I've got a pair of LX521.4 Mg ASP-powered speakers that I love, but had to put into storage while I'm spending a year or two on my sailboat. I have a pair of Genelec 8320a, but I'm really missing my "magic" speakers, so it's time to build a pair of LXMinis.
I'm going to start with the ASPs. At the end of Nelson's article, he suggests balanced mode requires two boards. I just wanted to verify what I think that means before I order them.
Does that mean one board is connected to the positive pin, the other board is connected to the negative pin, and the neutral is connected to ground/chassis? My preamp and amp (4-channel) is all XLR (truely balanced, not fake balanced.) Is this the right way to do it?
Can I run them off of a 24V battery? I was thinking in terms of audio quality and black background. If a wall-wart is sufficient, that's fine.
I'll go ahead and ask the last question which isn't of immediate concern, but eventually might be. I saw a post on OPLUG where someone built a double-barreled config for the lower speaker with the upper speaker pointed at the listener between the two lower. SL liked it and suggested one could lower the crossover point to 35Hz to allow it to play louder since the cones were not likely to max out the baskets as easily. (decrease low-pass filter in relation to high-pass filter and extend the bottom end a little.) Is that easily done on the circuit with a new cap/resistor pair? I found the Microcap simulation files and will study those in the next few days.
I'm going to start with the ASPs. At the end of Nelson's article, he suggests balanced mode requires two boards. I just wanted to verify what I think that means before I order them.
Does that mean one board is connected to the positive pin, the other board is connected to the negative pin, and the neutral is connected to ground/chassis? My preamp and amp (4-channel) is all XLR (truely balanced, not fake balanced.) Is this the right way to do it?
Can I run them off of a 24V battery? I was thinking in terms of audio quality and black background. If a wall-wart is sufficient, that's fine.
I'll go ahead and ask the last question which isn't of immediate concern, but eventually might be. I saw a post on OPLUG where someone built a double-barreled config for the lower speaker with the upper speaker pointed at the listener between the two lower. SL liked it and suggested one could lower the crossover point to 35Hz to allow it to play louder since the cones were not likely to max out the baskets as easily. (decrease low-pass filter in relation to high-pass filter and extend the bottom end a little.) Is that easily done on the circuit with a new cap/resistor pair? I found the Microcap simulation files and will study those in the next few days.
Two single ended crossovers will work as you describe, although SL's versions converted balanced to SE for thr filters and then created balanced output.
Let me make sure we're discussing the right one. The boards I plan to use are the ones on DiyAudioStore and I've got your article titled "art_lxmini crossover.pdf" where you mention in the closing paragraph:
"You can use two of these crossovers, one board for each channel, in balanced mode, with XLR connectors on the inputs and outputs if you like. The power supply mentioned will drive two boards. If you do this, be sure that the level potentiometers are set at the same values for the + and – circuits."
I know Frank has another version that includes the sub, but I don't think those plans were ever published.
"You can use two of these crossovers, one board for each channel, in balanced mode, with XLR connectors on the inputs and outputs if you like. The power supply mentioned will drive two boards. If you do this, be sure that the level potentiometers are set at the same values for the + and – circuits."
I know Frank has another version that includes the sub, but I don't think those plans were ever published.
You may have also meant to use the L+R on one board to be the inputs for positive phase and negative phase? + goes to Left and - goes to Right so that one board contains only one channel. I think this is what you meant instead of the way I interpreted it in my previous post.
Everyone knows that - goes to left and + goes to right.
Unless you are South of the equator.
Unless you are South of the equator.
I've got a couple more questions I hope someone can help me answer. One is case-related and one is power supply-related.
First, power supply. I've got two power supplies I think will work. One is a Crestron 24V power supply. That is my default right now because I know it will work. However, I also have a Mean Well P50A13D-R1B which has a +12V and a -12V pin. Is the Mean Well something I could use? +12V at R47 and -12V to the opposite of C26? I remember Nelson saying it was differential, so I was interpreting that as meaning +12V on one side and -12V on the other is a 24V difference. If not, no biggie I can use the Crestron. But I have no other use for this Mean Well right now and plenty of temporary uses for the Crestron.
The two boards are 5" x 5". The largest capacitor is 16v 3300uF which I think is 1" tall (don't know which brand, so I'm guessing.) What is a minimum-sized case that would comfortably hold the two boards? I'm thinking at least 11" wide and 8" deep. The deep is to accommodate the 6 XLR inputs and outputs. (No RCA, No external controls, just the power input and 6 xlr connectors.) How tall? is 2" sufficient to give the 3300uF clearance + the board + the mounting stand-offs underneath?
It seems like the only case on the Diyaudiostore site that would work is the 80mm x 280mm x 330mm case. Seems like two 5"x5" boards would be swallowed whole with plenty of room left over, which is fine, but I'd prefer a 2" tall case to a 3" tall case. Any case suggestions welcome. I'm also getting pretty good at riveting aluminum together as I'm slowly building an RV based airplane in my limited spare time. I might just build an aluminum box from scratch for the sheer cool factor. Speaking of which.... how much cooling does the case need to provide? I'm thinking it's probably not going to get really hot inside the case, though I don't know if that means I can fully enclose it with no cooling holes/slots.
