Thoughts on AR3 midranges

[stuckinthe70s]

Here's my situation- I have a matching pair of AR3's, s/n's 32512 and 32513. A couple of years ago one of my mids died. I didn't really know what I was doing at the time and I purchased a pair of 3a mids from the big auction site. Per the 3a restoration document, my replacement mids are identified as p/n 4500-1, fig. A11. I currently have both of them installed, however the output is much greater than the originals, in fact I am only running the pots at about 1/4 of full on. They also can get a bit "honky"(lack of a better term) with certain music types. So my question would be regarding the crossovers. I've looked through the documents on this site and I'm not certain what changes to make. My thought is to add the components that AR did with the 3's when they ran out of original drivers and had to install a later 3a mid driver. That would be adding a 6-uf cap and a .4mh coil. Does this make sense, and would it "calm down" my mids? The other option would be trying to find a pair of original 3 mids, however I haven't been successful with that in the last year. I would need a pair as the one working original mid driver that I removed seems to have very low output and prefers to sit on the shelf.

I'm just looking for some advice here from the experts. If these crossover changes don't seem appropriate, could any of you make a better recommendation for this situation?

Thanks for any help.

[RoyC]

Here's my situation- I have a matching pair of AR3's, s/n's 32512 and 32513. A couple of years ago one of my mids died. I didn't really know what I was doing at the time and I purchased a pair of 3a mids from the big auction site. Per the 3a restoration document, my replacement mids are identified as p/n 4500-1, fig. A11. I currently have both of them installed, however the output is much greater than the originals, in fact I am only running the pots at about 1/4 of full on. They also can get a bit "honky"(lack of a better term) with certain music types. So my question would be regarding the crossovers. I've looked through the documents on this site and I'm not certain what changes to make. My thought is to add the components that AR did with the 3's when they ran out of original drivers and had to install a later 3a mid driver. That would be adding a 6-uf cap and a .4mh coil. Does this make sense, and would it "calm down" my mids? The other option would be trying to find a pair of original 3 mids, however I haven't been successful with that in the last year. I would need a pair as the one working original mid driver that I removed seems to have very low output and prefers to sit on the shelf.

I'm just looking for some advice here from the experts. If these crossover changes don't seem appropriate, could any of you make a better recommendation for this situation?

Thanks for any help.

Yes, adding those crossover components to match the later version of the AR-3 should improve things.

Rather than adding the 6uf cap to the 24uf cap, I would simply replace the 24uf cap with a new 30uf cap.

Roy

[stuckinthe70s]

Yes, adding those crossover components to match the later version of the AR-3 should improve things.

Rather than adding the 6uf cap to the 24uf cap, I would simply replace the 24uf cap with a new 30uf cap.

Roy

Thanks for the info Roy. Now just a question regarding the coil- I found a Jantzen .40mH 18 AWG, would that be appropriate? The main thing I'm not sure about is the guage of the wire, does that make a difference? It seems like either 18 or 20 AWG are the options.

Thanks again,

Ron

[RoyC]

Thanks for the info Roy. Now just a question regarding the coil- I found a Jantzen .40mH 18 AWG, would that be appropriate? The main thing I'm not sure about is the guage of the wire, does that make a difference? It seems like either 18 or 20 AWG are the options.

Thanks again,

Ron

Hi Ron,

The 18 gauge Jantzen will work perfectly!

BTW, welcome to CSP!

Roy

[stuckinthe70s]

Hi Ron,

The 18 gauge Jantzen will work perfectly!

BTW, welcome to CSP!

Roy

Thank you sir, I will get the parts on order.

CSP seems like a great place to hang out, there is a lot of knowledge here. I'll be reporting back here with results once I get the new parts in.

Ron

[RoyC]

Thank you sir, I will get the parts on order.

CSP seems like a great place to hang out, there is a lot of knowledge here. I'll be reporting back here with results once I get the new parts in.

Ron

Ron,

You are very welcome!

If you haven't already done so, it would not hurt to replace the tweeter caps as well.

