DQ-10 Capacitor Replacement Article

[Boom3]

Here's an account of my capacitor replacement for my pair of DQ-10s.

DQ10A.pdf

[Carlspeak]

Nice job boom3 and thanks for sharing.

[Boom3]

Nice job boom3 and thanks for sharing.

Thanks!

[justw]

Thanks, nice pictures and text for someone to follow.

Are you certain your schematic is correct? The placement of C1 may be different. The reason I ask is my DQ-10 crossovers are very similar to yours but don't match your schematic in the low freq. leg of the network.

Referencing you picture, the white lead from the woofer are conected to the lower end of C1 and the green lead to the lower leg of R1. On my crossovers the upper leg of C1 and R1 are tied together. This makes R1 in series with C1

and connected parallel with the woofer. This is then in series with the mid-woofer. I attached a drawing of just the bass leg of my crossover to explain. This is different from any schematic of a DQ-10 that I have seen posted anywhere.

[Boom3]

Thanks, nice pictures and text for someone to follow.

Are you certain your schematic is correct? The placement of C1 may be different. The reason I ask is my DQ-10 crossovers are very similar to yours but don't match your schematic in the low freq. leg of the network.

Referencing you picture, the white lead from the woofer are conected to the lower end of C1 and the green lead to the lower leg of R1. On my crossovers the upper leg of C1 and R1 are tied together. This makes R1 in series with C1

and connected parallel with the woofer. This is then in series with the mid-woofer. I attached a drawing of just the bass leg of my crossover to explain. This is different from any schematic of a DQ-10 that I have seen posted anywhere.

I'll check and post what I find.

[Boom3]

I'll check and post what I find.

I looked at my DQ-10s again, but I did not unmount the boards and turn them over. When I was recapping my units, I took the schematic that has run around the web for many years (for s/n 4134 I think) and checked my units with a DMM to see what was what. The schematic of the 4134 was identical to my s/n 1063 _except_ that I have a single 4 ohm resistor in parallel with the woofer.

I can't address why your units are different. It makes me wonder if your units might be miswired. The published schematic of the DQ-10 has always bothered me. If L1 is in series with the woofer/midwoofer string, and L2 is in parallel with the midwoofer, then the midwoofer has a low-pass filter (L1) ahead of it and a low-pass filter (L2) around it. This means that the response of the midwoofer should be "choked off" (pun intended) above 400 Hz, and below it as well, since L1 and L2 are identical. If I was drawing a similar circuit on a cocktail napkin, I'd tie the hot pole of the midwoofer ahead of L1, take the signal through C1 as a high pass at 400 Hz, and then put L2 in series with C1, to give bandpass effect between 400 Hz and 1 KHz. I have the feeling that I am missing something here. I work with several EEs and I will ask some of the ones who still remember analog circuits to try to trace this out for me.

BTW, I know my re-cap article has a small error; the third crossover point is 6 KHz, not 5. I am writing a comprehensive essay on the DQ-10 that I will post here in the near future and it will correct that statement.

[justw]

Thanks. Mine were recapped at some point to the upgrade "yellow" caps. Maybe someone mucked around with the wiring then. Although by the looks of it they recapped from the top of the board by cutting out the old caps and soldering on the newer ones so it would have taken some doing to do that rewire like that. I had imagined that these were the original configuration but as yours are earlier I guess not. Anyways I decided to wire them as per the later schematics and they sound as sweet as I remember. Looking forward to your paper. There is a dearth of information about the DQ-10s and a single, comprehensive, document is sorely needed.