First, power supply. I've got two power supplies I think will work. One is a Crestron 24V power supply. That is my default right now because I know it will work. However, I also have a Mean Well P50A13D-R1B which has a +12V and a -12V pin. Is the Mean Well something I could use? +12V at R47 and -12V to the opposite of C26? I remember Nelson saying it was differential, so I was interpreting that as meaning +12V on one side and -12V on the other is a 24V difference. If not, no biggie I can use the Crestron. But I have no other use for this Mean Well right now and plenty of temporary uses for the Crestron.
The two boards are 5" x 5". The largest capacitor is 16v 3300uF which I think is 1" tall (don't know which brand, so I'm guessing.) What is a minimum-sized case that would comfortably hold the two boards? I'm thinking at least 11" wide and 8" deep. The deep is to accommodate the 6 XLR inputs and outputs. (No RCA, No external controls, just the power input and 6 xlr connectors.) How tall? is 2" sufficient to give the 3300uF clearance + the board + the mounting stand-offs underneath?
It seems like the only case on the Diyaudiostore site that would work is the 80mm x 280mm x 330mm case. Seems like two 5"x5" boards would be swallowed whole with plenty of room left over, which is fine, but I'd prefer a 2" tall case to a 3" tall case. Any case suggestions welcome. I'm also getting pretty good at riveting aluminum together as I'm slowly building an RV based airplane in my limited spare time. I might just build an aluminum box from scratch for the sheer cool factor. Speaking of which.... how much cooling does the case need to provide? I'm thinking it's probably not going to get really hot inside the case, though I don't know if that means I can fully enclose it with no cooling holes/slots.
The Mean Well supplies I have used are marked V+ and V- for the 12v, 36v and 48v supplies. I think the +12v and -12V is a 12v supply. Measure the voltage between those pins to make sure.
Mine is 290mm deep X 230mm wide and 85mm tall. Here are pics
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I have another question about this project.
I decided to liberate my Crestron 24V power supply of it's chassis and put it directly in the chassis of my balanced LXMini build. Now I'm wondering where I need to place it in relation to the other two boards, and do I need to build a shield around the power supply.
My thoughts are to put it in the front of the enclosure and run the ac input down one side, and put the two LXMini boards at the back as close to the XLRs as feasible. I think I'm going to put the inputs next to each other in the middle of the chassis, then put the two outputs on either side of those.
Advice? Or is this as good an approach as any?
(I did eventually stumble on to the LXMini article thread, so if this post belongs there or some other part of this site, please let me know.)
I decided to liberate my Crestron 24V power supply of it's chassis and put it directly in the chassis of my balanced LXMini build. Now I'm wondering where I need to place it in relation to the other two boards, and do I need to build a shield around the power supply.
My thoughts are to put it in the front of the enclosure and run the ac input down one side, and put the two LXMini boards at the back as close to the XLRs as feasible. I think I'm going to put the inputs next to each other in the middle of the chassis, then put the two outputs on either side of those.
Advice? Or is this as good an approach as any?
(I did eventually stumble on to the LXMini article thread, so if this post belongs there or some other part of this site, please let me know.)
I like the XLR's.
See if you can find an IEC connector with a built in fuse, less wires.
Looks like a good place for the P/S, good place for ON/OFF switch too.
I've got quite a bit of Belden 8423 left over from my first set of LX521.3 speakers I planned to use for the XLR to board connections. Mainly because it's tin-plated copper, which I've recently discovered is a much better conductor than silver, gold, and the other fancy coatings. My sailboat has the same kind of tin-plated wire. It keeps the copper from oxidizing. Hell, maybe I should try that since I've got a few feet left over from my wind instruments install. But I also have a boatload of Cat-5. Literally. 😆
I know I've got two ferrite beads somewhere, but no idea which box in my storage unit it might be in. So, that helps even with everything being fully balanced input to output?
Thanks for calming my nerves on the power supply. I know Crestron builds quality stuff as they don't want to blow up all of the downstream expensive gear or have hum coming over the audio channels. Hard to believe you can pick up these 24V boxes for $30 on eBay these days. I've got two left over from a project from a decade and a half ago when they were just a bit more expensive.
I made this brushed front panel out of a big thick sheet of 2024 aluminum I had in the shop. This is going to be so cool once I get it all together!
I know I've got two ferrite beads somewhere, but no idea which box in my storage unit it might be in. So, that helps even with everything being fully balanced input to output?
Thanks for calming my nerves on the power supply. I know Crestron builds quality stuff as they don't want to blow up all of the downstream expensive gear or have hum coming over the audio channels. Hard to believe you can pick up these 24V boxes for $30 on eBay these days. I've got two left over from a project from a decade and a half ago when they were just a bit more expensive.
I made this brushed front panel out of a big thick sheet of 2024 aluminum I had in the shop. This is going to be so cool once I get it all together!
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I don't know, I only have single ended inputs on my Threshold preamps. I've never used them with balanced inputs, never had an issue with hum. Here is a pic of the phono preamp with the ferrite beads:
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This was a fun project! The boards are perfect! My attempt at building an aluminum enclosure from bare aluminum sheet was ok; I learned some things that work and some I can improve on the next time. But I'm most proud of the logo/led integration. I have to pat myself on the back for that one. I used Adobe Illustrator to create the logo, Fusion to extrude it, then 3D printed it. Next time I also need to leave more room for the XLR wiring in the back and create a little more room for the AC input and wires.
