Truextent diaphragms measurements

[pos]

Here is a set of measurements I made of the Truextent Be4016 beryllium dipahragn (16ohm version) in a 2450SL core (1.5") on the rectangular 90x50 PT waveguide (PT-F95HF).
For comparison purpose the measurements also include other JBL OEM diaphragms.

All measurements were taken under the exact same conditions:

- dayton mic calibrated by cross spectrum
- mic at ~40cm from the horn mouth (not far enough to get a meaningful response curve, but ok for comparison purpose), exact same position for all measurement
- Studio Projects VTB1 V preamp ("tube blend" turned off)
- creative labs sound card (line level), not calibrated
- holmimpulse software in sweep mode
- Ev dx46 active crossover in digital input mode, no eq or filter except a FIR HP at 600Hz (no influence on phase)
- Ram-audio S4044 power amp set to a very moderate SPL
- 75uf protection capacitor (shall not have much influence on phase above 1.5khz, even for the 8ohms diaphragms)
- PTF-95HF horn (no really usable under 1khz, so only the HF response can really be compared)
- 2450SL core (1.5" coherent wave phasing plug, 4" diaphragm, neodymium motor)

The diaphragms under test are:

- JBL D8R2450SL (2450SL): 8 ohms 4" Titanium diaphragm without ribs but with aquaplas, used in the 2450SL, 2452H-SL, and 475nd
- JBL D8R2450 (2450Ti) : 8 ohms 4" Titanium diaphragm with ribs, used in the 2446H/2450H/2451H
- Truextent Be4016 (2450Be) : 16 ohms 4" Beryllium diaphragm

The 16ohms truextent diaphragm was of course given 3dB more level in the active crossover, so every diaphragm received approximately the same wattage, as is confirmed by the fact that the levels are matched in the low end.

As you will see the measurements do track the ones found in the Truextent white paper quite well:
http://www.audioheritage.org/vbullet...351#post305351


In a second set of measurements, post #4, the 2450Be is compared to a 2435HPL

[pos]

amplitude


phase


noise


THD


2nd harmonic distortion

[pos]

3rd harmonic distortion




impulse comparisons

[pos]

Hereafter is a second set of measurement, taken under very similar condition as the first one, this time comparing the 2450SL with Truextent diaphragm (2450Be) to a not aquaplassed 2435HPL (2435).

Note: it is well known that the 2435 short phasing plug has a "problem" with the PT-F95HF that results in a dip at ~13khz (as well as very poor off axis behavior). This problem does not exists (or to a much lesser extend) on the H9800 and some other horns (the off axis behavior remains bad in the UHF tho, because of the 3 slits phase plug)

amplitude


phase


2nd harmonic distortion


3rd harmonic distortion


impulse

[Mr. Widget]

Cool... any other horns on the horizon?

Widget

[pos]

I have pairs of 2332 and H9800 that I will also try to measure (but probably only with the Be, and not the other diaphragms anymore).
I chose the PT waveguide as it was the most well behaved in the HF, and the most representative of the natural behavior of the driver.
The H9800 will probably be the horn I will use in my final system.

[jw5115]

Any JBL 2" format driver (except 2480,2482) will sound better, smoother , more detailed;
Than any Alum. or Ti. fitted driver PERIOD Field coil versions of the truextent 4" and 3" 2435 dia
are even better. Unless you are committed to a "vintage" sound .
The driver/horn combo must remain the same in your comparisons.
Frequency graphs will show "smoothness" but give no indication of detail,attack and decay,
which are all a part of proper music reproduction
jw5115

[pos]

A little update with a more recent measurement comparing a 2452H and a 2450SL with truextent diaphragm on a PT-F95HF waveguide.

It should be more reliable than the measurements on the first page because the noise/distortion coming from the amp has been minimized to have no impact on the measurement (using an autoformer or a Lpad, can't remember...).
It is the 3rd order harmonic distortion only, as my mic is not good at measuring 2nd order harmonic distortion...

[Mike Caldwell]

Here's a link to Vue Audiotechnik and their info article on using Truextent diaphragms in their latest products.
http://www.vueaudio.com/about/beryllium/

[Champster]

Here's a link to Vue Audiotechnik and their info article on using Truextent diaphragms in their latest products.
http://www.vueaudio.com/about/beryllium/

I had an opportunity to get a personal tour through VUE with Ken Berger, CEO. What a great guy and cool business. I wish I could work there... What great products too. Their DSP systems are killer. They have an isobaric sub with 4 - 18" drivers that I would love to try out at home. They are the only Pro company using Be as far as I know and, based on their growth, it sure looks like that gives them a great competitive advantage over the other guys.