That way I could power it off of a 12V wallwart instead of building a dedicated PS. The only feature I am interested in keeping is the below 40Hz switch since this allows the speakers to be used with lower powered amplifiers (<200W).Īlso, I would like to use op-amps to simplify things if possible. The original EQ had a couple of switches: a below 40Hz bass-reduction switch (read bass-boost off), a treble reduction switch (ditto), and a couple of treble 'contour' settings on a rotary switch. I have a little experience with a soldering iron, but the only circuit I've ever built from scratch is a c-moy headphone amp. My goal is to make an EQ box for less than $100, as that is about the going rate on the 'bay. I am thinking an EQ box, even a homemade one, will make them easier to sell. I am curious how they were meant to sound and, if nothing else, they are an interesting piece of audio history.ģ) I know that the EQ curve can be approximated by a regular EQ, but I don't have one of those. I made the purchase with the intent of restoring and selling them.Ģ) On the other hand, these are supposed to be one of the best speakers that Bose ever made. I am thinking about trying to build the equalizer for them myself.īefore I start, let me get a few things out of the way.ġ) I am aware that no other company faces the amount of derision from audiophiles and audio-snobs on the net.

I picked up some Bose 901 original's yesterday, but they came without the equalizer that is so important for making them sound right.

Bose 901 series iv equalizer