The long-awaited HUMAN 81 DK is now available.
Best viewed in "landscape" mode.
It is often the case that old speakers dating from the 70's, 60's and even the 50's, will be built in wonderfully finished, solidly constructed cabinets. However, the acoustic quality can be lacking at times (or the parts dead and gone). It seems like such a shame to throw away perfectly good boxes - so why not make them into something that sounds great and enjoy them again?
With a little ingenuity, they can be turned into some great sounding speakers, by gutting them and rebuilding them using parts by HUMAN Speakers that are designed to work together.
I will mostly consider the typical example: boxes in the 1 to 2.5 cubic foot internal volume range. These would have been considered "bookshelf" speakers, in the old days before everyone decided they wanted to hide their speakers under the couch, and manufacturers complied with a large amount of poor sounding products that supposedly could be hidden.... Hmm, I digress, though! Speakers of this size are perfect for building into eight inch two way systems similar to those described in the "DIY HUMAN 81" file.
The first step is to carefully remove the grilles (if you still have them) and all the parts and cabinet damping (usually fiberglass). Now you can survey what you have to work with. You will probably find that the front board is all wrong for whatever parts you want to install in it, and that the rear terminals are tiresome - there are a lot of yucky spring clips and really nasty thumbscrews out there. These problems can both be solved, of course.
The terminals are easy - you just remove whatever was there, and use a board I supply. My version comes with nice 5 way binding posts installed along with the crossover components and wires. They will be made large enough to completely fill the holes in the back of your boxes, with an inch or so of overlap to allow you to screw them into place nicely. The ACC 004 is about 5 by 6 inches, but I can make you any size you need out of 1/4" masonite if necessary.
The front panel will be a bit more work - sometimes it can be recut to fit the new parts, but it is unlikely.
Depending on how the boxes were constructed, there are a few ways to cope with this. Many of these old cabinets will have deeply recessed baffles - sometimes up to an inch behind the front edge of the side panels. These will come out best if you simply make a new front panel, cut the way you want, and attach it to the old panel (making sure to remove any old wood that is in the way of your new holes). This makes for a very strong front panel, which sounds good, and also moves the drivers forward, closer to flush with the front corners, which is also better.
You can also completely cut out the old front board and mount a new board that you make, using some rails and braces to attach it firmly to the existing box.
I performed a similar project once, using a pair of solid but rather decrepit boxes. Although I overdid the system a bit, duplicating the HUMAN 88-41 in two cubic foot boxes (I needed more power handling since my rear amp was 275 watts/channel), the basic concept is fairly well described and illustrated here, in case you are interested.
After setting up your front panel, you can add any bracing or extra damping material you desire, then install the crossover and board, stuff the box with fiberglass (or long fiber wild mongoose wool), hook up the wires to the drivers and screw them in. At that point the speakers are ready to test and play!
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