Bose AcoustiCrap Cube Speakers Mod?
Mar 20, 2008 at 9:27 AM Thread Starter Post #1 of 7

makasin

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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
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. 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 thinking of making a high pass filter with a 6dB or 3dB cutoff at around 400-500Hz. However, I dont really know what frequency I should use or if I should just go with the bandpass filter, and what the upper cutoff should be.

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.
 
Mar 20, 2008 at 4:46 PM Post #2 of 7
Yup- the speaker is the resistor and a cap in series will create a first order filter network. Tradition places it on the + lead (but it is a series circuit :wink: You should use a non polarized cap for this. A quick web search for crossover caps will give a lot of choices. Amp power is not a big issue as the average power will be a lot less then your amps capabilities.
 
Mar 20, 2008 at 6:07 PM Post #3 of 7
do you think its worth pursuing?
would an regular cap from radioshack work?
Do you think I would hear any noticeable difference?
I hear bose speakers have no crossover networks at all (well its in the subwoofer/amp )
 
Mar 20, 2008 at 8:46 PM Post #4 of 7
My approach would be to give it a try, without spending much money. Caps are pretty cheap and Radio Shack does have a small selection of non-polarized caps.
How do your main speakers sound when the subs and surrounds are disconnected? The tone balance issue you described make me wonder if your sub woofer is too loud compared to your main speakers.
 
Mar 21, 2008 at 4:59 AM Post #5 of 7
Not to be a wise ass but after the mod you may find that bose speakers are incapable of true highs, lows or anything in between. For a fact I know that they will dissolve when flushed down a toilet.
 
Mar 22, 2008 at 5:25 AM Post #7 of 7
Not very helpful.
How bout we work with him and what he has on hand. He can decide if they will do the job or not.
 

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