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Old 29th March 2004, 03:36 PM   #1
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Default Crossover Distortion?

OK to make a long story short, I built a passive crossover for a pair of MB Quart 6.5's in my car. I used the Crossover Calculator found -HERE- and decided to go with a Second Order (12db/octave).

The Crossover was calculated with a 3200 Hz freq range and 4 ohm speakers.

I built ONLY what is shown in the calculator diagram and hooked them up. I have my amp running at Full range and when the bass hits there is a lot of distortion. You can tell that the higher frequencies have been cut out, but even at a very minimal volume level, for lack of better words they "sound like crap".

I purchased the Inductors and Caps of Parts Express.

If it helps, I have tested the speakers on another amp without the crossovers and they are not blown. Also when I put the amp on High pass I get non distorted music from the speakers but it doesn't sound like the correct freq range.

Anyone know what could be wrong with these things?

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Old 29th March 2004, 04:17 PM   #2
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More details needed, although just looking at your crossover it looks like the inductors are way too close to each other to be left parallel.

State exactly which value inductors and capacitors you used.
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Old 29th March 2004, 04:39 PM   #3
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I used:

DAYTON 6.2uF-250V POLYPROPYLENE

JANTZEN .39mH 15 GA AIR CORE

I should have known that the inductors can't be placed that close together. Anyone else thinks thats the probelm as well. Thanks
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Old 29th March 2004, 04:50 PM   #4
Svante is offline Svante  Sweden
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I don't think that is the problem. It is *a* problem, but not as bad as you describe it. It would be nice with a diagram, and possibly a photo that reveals your connections a bit better.
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Old 29th March 2004, 05:44 PM   #5
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OK well, I made some Diagrams of the Crossover layout and simple schematics. I also have attached a picture of the wiring on the back of the crossover. It probably will not help since it's Point-to-Point wiring and the picture is hard to see.

Crossover Diagram:

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Simple Schematic:

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Pictures of Wiring:

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Hope this helps.

Brian
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Old 29th March 2004, 06:07 PM   #6
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The problem you might have with the arrangement of the inductors is magnetic field coupling from one inductor to another. With the inductor, laying down and in the same magnetic plane the low frequency can cross couple to the midrange inductors. You should take the inductors for the midrange drivers and stand them on edge at a right angle or increase the distance between them.
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Old 29th March 2004, 06:36 PM   #7
Svante is offline Svante  Sweden
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The schematics and component values seem reasonable. The potential mutual coupling between the coils can be handled by changing the direction of the two middle coils such that only the two coils at the far ends point in the same direction. There is also a slight risk that the iron in the screws increases the value of the coils a bit. But as I said both of these effects are small, and probably *not* the cause to your problem.
You have not yet said anything about the speakers, more than that they are 4 ohms. There is a risk if the woofer has a high voice coil inductance that there will be a dip in the impedance curve near the xover frequency. On the other hand, the symptoms you describe do not match this entirely. Also, you should not run this filter *without* the drivers connected, since this will lead to a very sharp impedance dip at the xover freq.
Could you post the brand & model of the speakers too?
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Old 29th March 2004, 08:47 PM   #8
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Ok, here is all the information that I can find on the driver. It's an MB Quart 6.5 (QM160 or RWC 160) taken from there RSB 218 component set a couple of years ago. It seems that the arrangement of inductors is the cause of at least some of the distortion so I will try this first. Thanks

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Brian
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Old 30th March 2004, 05:10 AM   #9
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Anyone have any other Ideas about a possible problem?
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