How Does 'PASCALITE' Diaphragm Sound ?

[Mirrophonic Sound System]

In 1987 the 299-16A driver Altec introduced a new diaphragm
called a PASCALITE that was high strength alloy combined with ARAMID FIBER voice coil.

It was claimed to have dramatically lower spurious sub-harmonic components
compared to larger 4"VC (JBL) drivers.

Has anyone done any subjective evaluation of these diaphragms ?
Are they hard to find now due to low production numbers

[Steve Burger]

Bill has them in stock at GPA. According to Jerry Hubbard they test out exactly the same as aluminum but handle 2.5X the power. I can't tell the difference though some claim aluminum is better for high fi.

[Murray Keidge]

Hello,
I would agree with Steve, that the Pascalite diaphragms work very well when compared to the Aluminium diaphragms. I believe that the Aluminium diaphragms are better for Hi-Fi, however, there is very little difference between the two & it really comes down to your personal taste in the end.

For a time, Altec seemed to have a quality control problem with the Pascalite diaphragms in both the 909 & 299 drivers. The Pascalite would "shatter" whilst the voice coil always kept working.

I can assure you that Bill has fixed this problem and I have never had any problems with the diaphragms that he manufactures. I have over 100 Pascalite diaphragms in service, on a daily basis in our concert production department and they work fine.

They are subjected to much more "stress" than if they were used only for Hi-Fi.

Bill still manufactures the Aluminium diaphragms if you want them and they too are excellent quality.

Please call if you need any more information with regard the Pascalite diaphragms.

Murray.

[scott fitlin]

Pascalite vs Aluminum? Pascalite diaphragms sound good, and they can handle more power than Aluminum diaphrgams!

But, for Hi-Fi use aluminum sounds slightly sweeter at the top end. In concert use, at the extremely high levels of ouput, and very high ambient noise level, you probably would not notice it, but for Hi-Fi use aluminum is a better choice. Mind you, its a very slight difference, but one that can be heard at home listening levels.

[Mirrophonic Sound System]

The information I had was based on an Ad in a trade publication
of that date. It showed that the 4" VC titanium JBL had some serious sub-harmonic
distortion products when driven with a "modest" 1W at 15khz.

But comparing it to a 3" VC Altec is a bit like apples & oranges .

[Jim D]

According to Jerry Hubbard, who was the lead designer of the Pascolite project, the small format version (909) tested and sounding absolutely identical to the regular low power alluminum version. I have also found this to be true. I have never A/B ed the larger format ones, but I know they are very similar. As for the subharmonics of the JBL V/S the 299, this is absolutely true. I was at the ALTEC meeting in Los Vegas when this was demonstrated. The 299 was clean throughout the range, only projected the fundimental on a simple sign wave sweep. The JBL produced multiple subharmonics in the identical test, including a 5K subharmonic at 10K that was measured at only 3dB less than the fundimental! While the test was backed up with instruments, the audio was immediately discernable to everyone. Several in the audience had a hard time beleiving it, which resulted in an in depth lookover of the setup, which even they admitted was OK. Made a beleiver out of me. JIM

[Mirrophonic Sound System]

Hi Jim,

Might explain why audiophiles have never taken to JBL's "new improved"
Titanium.

Another disastrous JBL "innovation" . Let's rank it alongside
the "Acoustic Lens", the wooden Difraction horn "chosen by many
recording studios" , and the "amazing stereo image" of the ridiculous PARAGON

And how about all those poor saps at rock concerts listening to JBL
Titaniums cranked up real loud

Who needs a Fuzz Box when you've got JBLs

[joyspring]

Mirrophonic,

Please describe the merits of Altec's `Biflex' and 605-series Duplexes (I have six of these, BTW); no company can claim a perfect record.

And you're forgetting about JBL's many innovations that have appreciably improved the art and science of transducer design. Here are just a couple:

1. Symmetric Field Geometry(tm) - Produces a symmetric flux field in and about the voice coil gap of a ferrite magnet(ic) structure that significantly reduces second- and third- harmonic distortion below that of comparable Alnico magnet drivers WITHOUT the demagnetisation inherent with Alnico. The result is better sound, more consistent performance.

2. Bi-Radial HF horns - These have the even power response and constant directivity that their predecessors from E-V and Altec (Mantaray) possess with one significant difference: much lower cutoff frequency for the same physical size.

