The Quintessentially German Loudspeaker of the 70th. Modern Interpretation.

[Joachim Gerhard]

Here is a picture of the internal construction.....

 

[Joachim Gerhard]

I like the way traditional english speakers mount the baffle with screws.

 

[Joachim Gerhard]

For the baffle we can use Siebdruckplatte, i think the english translation is silk screen-flat.
It is a very strong material.

Holz Wicharz GmbH - Ihr Holzhandel in Köln seit 1885 - Siebdruckplatten

 

[OnAudio]

Interesting 😉

Here are the xover frequencies and the steepness of the crossover of the CL190.
Maybe 12dB/Oct is electrical. I think KEF was the only company at that time that new that the xover slope has to be acoustical.

 

[Joachim Gerhard]

Here is an alternative midrange that looks a bit more authentic :
MONACOR INTERNATIONAL : SPH-130
The price is not much cheeper then the better made Scan-Speak though.
I am really a bit surprised how high Monacor is pushing prices up nowadays for quite good but not exceptional drivers.

 

[Joachim Gerhard]

This could be a candidate when you want to use two midranges :
http://www.tymphany.com/files/SDS-P830656 Rev1_0_0.pdf

 

[Joachim Gerhard]

Here are some big sized tweeters :
Large domes
For example with the 30cm Peerless SLS woofer, two midranges, the Audax 34mm and the Monacor 25mm an even better copy of the DUAL can be made.
Maybe later.

 

[ivanlukic]

I think that 60 litres net won't be a problem with sealed box. With sealed box Q up to 0,9 is not problematic. (There is no need to go for such low Q of 0,5 like in Martin Colloms "The Rhythm King" project) In fact relatively cheap woofer, like the one you chose, will probably sound better in sealed box than expensive woofer in reflex loaded cabinet. Only if one intends to listen very loud, which is unlikely in city apartments, will he need reflex loading.

 

[franzm]

...Maybe 12dB/Oct is electrical. I think KEF was the only company at that time that new that the xover slope has to be acoustical.

Schwamkrug/Römer?!

 

[Joachim Gerhard]

I had that book but not any more. I definitely saw acoustic filters first in KEF speakers although academics may have known that before.
Whereas british speakers of the 70th where mostly reflex in germany only one company made reflex boxes in the 70th ( more to the end ), that was Kücke.
When this speakers came out we first thought that closed is history, and so it goes....
Here is the KS E80 "Mega"

 

[Joachim Gerhard]

There was another company that experimented with reflex and transmission line : Arcus.
That was at the end of the 70th and they gained a lot of momentum in the 80th.
By the mid 80th closed was more or less out of fashion.

 

[Joachim Gerhard]

When i understand the Rhythm King correctly it is designed to be put close to the front wall.
Then the Ot 0.5 makes sense to me.
I think the DUAL was mostly put into a cupboard so that is close to a wall too.
We listened to the restored speaker in a more contemporary setup away from the front wall, maybe 1.2m, and it still sounded a bit full.

 

[ivanlukic]

Thirty years ago I persuaded a friend of mine, who had a lot of money at that moment, to buy Gale GS401 loudspeakers (sealed box). I think that is exceptional loudspeaker even by today's standards. He still has them but unfortunately tweeters are defunct. (A rarity for any small town, not only for a small Serbian town) There was Wilmslow Audio 100/3 diy version of it, but with one 10" woofer instead of two 8" woofers. Sealed box 3 (or 4) way loudspeakers have certain charm, at least for me. I think that your idea has a potential to resurrect the variation of that concept.

 

[Joachim Gerhard]

I heard the Gale when it was new with a Levinson Master and i was very impressed.
It went really loud without problem.
Looks cool too.
Google-Ergebnis für http://funkygibbins.me.uk/wp-content/uploads/2009/05/stand.jpg

 

[Joachim Gerhard]

Google-Ergebnis für http://funkygibbins.me.uk/wp-content/uploads/2009/05/stand.jpg

 

[Joachim Gerhard]

They had some flaws though :
GS401 Speaker | galeaudio.com

 

[ivanlukic]

I hope your interpretation of Dual will not be amp killer! No need to use two woofers. I think your first idea will be just fine: 1 woofer, 1 midrange (with it's own compartment), 1 tweeter + big closed box.

 

[Joachim Gerhard]

I think i can design crossovers that do not tax the amp to much.
Yes, i will go the easy way :
One 25cm woofer in a closed box, one 13cm in a closed box and one 25mm soft dome.

 

[Joachim Gerhard]

I bought some typical cone tweeters that where in use before AR i think where the fist ones that went into dome tweeters. Maybe there was some earlier stuff even and i do not know who invented the soft dome. Maybe Dr. Müller. I was interested in what had changed in the 70th. Some think that all that came after the 50th is crap. I do definitely not think so.
I had a long discussion with Joe Roberts about that on ETF2012.
To my surprise he told me that 90% of the really old stuff is crap, just like today.
I will publish some measurements and pictures.

 

[Joachim Gerhard]

This are the cone tweeters i have :
RFT P551 tweeter 10 cm
They are made in east Germany in the 50th.
They look very similar to SABA and i do not know if they are better or worse so please do not draw any ultimate conclusions based on my measurements.