AR-2 tweeter repair

[genek]

5) ewaves are on The List. But at this moment I'd probably start from scratch, rather than trash an antique.

I am running these horizontal.

Not really necessary to trash. You could put the ewave (or any other auxillary tweeter scheme) on top of the existing cab and just remove the jumper to disengage the tweeter end of the crossover and use the 2 for its woofer. An add-on would require its own crossover anyway.

Considering the low original performance level of the 1959 stock tweeters and the fact that you'll have no way of ever knowing if you've successfully restored it, having them rebuilt may be over the cost/benefit line.

Internally, the easiest AR-original upgrade may be to make a filler panel for the crossfired array opening and install a single AR-2ax midrange (frequently available on eBay for around $15 each). That would bring your 2 up to a 2x with an extra 2-3kHz high end extension to 15kHz. The 2x had the same 2kHz crossover frequency as the 2; I don't know how the 2's tweeters were wired up, but if they're two 4 ohm units in series to make 8 ohms, you shouldn't need a crossover mod.

[JKent]

Gene,

Your suggestion to turn them into 2x's sounds (to me) like the best solution so far. Less expensive than having all 4 mids rebuilt and probably better sound and better reliability. And still original AR. What do you think of this: Go all the way by adding the filler panel, 2ax mid AND one of Roy's modded HiVi tweeters. There are 2ax crossover schematics in the Library and the parts should be easy enough to get (I'm sure many of us have spare inductors lying around).

Kent

[genek]

The 2ax used an updated woofer, dropped the woofer crossover frequency from 2kHz to 1.4kHz and positioned the mid and tweeter obliquely. There's probably room to put the mid and tweeter on the filler panel, but they'd be inline with the woofer. If these were mine, I think I'd keep the internal mod to a minimum, leave the woofer cross at 2kHz, install the 2x tweeter and then maybe drop a MA array on top of that.

[dxho]

Not really necessary to trash. You could put the ewave (or any other auxillary tweeter scheme) on top of the existing cab and just remove the jumper to disengage the tweeter end of the crossover and use the 2 for its woofer. An add-on would require its own crossover anyway.

Considering the low original performance level of the 1959 stock tweeters and the fact that you'll have no way of ever knowing if you've successfully restored it, having them rebuilt may be over the cost/benefit line.

Internally, the easiest AR-original upgrade may be to make a filler panel for the crossfired array opening and install a single AR-2ax midrange (frequently available on eBay for around $15 each). That would bring your 2 up to a 2x with an extra 2-3kHz high end extension to 15kHz. The 2x had the same 2kHz crossover frequency as the 2; I don't know how the 2's tweeters were wired up, but if they're two 4 ohm units in series to make 8 ohms, you shouldn't need a crossover mod.

Nice. I like that option as a possibility. It's more attractive than repairing lesser speakers, unless the speaker shop thinks something will change. I'd like to investigate these choices before considering more major changes.

The originals are 3+ ohms each, wired parallel? I only have this schematic:

[genek]

The originals are 3+ ohms each, wired parallel? I only have this schematic:

With a single driver representing both, there's no way to tell from this, though the cap value shown does seem to suggest a nominal 8 ohm tweeter impedance, which would result from wiring the values you describe in series. But if you unscrew the crossfire housing, you should be able to tell for certain how they're wired. If it is parallel, you might need to modify the tweeter capacitor value.

[RoyC]

Internally, the easiest AR-original upgrade may be to make a filler panel for the crossfired array opening and install a single AR-2ax midrange (frequently available on eBay for around $15 each). That would bring your 2 up to a 2x with an extra 2-3kHz high end extension to 15kHz. The 2x had the same 2kHz crossover frequency as the 2; I don't know how the 2's tweeters were wired up, but if they're two 4 ohm units in series to make 8 ohms, you shouldn't need a crossover mod.

I almost mentioned conversion to an AR-2x earlier in this thread, but after checking the Library it appears that the AR-2x tweeter was a different (smaller) driver than the AR-2ax midrange. I think Steve F. had a good post about this awhile back....will try to find it.

I just checked some notes regarding differences between AR-2, 2a, 2ax conversion, and the 2ax.

To summarize:

-The AR-2a (like the later 2ax) replaces the AR-2 crossover with a 4uf cap for the new tweeter, and uses a single 6uf cap for the mid.

(You are correct, Ken...the 2a's dual mids, your current tweeters, are wired in parallel.) The typical Pollak 15 ohm pots are now used for the tweeter and mid, *BUT only the series pot leg is used for the dual 2a mids*.

-The early 2ax, replaces the dual mids with the single fiberglass covered cone mid, and uses the whole pot (series and parallel legs) for attenuation. The 2a to 2ax conversion kit doesn't change the pot wiring, but adds a parallel resistor to lower the replacement mid's 6 ohm dcr to around 3 ohms (conversion kit only...see photo).

-Later 2ax has the smaller 3/4" dome tweeter and a foam surround woofer...same 2ax mid, crossover, and pots, but a larger, #7 woofer coil.

-Last 2ax has a ceramic magnet woofer. Mid looks the same, but dcr is raised to 9 ohms from previous 6 ohms.

Just a thought....A possible, easier out-of-cabinet tweeter candidate, which could be used with the dual mid/tweeters (or the later 2ax fiberglass covered midrange driver) would be this one:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=297-409

It behaves much like the HiVi Q1R, and may be easier to work with. It would, however, require a small parallel inductor the Q1R, and all other non-AR replacement tweeters, need to maintain an early AR tonal balance.

