Horn/Driver Comparisons

[Mr. Widget]

As most all of you know Zilch has been working on a variety of 2-way designs using a variety of JBL compression drivers and CD horns for his "Quick and Dirty 4430" thread. Today we spent a few hours comparing five CD horns and six different JBL compression drivers. We set them up and took quasi-anechoic measurements with Clio.

We used the following horns:

1) PT-F1010 - 100° X 100°, 6.5" X 12"
2) PT-H1010, 100° X 100°, 12" square
3) PT-F64, 60° X 40°, 6.5" X 12"
4) SF-95, (Sound Factor), 90° X 50°, 1" thread-on throat, 6.5" X 12"
5) P-Audio PH-230, 100° X 100°, 2342 Clone, 1" bolt-on throat, 9" Square

And we used these drivers:

1) 435Be 3" Beryllium Diaphragm 1.5" exit from JBL Consumer
2) 2435HPL 3" Beryllium Diaphragm 1.5" exit
3) 2431 3" Aluminum Diaphragm 1.5" exit
4) 2418 1.75" Titanium Diaphragm 1" exit
5) 2426 1.75" Titanium Diaphragm 1" exit
6) LE85 1.75" Aluminum Diaphragm 1" exit

[Mr. Widget]

Before we began our horn comparisons we wanted to explore the low end capabilities of the 2431 and 2435HPL compression drivers with their small back cap and compare them to the 435Be with it's large back cap. To do this we mounted the three drivers on a 500Hz 1.5" throat horn I have that is about the size of an Altec 511. It is not a CD horn so it's on-axis response is reasonably flat without compensation.

Here we see that the low end performance of the 435Be, 2435HPL, and 2431 are all quite good. It would seem that the larger back cap isn't necessary for performance below 1000Hz. We did not do any listening tests or power tests measuring distortion, but the initial measurements were surprisingly encouraging. I am not sure if it is due to the back cap or other tweaks, but the 435Be did exhibit, albeit by a small margin, the flattest overall response of the three.

[Mr. Widget]

Next we tried the 2431 on both the PT-F1010 and PT-H1010 horns. We have included the plot of the 2431 on the large horn to show how the LF limiting is due to these smaller horns. Also since these are CD horns they would need passive or active EQ to compensate for the HF fall off.

[Mr. Widget]

Next we tried the 2435HPL on the PT-F1010 horn. We left the 2431 plot up for comparison. We also plotted a second 2435HPL. This one (Shown in Green) seems to be defective... perhaps why it was available inexpensively on eBay?

[Mr. Widget]

Next we tried 4 different 2431 drivers on the PT-H1010. Zilch has one pair (Green and Purple) that were purchased about a year ago, and another pair (Red and Blue) that were purchased recently. Each pair seems closely matched... but the two pairs do seem a bit different from each other. Perhaps there was a slight design change between the two runs?

[Mr. Widget]

Next we tried the PT-F64. Here we have kept the plot of the 2431 on the PT-H1010 for comparison with the plots of the 2431 and 2435HPL both on the PT-F64. This horn is much deeper that the other in this test and while stile considered a CD horn, it obviously need far less compensation... at least below 9KHz.

[Mr. Widget]

Before we began our horn comparisons we wanted to explore the low end capabilities of the 2431 and 2435HPL compression drivers with their small back cap and compare them to the 435Be with it's large back cap. To do this we mounted the three drivers on a 500Hz 1.5" throat horn I have that is about the size of an Altec 511. It is not a CD horn so it's on-axis response is reasonably flat without compensation.

Here we see that the low end performance of the 435Be, 2435HPL, and 2431 are all quite good. It would seem that the larger back cap isn't necessary for performance below 1000Hz. We did not do any listening tests or power tests measuring distortion, but the initial measurements were surprisingly encouraging. I am not sure if it is due to the back cap or other tweaks, but the 435Be did exhibit, albeit by a small margin, the flattest overall response of the three.

I reposted this post to bring us back to the topic of the low end performance of the 2431, 2435, and 435Be.

Widget

[Mr. Widget]

Here is a post of the 435Be back on the large horn. We drove the driver to a fairly loud sounding 95dB (we had our fingers in out ears as the stepped sine wave screeched) to measure the second and third harmonic distortion levels. The distortion levels were raised by 30dB. The second harmonic is at a fairly low level, and the third is 60dB down through the usable portion of the spectrum.

[Mr. Widget]

Here is a plot of Zilch's "better" 2435HPL. We are not sure what the specs are for distortion, but this unit has significantly more third harmonic distortion that the 435Be.