And let's not forget that JBL LF drivers were raising the bar so far as power handling, low distortion, maximum sound pressure and reliability throughout the 1970s and 1980s. As recording and playback media S/N ratio and dynamic range improved, their transducers followed while Altec by comparison languished.

And let's also not forget that JBL has some of the best transducer engineers in the business, some of whom are Altec alums. A quick perusal of my Journal of the Audio Engineering Society library yields many significant articles from JBL engineers Keele, Gander, Margolis, Eargle, Ureda et al.

Yes, JBL made some awful products. So did Altec. Every audio company has...big deal. Altec had some brilliant products and innovations. JBL also has and still does :-/ Get over it.

BobR

[Todd W. White]

I hate to make a stink, but....

The JBL bi-radial horns do NOT have the same constant directivity factor of the Altec MANTARAY horns!

The MANTARAY design has THE MOST uniform dispersion control over their rated bandwidth of ANY of the c-d horns made by anyone. Period.

In fact, one of the things that made the Mantaray's hard to get accepted by the acoustical consultants WAS their directivity - they liked using the JBL's and EV's because they were LESS accurate...sooooo - when they did a cluster design, they could put in a bunch of bi-radials, for example, loverlap the living daylights out of them, and be assured of "adequate" coverage.

Not needed with the MANTARAY horns - overlapping is minimal, and the cutoff is precise. Thus, it took more work to design a system with PRECISE coverage horns than with ones which were less accurate.

Seems it is easier to cover yourself as a designer when you don't have such precise edges on the sound coverage patterns...

At any rate, the consultants, for the most part, didn't like the MANTARAY's, mostly because they just didn't know how to use them. We used to joke that they SAID they wanted a TRUE constant-directivity horn, but when Altec actually GAVE THEM ONE, they complained that it was too accurate.

Go figure...

[joyspring]

Todd,

I will agree that the MantaRay horns do have superior directivity control over the Bi-Radial but not by much -- in fact, the difference in DI, power response, etc. between both CD horns and their predecessors (radial, multicell, exponential, etc.) easily swamps any significant difference between the two CD designs. To sum, both designs are excellent and are a vast improvement over radials, multicells and other horns that have rising DI vs. frequency.

However, precision coverage was only one aspect of sound system design; space efficiency and even response near crossover is also very important as well.

In the AES paper "The Manta-Ray Horn" (Henricksen, Ureda. J. Audio Eng Soc., vol 26, p. 632, 1978 Sept.), Henricksen and Ureda state that the horn is "designed with low-frequency response as a secondary consideration". Unfortunately, this would be an important consideration for system designers.

For the same physical volume that each Manta-Ray consumed, the Bi-Radials provided a much lower cutoff frequency giving the sound system designer far more latitude in selecting crossover frequency (and ensuring even response below crossover) and controlling coverage in the difficult-to-control lower mid-band, facilitating an easier transition from the cone to horn/compression drivers in both amplitude response and directivity.

At least, this is what associates who've worked in sound reinforcement during the 1980s have told me. But what do I know? I've worked in the recording industry and my only real sound reinforcement experience was as a musician ;-)

I'll leave you with this excerpt (with my editorial comments in italics):

"16.6.6 Biradial Horns. Keele (designer of the first CD horn), by this time, had settled into the engineering department at JBL (the Evil Empire), which also needed a constant-directivity horn concept. He took the Manta-Ray concept and his own work a step further. A problem with discrete flanges (i.e. - the Manta-Ray) is that the abrupt change in angle can cause diffraction disturbances in the response. The BiRadial uses continuously varying flanges in both directions, ending in a continuous horn. The vertical diffration concept was used, except that an exponential expansion was fitted into the design, and a vertical and horizontal radial bell (thus biradial) was used. The biradials shown in Fig. 16-76 have both good directivity control and low frequency loading. They are fabricated from cast aluminum (throat section) and molded fiberglass (bell section) and fit 2-inch exit drivers."

That, BTW, was authored by Clifford Henricksen (the same Henricksen that designed the Manta-Ray) in "Electroacoustic Devices: Loudspeakers, Enclosures, and Headphones", Handbook for Sound Engineers, Howard W. Sams & Co., 1987, pp. 552-553.

Good engineers will always acknowledge improvements, even when they occur over their own designs.

BobR