Ar-3a Tweeter - Carl's & Roy's observations - Potential solution??

[onplane]

In a recent thread both Carl and Roy observed that the original tweeters in the AR-3a have lost sensitivity over time. That is, they no longer put out as much sound as they once did.

If the other two drivers suffered from the same syndrome, this might not be a terrible problem. The mid and woofer, however, don't seem to have suffered this same fate. This leaves the high frequencies coming from the Ar-3a somewhat "muted".

In that same thread genek mentioned: So AR speakers have no settings that "boost" mid or treble; "full" is what you use with an amp and recordings that don't have "excessive" highs …

Genek is correct! There is no “boost” setting and for a very good reason. Back when the AR-3a’s were designed the primary source of music was vinyl records and the vast majority of playback devices had ceramic phono cartridges, which were woefully inadequate in accurately reproducing high frequencies. So in order to sell their recordings, the record companies artificially “enhanced” high frequencies to compensate for this deficiency.

Fast forward 30 years and today with modern digital recording and playback devices no artificial enhancement is required or necessary.

Nevertheless, back in the days … AR knew that the vast majority of their customers had high quality magnetic phono cartridges (AR even sold a very high quality turntable at a very modest price). So AR’s customers needed a way to “cut back” on the high frequencies. Thus, those pots “trimmed” us down from a flat frequency response.

Now, once again fast forward 30 years … today due to gradual degradation in the tweeter, we need a way to “boost” the very high frequencies.

As many of you know I’m a proponent of “cheap solutions”. So I simply by-passed the tweeter pot and got a very, very slight boost. Is this enough of a boost …. Not even close!! Compared to the titanium tweeters in my AR TSW’s, we still have a long, long way to go.

So my next cheap solution for a boost is to use the mid-pot in conjunction with passive bi-amping. You are probably wondering how in heck the mid-pot can provide a boost to the tweeter.

Well, let’s say we adjust the mid-pot to cut back the mid-driver 2 to 3 db (leaving the tweeter pot totally by-passed). Now in order to balance the mid-driver to the woofer we would have to increase the volume control on the amp driving the mid/tweeter. This increase would cause the tweeter to experience more voltage and consequently ... more current.

This “cheap solution” works if those old tweeters will respond to an increase in current. That is, will they indeed put out more sound or is the tweeter's sound output now simply limited by the degradation and all we’d get is more heat in the tweeters.

Carl, and Roy what are your thoughts on the old tweeters. Will they respond reasonably correctly to an increase in current?

Regards,

Jerry

[Carlspeak]

Bi-amping is definitely an option. However, these drivers, I suspect, were somewhat power limited. Over time, high continuous high current load should shorten the life of the tweeter even more. JMHO.

[onplane]

Bi-amping is definitely an option. However, these drivers, I suspect, were somewhat power limited. Over time, high continuous high current load should shorten the life of the tweeter even more. JMHO.

Carl, that is exactly the issue that concerns me. I rarely listen at high power levels. My den is fairly small and most of the time I listen at under 1 watt.

Nevertheless, what happens when you put say 2, 3 and 4 volts to the AR-3a at 10,000Hz? Do you get SPL readings consistently increasing? Or do you see the SPL readings reaching a plateau, which would indicate the tweeters are no long operating in a linear mode.

(Now in testing this, you need to increase the voltage fairly quickly and then turn the voltage back down. A pure sine wave for protracted periods will destroy any speaker.)

Regards,

Jerry