IN CHASING FOR THE FINAL EXTRA BOOST IN THE TOP FREQUENCY RANGE

[♔Chello]

IN CHASING FOR THE FINAL EXTRA BOOST IN THE TOP FREQUENCY RANGE

Almost all tweeters have a "dip" in the frequency curve around 17kHz.

Although mine doesn't have this dip, the area around 2kHz will always dominate the soundscape, simply because our hearing is most sensitive in this range.

This difference in sensitivity is significant, and often results in the very lowest and very highest frequencies having a dip of up to 20-30dB..! compared to the rest of the frequency range, even if the frequency curve had been straight for the units - our hearing is not straight.

In addition, this sensitivity is highly influenced by dB level; the lower the dB, the weaker the outer edges of the frequency range are perceived.

I made a subwoofer many years ago that manages to reproduce the very lowest frequencies at a realistic level by using several power amplifiers, a separate preamplifier and a 31-band graphic equalizer that only affects the sub-amplifiers.

I could have made a similar system for the upper frequency range, but this requires additional amplifiers and additional preouts.


So how to achieve the same thing in another way ?
I have ordered a pair of bullet horn tweeters, which are compression driver-based, and specifically designed for use in the highest frequency range.

These are also only 4 Ohm, which results in 2 Ohm when connected in parallel with existing units, which is the standard connection method.

Low Ohm provide a higher efficiency, as the amplifier follows Ohm's Law and tries to deliver double the power.
One must therefore be very aware that the power tolerance can be exceeded.

NOTE:
2 Ohm is a very dangerous resistance for most amplifiers, but completely unproblematic for the one I have, and anyway my speaker system has a total impedance of just over 20 Ohm, which provides very good working conditions for the amplifier.
This can handle loads down to 1 Ohm without any problems, but everything sounds better at 20 Ohm loads.

This means that I can set a very high crossover frequency, and achieve a boost in the 10-20kHz range that would otherwise be impossible.

Alternatively, I can reduce the units' output greatly by connecting them in series, thereby doubling the resistance from 4 to 8 Ohm.

I'm trying 2 Ohm first, and have ordered the appropriate capacitors to hit the ideal frequency range, and hopefully achieve a sound pressure that matches the existing units.


I expect to receive the new units tonight/tomorrow morning, and will then first of all measure them to see what the impedance curve shows.


   

[♔Chello]

Bullet tweeters received.

Very unusual, it came with a capacitor of reasonable quality, but it is 2.2µF, which gives a crossover at 18kHz with a 4 Ohm load; far too high..?
I used a better capacitor of 3µF, which gives a crossover at 13kHz.

Very fine CNC work at its best - these could have been mounted in very expensive speakers.
The push-type connections are good, but only very thin cables will fit.

My measurement is as expected and hoped - it shows a steadily rising curve from 10kHz and up.

   


A COMPLETELY straight line is of course desirable, but then the price also increases dramatically.
I paid under 70 GBP including taxes, which is extremely cheap - I got them for half price.


So - how do they sound..?
I used my 3µF capacitors, which should be a good starting point - 13kHz.
I placed them on top of the Yamaha HS-5 monitors, which gives a good position for the best perspective.

WOW..?
One thing that is impossible to avoid noticing is that the perspective has now moved upwards.
The next thing is that the level of detail has increased in the upper frequencies, and brushes and the like are more delicately reproduced.

Negative:
Human voices are given a slight tendency to too pronounced S`s - very slight, but it is there.
Certain instruments such as electric guitars and acoustic pianos become a little too sharp; but again very little.

My chosen crossover at 13kHz turns out to be a bit too low, which is actually very good, because it can look as if the manufacturer's chosen frequency of 18kHz can work.

When I connect in parallel, the resistance is halved from 4 Ohm to 2 Ohm.
However, this is not exactly what happens, because:
The impedance drop will only occur in the frequency range covered by the tweeter. The impedance will still remain at 4 ohms below the tweeters crossover frequency.

The impedance will therefore only be 2 Ohm in the tweeter's operating range, which is determined by the capacitor.


These bullet horns are undoubtedly very good, and remind me of the experience I had in 1987 with bullet horns.
They also prove something I have claimed many times; that perspective can be controlled effectively with the highest frequencies.

So by placing them a little lower and choosing a lower µF, I will definitely achieve what I was trying to achieve.

I have several good tweeters lying around such as Fountek NeoPro 5i, Scanspeak Illuminator and Philips (Bang & Olufsen), but these Chinese bullet horns are able to outmaneuver them all.

They also have a signature that is very similar to my existing speakers, which is beyond all expectations.
Hallelujah.