Scandyna A30 Rebirth

Dedicated to those large boxes at one end of the room
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Tarkers
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Joined: Tue Apr 11, 2017 4:09 pm

#1 Scandyna A30 Rebirth

Post by Tarkers »

An old pair of Scandyna A30s with new tweeters and crossover (ok, just a resistor and capacitor on the tweeter in fact) have been my mainstay speakers for a while. However, the tweeter position is not ideal, being nearly half way down the baffle. I have also recently experimented with a pair of doped drivers and the Scandyna's tweeters in a 23 litre enclosure which I steel lined and where I also replaced the crossover with a simple resistor and cap on the tweeter. The results of the latter speaker were most satisfactory, but I still wanted some of what those 10 inch SEAS drivers offered in the Scandynas.

Therefore, taking all this on board together with Peter Comeau's WD25T design using the updated Seas driver has led to a 33 litre floorstander design where the top 60% or so houses the drivers and then vents aperiodically into a lower section. The principle is the same as employed by the Dynaco A35 which had a split cabinet and who's bass was regarded as being superior to the external aperiodic vented Dynaco A25. The top section is being steel and lead lined: steel where it can go easily, and lead for awkwardly shaped areas. I'm thinking of using polyester resin to about a 5mm thickness for lining the lower section (or 4 walls of it anyway).

The tweeter and bass driver efficiencies are identical at 91db, so a cap somewhere between 8.2 and 12uF should suffice. The Seas 10 inch driver has a very smooth roll-off from just above 2khz. The cabinets are largely there now. An interesting aspect is comparing the sound of a knuckle rap on a steel clad section with an unclad one. The steel clad panel has a much quicker decay with less ringing than the bare panel. The steel appears to offer a combination of damping/energy absorption and added mass. The resin on the lower section will make an interesting comparison. I do not expect to be using any internal stuffing except for 12 grams of fibreglass in the aperiodic port.

Pictures to follow, but I'm now away for a few days, so will not be completing the speakers until next week.
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