AR-3 Power Handling

[ninohernes]

I believe that we have discussed this before, but I just want to be sure that I am safe. I have upgraded the amplifier on my AR-3's from 50 watts per channel to 200 watts per channel. It is an Adcom GFA-5400, so the power is very very clean. The reason I wanted the increased power is so the amplifier stays in class A operation longer.

My AR-3's have the original alnico magnets. They have also been serviced by Bill Miller. The tweeters and midrange are also the original cloth dome, alnico magnet models. I am considering replacing them with newer 3a mid and tweeters from layne audio, to increase power handling.

[tysontom]

>I believe that we have discussed this before, but I just want

>to be sure that I am safe. I have upgraded the amplifier on my

>AR-3's from 50 watts per channel to 200 watts per channel. It

>is an Adcom GFA-5400, so the power is very very clean. The

>reason I wanted the increased power is so the amplifier stays

>in class A operation longer.

>My AR-3's have the original alnico magnets. They have also

>been serviced by Bill Miller. The tweeters and midrange are

>also the original cloth dome, alnico magnet models. I am

>considering replacing them with newer 3a mid and tweeters from

>layne audio, to increase power handling.

Joe,

Since the peak-to-average ratio of most music is so high, a 200-watt-per-channel amplifier should never be a problem with an AR-3 so long as the amp was not clipping, and you were not using test signals or certain types of music that concentrate a large percentage of power into the midrange and treble. Hitting peaks of 200 watts or more on "music" might not have average power of more than 2 or 3 watts, if that. Furthermore, you would probably clip a 200-watt amplifier before you would cause the AR-3 to overload as it is capable of handling more short-term power than that. Incidentally, what service was done to these speakers? Was anything modified or changed?

That said, however, you are dealing with forty-year-old instruments, and they are more fragile and susceptible to damage than when new. You are taking a risk of damaging these older speakers, of course, if you play them at 200-watt peak levels.

By the way, you can't just change the AR-3 drivers with AR-3a drivers without completely changing out the crossover. You basically change the AR-3 to an AR-3a, an option that AR offered for many years to upgrade owners of AR-3s. There was a "modified" AR-3a 1-1/2-inch midrange driver that was used as a replacement part for AR-3s after AR could no longer supply the 2-inch driver, but even this driver required a crossover modification, and the driver itself was slightly different from the standard AR-3a midrange.

--Tom Tyson

[ninohernes]

>Incidentally,

>what service was done to these speakers? Was anything

>modified or changed?

>

>--Tom Tyson

>

I had the woofers serviced by Bill Miller, he replaced the surrounds with new ones, he re glued the maisonite rings that attach the surround to the frame, and he installed new spiders. As far as the crossover goes, I built a new AR-3 crossover with new parts from layne audio. They are still AR-3's, I have not changed the crossover to the 3a design. I do however, need new midranges and tweeters in both speakers. They have a nasty buzzing sound. They have had this problem since I got them, I just did not have the time to do something about them before, now I do. Layne Audio only has 3a midrange and tweeters left, thats why I am forced to use them, and I am sure that thier power handling is better. I wouldent have a problem using original working 3 mid and tweeters, but dont the aluminum voice coils tend to fail from metal fatuge at high voltages?

[tysontom]

>

>I had the woofers serviced by Bill Miller, he replaced the

>surrounds with new ones, he re glued the maisonite rings that

>attach the surround to the frame, and he installed new

>spiders. As far as the crossover goes, I built a new AR-3

>crossover with new parts from layne audio. They are still

>AR-3's, I have not changed the crossover to the 3a design. I

>do however, need new midranges and tweeters in both speakers.

>They have a nasty buzzing sound. They have had this problem

>since I got them, I just did not have the time to do something

>about them before, now I do. Layne Audio only has 3a midrange

>and tweeters left, thats why I am forced to use them, and I am

>sure that thier power handling is better. I wouldent have a

>problem using original working 3 mid and tweeters, but dont

>the aluminum voice coils tend to fail from metal fatuge at

>high voltages?

Joe,

Since you are having problems with the drivers themselves, and need to change them, I would be inclined to take the crossover all the way to an AR-11, and use the AR-10/AR-11/AR-3a 1-1/2-inch midrange and the new-style AR-10/AR-11 3/4-inch soft-dome tweeter. Besides, the hard-dome AR-3a-style tweeter is long gone and difficult to find, and about the only way to locate these tweeters anymore is to cannibalize other AR speakers. However, the soft-dome 3/4-inch AR-11 tweeter is more readily available, and OEM replacement drivers are available that are "relatively" close in performance.

You will have to notch out the speaker holes to accomodate the back-wired tabs of the AR-11-style drivers. Later versions ("B") of this tweeter are ferro-fluid cooled. This would give you approximately double the power-handling you had before, with the attendant improvements of a lower woofer-midrange crossover as well as midrange-tweeter (575Hz and 5000Hz vs. 1000Hz and 7500Hz as in the AR-3). If you want to really get "technical," and the AR-3 cabinet is not in great condition, you could do the old radical "MIT" treatment and take off the entire front cabinet molding and grill and make the drivers completely flush with the outside of the speaker baffle. This pretty much eliminates diffraction effects from the cabinet molding, but makes for a very ugly speaker.

--Tom Tyson

[ninohernes]

I would rather keep them 3's or 3a's. Layne Audio has NOS 3a drivers in stock. I think I will go the 3a route.