The Latest Find: Outdoor Party Speaker Pair

Well, I have been on the look-out for highly efficient speakers that will play at reasonably high levels outside.  While I was mowing my lawn a few days ago, I noticed a yard sale in progress just up the street at a neighbor's house that had recently sold.  Somewhat impatiently, I finished mowing the lawn and then went inside to get my camera just in case anything of interest turned up at the sale.

Instead of taking pictures, I wound up acquiring, through an exchange of equal value, a pair of owner-designed and built bass-reflex cabinets.  Inside each cabinet, I found an Electro Voice SP12B, a Calrad CN-2 crossover, and an Atlas Sound HR-3 horn tweeter.




 Atlas HR-3 - Calrad CN-2 - Electro Voice SP12B

The Atlas HR-3 tweeter appears to date the bass-reflex project at sometime after 1958.  Here is some advertising from the magazine Audio, February 1958:



Atlas Sound HR-3 Horn Tweeter (Audio February 1958)

 

The Atlas HR-3 tweeters in these cabinets look like this:



Atlas Sound HR-3 Horn Tweeter 1



Atlas Sound HR-3 Horn Tweeter 2

Here are images of the Calrad CN-2 crossover:



Calrad CN-2 crossover label



Calrad CN-2 crossover schematic

The Calrad CN-2 pictured is a series dividing network.  As you may already know, this means that the woofer and tweeter are wired in series.  I verified this by drilling out the four rivets holding one of them together and peering inside at the innards.  The ferrite ring core inductor and leads are potted into the case so you cannot see them.  The inductor is tapped and there are two capacitors so that you can change from 2500Hz to 3500Hz by shorting or un-shorting a pair of screw terminals.  They are found configured at 2500Hz in this instance.

The SP12B woofers are the same as you will find in a previous post, Corner Speaker Pair with ElectroVoice SP12B Speakers.   Here is some advertising from Hi-Fi Stereo Review, February, 1962, courtesy of http://vintagevacuumaudio.com/:



SP12B Ad in Hi-Fi Stereo Review February 1962 - p1



SP12B Ad in Hi-Fi Stereo Review February 1962 - p2

Here are images of the interior of each cabinet:



Bass-Reflex Cabinet Interior 1



Bass-Reflex Cabinet Interior 2

And here they are set up outside for listening tests:



Bass-Reflex Pair Outside For Testing

These have a very lively sound and will definitely make great Party Speakers.  I moved these with the wheelbarrow pictured.  I am thinking of adding the Jensen tweeters found in the Magnavox speakers featured in the post,  More on Plywood Horns and Poor Man's Horn Driver, to the Corner Speaker Pair with ElectroVoice SP12B Speakers.