Allison 3 speakers: looking for help with driver replacement

jimjam71 · 23rd January 2021, 02:42 AM

Hello, I'm new here and I'm looking for someone with experience or advice on restoring a nice pair of Allison 3 speakers. Here's the backstory.
I picked up a pair of these from a nice older guy who had them from new sometime in the 80s. I got them cheap, and they're in very good condition which means I'm lucky. I've enjoyed them a lot since I got them almost a year ago. Recently I noticed that the sound seemed unbalanced, and it looks to me like the mid-range driver (3.5" "fried egg") on one of the units is not producing sound. I haven't gotten the multimeter out or checked the crossover yet, but I presume the voice coil on that driver has died.
Based on my brief research into these speakers, I've learned that these are considered by many to be a very good near-audiophile grade of speaker, but they are also relatively rare, very unique and not easy to repair.
Does anyone have advice to share about troubleshooting and possibly replacing the mid-range driver on my speaker?
Thanks a bunch!

freddi · 23rd January 2021, 03:50 AM

look at this page and check the midrange switch and caps

Allison Three crossovers - Allison - The Classic Speaker Pages Discussion Forums

boswald · 23rd January 2021, 04:00 AM

test:
1)VC continuity(inboard of terminals,barewire so easy)

2)switch continuity

3) caps

jimjam71 · 23rd January 2021, 04:09 PM

Thanks for the troubleshooting advice.
I have seen some posts that indicate that the driver needs to be removed from the crossover before continuity testing, but I'm not sure if you're comments about "inboard / bare wire" mean that it's not necessary for a basic continuity test.

Galu · 04:53 PM

Disconnect the wires at the mid's input terminals then measure its DC resistance with your multimeter.

No reading (infinite resistance) means an open circuit, either in the voice coil itself or in the wires connecting the input terminals to the voice coil (the inboard wires?).

If the voice coil circuit is intact i.e. continuous, then expect a reading of several ohms.

Galu · 23rd January 2021, 04:49 PM

P.S. I agree that the mid's level adjusting switch may be the problem.

Try operating it many times in the hope that will clean the switch contacts and restore the operation of the mid.

boswald · 23rd January 2021, 06:05 PM

These are 4ohm speakers, so 2.6+ ohms

23rd January 2021, 02:42 AM	#1
jimjam71 diyAudio Member Join Date: Jan 2021	Allison 3 speakers: looking for help with driver replacement Hello, I'm new here and I'm looking for someone with experience or advice on restoring a nice pair of Allison 3 speakers. Here's the backstory. I picked up a pair of these from a nice older guy who had them from new sometime in the 80s. I got them cheap, and they're in very good condition which means I'm lucky. I've enjoyed them a lot since I got them almost a year ago. Recently I noticed that the sound seemed unbalanced, and it looks to me like the mid-range driver (3.5" "fried egg") on one of the units is not producing sound. I haven't gotten the multimeter out or checked the crossover yet, but I presume the voice coil on that driver has died. Based on my brief research into these speakers, I've learned that these are considered by many to be a very good near-audiophile grade of speaker, but they are also relatively rare, very unique and not easy to repair. Does anyone have advice to share about troubleshooting and possibly replacing the mid-range driver on my speaker? Thanks a bunch!

23rd January 2021, 04:43 PM	#5
Galu diyAudio Member Join Date: Apr 2018	Disconnect the wires at the mid's input terminals then measure its DC resistance with your multimeter. No reading (infinite resistance) means an open circuit, either in the voice coil itself or in the wires connecting the input terminals to the voice coil (the inboard wires?). If the voice coil circuit is intact i.e. continuous, then expect a reading of several ohms. Last edited by Galu; 23rd January 2021 at 04:53 PM.

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23rd January 2021, 03:50 AM	#2
freddi diyAudio Member Join Date: Aug 2005	look at this page and check the midrange switch and caps Allison Three crossovers - Allison - The Classic Speaker Pages Discussion Forums

23rd January 2021, 04:00 AM	#3
boswald diyAudio Member Join Date: Jun 2014	test: 1)VC continuity(inboard of terminals,barewire so easy) 2)switch continuity 3) caps

23rd January 2021, 04:09 PM	#4
jimjam71 diyAudio Member Join Date: Jan 2021	Thanks for the troubleshooting advice. I have seen some posts that indicate that the driver needs to be removed from the crossover before continuity testing, but I'm not sure if you're comments about "inboard / bare wire" mean that it's not necessary for a basic continuity test.

23rd January 2021, 04:49 PM	#6
Galu diyAudio Member Join Date: Apr 2018	P.S. I agree that the mid's level adjusting switch may be the problem. Try operating it many times in the hope that will clean the switch contacts and restore the operation of the mid.

23rd January 2021, 06:05 PM	#7
boswald diyAudio Member Join Date: Jun 2014	These are 4ohm speakers, so 2.6+ ohms