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Old 14th January 2014, 01:56 AM   #11
WSJ is offline WSJ  United States
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Quote:
Originally Posted by tvrgeek View Post
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.
What is the effect of placing a resistor across an inductor?
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Old 14th January 2014, 01:03 PM   #12
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You could also build the model load Bob Cordell suggests ( fig 15.5, P 321).
I use it in Spice as a vague stab at a real load.
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Old 14th January 2014, 08:07 PM   #13
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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.
How can a simulation take into account unknown speaker parameters much less room acoustics? I have several experimental speakers with no part numbers or known parameters. What actually matters to me, is the acoustic output from the drivers in my listening room.
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Old 14th January 2014, 08:40 PM   #14
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Quote:
Originally Posted by tvrgeek View Post
You could also build the model load Bob Cordell suggests ( fig 15.5, P 321).
I use it in Spice as a vague stab at a real load.
I have the real load mounted in an enclosure with three sets of driver wires coming out the rear ready for the crossover testing. For acoustic measurements I use REW software with an EMM-6 Electret Measurement Microphone, EMU 0204 and a Hafler XL-280. I'm doing this project for fun.

Thank you for taking the time to respond to my post.

Last edited by WSJ; 14th January 2014 at 08:43 PM.
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Old 15th January 2014, 06:01 PM   #15
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Both inductor boards mounted together.

Click the image to open in full size.
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Old 15th January 2014, 06:16 PM   #16
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I see inductor cross-coupling everywhere.
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Old 15th January 2014, 07:24 PM   #17
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Originally Posted by Speedskater View Post
I see inductor cross-coupling everywhere.
I will not stack them and mount them with about 5" between the boards. The 8, 4 and 2 mH have some interaction, the 8 mH may not be use with the 4 or 2 mH. I should have found a larger box to allow more spacing. If turns out to be a problem, I have enough space to make 16" x 6" boards and mount them with some space between each board.
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Old 16th January 2014, 06:11 PM   #18
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Quote:
Originally Posted by WSJ View Post
I have the real load mounted in an enclosure with three sets of driver wires coming out the rear ready for the crossover testing. For acoustic measurements I use REW software with an EMM-6 Electret Measurement Microphone, EMU 0204 and a Hafler XL-280. I'm doing this project for fun.

Thank you for taking the time to respond to my post.
What I was suggesting is you are really building tools for two different functions. The first to make swapping parts for crossover tweaking easier, the second was the power load for amp testing. It was in that I suggest putting in an additional representative load. Maybe with a switchable horrible additional capacitance.

If we all were not doing this for fun, we would all be crazy. Or is it the other way around?
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Old 16th January 2014, 06:39 PM   #19
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Quote:
Originally Posted by tvrgeek View Post
What I was suggesting is you are really building tools for two different functions. The first to make swapping parts for crossover tweaking easier, the second was the power load for amp testing. It was in that I suggest putting in an additional representative load. Maybe with a switchable horrible additional capacitance.

If we all were not doing this for fun, we would all be crazy. Or is it the other way around?
I agree the high power loads should be in a second box. I plan to include lower power resistors in the L/C/R box for use within the filter networks. I will make changes to the inductor board to provide more space between inductors.

Thanks
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Old 17th January 2014, 10:30 PM   #20
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Having built several dozen crossovers over the years, I still suggest you will be far too limited with a switch box. The good news is you need all these parts in your kit anyway.

It is not just the space. It is the orientation. When coils are parallel, their lines will interact more than when they are perpendicular to each other. If each bank is only going to be one coil in test, just knowing the actual combined value including the mutual inductance is fine. No need to change. Be very aware in the actual crossover to keep the coils perpendicular or you can get undesired actions with the HP and LP filters having mutual inductance. Play with this. Take two coils in series and put your LCR meter across them. Move them around and see the results.

I have a box I keep 6 of every value between .5 and 12 Ohms in. I try to keep several of most values between 1 and 32uF in cheap electros and as many leftovers in film as I can keep on hand. I have fewer coils as well, they are expensive.
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