Wharfedale Super3-Focal T90 Comparison

This may seem like the classic case of comparing apples and oranges. It was done as a matter of curiosity, hopefully to try to determine why so many like the sound of the venerable Super 3, despite it's antiquity. It has one major disadvantage when compared to today's tweeters, namely the paper cone which has fallen from favour to the concave or convex domed tweeters, be they metal, mylar, soft fabric or ceramic Then there are the ribbons and planars. All have their good points and not so good points despite that most, if not all, claim to be the best. It's kind of reminiscent of a radio station ad I saw on the back of a bus in Toronto, Canada. The ad read, CHUM - number 2 radio. We must be. Everyone else is number one.

Again, this study is not intended to say that the old is better or as good as the new. Hopefully, the reader will understand that the claims made about a lot of things may be given more significance than deserved. In plain Englysshe, there's a lot of hype in advertising. While many of the claims made are true, many are of no significance at audio frequencies. For more on this, I recommend listening to Floyd Toole's lecture on psychoacoustics and loudspeakers. It can be found here It's an hour and fourteen minutes in length so grab your favourite beverage and maybe some cookies, sit back and listen.

Despite that the Super 3 has more harmonic distortion than the T90, that may be the reason why many like its sound. After all, harmonics are what make musical instruments sound different. Without harmonics, a pure tone would sound the same from all instruments negating the difference caused by the percussion of a plucked string vs that of one played with a bow. Played through the same amplifier and speaker, a signal generator with 1% distortion would sound different than one with 0.001% distortion.

Consider the old analogue telephone, the one on the wall or table the one that used to be on the wall or table. Those devices had a frequency response of about a decade, roughly 350hz to 3500hz. Despite that limited response, any musical instrument can be identified if played over the telephone; there are enough harmonics in that passband to make that differentiation. For more on that topic, google analog telephone frequency response

I have two vintage Wharfedale 3-ways in regular use. One is a stereo pair I built (photo 1) and the other is one built by a half-brother in 1957. (Photo 2) Also, there's a pair of Focal 3 ways I built in the early nineties. (photo 2) The corner Wharfies are used for just about anything except classical. That's where the Focals reign supreme. The 1957 system is mono and is used mainly for vintage jazz from the roaring twenties and the dirty thirties. The large cabinet in the lower right corner of photo 2 is two internally separated 7 cu.ft. enclosures, each housing a 15" woofwoof. (That's my dog imitation. Oddball of Kelly's Heroes) The bass unit of the 1957 system (center of photo 2) is 11 cu.ft. It comprises a W15FS, W10 FS/B and a Super 3 with a HSCR3/2 three way crossover. It driven by the original EICO HF-60 pre-amp and HF-30 power amp, both restored. The corner enclosures of photo 1 house the W15 FS, Super 8 and Super3 with the same crossovers and are driven either by the ADCOM amplifiers or a 1954 amplifier, a Herman Hosmer Scott (H.H.Scott) Model 99B, the second of his production, the first being the 99A. The little dark (purple) box on the left table in photo 1 switches the corner Wharfies between the Scott (mono) and the ADCOM (stereo) The 99b can deliver 17 watts into 4 ohms at 1% THD but it's rated at 22 watts with no THD specification given, My tests show that if pushed to 22 watts, THD rises to 5%.

Bias??? Maybe a little as that's difficult to remove. Nostalgia,?? A lot of that.

A detail on the 99B can be seen here More Wharfedale detail can be found in the Wharfedale Pages

'Nuff O Dat

1watt/1 meter and THD ~1% Left, Super 3; Right, T90

These photos may say the proverbial thousand words but they do not tell how they sound nor which one may be preferred by a listener; the test equipment used doesn't have ears. Admittedly, based on the data, per se, these charts do favour the T90 in one area; the T90 does extend well beyond the Super 3s 17khz. Both are quite linear in their passbands above 3khz despite that the T90 does rise about 6dB beyond 8khz. This isn't perceived as a problem as most ears lose sensitivity by middle age; the ear's sensitivity falls beyond 8khz under normal conditions by several dB. See Fletcher-Munson explained.

The T90 has an advantage of lower THD, less than 1% above 3khz. The Super 3 has about 1.8% THD between 3khz and 6khz but fares better above 6khz where it falls to about 0.7%; the T90 fares better at around 0.5%. It should be noted that these distortion curves stop at about 12khz and with good reason. The second harmonic at 12khz is 24khz which is beyond the hearing of the average ear.

The Super 3 is about 7dB more sensitive than the T90 above 3khz. The T90 data sheet states a sensitivity of 91.5dB, 1w1m. The Super 3 has a resonance around 3khz but this is below its intended use above 5khz. Some later units were labeled for use above 3khz. In the late seventies, I designed a horn for use above 400hz for the Super 3 which worked astonishingly well. That is described here

Many dislike the sound of metal dome tweeters, claiming they sound harsh. That may be due in part by their efficiency if not being well matched to the sensitivity of the mid-range unit and most likely due to THD. See Figure 3

In the two sets of curves of figures 1 and 2, the Super 3 has much more distortion below 3 khz than the T90 but that is of little consequence as both units are intended for use above 4khz.

The rapid drop in response of the Super 3 below about 3500hz is due to doublet action, that phenomenon that occurs when the wavelength approaches the diameter of the baffle. Here, the Super 3 is in the open, no baffle. Its diameter is 3.625" corresponding to a wavelength of 3754hz, just where the graph falls. The T90 is closed back, hence no doublet action. It's response falls mainly due to the small 1" diameter of the diaphragm and partly due to insufficient volume behind the diaphragm creating excessive load at lower frequencies.

A listening test hasn't been done due partly to possible bias on my part but mainly to my 79 year old ears which can't hear beyond 11khz at levels below 85dB.

FIGURE 1

FIGURE 2