Stephen M Posted June 22, 2020 Report Share Posted June 22, 2020 After recapping all but the 20uf and big compulytic 150uf, I grabbed some magnitude spectra, close mic'ing each driver. The crossover points I got were: Left low/mid - 497Hz mid/high - 6147Hz Right low/mid - 432Hz mid/high - 6261Hz I've now replaced the old compulytic 150uf with a mundorf bipolar electrolytic, and sealed the cabinets.The crossovers are now measuring: Left low/mid - 508Hz mid/high - 4787Hz Right low/mid - 506Hz mid/high - 4865Hz Attached some grabs of the second measurements. Quote Link to comment Share on other sites More sharing options...
Stephen M Posted June 24, 2020 Author Report Share Posted June 24, 2020 Does anyone else think these measurements indicate a problem with the midrange drivers? Quote Link to comment Share on other sites More sharing options...
ligs Posted June 24, 2020 Report Share Posted June 24, 2020 Can you also measure the frequency response of the speaker? If you overlay the total response with the that of the individual drivers then any problem will be more apparent. In properly designed speaker, the overall response tends to be smother than the individual drivers. Here is an illustration. http://averagejoeaudiophile.blogspot.com/2015/12/infinity-reference-r152-infinitys-high.html Quote Link to comment Share on other sites More sharing options...
Stephen M Posted June 24, 2020 Author Report Share Posted June 24, 2020 Here are a couple of full range sweeps with the mic at approx. 1m distance, pointing directly at the speaker at a point between the mid and tweeter. The room is untreated so there are several nulls I need to try to eliminate, but the general response may be seen in white. y Quote Link to comment Share on other sites More sharing options...
ligs Posted June 24, 2020 Report Share Posted June 24, 2020 Have you detected any difference in sound after recapping? When I recapped the 40uf in my AR11, I had to turn down the mid frequency control more than before to make it sound right for me. Quote Link to comment Share on other sites More sharing options...
Stephen M Posted June 24, 2020 Author Report Share Posted June 24, 2020 Well, I did quite a few other things when recapping, so it's hard to know what the individual effect of each was. I like the sound now, and sealing the cabinets has tightened up the bottom end a lot. Room treatment will be a big factor in the sound too. I'm just wondering whether it'd be worthwhile getting the mid range serviced. Quote Link to comment Share on other sites More sharing options...
ligs Posted June 24, 2020 Report Share Posted June 24, 2020 Would it be possible to buy a replacement midrange with the option for returning? The chance is 50/50 that one may find the sound of either one is fine, especially after carefully adjusting the mid frequency control. To me, your midrange does not show any glaring deficiency. Quote Link to comment Share on other sites More sharing options...
ligs Posted June 24, 2020 Report Share Posted June 24, 2020 I assume you have a pair of AT 3a improved midrange drivers. You can switch between them to see there is significant difference. At least you can determine which one is faulty. Quote Link to comment Share on other sites More sharing options...
RoyC Posted June 24, 2020 Report Share Posted June 24, 2020 5 hours ago, Stephen M said: I'm just wondering whether it'd be worthwhile getting the mid range serviced. What do you mean by "serviced"? Roy Quote Link to comment Share on other sites More sharing options...
Stephen M Posted June 24, 2020 Author Report Share Posted June 24, 2020 Hi Roy, There's a technician here in Melbourne who makes voice coils, and the thought crossed my mind that he might be able to do some work on these midrange drivers. Assuming they can be worked on... Stephen Quote Link to comment Share on other sites More sharing options...
Stephen M Posted June 24, 2020 Author Report Share Posted June 24, 2020 8 hours ago, ligs said: Would it be possible to buy a replacement midrange with the option for returning? The chance is 50/50 that one may find the sound of either one is fine, especially after carefully adjusting the mid frequency control. To me, your midrange does not show any glaring deficiency. The 3a Improved doesn't have a mid frequency control, it's a 2-way switch. Do you think the lower output of the midrange is to be expected? The tweeters are new HiVi substitutes, and might have a higher output than the originals, although this is a guess. 8 hours ago, ligs said: I assume you have a pair of AT 3a improved midrange drivers. You can switch between them to see there is significant difference. At least you can determine which one is faulty. I don't think either one is faulty, as they both have a very similar response. Another possibility might be that C2, a 20uf Solen MKP that is in the midrange path, needs replacing. This is the only cap in the crossover I haven't replaced, as it tested OK in both speakers. Quote Link to comment Share on other sites More sharing options...
RoyC Posted June 25, 2020 Report Share Posted June 25, 2020 4 hours ago, Stephen M said: The 3a Improved doesn't have a mid frequency control, it's a 2-way switch. Do you think the lower output of the midrange is to be expected? The tweeters are new HiVi substitutes, and might have a higher output than the originals, although this is a guess. I don't think either one is faulty, as they both have a very similar response. Another possibility might be that C2, a 20uf Solen MKP that is in the midrange path, needs replacing. This is the only cap in the crossover I haven't replaced, as it tested OK in both speakers. Stephen, The HiVi tweeter has significantly greater output than the original tweeter, and is the most likely source of any dissatisfaction you may have to this point. Additionally, compared to the limited settings provided by the switches of the 3a Improved, the variable level controls of the original AR-3a makes it much easier to dial in the desired balance. It's very doubtful anything will be accomplished by trying to replace the midrange voice coils (which, by the way, is a very unlikely possibility). Replacing the Solen capacitors is not going to significantly change anything either. Roy Quote Link to comment Share on other sites More sharing options...
Stephen M Posted June 25, 2020 Author Report Share Posted June 25, 2020 Thanks Roy, what you've said makes a lot of sense. There is definitely a trap when chasing the measurements rather than using my ears. The overall sound is very good, and I'm really happy with how things are now. I've done a bit more room treatment, and will attach the last measurement. Looks like I need to back off on the high range attenuation now, but things are in a good spot now for fine-tuning. Quote Link to comment Share on other sites More sharing options...
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