Hello all. I have scanned 10 pages of LXMini Crossover posts but I did not see any relating to my need, if I missed it I do apologize. Up until this afternoon I have been SO excited about a new build I am pulling together. The centerpiece is an active crossover that will drive 6 Purifi amps powering my beloved Spendor S100 3-way speakers. After much research, I decided that Nelson's LXMini crossover is just what I need, with an online calculator to allow me to change some resistors and caps to modify crossover points to mate with my speakers.
Then I thought "if only it could do single ended to balanced it would be perfect!" Perhaps unfortunately I found just that on the Linkwitz store website. It's called the Balanced LXMini - Sub R2, which I thought must be much the same as the LXMini +2 and the LXMini. All designed by Nelson Pass and all called LXMini. What could go wrong.
Well, today I reached the point of crossover assembly and soon realized that the crossover I have, although called LXMini, looks to be quite a different crossover. Not at all sure the LXMini online calculator will work with it to modify R and C values to work with my speakers. And if I can't adapt it to work with my speakers, it's useless. I contacted Frank at the Linkwitz store and he will not take it in return. He did say the crossover should be able to adapt for use on a 3-way speaker, but that he cannot help me.
Can anyone here help me to adapt this crossover for use? If it is like the LXMini, I should be able to change the values of a few resistors and caps and that is all it takes to modify it for my speaker's crossover points. But the boards look different, so not sure the topology is the same so that the LXMini online calculator applies. Also the component numbering is different so not sure which Rs and Cs on my board correspond to the Rs and Cs referenced by the online calculator. Here is what it looks like:
Then I thought "if only it could do single ended to balanced it would be perfect!" Perhaps unfortunately I found just that on the Linkwitz store website. It's called the Balanced LXMini - Sub R2, which I thought must be much the same as the LXMini +2 and the LXMini. All designed by Nelson Pass and all called LXMini. What could go wrong.
Well, today I reached the point of crossover assembly and soon realized that the crossover I have, although called LXMini, looks to be quite a different crossover. Not at all sure the LXMini online calculator will work with it to modify R and C values to work with my speakers. And if I can't adapt it to work with my speakers, it's useless. I contacted Frank at the Linkwitz store and he will not take it in return. He did say the crossover should be able to adapt for use on a 3-way speaker, but that he cannot help me.
Can anyone here help me to adapt this crossover for use? If it is like the LXMini, I should be able to change the values of a few resistors and caps and that is all it takes to modify it for my speaker's crossover points. But the boards look different, so not sure the topology is the same so that the LXMini online calculator applies. Also the component numbering is different so not sure which Rs and Cs on my board correspond to the Rs and Cs referenced by the online calculator. Here is what it looks like:
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Hello Nelson. Thanks so much for your reply! Not much documentation. Certainly no 'how to'. A parts list, a drawing (not a schematic) of the board, a few comments from Frank. But that was it.
When I asked for help he did offer this:
"As this LXmini+2 from NP is a 3-way design, it is theoretically feasible to vary Rs and Cs to change filter characteristics. In principle, the XO is a chain of RC filters with intermediate JFET buffer stages. As NP did not publish the circuit on the 3 way XO, it can be quite cumbersome."
When I asked for help he did offer this:
"As this LXmini+2 from NP is a 3-way design, it is theoretically feasible to vary Rs and Cs to change filter characteristics. In principle, the XO is a chain of RC filters with intermediate JFET buffer stages. As NP did not publish the circuit on the 3 way XO, it can be quite cumbersome."
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Ah hah! After matching up R and C values between LXMini and my balanced board, I now see "Woofer Hi-Pass" left/right and "Full Range Hi-Pass" left/right on my board have the same R and C values as the resistors on the LXMini board that are manipulated by the resistor calculator (i.e. "Lo Hi-Pass" left/right and "Hi Hi-Pass" left/right). I hope this means the LXMini calculator will work to change crossover points by changing R and C values for my woofer hi-pass and full range hi-pass.
Nelson, I much appreciate if you can verify this. Also can you tell me what parts of the balanced board need to be populated for my 3-way situation, and any key things I need to know or do besides stuffing those areas of the board? For instance, not sure what needs to happen in the boxes marked "balanced input" and will I need to jumper over unused sections, etc. Frank did give me expected voltages at test points.
Nelson, I much appreciate if you can verify this. Also can you tell me what parts of the balanced board need to be populated for my 3-way situation, and any key things I need to know or do besides stuffing those areas of the board? For instance, not sure what needs to happen in the boxes marked "balanced input" and will I need to jumper over unused sections, etc. Frank did give me expected voltages at test points.
Hello Nelson, I also purchased this board from the Linkwitz store. It came with a BOM and instructions on selecting the R Bias / setting bias. Any additional documentation would be helpful.
OK, be patient and I will assemble the information.
Before you commit to a particular set of crossover settings with a soldering iron, you might have a whack at modeling the system with some software. There are several programs that will model a system with an active crossover nicely. Boxsim, a free download from Visaton will do it along with modeling the response of the drivers in boxes including the response due to the baffle. VituxCAD or Xsim would also work. Rapid prototyping the system using a miniDSP 2x4HD or equalizerAPO and a four channel output soundcard or DAC would let you hear it before you heat up the iron to build the analog filters.
I also bought this board but I have no idea to modify with other drivers, then now it still keep it in my bag.
