1.25" paper tweeter power handling

[RobHolt]

Thinking about this today, it occurred to me that while these tweeters have a response naturally tuned for use with a single 5/6uf capacitor, such a first order electrical filter will stress the tweeter harder than the more typical 2nd-4th order filters at a higher crossover frequency.

Can anyone comment on the power handling of these small paper tweeters?

Were dealer repairs/swap-outs common, and are there any figures for the actual power handling?

[Steve F]

I have no way of knowing for sure, but I would say that AR did not specify to their design team any official corporate guidelines about how they used their drivers.

As anecdotal evidence to that, I present the AR 4x's 2 1/2" tweeter, which crossed over at a very low 1200 Hz and was the victim of frequent failures due to being stressed so hard. I'd guess (never actually seeing the T-S parameters for that driver) that an x-o frequency of 2000-2500 Hz would have been far more appropriate.

Actually, if you look at later AR lit like the ADD line of 1975-76 (that lit was much more detailed), it tells you the FAR of the various drivers, which you can then compare to the x-o points. For instance, I believe the 1 1/2" dome midrange had a FAR of 400 Hz and it crossed over at 525 Hz.

Conventional loudspeaker design wisdom says that a driver should be crossed over at least an octave above its resonance for optimum PH and low distortion. That means the dome mid should have had at least an 800 Hz x-o.

A "very well-known" speaker company's president did have an official design policy: At least -18 dB at resonance for the tweeter. That means that when you ran the x-o's voltage curves, the tweeter's voltage curve would be at least 18 dB below '0' dB at the tweeter's resonance point.

"Sure, we'll sacrifice a little tiny bit of midrange dispersion--which is so overrated as an audible factor--but we won't blow any tweeters. Customers will appreciate their speakers working and not having to go back for repair a lot more than they'll miss 2 dB 75 degrees off axis at 4000 Hz."

Wise man.

Steve F.

[RobHolt]

Thanks Steve, useful information.

I'm thinking of exhibiting a vintage system at an enthusiasts (non commercial) hi-fi show here in the uk next year.

Naturally visitors tend to like nudging up the volume so I think I'll just conservatively fuse the loudspeaker lines with 1-1.25A.

It's an 8" bass and 1.25" tweeter in a small room so it should still play decently loud given 86dbw sensitivity.