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Multi-Way Conventional loudspeakers with crossovers

Modify Minimus 7
Modify Minimus 7
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Old 9th November 2017, 09:19 PM   #1
BobCat1950 is offline BobCat1950  United States
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Default Modify Minimus 7

I have a pair of M7 die cast Aluminum speakers and have the crossovers from another pair; question: can I take the 4.7uF capacitor and 0.4mH inductor and make a true 2-way crossover by adding the cap in parallel and inductor in series to the woofer or is that going to screw things up?
Currently the crossover only filters low frequencies to the tweeter. Check pic and diagram. First pic and diagram is the original crossover; the 2nd diagram is what I am proposing.
thx
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File Type: jpg DSC02459 (2).JPG (246.6 KB, 145 views)
File Type: jpg Minimus 7 7W Original X-over.jpg (30.0 KB, 145 views)
File Type: jpg Minimus 7 modified X-over.jpg (33.1 KB, 143 views)
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Old 10th November 2017, 12:29 AM   #2
phivates is online now phivates  United States
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That would be an old school "textbook" crossover that does not take into account the impedance of the drivers at the crossover frequency, or their acoustic responses. PB2 has one around here somewhere...
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Old 10th November 2017, 02:20 PM   #3
BobCat1950 is offline BobCat1950  United States
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Quote:
Originally Posted by phivates View Post
That would be an old school "textbook" crossover that does not take into account the impedance of the drivers at the crossover frequency, or their acoustic responses. PB2 has one around here somewhere...
I am new to all this modifying speaker stuff; I had just replaced the old original crossover, as it were, in my M7W's with a 2-way, not a sophisticated 1 but a better 1 nonetheless It was a difficult choice for me but I did it. I didn't want to throw away the parts fro the old one, so I went to sites to calculate C1, C2, L1 and L2 of a 2-way crossover with 8 ohm tweeter and woofer. I found that 2nd order crossovers had different names like Butterworth, Linkwitz-Riley and Bessell and at 12db/octave they showed the C1=C2, L1=L2 but different values for each and different values for the frequency; I could not find 1 that gave me the C1, C2 and L1, L2 values I had after changing the frequency value. I thought maybe if the db/octave was different but I could not find a calculator for known C1=C2 and L1=L2; so I experimented and it works, there may be some difference in the woofer.


BTW what is PB2
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Old 10th November 2017, 03:02 PM   #4
phivates is online now phivates  United States
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Pete Basel. He has a crossover and circuit board example in the construction tips forum for the M7, and might direct you to a starting point for this learning curve that I am also on. Also the "crossovers without measurements" thread by AllanB in the stickies is packed with the basics.
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Old 11th November 2017, 01:10 AM   #5
eriksquires is offline eriksquires  United States
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Hi BobCat,

Of course, you can play around with anything.... but there's no guarantee you'll end up with something better. You might want to take a look at the Seas A26 kit as well as the discussions here about simulating and modifying it.

The A26 has, by design, a tweeter only crossover. Lojzek has suggested going from 1st to second order on the tweeter is a good improvement in that design.

The only way to make such radical changes reliably with speakers is to fully analyze the electronica AND acoustic outputs, and simulating changes via a tool like XSim.

I encourage you to see Troel's Graveson's site and see some of the upgrade kits he offers, and just how much goes into it.

If you are just desperate to play, I suggest you replace the cap with a Mundorf MKP of the same value. About $7, well worthwhile.

Best,

E
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Old 11th November 2017, 04:20 AM   #6
Top Shelf is offline Top Shelf  Canada
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Check out Zilch's Minimus 7 upgrade thread over on audiokarma.
He and Pete battle it out over that one. He won't be able to answer any questions though, may he rest in peace.
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Old 11th November 2017, 01:59 PM   #7
djn is offline djn  United States
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I modified a pair of Minimus 11s and they turned out great. The hardest part was polishing the cabinet. But it is worth the time and effort.
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Old 13th November 2017, 02:04 PM   #8
BobCat1950 is offline BobCat1950  United States
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thx to all for the replies; I am a beginner and didn't want to waist the parts I salvaged. I did replace the M7W speakers like I said and thought i'd play with the others. I did notice some change in the M7 after I did this but my M7W new crossover did make a substantial difference. It now has the crossover below that I found on Amazon. I didn't want to buy the homemade pair on ebay or build 1 from the parts mentioned in the PZ 2.1 (crossover mod by Zilch & Pete) That would have been more $$. I just didn't want to "waist" the parts. I may eventually replace the modified M7 with the newer x-over down the line.
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File Type: jpg 7W new crossover (a).JPG (67.0 KB, 22 views)
File Type: jpg Minimus 7W modified X-over.jpg (31.1 KB, 19 views)
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