A friend at work has given me some Braun 1005 loudspeaker for repair after they have been in his loft for a some time.
Obviously he has a good loft or he protected them well as they are in very good condition for their age. He remembers buying them in the early 80s. Ideally he want to have them working again for his office space.
The woofers need a refoam and the one of the woofer domes and the midrange cone also has a dented dust cap. I have opened up one of them to get some info on the crossover. The inductor mounting screw and the pcb retaining screw are both made of brass which is a nice touch
The bass has a ferrite cased inductor which I measure as 3.9mH plus a parallel 47uF marked ElKo electrolytic. which i measured at 50.3 uF.
The small midrange cone is fully enclosed as a single unit , much like the sealed tweeters of old. It has three components in series with it 0.2mh, 6.8uF, a 7.2ohm resistor and then a 4mH inductor in parallel. I haven't measured it series resistance yet but I think it will be high as it is a very small inductor for a value of 4mH.
The tweeter is fed from a 3.3uF with 0.4mh inductor in parallel.
Right now I am awaiting replacement woofer foams from a company in Germany.
Today I measured the impedance of the drivers and then added that info with the Xover components into FineX. just to get a view on how the crossover was working. I now have some basic info to begin with, once the Bass cones have been re-foamed I will get some measurements done and see if anything else needs adjustment.
The tweeter is a bit of a concern as the one i tested was possibly a bit too quiet and its impedance plot doesn't show much of a bump. I wonder does anybody know if they were one of the early speakers to use ferrofluid in the tweeters.
It would be nice to get some supporting information from others here, after measuring the capacitors I am inclined to leave them as they are not out of tolerance and they seem to be well made the smaller ones appear to have a copper jacket. Any info regarding the drivers, are they all Braun's own designs?
I have tried internet searches but apart from some images I haven't found a lot yet. There does seem to be a similar model that used a 50mm mid dome. I do not know if the 1005 was just before that design?
I will post some images when i move them across from my phone.
The FineX info relates to the driver impedance and Xover values I measured the frequency response are not representative of the actual loudspeaker and the attenuation resistor's on the tweeter are not part of the design, i inserted them to see how flat the response could be.
Obviously he has a good loft or he protected them well as they are in very good condition for their age. He remembers buying them in the early 80s. Ideally he want to have them working again for his office space.
The woofers need a refoam and the one of the woofer domes and the midrange cone also has a dented dust cap. I have opened up one of them to get some info on the crossover. The inductor mounting screw and the pcb retaining screw are both made of brass which is a nice touch
The bass has a ferrite cased inductor which I measure as 3.9mH plus a parallel 47uF marked ElKo electrolytic. which i measured at 50.3 uF.
The small midrange cone is fully enclosed as a single unit , much like the sealed tweeters of old. It has three components in series with it 0.2mh, 6.8uF, a 7.2ohm resistor and then a 4mH inductor in parallel. I haven't measured it series resistance yet but I think it will be high as it is a very small inductor for a value of 4mH.
The tweeter is fed from a 3.3uF with 0.4mh inductor in parallel.
Right now I am awaiting replacement woofer foams from a company in Germany.
Today I measured the impedance of the drivers and then added that info with the Xover components into FineX. just to get a view on how the crossover was working. I now have some basic info to begin with, once the Bass cones have been re-foamed I will get some measurements done and see if anything else needs adjustment.
The tweeter is a bit of a concern as the one i tested was possibly a bit too quiet and its impedance plot doesn't show much of a bump. I wonder does anybody know if they were one of the early speakers to use ferrofluid in the tweeters.
It would be nice to get some supporting information from others here, after measuring the capacitors I am inclined to leave them as they are not out of tolerance and they seem to be well made the smaller ones appear to have a copper jacket. Any info regarding the drivers, are they all Braun's own designs?
I have tried internet searches but apart from some images I haven't found a lot yet. There does seem to be a similar model that used a 50mm mid dome. I do not know if the 1005 was just before that design?
I will post some images when i move them across from my phone.
The FineX info relates to the driver impedance and Xover values I measured the frequency response are not representative of the actual loudspeaker and the attenuation resistor's on the tweeter are not part of the design, i inserted them to see how flat the response could be.
Attachments
The Braun SM 1005 were the ones with the 50mm dome midrange, your speakers are the Braun
IC 1005. The slash + number was used for the iteration, the speakers were modified slightly over time.
I don't remember Braun using FF in the tweeters, but I might be wrong there. It could be some dirt or dust in the air gap too. Since the capacitors are electrolytes, I'd rather change them before disassembling the tweeters, after 40 years it's suggested anyway (all of them) for the tweeters use a foil capacitor, on the mid too if it's not too expensive, for the bass just use a good electrolyte (it's just parallel anyway).
When disassembling the tweeters (yes, do both! You don't want them to sound different) there aren't any secrets but on reassembling you have to be careful since they are likely not self centered.
If they don't have FF, you can center them with a thin 0,2mm plastic foil, which you can pull out before tightening the screws. With FF that doesn't work, you get the FF everywhere.
If they have FF, remove it and either replace it (to get the correct viscosity is a gamble though) but you might have to center the VC manually. You can do that by ear, give them a sine at 1,5k--2k of ~0,3V and move the front plate a tiny bit and settle on a position that doesn't distort. Tighten the screws and give the tweeters a glide sine 1-10k of 1V and listen to them for distortion. If they do, loosen the screws and repeat.
Do you know how to un-dent the dustcaps?
IC 1005. The slash + number was used for the iteration, the speakers were modified slightly over time.