[Mr. Widget]

Here is a plot of the 2431. Again we aren't sure if this is within specs, but the distortion is significantly greater than the 435Be. Hopefully we can get them tested by JBL and then we can measure them again to see if these plots are indicative of their performance. When we measured this driver we heard a noticeable buzzing sound as the frequency swept through the lower frequencies.

[Guido]

Here is a plot of Zilch's "better" 2435HPL. We are not sure what the specs are for distortion, but this unit has significantly more third harmonic distortion that the 435Be.

Widget and Zilch,

Was this measurement redone with the refurbished 2435? I was looking for this info but couldn't find it.

[Too Tall clist]

Here is a plot of Zilch's "better" 2435HPL. We are not sure what the specs are for distortion, but this unit has significantly more third harmonic distortion than the 435Be.

Hi,
I just started working on a passive xover with a 2435HPL.
I can’t give you any useful measurements right now because the 1.5” throat driver was mounted on a 2” throat horn. So right now someone is looking for some 1.5” throat horns that will fit in the cabinet.

I did have some question pertaining to the driver itself.
I have heard some outrageous quotes for what the driver will sell for.
If you go here you will see a retail replacement cost of the diaphragm (I presume) of $756.00

http://www.jblproservice.com/pdf/Tra...rts%20List.pdf

All this because of the use of Beryllium.

Note on the same spreadsheet the 2431 diaphragm retails at $138.00.

I have seen several 2435HPL on ebay for around $240 each.
About 1/3rd the cost of its diaphragm?

So I wanted to know if there were after-market diaphragms made from something less expensive like aluminum? And that is why they were going so cheap on ebay?

Considering the cost of the diaphragm it would seem fool hardy to use these for anything less lucrative then corporate gigs or something else that pays as well.
Frying one in a 150 seat night club in the middle of a 80s rock tune might cause you to be clinically depressed.
The Talking Heads are important, but not THAT important.

I decided to attach a picture (If I can figure out how…). Note again it is mounted on a 2” throat Selenium HMA4750-SLF 90x40 horn.
No throat adapter was used, which is why the high frequencies above 6.7kHz are obliterated.

The frequency response below that should be valid.

For measurement background-
Measurement program is Praxis with a Praxis mic.
The horn was dropped into a wastebasket to point it straight up and a mic 1 meter above the mouth pointing down. So there was no baffle, just the horn itself.
The IR was gated at about 10ms to remove the ceiling bounce. The window was about 7ms long (I think).

If you look at the top of the plot it says 9.03dB offset.
Praxis measures referenced to 1-volt. To find 1-watt 2.83V into 8ohm you add 9.03dB
And this is an 8-ohm nominal driver with everything in its useful range at 6ohms (except for resonant peaks.)

So the frequency SPL is correct for the horn used.

If I figure it out I will post the z plot too.

I hope someone can help me out with the after-market diaphragm question.
Thanks.

[whgeiger]

To All,



Only a PWT load will provide a rational means for measuring driver performance. Otherwise, what is being measured is a combined driver/horn response dominated by horn artifacts at the frequency extremes; i.e.:



1) When the test signal frequency approaches horn [fc], the driver becomes un-loaded while at the same time the horn mouth becomes acoustically small and the intensity of the resulting back-waves that impinge on the diaphragm is increased. This leads to erratic diaphragm excursions even though the drive signal may be relatively small.



2) On axis response and power response are different animals. In the former, beaming of horn output hides roll-off at the upper end; so, here again horn influence is masking driver capabilities.



Regards,



WHG

[Mr. Widget]

True.

However what we were attempting to do was compare the 435Be with it's large back cap with these similar drivers. We chose this particular horn because it has a [fc] below 500Hz which is well below the frequency range we were interested in. I would agree that a plane wave tube would be ideal, but since we don't have one, and a home brewed PWT would only add to the questions, I am quite happy with the results of our comparisons. Once we have verified drivers to test we should be able to come to some reasonable conclusions. These will be relative conclusions between these drivers, not idealized conclusions.

Widget

[B&KMan]

Dear Mr. Widget and zilch,


Superbe jobs and very thanks for all precous times test for evaluation driver and horn...

the manys responses test and THD curve is expose many critical information...

thanks again...




for more deterministic test it is interesting to expose test response in many angle ??? ( 0°, 15° and 30° )

this test is expose a important aspect of quality of driver...

2--- it is interesting to expose more parameters experiences: rectangle pulse, distance mic etc...


Thanks for all big works and give at this communauty...