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AA Crossover refresh?


alzinski

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On 4/27/2017 at 11:43 PM, djk said:

Measure the ESR, if it is over about 0.5Ω, replace.

 

 

 

 

The large 12uF I measured .4 ohms.

 

The smaller 2uF caps measured .5 and .6 ohms. 

 

For kicks I measured some bipolar electrolytics that are much smaller and brand new, they were ~2 ohms.

 

The capacitance has drifted off though, I measured 17uF for the large one (should be 12uF) and 3uF for the smaller ones (should be 2uF).

 

Not sure how to proceed. I was more worried about the ESR than the capacitance but now I am thinking the crossover points have been lowered. I remember reading somewhere that people actually mod the squawker to cross a bit lower, like ~400Hz?

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  • 11 months later...

I am going to hijack this thread for a quick couple questions that are still pertinent to the subject thread title if that is okay. 

 

I am going to rebuild my AA crossovers for my LaScalas.  Per my other thread I have a little less output on one of the speakers, primarily in the middle frequencies it appears where voice etc resides. (One of those situations where as I listen I question if I am losing a little hearing in one ear) 

 

Flirted with the idea of the Russian MBGO PIO's, but since there is no straight up 13uF option, never mind.   Looking at caps, apparently Bob has faith in the Sonic Cap Gen 1 so I might as well stick with those.  I may order some of the PIO's for the 2 2uF in the tweeter circuit and mix in the 13uF Sonic Cap.  Am I heading in teh right direction as I attenpt to put things back to original?

 

My 2nd question is should I replace all the original hook-up wire?  If yes, what with?  I can add some to my cap order to get the best option.

 

3rd, both mid horn drivers (55-V) register 10.5 ohm with my meter.  Sound about right?  Does that tell me anything in terms of their condition other than they are not open?  I tested them to see if the one that I believe is putting out less sound might read a different value than the other but they are the same reading.  Of course I wonder if the diaphragms should just be replaced at this point on both with the Crites option.  Unfortunately I don't know if they ever were previous.

 

Thanks

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Guest wdecho

You can start with sonicaps and look else where if they are too bright for your taste. One can parallel a 12uh with a 1uh and make 13uf easy enough. capacitors in parallel add. I recently built a pair of AA's and used a pair of these. Sound great to me.  https://www.ebay.com/itm/AC-450V-13uF-Cylindrical-Motor-Capacitor-CBB65-W7G9/253489139858?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649 . Along with some of these for the tweeter, https://www.parts-express.com/jantzen-audio-22uf-400v-crosscap-capacitor--027-916. Jantzen makes great caps and I have been using the crosscaps in some of my amplifiers lately. 

 

Wire is wire and as long as it is not corroded I would not bother. Regular 18 gauge is good enough at my house. In fact I used 20 gauge in my AA builds. 

 

10.5 ohms is a correct reading for the K55V. You possible could have a bad connection in your crossover or other connection for reduction of sound. I personally do have better hearing in one ear than the other. I expect everyone does to some degree. 

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On those Russian MBGO caps; I emailed one the the online sellers about matching caps as I was thinking like you with the 13uf part.  So, he matched up (2) 10.9uf caps and (2) 2.1uf caps which gave me the 13uf needed.  I used those for a little while as they didn't cost a lot of money and I still have them all together.  They sounded a little flat and dull to me.  I ultimately built a complete new set with new autoformers, caps, coils, connectors, wire, etc., as I figured I had just built a "new" pair of Belle's so they should have new crossovers.  The AA's with the MGBO caps will probably get stripped down and turned into a set of Type A crossovers just so I can hear the difference.  It's not as detrimental for the AA protection circuits with mine since I have all new drivers and I didn't use the zener diodes in the new build.

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