Add Supertweeter to the AR-3a

[Guest]

Any members have tried to add a supertweeter such as Tannoy ST-100 to the AR-3a for high frequency extension? Any thoughts?

[Guest]

If you are not satisfied with the top end performance of the stock AR tweeter, the real answer is to replace it with a higher quality modern unit rather than trying to graft on a "supertweeter". This is a band-aid approach to the problem, the more appropriate “cure” is actually cheaper and easier.

Despite the AR literature claims of 20K+ top end response, the AR 3/4" paper and cloth domes drop off quite a bit beyond 17-18K. The older 1st generation tweeters [1.25" resin coated cloth] have very low overall output and are dead above 13K. A decent modern 1" soft dome will have good top end extension to 20K and beyond, as well as more detail and smoother overall response. There are several appropriate replacements that cost as little as $25-$35, and will be a huge improvement over the stock tweeters. Which one to choose simply depends on how "hot" or "mellow" you want the top end. Mounting standard 4" diameter faceplate tweeters is now a bit easier as we have finally found someone to machine up a batch of adapter plates.

Why not a modern 3/4" dome tweeter? Full 1” domes are available in many more “flavors”, and provide considerably better power handling. AR dropped to a 3/4" dome simply because their material and design limitations of the day made it difficult to get any output above 15K from a 1” dome. Today that is not really an issue.

[Guest]

I remember the Micro Acoustics tweeter ( electrostats ) box that some put on top of there AR3's. Outside of that any good tweeter like Dynaudio, Focal, Vifa among others would be fine. Just be sure to match efficency of the other drivers. Also be sure the crossover point is within the range of the AR3's.

Let us know how it turns out!

[tysontom]

"Despite the AR literature claims of 20K+ top end response, the AR 3/4" paper and cloth domes drop off quite a bit beyond 17-18K. The older 1st generation tweeters have very low overall output and are dead above 13K. A decent modern 1" soft dome will have good top end extension to 20K and beyond, as well as more detail and smoother overall response..."

AR never "claimed" 20K+ top-end response, but they objectively demonstrated the response of the tweeters measured in anechoic chambers. Both the AR-3's 1-3/8-inch tweeter -- the one you say is dead above 13K -- and the 3/4-inch version used in the AR-3a are capable of response well in excess of 20kHz. measured separately. Perhaps you were referring to the AR-1's 8-inch tweeter which did, indeed, have little above 13 or 14 Khz. In fact, the AR-3's tweeter is actually rising slightly at 20kHz. when taken on axis, and would have response out to 25 kHz. or so before falling off. The AR-3a 3/4-inch tweeter has response out to beyond 25 kHz. when measured separately and on-axis.

What I think you are missing is that the AR-3/3a system frequency response, when comparing the tweeter's output to that of the midrange, is down slightly at the highest frequencies. It is not a deficiency in the tweeter; it is a lack of efficiency in those drivers when compared to the midrange and woofer. This reduced output of the tweeters caused both the AR-3 and the AR-3a to sound reticent compared to some modern speakers with their high-output on-axis response. However, due to the superior off-axis response and smoothness of both the AR-3 and AR-3a, the acoustic-power response of either is better than the majority of the newer speakers on the market. What this means is that, well back into a reverberant listening environment (far field), the AR-3 or AR-3a gets more of its high-frequency output into the room than a speaker with a newer tweeter that may sound bright on axis in the near field, but is significantly down in off-axis response and smoothness. This superior acoustic-power response is largely responsible for the illusion of smoothness and natural-sound characteristics indigenous to these AR speakers.

"AR dropped to a 3/4" dome simply because their material and design limitations of the day made it difficult to get any output above 15K from a 1” dome."

AR introduced the 3/4-inch dome tweeter in the AR-3a to improve dispersion, and thus acoustic-power response, of the speaker when compared to the AR-3. The material in the AR-3a tweeter -- treated paper -- was actually less exotic than in the AR-3 tweeter, a phenolic dome. Once again, either tweeter could respond on axis, without falling off, to beyond 20 kHz. when measured anechoically.

"A decent modern 1" soft dome will have good top end extension to 20K and beyond, as well as more detail and smoother overall response. There are several appropriate replacements that cost as little as $25-$35, and will be a huge improvement over the stock tweeters...."

A decent modern 1-inch soft dome will improve the AR-3 or AR-3a only in efficiency, or in driver matching and power-handling ability. Taken anechoically, and in terms of quality -- both on-axis and off-axis -- the newer stuff is probably not as good as the original designs, certainly no better. I don't think you could find any of the newer crop of tweeters that are actually smoother in response than either of the earlier AR designs, if the early AR's are working as originally designed. You can find brighter-sounding tweeters, but that does not make them better. There are no abberations or anomolies in the response of either the AR-3 or AR-3a tweeters, but those tweeters have nowhere near the efficienty or power-handling capability of the new stuff.

--Tom Tyson

[ar_pro]

I've noticed the same characteristic of AR3a tweeters that Tom mentions...I've also experimented with a variety of "modern" tweeters (vifa, seas, JVC ribbon), and found the original AR driver to be a better overall match than the others. Strictly speaking, the power-handling capability of the tweeter should not be a real-world problem, unless you're trying to use the loudspeaker as a sound-reinforcement or "special-effects" speaker. With an adequate amplifier, the speaker should produce sufficient output in most people's listening rooms...otherwise, a pair of Altec A-7s might be a better choice for volume!

Another "far-field" aspect of AR design can be found in the AR-9...the low-end response is SIGNIFICANTLY different from 15 feet away...what sounds like a weak bass response completely fills out at a distance, putting most sub-woofers to shame!