RoyC Posted August 9, 2018 Report Share Posted August 9, 2018 6 hours ago, Aadams said: IS it practical to a adapt a 3a mid to 8ohm use in an AR 5? Sure, a 2.5 ohm resistor in series with an AR-3a mid will bring it very close to an AR-5 mid. Roy Quote Link to comment Share on other sites More sharing options...
ctjetta Posted August 9, 2018 Report Share Posted August 9, 2018 12 hours ago, Jimmie Holland said: I just happened to stumble across the ebay listing a couple days ago and the seller had it listed for $89.99 and it was the second driver he sold. I wish I could have purchased both midrange drivers as they are difficult to find in good condition. Jimmie Lucky for you he had only the one; if had two I would have long ago purchased them. I'm happy you were able to use it. Quote Link to comment Share on other sites More sharing options...
JKent Posted August 9, 2018 Report Share Posted August 9, 2018 9 hours ago, RoyC said: a 2.5 ohm resistor in series with an AR-3a mid will bring it very close to an AR-5 mid. So if my reading of the AR-3a restoration manual is correct, that would also apply to mids from the 10-Pi, 11 and LST. Also, a mid from an LST-2 should be a direct replacement for the 5. So there are "some" choices. Kent Quote Link to comment Share on other sites More sharing options...
RoyC Posted August 9, 2018 Report Share Posted August 9, 2018 2 hours ago, JKent said: So if my reading of the AR-3a restoration manual is correct, that would also apply to mids from the 10-Pi, 11 and LST. Also, a mid from an LST-2 should be a direct replacement for the 5. So there are "some" choices. Kent Yes...and all of the LST-2 drivers are the same as the AR-5 drivers. Roy Quote Link to comment Share on other sites More sharing options...
Pete B Posted August 10, 2018 Report Share Posted August 10, 2018 On 8/9/2018 at 1:13 AM, RoyC said: Sure, a 2.5 ohm resistor in series with an AR-3a mid will bring it very close to an AR-5 mid. Roy Do you know the DCR of the AR-5 midrange? I saw 4.8 in an ebay ad but who knows if they zeroed the meter. I measured AR-11 mids at 3.8 DCR so based on this we could probably get away with just 1 to 1.5 ohms in series. 2.5 will give up a lot of sensitivity have you tried it and compared? Quote Link to comment Share on other sites More sharing options...
RoyC Posted August 10, 2018 Report Share Posted August 10, 2018 50 minutes ago, Pete B said: Do you know the DCR of the AR-5 midrange? I saw 4.8 in an ebay ad but who knows if they zeroed the meter. I measured AR-11 mids at 3.8 DCR so based on this we could probably get away with just 1 to 1.5 ohms in series. 2.5 will give up a lot of sensitivity have you tried it and compared? Pete, Earlier front-wired 3a mids measure below 3 ohms. Later back-wired mids through the AR-9 typically measure 3.2 to 3.5 ohms. (Your AR-11 mid seems to be a bit on the high side.). Two later back-wired AR-5 mids I recently measured were both 5.2 ohms. All the AR-5 mids I've measured in the past have been around 5 ohms, with earlier front-wired specimens, like the 3a mids, being on the lower end of the range. I estimated the series resistance on the high side primarily because the white dot/"normal" setting of the AR-5 mid pot is nearly 50% off maximum (around 6.5 ohms in series), so there is plenty of output to be had with the AR-5 mid. The prudent way to go would be to measure dcr and add enough series resistance to the intended low impedance mid to achieve 5 ohms. This would put it well within the desired spec. It should also be noted that the original "15 ohm" pots can vary by as much as .5 to 1 ohm one way or the other, and should be measured as well. Roy Quote Link to comment Share on other sites More sharing options...
Pete B Posted August 10, 2018 Report Share Posted August 10, 2018 This is the first I've heard that the front wired are so different from rear, didn't know that. Seems the resistance depends on what you have to work with. Quote Link to comment Share on other sites More sharing options...
Pete B Posted August 15, 2018 Report Share Posted August 15, 2018 On 8/10/2018 at 5:17 PM, RoyC said: Pete, Earlier front-wired 3a mids measure below 3 ohms. Later back-wired mids through the AR-9 typically measure 3.2 to 3.5 ohms. (Your AR-11 mid seems to be a bit on the high side.). Two later back-wired AR-5 mids I recently measured were both 5.2 ohms. All the AR-5 mids I've measured in the past have been around 5 ohms, with earlier front-wired specimens, like the 3a mids, being on the lower end of the range. I estimated the series resistance on the high side primarily because the white dot/"normal" setting of the AR-5 mid pot is nearly 50% off maximum (around 6.5 ohms in series), so there is plenty of output to be had with the AR-5 mid. The prudent way to go would be to measure dcr and add enough series resistance to the intended low impedance mid to achieve 5 ohms. This would put it well within the desired spec. It should also be noted that the original "15 ohm" pots can vary by as much as .5 to 1 ohm one way or the other, and should be measured as well. Roy My mistake, I just looked at the AR-11 mid that I was talking about and I wrote 3.18 ohms on the back not 3.8. That suggests that 1.6 ohms would might still be enough. Quote Link to comment Share on other sites More sharing options...
Terkel Posted February 7, 2020 Report Share Posted February 7, 2020 I have a pair of original AR 5 units! Quote Link to comment Share on other sites More sharing options...
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