I've never seen that kind of setup. Some of the concerns I have with the ASW setup:
1) You would have to be able to electronically sync the transmit/receive gates so you aren't pinging into the other set of hydrophones while they are in listen.
a) This would be problematic if you are in different range scales
2) Each sonar set would require it's own set of transmit/receive cabinets, power supplies, cooling water, signal conditioners, etc etc. Two sonar domes, means two pressurization systems, double the amount of valves, strainers etc
a) you would have to have two sets of operators and maintainers for each sonar system. From a budget stand point it would make sense to have just the one more powerful sonar with a search processor and a track processor.
The range of world war 2 sonars where more limited by the ridiculously high transmit frequencies then by source level (dB). I would nix the smaller one.
The fact is that the search sonar in the 'destroyer' dome would be purely there for redundancy, I think. They would not be on at the same time, so these issues would not be there.
Keep in mind, I will most likely know less about the sonars of that time period then you and other people here, but fact is this is not the only ship with dual retractable sonar domes in this same time period, so they should make some sense, don't you think? The USN DLG's, for example.
During the development of the modified design of the Eendracht Class cruiser in 1946, there was some ongoing discussion about the priorities of the armament of the vessels. according to an report, send in to the navy staff 20 november 1946 where it was mentioned the requirements for the main armament of the cruiser would need to have the following targets, in order of priority:
2. submarines
but what if the main armament was changed to fully AA capable, ASW mortars, homing torpedo's and more sonars were to be added and the secondaries kept as powerful as originally designed? then the ship would loose some marks in 4 and 5, however she would be far more capable in point 1,2 and 3.
Sorry Ace, but:
Usually guns-cruisers were very bad ASW ships :
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Too big (with too much high silouette)
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Not enough maneuvering (a too large tactical-diameter...compared to destroyers)
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Still very vulnerable to torpedoes hits (usually 1 torpedo-hit severely damage the ship & 2-3 hits sink them)
- Lightly slower (28-33 knts) compared to destroyers (30-36 knts)
You might be right about that, but fact is that an ASW capability was proposed, even if only self defensive (the real life ship had ..... depth charges and sonar for that reason) makes it an interesting thought experiment, but I will not speak against the fact that it is flawed. larger tactical diameter and too high a silhouette, certainly! vulnerable for torpedo's too, but all that is true for any cruiser, and if any cruiser would be vulnerable, would it not make sense to give your fleet flagship something to protect itself?
In case of the dutch navy, the cruiser would also be just as fast as the destroyers of the 1947A class, while it could keep that speed in higher sea states (and it did actually have space on board for the crew of both sets of engines, being able to go that fast under peacetime conditions as well) which under those conditions make it faster then the 1947B class as well.
So no need to apologize, but I think this idea is not entirely bad, or at least not as bad as you make it sound