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Multi-Way Conventional loudspeakers with crossovers

Is this crossover right for these two-way speakers?
Is this crossover right for these two-way speakers?
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Old 13th March 2018, 06:32 AM   #11
AllenB is offline AllenB  Australia
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A small value would be a fraction of an ohm if the capacitors change things, but I can't see any great deal of accuracy in the original design so I guess you could make a subjective call yourself. Maybe you'd be inclined to use up to a few ohms for whatever reason.

If you just put in resistors the response can be altered slightly other than just the level. Not necessarily enough to be a problem in this early stage but you might try a resistor in different positions. Maybe first you could try it before the capacitor. Later you could try it between the capacitor and the driver. The first option would create less unexpected change.
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Old 13th March 2018, 06:42 PM   #12
system7 is offline system7  United Kingdom
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It's actually a fairly standard sort of configuration.

What we have here is a 0.8mH coil on the metal dustcap (!) 8" bass to roll it off a bit and subjectively boost the bass.

Then a second order tweeter filter on a 1" soft dome. Usually around 3kHz. Coil is possibly around 0.5mH. Everybody has got it wrong on the 75mm chassis 1" dome tweeter capacitor. It's actually two 10uf electrolytic polars connected back to back to make a 5uF NP type.

So, me, I'd just replace the twinned tweeter capacitors with a 5uF non polar electrolytic at 5uF/50V or so. 4.7uF/50V will do.

AFAIK, this is a positive polarity filter, which will sound less echoey or phasey than negative polarity.

Last is a sim of how this sort of speaker works. If all goes well.
Attached Images
File Type: jpg Isophon crossover.JPG (49.8 KB, 28 views)
File Type: jpg Isophon crossover top.JPG (61.8 KB, 27 views)
File Type: jpg Isophon KK75-8 tweeter.JPG (40.5 KB, 27 views)
File Type: jpg Isophon PSL225-8.JPG (44.5 KB, 27 views)
File Type: png Monitor Audio R300-MD Original.PNG (5.8 KB, 28 views)
File Type: png Monitor Audio R300-MD FR.PNG (18.5 KB, 18 views)
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Best Regards from Steve in Portsmouth, UK.

Last edited by system7; 13th March 2018 at 06:44 PM.
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Old 13th March 2018, 08:20 PM   #13
AllenB is offline AllenB  Australia
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Good call Steve. I take back post 5.
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Old 13th March 2018, 11:57 PM   #14
JohnnyLemonhead is offline JohnnyLemonhead  Israel
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Good call, Steve! I was going mad trying to compare the PCB to other second order crossover schematics. Thank you and everyone involved for taking the time to help out. You're making the internet and the world a better place by sharing your knowledge so generously.

By the way, the actual drivers in my speakers are not identical to the ones I found the datasheets for. I don't think my woofers have a metal dust cap. Well, it isn't shiny, at least.

I'll try to update after sourcing and installing the capacitors, for posterity's sake.
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