Roy

[stuckinthe70s]

Ron,

You are very welcome!

If you haven't already done so, it would not hurt to replace the tweeter caps as well.

Roy

Actually I replaced all the caps and pots about a year ago with parts from Larry, so the tweeter circuitry is good. I still need to get a couple of intermittent woofers repaired, but that will have to wait a while. Being unemployed sucks. But at least I still have lots of music to listen to! Hopefully once I get these parts installed I won't have to mess with the internals for a while. The cabs are pretty decent, a few scratches but nothing bad. The grills need some work though so the speakers are currently running naked.

BTW, last spring I had a brief conversation with you over on AudioKarma about a possible odd ball AR3 that I had acquired for parts. I was going to send you some pics and you also mentioned bringing it to Tom's attention to see if he had any further info. Well that was in the spring(when I was still working) and with summer beginning one thing led to another and I never got the pics sent- my apologies. So I was just curious if you still would like to see it, the odd parts were the midrange driver and the terminal board on the front baffle. I can post some pics here or email them to you, doesn't matter to me.

Thanks again,

Ron

[RoyC]

Actually I replaced all the caps and pots about a year ago with parts from Larry, so the tweeter circuitry is good. I still need to get a couple of intermittent woofers repaired, but that will have to wait a while. Being unemployed sucks. But at least I still have lots of music to listen to! Hopefully once I get these parts installed I won't have to mess with the internals for a while. The cabs are pretty decent, a few scratches but nothing bad. The grills need some work though so the speakers are currently running naked.

BTW, last spring I had a brief conversation with you over on AudioKarma about a possible odd ball AR3 that I had acquired for parts. I was going to send you some pics and you also mentioned bringing it to Tom's attention to see if he had any further info. Well that was in the spring(when I was still working) and with summer beginning one thing led to another and I never got the pics sent- my apologies. So I was just curious if you still would like to see it, the odd parts were the midrange driver and the terminal board on the front baffle. I can post some pics here or email them to you, doesn't matter to me.

Thanks again,

Ron

Ron,

I was wondering what happened to you. Hang on to that relic midrange for historical purposes if nothing else. It would be interesting to find out when the metal grille was added to the AR-3 mid. Between historians like Tom T. and Steve F., and CSP AR-3 owners, we may be able to figure out a time line for the evolution of the AR-3 midrange driver.

I think you are making a good move by staying with the later mid driver.

Roy

[stuckinthe70s]

Ron,

I was wondering what happened to you. Hang on to that relic midrange for historical purposes if nothing else. It would be interesting to find out when the metal grille was added to the AR-3 mid. Between historians like Tom T. and Steve F., and CSP AR-3 owners, we may be able to figure out a time line for the evolution of the AR-3 midrange driver.

I think you are making a good move by staying with the later mid driver.

Roy

My parts came in yesterday and I now have then installed in both speakers. Initial listening tests indicate that things are improved. I also made a change to 1 of the speakers- I had been using L-pads that I installed at the same time I replaced the caps about a year ago. After digging around in here I read some posts regarding the use of L-pads and how it can change the sound, so I took those out and put the potentiometers back in, only in 1 speaker(I have 4 good working original pots, refurbished units from Larry). So now when comparing the 2 speakers, I believe I can hear a difference, the one with L-pads seems to have slightly higher output to the mid and tweeter. However, I like the midrange sound better from the one with original pots, but the tweeter is better on the L-pad speaker. So, as a final setup I think I will use a potentiometer on the midrange and L-pad on the tweeter. That won't cause any sort of problems will it? Roy if you're reading this, I think I saw somewhere you mentioned doing something similar by using a resistor on the mid L-pad only to bring it functionally closer to a pot, correct?

Also, I have a question about the wiring of the midrange inductor. In looking at the schematics I noticed that on the early 3's that had a coil in the midrange circuit, it was wired in between the cap and the pot, but on the later speakers when AR had to use a 3a mid driver they put the coil between the 2 leads going to the mid driver. I'm just curious as to why they did it this way, would the sound be altered in any way according to where that coil was in the crossover? I wired mine the same as the later crossover setup. I've attached a pic of my second speaker innards before I closed it up, please let me know if you seen anything out of order, I think I got it together correctly.

