- Joined
- Jun 11, 2010
- Messages
- 6,849
- Location
- Powhatan, Virginia, United States
- Tagline
- WassupYa Mang?
So the other night I found some audio test recordings. One of which was a frequency sweep of sorts. I played it, and man... even though I can SEE the signals between right and left were the same as the frequency went up, there were several steps in the sweep to where the tone would actually shift from center. I'm suspecting the crossover needs some work, as I have already replaced the tweeters with new ones.
So I am looking here... and basically per crossover we have 3 caps. A 12uF, 20uF, and finally a 40uF. The 12 is used as part of a high pass to the tweeter, the 20 part of a low pass to the normal/stereo mid/woofer, and finally the 40 is used as part of a low pass to the "dimensional" mid/woofer. (remember that these are SDA's, which have a 3rd cable that goes between the two speakers and through the "magic" of the xover creates the "SDA effect" which cancels the crosstalk between L and R).
From reading up on the Polk forums, the recommended capacitors are these "Solen FastCaps" type. I found the 12's and the 20's at PartsXpress, but for the life of me I can NOT find the 40's anywhere... even at Solen's main site. Seems Solen discontinued those.
Now.. I can't find the 40uF's, but I CAN find 39uF Solens. So I am wondering... how much of a difference will 1 single microfarad make? I would imagine it would shift the crossover point to the dimensional mid/woofer, but is it really of any significance? But also.. in looking at and reading up on crossovers, LCR circuits, and whatnot, It seems that there is a direct correlation between the value of the capacitor and the value of the associated inductor or coil. The coil in the dimensional mid/woofer is 1.25mH, BUT... since it IS the SDA driver, there's another coil somewhere in the circuit that is rated at 16mH. Take a look at the attached skeezer and you'll see what I mean. The "IC" plug is on the left side, and would be connected to the other speaker - crossed over or straight, I do not know.
Soo.. would just 1uF difference really be a bad thing? What do you guys think?
Here's a link to the PDF..
http://www.phxaudiotape.com/images/sda2b.pdf
So I am looking here... and basically per crossover we have 3 caps. A 12uF, 20uF, and finally a 40uF. The 12 is used as part of a high pass to the tweeter, the 20 part of a low pass to the normal/stereo mid/woofer, and finally the 40 is used as part of a low pass to the "dimensional" mid/woofer. (remember that these are SDA's, which have a 3rd cable that goes between the two speakers and through the "magic" of the xover creates the "SDA effect" which cancels the crosstalk between L and R).
From reading up on the Polk forums, the recommended capacitors are these "Solen FastCaps" type. I found the 12's and the 20's at PartsXpress, but for the life of me I can NOT find the 40's anywhere... even at Solen's main site. Seems Solen discontinued those.
Now.. I can't find the 40uF's, but I CAN find 39uF Solens. So I am wondering... how much of a difference will 1 single microfarad make? I would imagine it would shift the crossover point to the dimensional mid/woofer, but is it really of any significance? But also.. in looking at and reading up on crossovers, LCR circuits, and whatnot, It seems that there is a direct correlation between the value of the capacitor and the value of the associated inductor or coil. The coil in the dimensional mid/woofer is 1.25mH, BUT... since it IS the SDA driver, there's another coil somewhere in the circuit that is rated at 16mH. Take a look at the attached skeezer and you'll see what I mean. The "IC" plug is on the left side, and would be connected to the other speaker - crossed over or straight, I do not know.
Soo.. would just 1uF difference really be a bad thing? What do you guys think?
Here's a link to the PDF..
http://www.phxaudiotape.com/images/sda2b.pdf
Although the IS2 connectors make it a bitch to work on. 
