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Old 7th January 2014, 05:11 AM   #1
WSJ is offline WSJ  United States
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Default Binary L/C substitution unit for crossover evaluation

Real time crossover evaluation can be tedious and time consuming, however, an L/C substitution unit should address some of these issues.

The advantage of a binary L/C substitution unit is to allow the maximum number of values with a practical number of components. This design can be configured to provide HP, BP or LP 2nd order filters for evaluation in real time. The unit incorporates two capacitor sections and two inductor sections that can be configured with banana cables. The capacitance range is 1 to 165 uF in 1 uF increments and the inductance range is 0.1 to 16.5 mH in 0.1 mH increments.

Any recommendations for crossover design programs?
Please let me know what you think and what improvements or corrections could be made.


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This is the input/output bus schematic.

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Last edited by WSJ; 15th January 2014 at 12:43 AM.
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Old 10th January 2014, 02:00 AM   #2
WSJ is offline WSJ  United States
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This is the capacitor board with binary weighted values: 1, 2, 4, 8, 10, 20, 40 and 80 uF.
I used a small cut off wheel to make the slots on the board.

Click the image to open in full size.

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Old 10th January 2014, 01:20 PM   #3
tvrgeek is offline tvrgeek  United States
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Very soon you will realize crossovers have a LOT more parts in them. You could make several sets of course. Some for the crossovers, some for serial and parallel filters, Zobels etc. You will need several of each resistor from 1 to 12 or so as well.

I have resigned to a big box of values and a pile of jumper cables. As things get closer, I switch to euro-style terminal strips cut into small chunks. Closer still, I tack solder things.

If you use a tool like PSD Lite, and measure well, you will see that the amount of final tweaking is greatly cut down. It is always clumsy.
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Old 11th January 2014, 03:45 AM   #4
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Quote:
Originally Posted by tvrgeek View Post
Very soon you will realize crossovers have a LOT more parts in them. You could make several sets of course. Some for the crossovers, some for serial and parallel filters, Zobels etc. You will need several of each resistor from 1 to 12 or so as well.

I have resigned to a big box of values and a pile of jumper cables. As things get closer, I switch to euro-style terminal strips cut into small chunks. Closer still, I tack solder things.

If you use a tool like PSD Lite, and measure well, you will see that the amount of final tweaking is greatly cut down. It is always clumsy.
I have a large enclosure for the project.
Additional sections will include 1-16 ohms, for the crossover.
1-16 ohms, at 100 Watts for Loads, with fan.
Also a sound card protection network.
This is the inductor board; the cuts were made with a small trim router.

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Old 12th January 2014, 07:45 PM   #5
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This is the inductor board with binary weighted values: .1, .2, .4, .8, 1, 2, 4 and 8 mH.
The inductor values were adjusted by adding or removing windings.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Last edited by WSJ; 12th January 2014 at 07:51 PM.
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Old 13th January 2014, 01:31 PM   #6
tvrgeek is offline tvrgeek  United States
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Plus and minus mutual coupling issues. Still, you need a LOT more sets of parts. I get the impression you believe you can use textbook filters only and am not thinking about the tweaks necessary for decent response. Please, download something like PSD lite and look at the options he gives you.

Depending on driver quality, a simple 2-way 3rd order electric crossover for ill-behaved drivers can have upwards of a dozen components. I have modeled at 16 ( then tossed out the drivers as too hard to use junk.) When you get to final voicing, you need two sets.

I would build my load box separate, It is for amp stability testing, not for crossover tweaking. My load plate is made of 4 2-Ohm 50 Watt'ers. They are inductive wound which is actually better for an amp. For stability and distortion testing, you really need to go to active loads where you can control the complex impedance. The famous load cube concept. Don't take my word for it, go model it is SPICE. You may be surprised what happens at clipping into a reactive load.
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Old 13th January 2014, 02:16 PM   #7
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Quote:
Originally Posted by tvrgeek View Post
Plus and minus mutual coupling issues.
Do you mean the inductors are too close together? Each inductor value is about 1% after tweaking the windings, but the total inductance is 13% high.

Quote:
Originally Posted by tvrgeek View Post
Still, you need a LOT more sets of parts. I get the impression you believe you can use textbook filters only and am not thinking about the tweaks necessary for decent response. Please, download something like PSD lite and look at the options he gives you.
I traced the circuit of a few NHT crossovers, this one about 20 parts for a 3 way system. I have some of the midrange drivers from this system and parameters, I realize the enclosure has an effect on the characters. I just started looking at PSD lite.
Click the image to open in full size.

Quote:
Originally Posted by tvrgeek View Post
I would build my load box separate, It is for amp stability testing, not for crossover tweaking. My load plate is made of 4 2-Ohm 50 Watt'ers. They are inductive wound which is actually better for an amp.
That sounds good, I have several 50 W. 2 Ω which can make a binary weighted load 1, 2, 4, 8.

Thank you.
Wayne
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Old 13th January 2014, 09:29 PM   #8
tvrgeek is offline tvrgeek  United States
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Looking at NHT should be a good help. They use pretty fair drivers and overall do pretty well with them; better than many big name higher priced companies. Look up an LS3-5A crossover.

It is not just that the inductors are close, but they are parallel. If you only used one at a time, it might not matter, but two at a time it does. If they are used in different parts of the circuit, ugly things can happen.

Enclosures have a LOT of effect. The obvious is the T/S tuning, but after that you get into all the baffle size and shape issues. While pulling in free software, grab the Edge for diffraction simulation. I don't get too wrapped up in magic materials, but I can't explain enough times what doing a 3/4 inch roundover on all 12 sides can do for top end smoothness. It takes a brittle over bright metal dome and makes it clean and detailed. ( provided it is a decent one to begin with)

I also have a habit of documenting in LTSpice my crossovers so I can keep their independent transfer functions in my mind. It does not tell you what will happen in the circuit, but helps me when I get confused.
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Old 13th January 2014, 11:47 PM   #9
sreten is offline sreten  United Kingdom
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Hi,

Its very old school and gets nowhere near the possible
complexities of crossovers. Simulation is far better.
Measurements and simulation even better.
Such things have no place in modern speaker design.

rgds, sreten.
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Old 14th January 2014, 12:01 AM   #10
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Quote:
Originally Posted by sreten View Post
Hi,

Its very old school and gets nowhere near the possible
complexities of crossovers. Simulation is far better.
Measurements and simulation even better.
Such things have no place in modern speaker design.

rgds, sreten.
What measurements are you talking about?
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