toddalin
01-25-2006, 11:31 AM
Those who have following my saga know that I was going to build new crossovers for my 2235/LE175-HL91/075s in L200 cabinets. The cabinets currently include N1200s and N8000s from when they had 130As and I wanted better tune the crossovers to the new woofers.
The initial intent was to construct the N200B crossover used in the L200B using better quality parts while keeping costs down. (Yeah right, total costs will end up about $120 each.) This would replace the N1200 and the N8000 would be retained for $$$ reasons and to fill the existing holes in the cabinets. I then resolved that it made little sense to use quality parts in the 2-way just to subsequently pass the signal through the inferior parts of the 25-30+ year old N8000. The project was escaladed to a 3-way design that would include the high pass element.
Prior to having the N8000s in these cabinets, I had N7000s. I actually prefered these with the LE175s that don't have quite the top end of the LE85 used in the L200s. As long as I was making this a 3-way, I could select any frequency I choose keeping the high pass between about 7,000-8,000 Hz.
The only difference between the N7000 and N8000 is the size of the chokes. N7000s use a 0.6 mH choke while the N8000 uses a 0.3 mH choke. All caps are the same. So selecting the frequency was just a matter of selecting the proper value choke. I initially wanted to use a 0.4 mH, ERSE reducing the frequency to about 7,670 Hz but these were out of stock as was my next selection, 0.33 mH. I settled on the 0.5 mH as they PE had them available. I estimate this to put the high pass at about 7,350 Hz, which may actually be the better choice with the LE175s.
The board was made compact and is to be attached to the gutted N8000 "can." This will allow me to install the boards through the existing openings and retain a stock appearence. The horn and tweeter outputs on the "can" will retain their existing layout. The existing "input" to the can will become the output for the woofer. This would allow me to disconnect the drivers for bi-amping or ??? if ever desired. To make installation easier, the input to the crossover comes from an input terminal cup, located at the bottom back of the speaker (already in place), to a gold RCA plug on the board. This will allow me to simply plug in the board, slide the assembly in place, and attach the speaker wires as usual.
Because the assembly needs to fit through the existing 4-1/8" wide hole in the back of the cabinet, size, and the placement of components becomes critical. A circuit board had to be cut down to size and several arrangements were comtemplated before the final product you see here. Coils were arranged to best take advantage of the space while minimizing cross talk.
All caps are Solen and include Theta 0.01 by-pass caps. All resistors are Mills and all coils are ERSE. The by-pass caps and resistors are not readily visible as they are tucked under the larger components. The existing tweeter L-pad on the "cans" will be retained so are not shown here. The large coil is held to the board using nylon screws/nuts and the board will be attached to the "can" using brass screws/hardware.
I'll try some initial testing on this one prior to constructing the other two (one for the center channel).
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Crossover1.jpg
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Crossover2.jpg
The initial intent was to construct the N200B crossover used in the L200B using better quality parts while keeping costs down. (Yeah right, total costs will end up about $120 each.) This would replace the N1200 and the N8000 would be retained for $$$ reasons and to fill the existing holes in the cabinets. I then resolved that it made little sense to use quality parts in the 2-way just to subsequently pass the signal through the inferior parts of the 25-30+ year old N8000. The project was escaladed to a 3-way design that would include the high pass element.
Prior to having the N8000s in these cabinets, I had N7000s. I actually prefered these with the LE175s that don't have quite the top end of the LE85 used in the L200s. As long as I was making this a 3-way, I could select any frequency I choose keeping the high pass between about 7,000-8,000 Hz.
The only difference between the N7000 and N8000 is the size of the chokes. N7000s use a 0.6 mH choke while the N8000 uses a 0.3 mH choke. All caps are the same. So selecting the frequency was just a matter of selecting the proper value choke. I initially wanted to use a 0.4 mH, ERSE reducing the frequency to about 7,670 Hz but these were out of stock as was my next selection, 0.33 mH. I settled on the 0.5 mH as they PE had them available. I estimate this to put the high pass at about 7,350 Hz, which may actually be the better choice with the LE175s.
The board was made compact and is to be attached to the gutted N8000 "can." This will allow me to install the boards through the existing openings and retain a stock appearence. The horn and tweeter outputs on the "can" will retain their existing layout. The existing "input" to the can will become the output for the woofer. This would allow me to disconnect the drivers for bi-amping or ??? if ever desired. To make installation easier, the input to the crossover comes from an input terminal cup, located at the bottom back of the speaker (already in place), to a gold RCA plug on the board. This will allow me to simply plug in the board, slide the assembly in place, and attach the speaker wires as usual.
Because the assembly needs to fit through the existing 4-1/8" wide hole in the back of the cabinet, size, and the placement of components becomes critical. A circuit board had to be cut down to size and several arrangements were comtemplated before the final product you see here. Coils were arranged to best take advantage of the space while minimizing cross talk.
All caps are Solen and include Theta 0.01 by-pass caps. All resistors are Mills and all coils are ERSE. The by-pass caps and resistors are not readily visible as they are tucked under the larger components. The existing tweeter L-pad on the "cans" will be retained so are not shown here. The large coil is held to the board using nylon screws/nuts and the board will be attached to the "can" using brass screws/hardware.
I'll try some initial testing on this one prior to constructing the other two (one for the center channel).
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Crossover1.jpg
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Crossover2.jpg