Bose Cube crossover mod?


2008-03-20 9:13 am
Hey guys, I\'m probably gonna get flamed for posting about Bose in an audiophile forum but here goes nothing.
So Ive got a speaker setup in my living room with a Harman/Kardon AVR 125 receiver, Infinity Primus 250 Floor Standing speakers as my Left and Rights, a Sony Center Channel and the cubes as my surrounds. I didn\'t pay for these, dont worry. I jacked em from my mom instead :). I convinced her to give them to me because she knows nothing about sound and decided to place them underneath he couch as to not \"be obvious\", resulting in the inability to hear them AT ALL.

Anyways, Ive got this setup in my living with all the speakers pointed in one direction (as in no reall 5.1 surround per se), and I noticed that the combo of my amp and the floorstanders (as well as my 12 inch sub) leave a slight lacking in the high department. The highs are there and clear, but not as strong as they should be to make a optimally balanced sound. So ive been using the cubes with some success as tweeters, since they cant produce anything below 280Hz. My question/idea is this: Would designing a bandpass filter (or just highpass crossover for now) improve the sound to any appreciable degreee? I basically want to use them solely as tweeters, as I feel they could sound pretty good (good as in free, I know there are better solutions, but im a poor college kid, gotta take what I got).

I\'m an electrical engineering student at UC- San Diego, third year, so I\'ve got some analog circuit design skills under my belt. I know how LPF, HPF, and BPF\'s work, but I dont quite know how it works in terms of speakers.

Do I just use a capacitor (calculated that a 50uF cap should be good for around 400Hz cutoff at 6dB) and no resistor, assuming the speakers are the resistor in this network? Or do I use a resistor as well? Ive done some research regarding those infamous overpriced cubes, and discovered that the frequency response is 280Hz-10.3KHz within 10dB (I know what youre thinking, \"eww\"). However, Ive got all the lows and mids I need. My goal is to sweaten it up a little bit with some more energetic highs. I measured the DC resistance of the 2-driver cube speaker to be 7.2Ohm.

Any thoughts? To accomplish the basic high-pass filter, do I just place the cap of my choice in line with the positive terminal? Which rating cap should I use?
The amp I have says its a 45W per channel but its designed to be very high current, apparently on the manual saying its +-25A current capability, with a 40V/usec slew rate.

Yes you can add a cap but the Bose cube doesn't go high enough to be considered a tweeter. It's a 2" driver if I remember correctly so your dispersion pattern isn't going to be great either. To match the cap to the frequency you will need to know the impedance at the frequency you wish to XO, otherwise it will be an estimation only. There are online calculators you can use to approximate.

And you're right, there are those who will flame you just for trying to get it to sound right. Bose is a four letter word here. ;)


2007-05-15 8:57 pm
i´m into building such a mod for learning at this time, but i´m raping some aiwa 6,5" + bose kombi instead. my webserver for hosting pics is currently down.
although i´m owning meausure equipment i guessed my crossing frequency and builded "something" with 47mikrofarad and 5 ohm in series. at the moment my 6.5" should play around 80-2000hz. my dipol subwoofer takes the range below 80hz. if i got some sparetime i will go guess my highpass for the cubes. i know the project makes no sense in terms of audiophile use, i believe its good for learning though.