Monoblockguy
New Member
Hi everyone. I recently acquired a nice pair of Janszen model z40 electrostatic hybrid speakers. These were made in 1974.
They actually retailed for a whopping $4000 in 1974 according to several different sources. This roughly equates to $21,000 if you factor in inflation. There is another thread on here where someone remembers them being $400 a pair. But I have seen 3 different sources say $4000. So I would guess he is missing a digit. So suffice to say, these were high end boutique speakers back in the day. Janszen now sells speakers for 20-30k so it doesn't surprise me.
Here is a picture of an ad for them. Unfortunately I haven't been able to find a higher definition picture than this so making out details is hard. However it looks like they claim response to 40khz. Which is doubtful but interesting.
The first thing about this speaker which will have many people confused is just how the heck do you get the grills off them. I ended up having to call the lady who sold them to me, who was very knowledgeable and helpful. It turns out there are velcro strips on the top which hold the fabric tight to the frame. Just pull these off gently and then slide the fabric down the frames. At the bottom there are 4 machine bolts to undo. And then the frames slide off. Although they are a little tight and in the past they took some paint off the underlying structure. Not a big deal since you can't see it anyways. This whole process takes about 10-20 minutes. It is a bit tedious.
As you can see the passive radiators are gone. Or so it would seem. They actually have a very unique design and when the foam degrades the cone simply falls right off.
As you can see its a fiberboard wood circle cone in the middle about 1/8 inch thick and another cut out circle on the outside making the basket. An interesting yet effective design. You can easily control the weight of the cone by changing the size / thickness of the inner cone. Cool!
Here is a picture of the woofer. Now if you look closely you might notice that this woofer doesn't look exactly like the ones in the ad. Which made me suspect these are not original. However there are MANY things pointing to the fact that this is the original woofer.
1 - it's an OEM woofer made by redline audio without a model number.
2 - it's made in the same place these speakers are made.
3 - there was only enough foam in the speaker for one speaker surround.
4 - it fits very nicely in the hole.
5 - it's early 1970s era.
However it could certainly be the incorrect woofer. There is really no way to confirm for 100% sure. But if I had to guess I would say it is the right woofer.
Here is a picture of the crossover sitting nicely down in the speaker.
They are pretty complicated crossovers at first look. But really they are pretty simple.
It is basically a standard 12db per octave 3 way crossover. Except the outputs for the mid / high frequency go through large step up transformers in order to create push pull electrostatic fields. Probably in the range of 100 : 1 ratio step up.
And in addition it has a DC to DC boost converter to convert 12v into about 220v which then goes through a 5x voltage multipler to about 1100v. This creates the electrostatic field around the mylar diaphragm. Pretty simple stuff.
If anyone wants a schematic I could reverse engineer you one.
First I refoamed the woofers which was a pretty easy task. I hand aligned them just fine. Yes I know I could remove the dust caps and shim them but I can honestly hand align it WAY faster and just as good. You can push down on the cone in any corner as hard as you want without voice coil rub.
I used toluene glue because it sets within 1 minute and I don't have to hold the cone against the surround for a long time like I do with standard glues. In addition toluene glue can be rubbed off the cone if you happen to spill a little bit on it. I like this feature. Toluene glue is what most professional shops use for cone to surround / surround to basket.
I forgot to take pictures of this process sorry.
Then I recapped the crossover with Audyn capacitors for the smaller values and non polarized electrolytics for the high value mid / woofer section. Unfortunately I also forgot to take pictures of this.
Now for the complicated and confusing part. Fixing the passive radiator.
Many people would be inclined to just put a standard 10 inch surround on it and be done with it. However this is clearly not how it was done originally. Originally it used a large flat piece of 1/32 foam to form the surround. Take a look at what I mean.
See how there is foam over the entire backside? That isn't a standard foam kit.
That's why I ordered 1/32 inch urethane foam. Polyether foam (what is used for foam nowadays on speaker surrounds) is a urethane based foam. This should work nicely.
Make sure you scrape the original foam off and then use acetone to get any residue off. Although it doesn't need to be perfect get it as best as you can.
Here you can see the urethane foam and how I will be glueing it.
Again I used toluene glue to glue this. It dries clear and can be rubbed off any surfaces you happen to spill it onto. Although I was very neat and didn't have any spills.
The finished product trimmed and ready to go.
And here it is installed in the speaker.
The rest of the restoration was just basic reassembly and testing. I put new white non allergenic stuffing in the speaker cabinets because the original stuff was falling apart. It was basically disintegrating as you touched it.
Generally I braid and replace cables but this time I didn't because I didn't want to mess with the high voltage cables already installed. Also avoiding damage to the acoustic lenses while redoing the cables would be difficult.
And here they are being listened to. I also bought new 12v power supplies for them as the originals were missing. I think I will build some better looking 12v supplies when I have some spare time. It is important that you get 12v supplies that output 12v under no load. Otherwise you will overvolt the tweeters / mids and they make a nasty sizzling noise.
Overall they sound really nice. Amazing imaging. Very bright though. I need to take some measurements and balance them out with the tone controls on the bottom.
If anyone has a pair of these in need of attention I hope this thread will give you an idea of how to go forward and make these incredible speakers sing again.
