she designs, many of them being square wafe generators and she never had one fail in that context. It isn't perfect, but it works.
I also remember forming a bunch of elcos and hooking one up to the dc supply the wrong way around. It got quite hot but took the thirty volts. I reformed it gently and it measures ok. (and is living in the parts bin for now
)
I also remember forming a bunch of elcos and hooking one up to the dc supply the wrong way around. It got quite hot but took the thirty volts. I reformed it gently and it measures ok. (and is living in the parts bin for now
)
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