TEST OF JBL 2445JPL Compression Drivers with horns

[♔Chello]

TEST OF JBL 2445JPL Compression Drivers with horns

I got them from my son Arius, and they cost about $900 (plus shipping) on the used market.

The horns mounted on these drivers are not original, and are much larger than these - 47cm x 29cm x 33cm (W x H x D).
They also weigh considerably: 13.8kg without horns (16kg with horns).


I placed them on top of my existing horns, so now each speaker weighs about 90kg, and towers well in the landscape with its 55cm x 155cm x 80cm (W x H x D).

I have not measured them yet, but studied available measurements, which showed that they can play very loud (118dB).

The resistance is unusual - 12 to 16 Ohm.

The frequency range is 500Hz - 20kHz +/- 3dB.
I made a simple crossover filter that cuts at 550Hz with 6dB per octave with a Sidereal capacitor of 18µF (400V).

The unusually high resistance should theoretically make them less effective together with my 8 Ohm horns.


But how do they sound ?

WOW!
Details I had never heard before appeared crystal clear (too clear?) - all instruments got more detail, and especially the double bass and brushes were reproduced as well as I have heard on the best equipment ever.

But 2 things happened that I didn't like:
The bass disappeared !

And human voices became a little shrill; but extremely clear and dynamic.
At moderate volume the voices were unproblematic, but when the volume was increased, the tendency also increased.

It is absolutely wild that these drivers are as detailed far up in the frequency range just like my Fountek NeoPro 5i..!

I got the sound image a little less shrill by pushing the JBLs back a little, and will probably achieve some improvement when I connect the Philips horns, which are disconnected for the occasion.
I am in the process of rebuilding these so that they can be placed inside the main horns, and I will also make new dipoles for these, which is very difficult.

I fixed the bass by adjusting the subwoofer:
Before I installed the JBLs I could barely adjust the volume before it became too loud.

That says a bit about how effective the JBLs are, when I can now adjust it up to 12 o'clock for the bass to be just as powerful, but now the sub range is also much more powerful than before.

This test will be followed up with another one when I have finished making the Philips horns, and I will also make dipoles for the JBLs as an experiment, largely because they have been given quite a harsh treatment and have many ugly marks that will be hidden by the dipoles.

PS:
I've never heard a drum crash so explosively rendered before, and the Pa5X also sounds much more dynamic than before..!


   


   

[♔Chello]

CONTINUED LISTENING TEST

I can't remember experiencing anything like this - I've been listening to these JBLs since I installed them.

I now know what's unique about these:
They highlight the signature of all instruments and human voices in a way I haven't heard before; John Hiatt's voice is highlighted with its special character - this is one of the most difficult human voices to reproduce over audio equipment, because the voice has a tendency to become shrill if everything is not optimal.

The strange thing is that his voice is now not perceived as shrill, but still clearer; it is easier to hear that it is precisely John Hiatt who is singing than it was before.

Another human voice that is extremely difficult to reproduce correctly is Marie Bergman - her "Someone To Watch Over Me" will in most cases become shrill if played loudly.
It does that now too (it does that even with the best speakers), but not in a directly annoying way, because her signature is amplified.
At the same time, all the piano sounds are clearer than before, the drum brushes are absolutely fantastic, and the double bass is as good as ever heard over a pair of huge Tandberg speakers over 40 years ago.

One of my favorite tracks is "You And My Guitar" by John Williamson - it's almost like standing in front of the stage with these JBLs !

Another thing that is quite exceptional is that all details appear clear and distinct even at very low volumes, which is a rare sign of high quality.

My horns that I have designed and built myself sound cleaner, but do not have the same dynamics and authenticity.


I will soon connect the Philips horns, so that they contribute to the Seas fullrange units to give more effect, plus they will pull the perspective down a little, because it is now a little too high due to the placement of the JBLs on top of the main horns.

[♔Chello]

TODAY'S GENIUS

I've been thinking about solutions to solve the problem that my new JBL horns are too powerful compared to my main horns.

I saw the solution when I fell asleep:
The main horns are connected in parallel, which turns 8 Ohm into 4 Ohm.

The JBLs were also connected like this - they are 16 Ohm, but became 8 Ohm in parallel.


