Stephen M
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Posts posted by Stephen M
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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.
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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
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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.
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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
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Does anyone else think these measurements indicate a problem with the midrange drivers?
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Roy has offered some advice regarding these tweeters. He pointed out that the AR-3a Inproved crossover already has a 0.1mH inductor across the tweeter, and suggested keeping this in place and testing before making any changes. At the moment I'm pretty happy with this setup, but time will tell.
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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.
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Thanks Kent and Roy,
At this point I'm not inclined to change the polarity, as I like the sound as-is. Following up on Kent's post, I've done some more reading and have learned that there are indeed instances where the phase of tweeter or midrange are inverted, depending on the crossover. I don't have the knowledge of crossovers or filter circuitry to understand the reasoning behind this fully. I'm sure the authors of this schematic got it right.
The HiVi tweeters sound very good to my ears. Initially the system seemed very bright, but it has improved greatly since I put a rug over the bare floorboards between the speakers and my listening position. I intend to continue tuning the room to flatten the response as much as possible, starting with bass traps to address significant nulls at 72Hz and 216Hz.
Cheers
Stephen
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I've also done a quick survey of other schematics posted here. In each case the tweeter is wired with the same polarity as the other drivers. I'm retuning to my initial question: Is it possible that the tweeter should be wired opposite to what is shown in the above schematic?
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Hi Mike,
Thanks, I guess I should have asked a different question:
"Why is the tweeter wired differently to the other drivers? Why is tweeter +ve wired to the -ve side?"
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Hi,
I'm a bit confused about the wiring of the tweeter in this schematic. It seems to me the +ve terminal of the tweeter should be connected to black, not yellow as shown below. I'm basing this on the fact that the woofer and midrange have -ve to ground, and so it logically follows that the tweeter should too. I'm also assuming the yellow dot on the tweeter terminal indicates +ve.
Am I wrong, or is the schematic? I suspect I'm wrong, but anyway....
Cheers
Stephen
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Hi,
Just wondering if anyone has set up their AR-3a's sideways rather than vertical? Interested to know how they are set up horizontally, facing the listener - woofers to the inside?
Cheers
Stephen
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Thanks for the replies.
I ended up taking the speaker outside and using the soldering iron to soften the glue (very smoky job!). I then cleaned as much as I could with isopropyl alcohol and did the recap.
Cheers
Stephen
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Hi,
I have a general question about removing old hot glue from my AR-3a Improved crossovers. I'm re-capping them, and there is a huge amount covering the switch and terminal posts that I need to remove. I've tried using my soldering iron to soften the glue and then tease out the wires, but I've realised that I need to remove it and clean up the residue so the solder will stick when I install the new caps.
Are there any tricks to doing this? I have a heat gun but am hesitant to heat up all the components on the crossover.
I've attached a photo with an arrow pointing to the blob in question.
Cheers
Stephen
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Just a quick follow-up question: what variety of the 8-ohm L-Pad is recommended? Parts express have 15W, 50W and 100W, with 3/8" and 1" shaft...
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Thanks Roy.
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Hi,
Can anyone suggest a source for a .07mh 18 gauge inductor? I've managed to track down a pair of HiVi Q1R tweeters, and am now looking get the inductors.
It seems the tweeters are becoming hard to get - parts-express are out of stock until late May. Maybe coronavirus is starting to affect shipments?
Cheers
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Thanks Kent and Stimpy, great info.
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8 hours ago, Aadams said:
Are you swapping the original drivers for new components?
I'm going to use HiVi Q1R tweeters. The rest are original.
I'm aware of the need to use an inductor coil with these tweeters. Is this the only mod necessary?
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Hi,
I'm going to recap the crossover in my pair of Ar3a Improved speakers, and have some questions I hope can be answered here. I'm not trying to recreate the original sound of these speakers - my aim is to have them sounding as good as is reasonably possible, using modern components of high quality.
Is it worth considering a conversion to the AR3a crossover? My reasoning is that this would give more tonal control via the pots, rather than the switch of the AR3a improved crossover.
What is the best way to remove the crossover from the cabinet? It seems to be glued and I'd hate to break anything trying to get the board out...
What are some recommended replacements for the caps? In other gear I've built (Pultec style EQs, LA2A compressor) I've used V-Cap and Mundorf, but the price of an exotic 150uf Cap is $$$...
Thanks in advance,
Stephen
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Sounds like good advice, thanks Roy.
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Thanks for all the replies.
I paid $200 USD for these speakers, so even if I spend another few hundred I will still be ahead I think. Having heard the bass response from the working speaker I would very much like to have the pair up and running.
I have seen the seller "VintageAR" on eBay, so it is good to know your expertise is involved there Roy.
2 hours ago, DavidR said:Lacquer thinner may soften the old glue. If not perhaps toluene but I doubt it.
I will think about trying this. There is also a speaker repair shop that has been recommended so I will talk to them tomorrow (today is a public holiday in Australia).
3 hours ago, RoyC said:Unfortunately, removing the old voice coil is very difficult without destroying the cone, as it was glued to the cone with an epoxy type of glue.
At what point does the cone become "destroyed"? The closeup pic below shows a gap between the old voice coil. If I was to be able to keep the cone close to this condition would it still be useable? It seems there is some material upon which the voice coil is glued, between the voice coil connection and the cone material. If I'm able to maintail the radius of this mounting area and fill any small gaps with epoxy when connecting the new voice coil would this work?
I'm considering a painstaking application of toluene to the old voice coil, which would hopefully soak through and reach the old epoxy. After a few hours soaking I would then use an Exacto knife to remove the old material.
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I've has a quick look at replacement woofers, and the price is in the hundreds, plus shipping. Quotes on eBay for shipping to Australia are $200AUD!!!
I'm hoping it's possible to replace the voice coil. I don't know anything about this procedure, but is it possible to replace the voice coil only, or does it require the cone and foam surrounds to be replaced as well? The cone and foam are in excellent condition.
Are there specific kits available for this woofer? I imagine it would be a lot cheaper to ship a kit than the whole driver.
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Thank you Frank and Roy, I'm very grateful for this advice.
I've removed the dust cap, and it's clear that the voice coil casing has broken down. The copper wire connection seems intact, so this would explain the correct resistance reading at the terminals.
My next question is: should I take to a repair technician, or is this something I could repair?
AR-3a Improved new shunt measurements
in Acoustic Research
Posted
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.