Roy

[RoyC]

I almost mentioned conversion to an AR-2x earlier in thread, but after checking the Library it appears that the AR-2x tweeter was a different (smaller) driver than the AR-2ax midrange. I think Steve F. had a good post about this awhile back....will try to find it.

Roy

Steve's comments regarding the AR-2x tweeter are in this post:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=6000&st=0&p=85302&hl=+ar-2ax%20+steve%20+f&fromsearch=1entry85302

Apparently it used two different tweeters, with the last having a smaller cone than the 2ax mid.

Roy

[genek]

Looks like we're back to needing to test a 2ax mid to see how high it goes when used as a tweeter. The smaller tweeter is likely to be just as much unobtanium as the AR-2 cross-fired tweeters.

[JKent]

Just a thought....A possible, easier out-of-cabinet tweeter candidate, which could be used with the dual mid/tweeters (or the later 2ax fiberglass covered midrange driver) would be this one:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=297-409

It behaves much like the HiVi Q1R, and may be easier to work with. It would, however, require a small parallel inductor the Q1R, and all other non-AR replacement tweeters, need to maintain an early AR tonal balance.

Roy

Great minds think alike, Roy

Check post #23, item #3

Kent

[RoyC]

Great minds think alike, Roy

Check post #23, item #3

Kent

Well, maybe so, Kent...but I should have clicked on your link in the first place!

I only had a brief encounter with that tweeter awhile back, before the Q1R, and have been looking for an excuse to order another pair. It was when I began realizing that HiVi tweeters were better than anything AB Tech was offering. It certainly could have possibilities as a relatively easy cabinet top enhancement for old timers like the AR-2.

Incidentally, I am having some ABS plastic adapter rings made by a partner in crime for this tweeter:

https://www.madisound.com/store/product_info.php?cPath=45_229_324&products_id=8316

It is a 3/4" dome, and I have been wanting to experiment with it in the 3a. There is an 8 ohm version as well. If they prove worthy, they could also be used as a "cabinet top tweeter".

Roy

[soundminded]

Looks like we're back to needing to test a 2ax mid to see how high it goes when used as a tweeter. The smaller tweeter is likely to be just as much unobtanium as the AR-2 cross-fired tweeters.

A 5" driver or even a 4" driver such as Bose used makes for an awful tweeter. The inertial mass is high and even if it could produce high frequencies, dispersion would be entirely on axis, exactly the opposite of AR's design goals and IMO the correct goal for a high fidelity loudspeaker. Therefore when such drivers are used as midranges, it is best to use a bandpass filter to restrict their high end. What high frequencies they do produce only detracts from the uniformity of output as a function of angle of the tweeter.

[genek]

A 5" driver or even a 4" driver such as Bose used makes for an awful tweeter. The inertial mass is high and even if it could produce high frequencies, dispersion would be entirely on axis, exactly the opposite of AR's design goals and IMO the correct goal for a high fidelity loudspeaker. Therefore when such drivers are used as midranges, it is best to use a bandpass filter to restrict their high end. What high frequencies they do produce only detracts from the uniformity of output as a function of angle of the tweeter.

True, but keep in mind we're talking about potential replacements for a pair of cross-fired 5" drivers. The 2ax mid (which according to the 2x/2ax brochure is actually 3.5", not 4"), even with the dispersion issues you describe, was apparently the tweeter for the original 2x, even though the timeline in the library says the later 70-71 version used a smaller 2.5" unit.

[dxho]

Millersound says they can't get the correct cone for these tweeters.

I'll be watching the auctions for used components.

[JKent]

Millersound says they can't get the correct cone for these tweeters.

I'll be watching the auctions for used components.

Or, you could buy the pair of AR-2s that are on ebay now for only one THOUSAND dollars!!!

[genek]

Based on that old AR2x/2ax brochure and the description in the timeline, I'm speculating that the original 1966 2x used the same cloth surround woofer and 2kHz crossover as the 2 and 2a with the 3.5" driver that was also the 2ax midrange, and that the 1970 update dropped the crossover to the same 1.4kHz as the later 2ax and used a foam woofer and the same tweeter as the 4x. If this is the case, the easiest (and cheapest) "quick fix" would be to bolt in a plywood panel and a 2ax mid with no crossover change, and that would get the speakers working in an authentic AR configuration with no change to the crossover or cabinet while you hunt for original 2 tweeters if you still want to put the crossfire housing back in eventually.

[Steve F]

.... and that the 1970 update dropped the crossover to the same 1.4kHz as the later 2ax .....

For whatever reason, the 'new' 2x used the same 1200 Hz x-o as the 4x, not the 1400 Hz x-o of the new 2ax. Remember, the 'new' 2x was crossing over to the 2 1/2" driver (as did the 4x), while the 'new' 2ax was crossing over to the 3 1/2" driver. Slightly different driver characteristics apparently dictated slightly different x-o points. I asked Roy Allison about this in a letter. He confirmed the 2x's 1200 x-o, but said the difference between 1200 and 1400 was "not significant."

But for historical accuracy, the 'new' 2x x-o was 1200 Hz.

Steve F.

[genek]

Thanks Steve. I think we've figured out more about the 2x in this thread than we ever knew before.

[RoyC]

Millersound says they can't get the correct cone for these tweeters.

I'll be watching the auctions for used components.

Ken,

I've located original drivers...sent you a PM.

Roy

[dxho]

Millersound says they can't get the correct cone for these tweeters.

I'll be watching the auctions for used components.

Thanks to Roy C, I replaced the blown units with another set of used ones.

However, I've found a company that manufactures cones, oval and round, down to 2". I don't know if they sell retail, but at least the cones are being made: http://www.loudspeak...com/index.html. If they don't stock it, they'll make it (for a fee :-))