Thanks,

Ron

[RoyC]

please let me know if you seen anything out of order, I think I got it together correctly.

Thanks,

Ron

Nice job, Ron. Everything looks good from here.

I have been handling some restorations for Ebay's Vintage AR, as well as some fellow CSP members, and, when not retaining original pots, I always use an l-pad on the tweeter and an l-pad with a 25 ohm resistor in parallel with the midrange. (If the midrange pot is able to be restored I simply keep that in place.) The l-pad increases output and lowers the crossover point slightly. With care not to overdrive the increasingly decrepit original tweeters, the l-pads provide them with a bit more oomph. As you observed, the sonic effect of a straight l-pad on the midrange is not desirable.

The original .06mh coil in series with the AR-3 midrange has a different function than the .4mh parallel coil you just installed. The small series coil rolls off the earlier mid's high range very slightly, and the later, parallel coil rolls off the later mid's low range more quickly. In the AR-3a, both coils are used... a .05mh coil in series and a .88mh coil in parallel with the mid. AR was continually making adjustments along the way.

Roy

[tysontom]

Ron,

I was wondering what happened to you. Hang on to that relic midrange for historical purposes if nothing else. It would be interesting to find out when the metal grille was added to the AR-3 mid. Between historians like Tom T. and Steve F., and CSP AR-3 owners, we may be able to figure out a time line for the evolution of the AR-3 midrange driver.

I think you are making a good move by staying with the later mid driver.

Roy

Hi Roy,

Are there any images of the midrange driver(s) in question? To my knowledge, the metal grill was always a part of the 2-inch midrange (my AR-3 No C0005 has it), but there were quite a few other changes to the drivers with respect to fiberglass under the grill in later versions and a change in magnetic structure from the huge Alnico 5 magnet to a potted-structure. There were, also, changes to the crossover over time, as well as polarity changes. None of these had a hugely noticeable effect on the general sound quality.

The first prototype AR-3 had both the midrange and the tweeter on a single cast-aluminum plate, but this was changed by the time the speaker went into production.

Thanks,

Attachment: 1958 AR-3 prototype unit

--Tom Tyson

[RoyC]

Hi Roy,

Are there any images of the midrange driver(s) in question? To my knowledge, the metal grill was always a part of the 2-inch midrange (my AR-3 No C0005 has it), but there were quite a few other changes to the drivers with respect to fiberglass under the grill in later versions and a change in magnetic structure from the huge Alnico 5 magnet to a potted-structure. There were, also, changes to the crossover over time, as well as polarity changes. None of these had a hugely noticeable effect on the general sound quality.

The first prototype AR-3 had both the midrange and the tweeter on a single cast-aluminum plate, but this was changed by the time the speaker went into production.

Thanks,

--Tom Tyson

Hi Tom,

Ron's mids have just a metal grille over the dome. I have seen a number of those...no photos.

Attached is an old AR-3 ad showing a naked mid. Based on this, I assumed some early mids had no metal grilles at all.

Roy

[tysontom]

Hi Tom,

Ron's mids have just a metal grille over the dome. I have seen a number of those...no photos.

Attached is an old AR-3 ad showing a naked mid. Based on this, I assumed some early mids had no metal grilles at all.

Roy

Hi Roy,

The picture you show of the drivers used in the response-curve brochure (showing the extremely impressive anechoic-response curves of those drivers, by the way) was derived from the original artwork and photographs of the drivers themselves. This artwork depiction doesn't even show the suspension parts -- only the raw elements of the drivers themselves. However, I believe that once the AR-3 was put into production in early 1959, all of the 2-inch midrange drivers had the aluminum screen in place.

The attached file shows the 1958 artwork used in an ad that appeared during this period describing the AR-3 domes.

--Tom Tyson

AR_3_1959_Ad_Dome_Tweeters.pdf