The solution was simple:
I connected the minus of one JBL to the plus of the other (connected in series), and then 16 Ohm becomes 32 Ohm.

Most "experts" would have surely designed a power-reducing circuit consisting of different components to achieve the same thing, but I am fundamentally against using any circuit if this can be avoided, and I can do it by doing it the way I have done.

Many will say no, but I am sitting here with proof that this works !!!


Increasing the impedance of speaker as I have done from 16 ohms to 32 ohms also has a great advantage:
When a loudspeaker is connected to an amplifier output, the amplifier provides better control of the speaker motion and the speaker has a flatter frequency response if the output impedance of the amplifier is a lot lower than the impedance of the speaker. 

This is most often specified as the “amplifier damping factor” into 8 ohms, rather than the actual amplifier output impedance. If the amplifier has a damping factor of 250, the output impedance is 8 ohms divided by 250, or 0.032 ohms. With such a low output impedance, the frequency response of the voltage supplied to the speaker is very flat and the amplifier maintains good control over the cone motion at low frequencies.


Now there is significantly more pressure on the main horns and the sub-bass, and the tendency for shrill human voices is non-existent.
NON-EXISTING..!

I didn't have the wildest imagination that this could work as well as it does.

Finding some compressor-driven horns that have the same signature as my others would normally have been very difficult; in fact almost impossible.

Talk about luck.

And the system can still be improved by making dipoles for the JBL and Philips horns, which will be the next and final work.


   

[♔Chello]

Still listening test

I have now listened through all my 350 reference tracks, and can establish some absolutely outstanding:

Tracks that were previously pronounced stereo, this is no longer - everything is placed between the speakers in a newly discovered perspective ..!

Now all tracks have a certain perspective; Also those who did not have this before.
Scary.

The general (actual) sound quality is also clearly revealed much more than before.

I don't have speakers in front of me anymore, but a scene, where I can see where the individual musician is located (to some extent).


Moreover, something has arisen when I watch movies:
Several times I experience sounds next to me or behind me, and my equipment is not set up as surround ..!

It can't be better ..?
These JBLs are insane !!!

[♔Chello]

I have obviously been away from theoretical calculations of speakers for too long..?

Now I know why the JBLs sounded a bit aggressive on human voices:
The first setup was connected in parallel, which halved the resistance, which I assumed was 16 Ohm.
The second setup was clearly better, which was connected in series, which doubled the resistance, which based on the assumed impedance should have been 32 Ohm.

Along the way, I imagined that the crossover frequency had been somewhat higher than the theoretical one, and made a measurement:
This showed only 6.6 Ohm!

This means that the first setup gave a crossover at about 1400Hz, and the next at 700Hz.
When I calculated a new value for the capacitor based on the measured resistance and took into account that this was doubled as a result of the series connection, I ended up with a little more than doubling the value (40µF), and the crossover frequency was then about 300Hz at just over 13 Ohm load (series connection).

This sounds MUCH better - now all aggressive tendencies are gone. 

I also have some strange experiences that some of the sound sometimes comes from the side behind me, and that all recordings are now pleasant to listen to - even those that were bad before - all have a clear perspective, completely without negative stereo effects.

And although JBL recommends cut at a minimum of 500Hz with a 2nd order filter, it works great at 300Hz and a 1st order filter.


It is very strange that my measurement shows only 6.6 Ohm, while all found variants of the series are stated at 16 Ohm.

However, I am fairly certain that the actual impedance is somewhat lower than what I measured, because my ears perceive the crossover frequency as higher than 300; more around 500.

This is in any case far above the expected and hoped-for result, and I can finally put the finishing touches on the work by making the dipole membranes on the outside of the horns.

[✪welsh wizard]

You could make these for people to experience the sound....

[♔Chello]

You could make these for people  to experience the sound....

✪welsh wizard


Several people have said this, and I have actually made them so that they can be disassembled.

So I can produce them modularly piece by piece, but it would have been a terribly high shipping cost, because they weigh just over 90 kg each complete.

This project has been going on for many years and I have spent an insane amount of man-hours on adjustments, but it has been worth it - a speaker system like this would have cost several $10,000.

I can build them quite cheaply, however, because I have made them so that they can be mass-produced in a simple carpentry workshop.


I recommend everyone to invest in a horn system (not mine..?), because no other system can give such an experience of real sound.