If you read all of that than I really appreciate it!
Thanks so much everyone!
They actually retailed for a whopping $4000 in 1974 according to several different sources. This roughly equates to $21,000 if you factor in inflation. There is another thread on here where someone remembers them being $400 a pair. But I have seen 3 different sources say $4000. So I would guess he is missing a digit. So suffice to say, these were high end boutique speakers back in the day. Janszen now sells speakers for 20-30k so it doesn't surprise me.
Here is a picture of an ad for them. Unfortunately I haven't been able to find a higher definition picture than this so making out details is hard. However it looks like they claim response to 40khz. Which is doubtful but interesting.
The first thing about this speaker which will have many people confused is just how the heck do you get the grills off them. I ended up having to call the lady who sold them to me, who was very knowledgeable and helpful. It turns out there are velcro strips on the top which hold the fabric tight to the frame. Just pull these off gently and then slide the fabric down the frames. At the bottom there are 4 machine bolts to undo. And then the frames slide off. Although they are a little tight and in the past they took some paint off the underlying structure. Not a big deal since you can't see it anyways. This whole process takes about 10-20 minutes. It is a bit tedious.
As you can see the passive radiators are gone. Or so it would seem. They actually have a very unique design and when the foam degrades the cone simply falls right off.
As you can see its a fiberboard wood circle cone in the middle about 1/8 inch thick and another cut out circle on the outside making the basket. An interesting yet effective design. You can easily control the weight of the cone by changing the size / thickness of the inner cone. Cool!
Here is a picture of the woofer. Now if you look closely you might notice that this woofer doesn't look exactly like the ones in the ad. Which made me suspect these are not original. However there are MANY things pointing to the fact that this is the original woofer.
1 - it's an OEM woofer made by redline audio without a model number.
2 - it's made in the same place these speakers are made.
3 - there was only enough foam in the speaker for one speaker surround.
4 - it fits very nicely in the hole.
5 - it's early 1970s era.
However it could certainly be the incorrect woofer. There is really no way to confirm for 100% sure. But if I had to guess I would say it is the right woofer.
Here is a picture of the crossover sitting nicely down in the speaker.
They are pretty complicated crossovers at first look. But really they are pretty simple.
It is basically a standard 12db per octave 3 way crossover. Except the outputs for the mid / high frequency go through large step up transformers in order to create push pull electrostatic fields. Probably in the range of 100 : 1 ratio step up.
And in addition it has a DC to DC boost converter to convert 12v into about 220v which then goes through a 5x voltage multipler to about 1100v. This creates the electrostatic field around the mylar diaphragm. Pretty simple stuff.
If anyone wants a schematic I could reverse engineer you one.
First I refoamed the woofers which was a pretty easy task. I hand aligned them just fine. Yes I know I could remove the dust caps and shim them but I can honestly hand align it WAY faster and just as good. You can push down on the cone in any corner as hard as you want without voice coil rub.
I used toluene glue because it sets within 1 minute and I don't have to hold the cone against the surround for a long time like I do with standard glues. In addition toluene glue can be rubbed off the cone if you happen to spill a little bit on it. I like this feature. Toluene glue is what most professional shops use for cone to surround / surround to basket.
I forgot to take pictures of this process sorry.
Then I recapped the crossover with Audyn capacitors for the smaller values and non polarized electrolytics for the high value mid / woofer section. Unfortunately I also forgot to take pictures of this.
Now for the complicated and confusing part. Fixing the passive radiator.
Many people would be inclined to just put a standard 10 inch surround on it and be done with it. However this is clearly not how it was done originally. Originally it used a large flat piece of 1/32 foam to form the surround. Take a look at what I mean.
See how there is foam over the entire backside? That isn't a standard foam kit.
That's why I ordered 1/32 inch urethane foam. Polyether foam (what is used for foam nowadays on speaker surrounds) is a urethane based foam. This should work nicely.
Make sure you scrape the original foam off and then use acetone to get any residue off. Although it doesn't need to be perfect get it as best as you can.
Here you can see the urethane foam and how I will be glueing it.
Again I used toluene glue to glue this. It dries clear and can be rubbed off any surfaces you happen to spill it onto. Although I was very neat and didn't have any spills.
The finished product trimmed and ready to go.
And here it is installed in the speaker.
The rest of the restoration was just basic reassembly and testing. I put new white non allergenic stuffing in the speaker cabinets because the original stuff was falling apart. It was basically disintegrating as you touched it.
Generally I braid and replace cables but this time I didn't because I didn't want to mess with the high voltage cables already installed. Also avoiding damage to the acoustic lenses while redoing the cables would be difficult.
And here they are being listened to. I also bought new 12v power supplies for them as the originals were missing. I think I will build some better looking 12v supplies when I have some spare time. It is important that you get 12v supplies that output 12v under no load. Otherwise you will overvolt the tweeters / mids and they make a nasty sizzling noise.
Overall they sound really nice. Amazing imaging. Very bright though. I need to take some measurements and balance them out with the tone controls on the bottom.
If anyone has a pair of these in need of attention I hope this thread will give you an idea of how to go forward and make these incredible speakers sing again.
If you read all of that than I really appreciate it!
Thanks so much everyone!
