ElectroVoice T35

A Brief Analysis and Comparison

 

A few years ago, (2017) I found a T35(A) on the bay and couldn't resist.  Nothing was done to or with it until I saw another a few months ago, (2022) which I knew didn't work.  That didn't matter as there were two new replacement diaphragm assemblies available in my cache.  After replacing the diaphragm in the non working unit, it was noticed that they tested and sounded different.  The unit A was disassembled and what was noticed was that the diaphragm was a much darker colour.  The voice coils were the same physically and electrically so the difference was attributed to the age of the darker coloured assembly.  This was replaced and the two units are now very close to identical.  See figs 1 and 2

There's two earlier pages on the T35 and T350   HERE   and   HERE

Despite my nostalgic attraction for the T35, the Focal, in my humble opinion, does sound nicer despite its titanium diaphragm.  Some claim that metal diaphragms sound harsh, ergo soft dome tweeters. .However, if efficiency is what one is after, Viva La Horn.

One could ask, "What's the point of this?"  One answer would be "The point is, there is no point'"  However, to the curious mind, there is a point and that is trying to find out why they sound different.

 

 

 

PHOTO 1

The Usual Suspects

 

 

 

 

FIGURE 1

T35A   BLK=1w1m; GREY=THD

 

FIGURE 2

T35B   BLK=1w1m; GREY=THD

 

FIGURE 3

T350   BLK=1w1m; GREY=THD

The T350 appears to have less distortion.  Since they both use the same diaphragm assemblies, the difference may be attributed to the stronger magnet of the T350.  It also has a more linear response above 3khz.

 

FIGURE 4

Tc90   BLK=1w1m; GREY=THD

This shows considerably less THD above 1khz, far better than the venerable T35 and T350.  Keep in mind that these distortions are what makes one prefer one tweeter over another.  If all tweeters had zero percent distortion, they'd most likely all sound the same.

Actually, that is true for any speaker and actually any musical instrument.  It's what makes the sonic difference between an ordinary violin and a Stradivari1

It must be stated that the harmonics produced by the instrument are not distortions; they are the sonic signature of that instrument.  Distortion is anything that is added to the original signal.

A harmonic distortion analyzer measures THD+Noise by filtering out the fundamental; what is left is distortion.

I have yet to try this but deductive thinking says that if a THD analyzer were used to measure THD of a violin note and if the analyzer could detect the fundamental, all the rest would be considered as distortion.  This is as counterintuitive as is seems.

 

 

 

 

The spectrographs here are taken at 3khz, 4khz, 5khz, 7.5khz and 10khz.  While the fundamental is easy to see on the graphs, some of the components of distortion may be difficult to see as some may be aligned with the vertical ordinate, as in figs 13 and 14.

The measured total distortion of the equipment used is as follows.  This includes the mic, CLIO's internal generator, ADCOM GFP-565 pre-amp, ADCOM GFA-535L power amp.  The CLIO generator is rated at 0.008% THD+N.  There is no such spec for the mic but common sense will dictate that it has to be far less than that of the generator.

The THD+N measured from the system as measured into an 8W resistive load is as follows.  .

kHz/%THD+N    3/0.012; 4/0.035; 5/0.022; 7.5/0.023; 10/0.0.018

It was observed that the T35 distortion dropped substantially at 5 khz, to 0.686% from 6.544% at 4khz.  A measurement was then made at 4500hz and the THD was noted as 2.147% and again at 4700hz where is as noted at 0.535%.  The high THD at 7.5khz is possibly due to a resonance.  This frequency is close to an octave higher than 4khz where the distortion rose by 2.2% from that at 3khz and dropped later to 0.686% at 5khz.

The CLIO doesn't measure harmonics above a fundamental of 11khz so a THD figure at a frequency above 12khz showed 0%.  That harmonic would be 24khz and beyond practical human hearing.

THD was measured by feeding the CLIO's output into a Tektronix AA501 distortion analyzer.  The THD thus measured is the sum of the CLIO generator, pre-amp, power amp and the CLIO microphone.  The GFP565 THD is 0.0025%, the GFA535 is less than 0.04% and the CLIO generator is 0.008%.  This sums to 0.0505% THD+N, far less than the measured THD of the tweeters.  Thus, the actuqal THD of the tweeter can be determined by subtracting 0.0505 from the measured THD.

The T35 dates to the sixties and its most notable use outside EV systems was by Klipsch and Associates

Modern tweeters have diaphragms of some soft material, like silk.  Such tweeters were used in such systems as the AR, KLH, to mention two that come to memory.  Later, metals such as aluminum, beryllium, titanium and some alloys thereof were employed as well as exotic ceramics (Accuton)

I recall a tweeter with a diaphragm made of very small diamond particles (dust),  However, the adhesive used to hold these particles together would have some sort of elasticity, thus countering the claim of a rigid diaphragm.  Now, if the diaphragm could be made of a solid sheet of diamond, one might have something.  But, the diaphragm would have to be very thin to keep the weight low.  This may be next to impossible to do with diamond and if it could, would require some delicate grinding resulting in a lot of waste.  Again, even if done, the resultant diaphragm may be very sensitive to breakage.  Interesting thought, though.

 

 

Electro-Voice T-35

 

Focal Tc90 TDXT

 

FIGURE 5  3khz 4.344% THD+N

 

FIGURE 6  3khz  0.191% THD+N

 

FIGURE 7  4khz 6.544% THD+N

 

FIGURE 8  4khz 0.066% THD+N

 

FIGURE 9  5khz 0.686% THD+N

FIGURE 10  5khz 0.076% THD+N

FIGURE 11  7.5khz 3.151% THD+N

 

FIGURE 12  7.5khz 0.116% THD+N

 

FIGURE 13  10khz 0.271% THD+N

The component of distortion can be seen superimposed on the 20khz vertical ordinate

FIGURE 14  10khz 0.093% THD+N

The component of distortion can be seen superimposed on the 20khz vertical ordinate.  Here it is less than half that of the T35

 

The name Stradivarius implies a copy.  The originals, if labelled, are Stradivari, after the maker, Antonio Srtradivari.    Smithsonian Institute

 

Back to the loudspeaker main page