Hello Olsond3 - Yes I have thought about taking your approach. Although I'm working with 3 channels and so it makes the DSP and DAC purchase more expensive. My hope is to avoid modeling or a lot of trial and error because the speakers are a known quantity and tone and integration of drivers is perfect. So I've only one variable to contend with, the crossover. And, my intent is to keep the factory crossover frequencies and slopes. There is an online calculator that will tell me the needed values of certain resistors and caps to arrive at the slope and frequencies I need. And for fine tuning I have already been working with the Focus Fidelity program which will allow me to tweak in-room phase and frequency via convolution filters. BUT this is my first time crack at active crossovers, so I might be naive!
Hello Marcus -- I bought this XLMini+2 board thinking it was simply the XLMini board but with two channels added. So I thought this board will be compatible with the online calculator which was designed for use with the XLMini board. That calculator allows you to choose the target frequency and slope you want the system to have and then the calculator tells you what values of certain resistors and caps you need to substitute on the board to achieve your result. I need Nelson or others to confirm, but I hope that that calculator will work the same way with this board we have.
After today, my active crossover project will be complete except for building of the crossover itself. Here are some pics of my project that I hope can use the LXMini+2 Crossover. First pic shows braces on back of speakers to accept the 3-way amplifiers. Amps will be mounted using rubber and sorbothane isolators. The braces are mounted and cables are run using existing holes that were already in the back panel. The new cables will run directly into the amp cases.
Below are the 3-channel amplifier cases that will hang on the back of each speaker. I am filling them out now with 3 Purifi modules with Neurochrome buffers and the Hypex power supplies. That 4th input XLR is there to allow for the possibility of adding a sub channel at a later time or if the LXMini crossover cannot be used, the cases can be used for something else. 😕
Below is the case for the crossover. A single channel 6DJ8 preamp stage sits at each input to the crossover. The remainder of the space in the foreground will be taken up with coupling caps. A tube-rectified 165/6.3V outboard power supply feeds the preamp and a separate +/-15VDC outboard supply feeds the crossover.
Below are the 3-channel amplifier cases that will hang on the back of each speaker. I am filling them out now with 3 Purifi modules with Neurochrome buffers and the Hypex power supplies. That 4th input XLR is there to allow for the possibility of adding a sub channel at a later time or if the LXMini crossover cannot be used, the cases can be used for something else. 😕
Below is the case for the crossover. A single channel 6DJ8 preamp stage sits at each input to the crossover. The remainder of the space in the foreground will be taken up with coupling caps. A tube-rectified 165/6.3V outboard power supply feeds the preamp and a separate +/-15VDC outboard supply feeds the crossover.
Hello Nelson, please let us know if you were able to put up some information regarding the board.
Thank you.
Thank you.
These are from my files, signed off by SL, the filter component values and curves for the LXmini+2.
The part numbers will probably not match the board you have but the topology will be the same,
you just have to translate the numbers.
You can run these through a simulator such as LTSpice or Microcap or other filter emulator in order
to customize the response.
The part numbers will probably not match the board you have but the topology will be the same,
you just have to translate the numbers.
You can run these through a simulator such as LTSpice or Microcap or other filter emulator in order
to customize the response.
Hi Nelson --
Thanks for your reply. I am trying to find the way forward for me and am a bit confused. (Not your problem and nothing new!) But when I decided to use the LXMini+2 crossover, it was after reading your paper on the 6-24 crossover. I assumed (maybe bad assumption) that the LXMini and LXMini+2 crossovers were built on the 6-24. You mentioned in that paper "DIY patron saint Mike Rothacher has put together a filter calculator for these circuits, available for download. Works like glue, and no rocket science involved." I checked out the calculator here: http://doublesecretlabs.com/apps/passxo/ and it looked to be exactly what I needed. Best of all I actually understood it. And I even thought I could associate component locations on my board with the resistors and caps Mike was referencing in his calculator.
I am not familiar with LTSpice or Microcap. Is it possible to identify the caps and resistors that need to be changed on my LXMini+2 board using Mike's calculator? If not, am I starting from scratch to design a crossover, and are the LXMini+2 board and parts of any use to me?
[BTW we were once neighbors, back in the 90's. I was building a house in Applegate when you were moving your operations to Foresthill. I meant to get up there to check things out but life got in the way.]
Thanks for your reply. I am trying to find the way forward for me and am a bit confused. (Not your problem and nothing new!) But when I decided to use the LXMini+2 crossover, it was after reading your paper on the 6-24 crossover. I assumed (maybe bad assumption) that the LXMini and LXMini+2 crossovers were built on the 6-24. You mentioned in that paper "DIY patron saint Mike Rothacher has put together a filter calculator for these circuits, available for download. Works like glue, and no rocket science involved." I checked out the calculator here: http://doublesecretlabs.com/apps/passxo/ and it looked to be exactly what I needed. Best of all I actually understood it. And I even thought I could associate component locations on my board with the resistors and caps Mike was referencing in his calculator.
I am not familiar with LTSpice or Microcap. Is it possible to identify the caps and resistors that need to be changed on my LXMini+2 board using Mike's calculator? If not, am I starting from scratch to design a crossover, and are the LXMini+2 board and parts of any use to me?
[BTW we were once neighbors, back in the 90's. I was building a house in Applegate when you were moving your operations to Foresthill. I meant to get up there to check things out but life got in the way.]
WOW! Now that's a XO! I've built the 6-24 and the LX-Mini/ACN, they look like child's play compared to this PCB. I counted 44 JFET's for EACH channel to make a 3 way XO. When I bought the kits from the diystore, they came with MATCHED J113's and the correct bias resistors for the CCS. The J113's are matched for lowest distortion in the buffers, I converted both of mine to use 2SK170's for the buffer and the J113's for the CCS.
Do you have 88 MATCHED J113 JFET's with the BIAS resistors?
What about the OFFSET resistors I see with some of the buffers?
Do you know the XO frequency for each driver?