Crossover Network Diagram for OD-11, OA-12, and OA-14

[nevadamistermom]

Since the OD-11, OA-12, and OA-14 all use the same crossover network, I thought I would make a little schematic drawing that shows the original component values in the circuit, along with the arrangement of 8- or 16-ohm high frequency elements for each loudspeaker model. You can see the schematic using the link below.

http://www.carlssonplanet.com/forum/alb ... pic_id=861

Does anyone know whether the new KT23-OA will be available in only an 8-ohm version, or also a 16-ohm version as needed in the OA-12?

If available in only the 8-ohm version, does anyone know if there will be a modification published for the crossover network allowing it to accommodate these properly instead of the original 16-ohm design?

I downloaded a modified crossover network diagram several years ago from this forum, showing how to use two Peerless CT62 tweeters in place of the original 16-ohm tweeters on the OA-12. I am attaching a link to it here:

http://www.carlssonplanet.com/forum/alb ... pic_id=862

However, I do not know who designed the modification, how faithfully it preserves the original characteristics of Stig's design, etc. Can anyone provide additional information about this modification or know where it might have come from (designer, etc.)?

If I knew what the equivalent circuit for the new KT23-OA looked like from an RLC standpoint (resistance, inductance, and capacitance) I could design a crossover modification myself. However, I don't know how to model either the CT62 or the KT23-OA in terms of a simple RLC combination.

Looking forward to any assistance that anyone can provide.

[Martin Dellstig]

Hi

As soon as there are tweeters from serial-production available a filter-modification will be developed describing how to adopt the filter to the new tweeters.

Tweeters will be in 8-Ohms version only but a filter-modification for using them instead of 16-Ohms tweeters will also be developed.

Best regards

Martin

[nevadamistermom]

Thanks Martin. I know that an article on the new KT23-oa appeared in newsletter 62, but since I can't read Swedish, I wasn't able to determine when the new tweeter is expected to be released and where I will be able to purchase it...from SSC? Larsen Hi-Fi? Hifikit.se?

Please advise. I live in the USA.

--Steve Sabin

[Martin Dellstig]

Hi

The coming tweeter is a cone-tweeter developed specially by SSC.
No exact date is sofar set for the introduction of the tweeter.
As soon as it is ready you'll find info here on where to buy it!

Best regards

Martin

[phon]

I downloaded a modified crossover network diagram several years ago from this forum, showing how to use two Peerless CT62 tweeters in place of the original 16-ohm tweeters on the OA-12. I am attaching a link to it here:

http://www.carlssonplanet.com/forum/alb ... pic_id=862

However, I do not know who designed the modification, how faithfully it preserves the original characteristics of Stig's design, etc. Can anyone provide additional information about this modification or know where it might have come from (designer, etc.)?

If I knew what the equivalent circuit for the new KT23-OA looked like from an RLC standpoint (resistance, inductance, and capacitance) I could design a crossover modification myself. However, I don't know how to model either the CT62 or the KT23-OA in terms of a simple RLC combination.

Looking forward to any assistance that anyone can provide.

Hi Nevada, (wish I was there ... )

I did the filterdesign for that particular OA12 filter.

When upgrading to CT62 (no longer available) a new filter is recommended, with slightly different component values. Mainly it attenuates a slight peak from the tweeters at crossover freq.

In this special case someone here did not have access to the needed 16 ohm version of the CT62, and he liked to use two 8 ohms instead for his OA12.

The filter in case is designed to handle both the different output from these 8 ohm tweeters, and the crossover peak adjustment needed for the CT62. It is reported to be working as it should.

I have no idea if it will work with the new KT23's, but some kind of filter arrangement would be needed as there will only be the 8 ohm version as I understand.

Please feel free to PM any Q's, I think I have some measurments somewhere for this.

[Ile]

Since the OD-11, OA-12, and OA-14 all use the same crossover network, I thought I would make a little schematic drawing that shows the original component values in the circuit, along with the arrangement of 8- or 16-ohm high frequency elements for each loudspeaker model. You can see the schematic using the link below.

http://www.carlssonplanet.com/forum/alb ... pic_id=861

Should tweeters have reversed polarity in your schematic because both stages are second order?

Are obi tweeters connected with same polarity that bass driver because new tweeter filter is third order and bass filter remains second order?
http://www.hifikit.se/files/carlsson_1.pdf
This sketch have polarity for tweeters but not for incoming signal. Usually ground is at bottom, but it would be clearer if also that is marked. Least in this case when bass filter is not shown.

[Martin Dellstig]

Hi

Regarding the filters in the original form the OD-11 tweeter is connected out of phase but OA-12 and OA-14 are both connected in phase.

Regarding the new ones, signal on top, ground at the bottom.
Your assumption is correct.

Best regards

Martin

[Ile]

Thanks for answer.

Do you know why OA-12 original tweeters are connected in phase, even crossover are second order?
Is it because there is two parallel connected tweeters or omnidirectional nature of speaker?

[Ile]

I diassembled old tweeter filters and measured bass filter components. Other bass inductor is 1.78 mH as it should, but other is only 0.6 mH. It must have internal short somewhere in wounds. 10 uF caps are within 10% tolerance, but have 8% difference between speaker. 2.2 ohm resistors are both spot on.

I ordered two new 1.8 mH air core inductors made of thicker 1.0 mm wire. Original 0.7mm wire is only good for about 20W with 8 ohm element, but 1.0mm for 60W. DC resistance is also reducing from 1.2 to 0.7 ohm, bass should come tighter and cleaner when series resistance is reduced. 0.5 ohm is not that serious drop though.

New 5% 160V polyester caps was only few euros extra so I ordered also those. Not that I will hear that difference, but I will sleep better if I know they are closer match.