I don't remember Braun using FF in the tweeters, but I might be wrong there. It could be some dirt or dust in the air gap too. Since the capacitors are electrolytes, I'd rather change them before disassembling the tweeters, after 40 years it's suggested anyway (all of them) for the tweeters use a foil capacitor, on the mid too if it's not too expensive, for the bass just use a good electrolyte (it's just parallel anyway).
When disassembling the tweeters (yes, do both! You don't want them to sound different) there aren't any secrets but on reassembling you have to be careful since they are likely not self centered.
If they don't have FF, you can center them with a thin 0,2mm plastic foil, which you can pull out before tightening the screws. With FF that doesn't work, you get the FF everywhere.
If they have FF, remove it and either replace it (to get the correct viscosity is a gamble though) but you might have to center the VC manually. You can do that by ear, give them a sine at 1,5k--2k of ~0,3V and move the front plate a tiny bit and settle on a position that doesn't distort. Tighten the screws and give the tweeters a glide sine 1-10k of 1V and listen to them for distortion. If they do, loosen the screws and repeat.
Do you know how to un-dent the dustcaps?
Thank you for the useful response to my questions, and the correction of the speaker type.
I wasn't in a hurry to change the capacitors in case they are a particularly good type of German made capacitors known to have a long working life. When the speakers are refoamed I will look at the overall response and how they sound. If I have doubts over the measurement's achieved I will change them.
Tweeter re cantering looks like it maybe worth a try, so I may give that a go when I have found some suitable shim material, i may ask for more advice on how you remove the shims as you reassemble the tweeter.
I have used sticky tape, a hoover and the pin method to repair do dented domes. Possibly, I missed a trick by not ordering re placement dust caps for the woofers anyway. As they always look nicer than a repaired dome as the original crease lines tend to show on the repaired item..
If you have a really excellent failsafe way of repairing the domes, I and others I am sure would like to hear your tips.
Many thanks.
I wasn't in a hurry to change the capacitors in case they are a particularly good type of German made capacitors known to have a long working life. When the speakers are refoamed I will look at the overall response and how they sound. If I have doubts over the measurement's achieved I will change them.
Tweeter re cantering looks like it maybe worth a try, so I may give that a go when I have found some suitable shim material, i may ask for more advice on how you remove the shims as you reassemble the tweeter.
I have used sticky tape, a hoover and the pin method to repair do dented domes. Possibly, I missed a trick by not ordering re placement dust caps for the woofers anyway. As they always look nicer than a repaired dome as the original crease lines tend to show on the repaired item..
If you have a really excellent failsafe way of repairing the domes, I and others I am sure would like to hear your tips.
Many thanks.
Thank you. 🙂 You're already an expert, not much else that I can contribute knowledge wise. 🙂 I am reluctant to replace a dustcap on a cone midrange driver because it will change the sound. A dented dustcap on such a driver usually still sounds better than a replacement unless it has the exact same diameter and is glued into the same spot. The reason is it changes the tension and behaviour of the cone and its flexing will change. Measurement wise, it does not change much but it still sounds different, a subtle change some people are sensitive to and will notice while others will not. And believe me, a dented in mid dustcap really irks me too.
Soft dome mids can be un-dented by heating them up in an oven to ~60-70° C since that usually softens the coating and they spring back to their former shape or you can nudge them a bit to do so but it's important to not exceed that temperature to avoid charcoaling the fabric. Also, don't burn your fingers on them! Use medical gloves and just touch the dome or tweeter for a second. Don't try to do all the dents at once, be happy if you managed to get one or max dents go away, let it cool down, wait and repeat.
On a woofer in a 3-way the replacement dustcap doesn't change much, so a replacement is likely not noticeable sound wise. On a 2-way it can make a difference but it's still not a great change unless it's xo'd quite high.
You've already mentioned most successful methods of un-denting the dustcaps, not much to add there but how to stabilize the dustcap since it's weakened at the folding lines. To get it in better shape (literally 😀), you can use wood glue, diluted ~1:10 or wallpaper glue thinned down too.
Soft dome mids can be un-dented by heating them up in an oven to ~60-70° C since that usually softens the coating and they spring back to their former shape or you can nudge them a bit to do so but it's important to not exceed that temperature to avoid charcoaling the fabric. Also, don't burn your fingers on them! Use medical gloves and just touch the dome or tweeter for a second. Don't try to do all the dents at once, be happy if you managed to get one or max dents go away, let it cool down, wait and repeat.
On a woofer in a 3-way the replacement dustcap doesn't change much, so a replacement is likely not noticeable sound wise. On a 2-way it can make a difference but it's still not a great change unless it's xo'd quite high.
You've already mentioned most successful methods of un-denting the dustcaps, not much to add there but how to stabilize the dustcap since it's weakened at the folding lines. To get it in better shape (literally 😀), you can use wood glue, diluted ~1:10 or wallpaper glue thinned down too.
The information you have provided will help me going forward with this repair, many thanks for your help. 🙂
At the same time I am sure it will help others with their repair technique, there are many speakers out there that just need some time spent on rejuvenating them to get bring them back to being serviceable.
It will be interesting to hear these IC1005's as I have never heard a Braun loudspeaker before, and actually do not remember them being marketed strongly here in the UK. Possibly they were simply too expensive for me to ever consider at that time.
I still may need to discuss the tweeters as I progress through this.
I am expecting the foams tomorrow , maybe the woofers will be alive again later this weekend.
At the same time I am sure it will help others with their repair technique, there are many speakers out there that just need some time spent on rejuvenating them to get bring them back to being serviceable.
It will be interesting to hear these IC1005's as I have never heard a Braun loudspeaker before, and actually do not remember them being marketed strongly here in the UK. Possibly they were simply too expensive for me to ever consider at that time.
I still may need to discuss the tweeters as I progress through this.
I am expecting the foams tomorrow , maybe the woofers will be alive again later this weekend.