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Synergy Sub 12 active to passive re-purpose

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Dear all,

I recently came by a mint condition Synergy Sub 12 at a throw away price because its amp was blowing fuses. These seem to have a manufacturing fault by the number of reports I've read on the net, and by how perfectly untouched my example looks. I imagine the original owner was not impressed! It would be a shame to throw out a sub like this, simply because replacing the original, and seemingly fragile power amp, is too costly (and risky) compared to new.


As I'm in the process of following Dr Earl Geddes guide to better bass I figured that I could re-purpose this sub from active to passive and drive it with one channel  of my Crown XLS 2500's.


Perhaps if you have one lying around this can mean that your nice blown active sub can find new life too, as an equally nice passive sub, just with better power, depending on what you can power it with.


As I'm prone to do, but was actually necessary in this case, I opened up this sub to have a look around....


Like new exterior:



The dead amp...



The 12" woofer is likely worth more than I paid for the complete unit....



I'd call it better than average quality, really I was surprised at how hefty the driver was when it came out. I noticed that the terminals seemed unmarked for +ve and -ve so added some markings of my own before disconnecting it...



I'll bet the Klipsch punched basket is heaps more rigid than the traditional spoke design steel versions. Solid sized magnet, plenty of venting too.....



Not a very solid box however, rather average MDF with zero bracing...



No to worry, I love a little wood working. Holes cut to reduce internal volume displaced and reduce weight gain....



Two scrap pieces of pine glued across the top, held down with my low tech clamps while the glue dries...



A closer look now that the glue has set up....






Much more solid now, distinctly different sound from the box when giving the "knuckle rap test"....



Stuffing back in place...



I didn't want to remove the amp and then have a make up a blanking board for its hole.  So I pulled out my soldering iron, removed the wires and the shorting resister from a pair of the amps speaker level input posts (which are gold plated and really nice looking) and re-used the original wiring to connect the woofer to these two input posts....



Wired up as a test (before bracing went in) ...



So now she's all back together and in my system as one of my four passive subs.



Its a really nice sounding sub for what it is, not as authoritative as my HiSAF's in terms of depth, but really smooth, not at all boomy in my room (near-field just behind my couch against the back wall), sounds plenty deep and is quite efficient too. With the grunty Crown behind it it's a great sub, reborn.


One man's trash, is another's treasure...


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The Sub 12 was a highly regarded sub.  Being the Synergy series the cheap cabinet doesn't surprise me.  Glad you were able to make it work!

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