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Multi-Way Conventional loudspeakers with crossovers

Audio Concepts G3
Audio Concepts G3
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Old 12th July 2018, 01:10 PM   #1
pjblakey is offline pjblakey  United States
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Default Audio Concepts G3

I picked up a pair of ACI G3 three way floorstanders and have been searching for information on the factory crossover. Anyone have anything to share?
They appear to be in mint condition and have been in storage for many years but I sensed an “edginess” and harshness in the upper registers, so I disassembled the Vifa metal dome tweeters, carefully removed the dents in the domes and cleaned out the ferrofluid which had turned to a paste. Presently running gently without fluid. Sounds a little less harsh.
The crossovers are well glued into the cabinets and I would like to hear from anyone who may have upgraded them. There are a few electrolytic caps but can’t read the values in situ.
Cheers
Peter
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Old 13th July 2018, 08:49 PM   #2
system7 is offline system7  United Kingdom
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Old speakers always full of problems. Check for rubbing voicecoils on the basses by pressing them in. Rotating 90 degrees can help.

Poor connections are the worst thing usually. Those old spring clips on the back are rubbish. Best replaced with banana plugs hard soldered to fresh speaker cable. Crimped speaker connections benefit from redoing to fresh metal again.

It's a fun old speaker by the looks of it. Roy Allison style low woofer to avoid floor bounce. He wrote papers about this preferred arrangement.

I don't know what you are going to do about the crossover. You'll need to unattach it for any work or analysis.

W.Marshall Leach, Georgia Tech's finest son was good at this sort of thing. I think he even used your tweeter here! A Zobel network on the bass, just because he was good at that sort of thing.
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File Type: png Marshall Leach 3 way.PNG (31.3 KB, 451 views)
File Type: jpg Marshall Leach Vifa 3 way.JPG (24.8 KB, 446 views)
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Old 20th July 2018, 11:17 AM   #3
pjblakey is offline pjblakey  United States
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Thanks for the info.
All drivers seem to be working well.
When I get the urge, I’ll take a chisel or putty knife and attempt to remove the crossover boards. In the meantime, these are really growing on me.
Cheers
Peter
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Old 20th July 2018, 02:49 PM   #4
pkitt is offline pkitt  United States
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I built a pair of the G3s from kits many years ago. There was so little work to accomplish to make the build that I felt unsatisfied, thus leading me into DIY. At the time they sounded quite nice but in the long run I realized the midrange had a definite honk to it.
Paul
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Old 9th August 2018, 12:56 PM   #5
pjblakey is offline pjblakey  United States
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New ferrofluid from PE made a huge difference. Tweeter is now smooth and the speaker sounds great. The crossovers will stay in place.
The overall character of the G3 is very detailed with very very clean bass. Not a trace of bloom in my smallish room. Images like a narrow standmount.
Peter
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Old 9th August 2018, 06:06 PM   #6
system7 is offline system7  United Kingdom
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Nice work. I can't believe how much PE charge for ferrofluid, but when you need it, you need it badly...

I usually fit a 7.5R plus 0.68uF zobel to metal tweeters. It's a good theory because that supersonic resonance causes problems according to one of our brightest designers:
Sonics by Joachim Gerhard cabinets and kits.

That thread is good reading. Be good.
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Old 9th August 2018, 06:11 PM   #7
pjblakey is offline pjblakey  United States
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Thanks for the tip. I’ll try it out and report back.
Best
Peter
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Old 9th August 2018, 06:12 PM   #8
pjblakey is offline pjblakey  United States
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Thanks for the tip. I’ll try it out and report back.
Best
Peter
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