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August 15, 2010 / consort3

Mission Freedom & AR48LS

I have been given a pair of each. The Freedoms are well documented on wikipedia being the 770 Mk5. However the Teledyne acoustic research AR48LS are not so well documented. They are huuuuge, these days low WAF (wife acceptance factor) Also the foam surrounds have gone. Has a 10 inch woofer and the crossover in the diagram which I traced, measured and simulated. The crossover frequencies are 340Hz and 3.8k.  I am guessing they were made at the factory at Houghton regis as they have a UK serial no. I will use the cabinet for a 3 way as it has a nice compartment for a mid.

Update I had some drive units left over from othe projects and tried them in the cabinet, using the existing crossover. The result was impressive enough to make me want to measure the response and tweak the crossover to get the response flat. Put new drivers in the AR48LS namely DT75, 55-1855 and Mutant Conquest 10. The DT75 and 55-1855 were put on a new sub-plate. I used the existing crossover with series resistors on the DT75 and 55-1855 to match the sensitivity of the Mutant. Surprisingly good, I think the natural roll-off of the drivers was compatible with the original crossover. Meantime I found this circuit for a different version the AR48s (seems completely different) :

http://sites.google.com/site/baselaudiolabs/AR48sXO.jpg

Meantime a picture of the freedoms. They must be one of the first speakers with time aligned baffle also  mini horn on tweeter as they date from 1985. Will measure and listen to these as they appear to be in good condition.


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