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Here is my latest project. I hope some of you will find it interesting.
Two summers ago, I won a pair of RS100-4 midwoofers at the Atlanta DIY get together. They were in bad need of a home so I came up with this little speaker. I was intending to use them for side surrounds, but in the end they ended up as my son's computer surrounds.
These sound way better than their small size would indicate. However, they are not the most efficient speakers you will ever hear, so feed them well. 50 watts/ch should be plenty and less will do if you don't need to play them real loud. They also reach down to 70 hz easily, so they can be used alone or crossed to your favorite sub.
I discussed these briefly in Ryan's thread about his little speaker project, but I thought a few more details might be helpful for those who are looking for a speaker like this for a small room or maybe a computer.
These are a basic two way with a crossover around 3500hz. I say around 3500hz because the crossover is a bit atypical. The woofer rolls off above 2000hz and the tweeter kicks in electrically at 4300hz. I was trying to keep the parts count as low as possible, but still not compromise on the accuarcy. You can see this in these in room measurements:
The chart is a bit busy. First there are measurements of the woofer (with and without the notch filter) and tweeter separately. Then the composite with the tweeter in and out of phase electrically. The lowest point on the darker blue response curve with the tweeter in electrical phase with the woofer is at about 3500hz which corresponds to the null. (3500hz also roughly corresponds to A7 on the piano, and thus the name.) The null is not extremely sharp, which indicates that they are not 100% phase matched, but since the tweeter out of phase response is so flat, I didn't try to get a better reverse null. It still took eight components in the crossover to get this close and I didn't want to make it any more complicated since this was designed to be as simple as I could get it.
Here is a drawing of the crossover and the box plans. The 10" X 8.25" X 5.5" box is 1/2" MDF with a 3/4" front baffle. I didn't think I needed thicker MDF on such a small box and indeed it's pretty dead in the knuckle wrap test. But the cross brace is an absolute necessity. Sorry, but I don't know any of the cad programs to draw it nice and pretty, so I'm afraid this is all you will get
:
The crossover shows two variations. (I have other variations that I'll discuss later.) I ended up with the 4.3uF and 3.0 ohm tweeter highpass version. In the response chart above, I ran the two variations a few db higher to show them separately and so you could see the difference. The 4.3/3.0 version corresponds to the lower, light blue trace. The 5.1/2.2 version (purple) didn't sound bad at all, in fact some of you might prefer it, but when I used the speaker as a center channel, the over equalized high end on our local TV stations just made it too bright. But for regular music use, both versions sounded very detailed and quite musical without ever sounding harsh.
I'll go into more details later, but if this looks like something you might like, I think the RS100-4 is on sale for one more day at PE.
-Bob
Two summers ago, I won a pair of RS100-4 midwoofers at the Atlanta DIY get together. They were in bad need of a home so I came up with this little speaker. I was intending to use them for side surrounds, but in the end they ended up as my son's computer surrounds.
These sound way better than their small size would indicate. However, they are not the most efficient speakers you will ever hear, so feed them well. 50 watts/ch should be plenty and less will do if you don't need to play them real loud. They also reach down to 70 hz easily, so they can be used alone or crossed to your favorite sub.
I discussed these briefly in Ryan's thread about his little speaker project, but I thought a few more details might be helpful for those who are looking for a speaker like this for a small room or maybe a computer.
These are a basic two way with a crossover around 3500hz. I say around 3500hz because the crossover is a bit atypical. The woofer rolls off above 2000hz and the tweeter kicks in electrically at 4300hz. I was trying to keep the parts count as low as possible, but still not compromise on the accuarcy. You can see this in these in room measurements:
The chart is a bit busy. First there are measurements of the woofer (with and without the notch filter) and tweeter separately. Then the composite with the tweeter in and out of phase electrically. The lowest point on the darker blue response curve with the tweeter in electrical phase with the woofer is at about 3500hz which corresponds to the null. (3500hz also roughly corresponds to A7 on the piano, and thus the name.) The null is not extremely sharp, which indicates that they are not 100% phase matched, but since the tweeter out of phase response is so flat, I didn't try to get a better reverse null. It still took eight components in the crossover to get this close and I didn't want to make it any more complicated since this was designed to be as simple as I could get it.
Here is a drawing of the crossover and the box plans. The 10" X 8.25" X 5.5" box is 1/2" MDF with a 3/4" front baffle. I didn't think I needed thicker MDF on such a small box and indeed it's pretty dead in the knuckle wrap test. But the cross brace is an absolute necessity. Sorry, but I don't know any of the cad programs to draw it nice and pretty, so I'm afraid this is all you will get
:The crossover shows two variations. (I have other variations that I'll discuss later.) I ended up with the 4.3uF and 3.0 ohm tweeter highpass version. In the response chart above, I ran the two variations a few db higher to show them separately and so you could see the difference. The 4.3/3.0 version corresponds to the lower, light blue trace. The 5.1/2.2 version (purple) didn't sound bad at all, in fact some of you might prefer it, but when I used the speaker as a center channel, the over equalized high end on our local TV stations just made it too bright. But for regular music use, both versions sounded very detailed and quite musical without ever sounding harsh.
I'll go into more details later, but if this looks like something you might like, I think the RS100-4 is on sale for one more day at PE.
-Bob
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