[Bumpy]

I am currently using a single capacitor as high pass filter on my current Saba tweeter. The frequency of crossover is about 6-7 KHz

In my experience many 8" drivers get a bit ragged much above 1-2 KHz so I would like to crossover perhaps at around 2 KHz

This recent purchase is a 4" paper cone alnico tweeter of vintage origin - Siemens 6S Ela 3180b - which was one of the best tweeters in the day. My questions are:

1.  What is the lowest frequency it is safe to use it down to.
2.  For the region 1 to 7 Khz, is the best sound quality achieved by using the top end of the 8" driver or the bottom end of the 4" driver. Both drivers are paper cone, alnico magnets, and similar quality and sensitivity

[knotscott]

Do you know any parameters of the tweeter?  You'd need to know the Fs to calculate how low it can safely operate.  Without that info it's really a guess.  In general, 8" drivers operating that high will tend to beam and not have good off-axis response. 

[Mike B.]

You need to know a lot about the tweeter specs to make a accurate decision. Same for the 8" driver.

[Bumpy]

Unfortunately no TS parameters exist for the tweeter. - far too rare and vintage.

Here are the TS for the 8"
Seas Driver Range   SEAS EXOTIC
Nominal Impedance   8 OHMS
Nominal Power RMS   100/250W
Vas ( l)   78 L
Nominal Free Air Resonance Fs   36 HZ
Sensitivity (2.83V/1m)   94 DB
Nominal Rdc   6.0 OHMS
Qes   0.25
Qms   5.1
Qts   0.24

I am hoping someone may have an intuitive guess for the tweeter - obviously the one thing I want to avoid is killing it, but I'm guessing they are quite robust being run with less than 6wpc

[S Clark]

What are your goals?  What is your definition of success for this project?  How much time/money are you willing to commit? Think hard about the answers of these questions before moving forward.

Unless you can find an existing design, or are willing to spend to get someone to design a speaker, I'd just keep it simple
It will be hard to do more than just throw it in a box with a cap on the tweeter and a coil on the woofer unless you've got more info.  You need Frequency curves on both drivers in a test box to even have a chance at getting something workable.  And like you mentioned, most 8" woofers don't easily reach high enough without significant beaming, so something approaching a commercial kit is unlikely.

[WGH]

How is your German? The data sheet would probably be in German. Klangfilm has photos of the 6S Ela 3180b on their website. You can try contacting them but the site looks ancient.
Click on Pictures --> 2.4 Drivers
https://klangfilm.org/index.php?lng=0&music=&type=0&frame=1&item=&title=&dir=&num=

A wild guess is the original speaker from the '50's ran the 8" driver full range.
This is based on an eBay ad for a similar Siemens Klangfilm speaker that used an 8" driver with a 4" Alnico magnet tweeter
https://www.ebay.com/itm/334023967594?hash=item4dc561436a:g:FyIAAOSw2PdgrREe

[Bumpy]

How is your German? The data sheet would probably be in German. Klangfilm has photos of the 6S Ela 3180b on their website. You can try contacting them but the site looks ancient.
Click on Pictures --> 2.4 Drivers
https://klangfilm.org/index.php?lng=0&music=&type=0&frame=1&item=&title=&dir=&num=

Thanks, I have emailed them

[Bumpy]

What are your goals?  What is your definition of success for this project?  How much time/money are you willing to commit? Think hard about the answers of these questions before moving forward.

Unless you can find an existing design, or are willing to spend to get someone to design a speaker, I'd just keep it simple
It will be hard to do more than just throw it in a box with a cap on the tweeter and a coil on the woofer unless you've got more info.  You need Frequency curves on both drivers in a test box to even have a chance at getting something workable.  And like you mentioned, most 8" woofers don't easily reach high enough without significant beaming, so something approaching a commercial kit is unlikely.

This is not a generic problem. It really applies just to me and I didn't feel would benefit others by being aired. After years if riding motorbikes I have tinnitus in my right ear which for the most part is OK, but seems to be triggered by any sonic abnormalities from 1 to 10 kHz.

Having a wonderful system is somewhat tainted by the increasing levels of tinnitus whilst listening to music after sometimes less than 15 minutes. I have found by trial and error that a 1.0mH series inductor on the midrange removes much of what upsets my hearing.  I bought the best and smoothest cap I could afford, namely Jantzen 1.0 mH Wax Coil, Copper foil Inductor 47mm width, 12AWG.

Now I want to experiment with filling out the missing frequencies with the Siemens tweeter which may or may not prove to be sweeter, but it involves running it lower than the current high pass. Hence the question. My gut feel is there should be no damage running down to 1kHz with a paper cone driver but I wanted others perspective.

[S Clark]

It certainly sounds like you've got a handle on what works for your hearing.  I understand completely having lived with tinnitus for as long as I can remember.  With a 4 inch paper tweeter, it's entirely probable that it reaches down further than most modern tweeters... but probably doesn't reach nearly as high.  Not really a problem for many of us with older ears.  You might well be able to get away with a first order crossover on both drivers.  Played gently, a cap protecting at 1K might work.  It's hard to know how much that old voice coil can handle.

[Bumpy]

How is your German? The data sheet would probably be in German. Klangfilm has photos of the 6S Ela 3180b on their website. You can try contacting them but the site looks ancient.
Click on Pictures --> 2.4 Drivers
https://klangfilm.org/index.php?lng=0&music=&type=0&frame=1&item=&title=&dir=&num=

The Site is run by Andreas Schubert. He replied quickly to two messages and confirmed that running the tweeter above 1 kHz with a 6wpc amplifier is fine. That was excellent service from him.

Thanks for the link

[Bumpy]

Just for info. I am now running the tweeter using a 10uF capacitor high pass.

The crossover is now 2 KHz and there are no problems running from a 6 watt valve amp.

[FullRangeMan]

Its a 5 ohms nominal driver from the 1950s, recommended for a higher freq cut due the flat paper cone.
   https://www.worthpoint.com/worthopedia/matched-pair-siemens-klangfilm-s-ela-109106576

http://module-audio.com/blog/?p=1595

[Bumpy]

Its a 5 ohms nominal from the 1950s recommended for a higher freq cut due the flat paper cone.
   https://www.worthpoint.com/worthopedia/matched-pair-siemens-klangfilm-s-ela-109106576

http://module-audio.com/blog/?p=1595
 

That's interesting - minefields wherever you tread. So the crossover point is about 3 KHz