Using Fostex with a helper tweeter, should I cut off the whizzer?

[cotdt]

If I'm using a fullrange driver, a Fostex 207E with a ribbon tweeter, would it sound better if I cut off the whizzer? Has anyone tried?

What about with the Fostex 167E? Should I cut off the whizzer?

[Geek]

I've heard those with a Planet10 phase plug & Enable treatment. - that's the way to go, IMO.

Cheers!

[cotdt]

Originally posted by Geek
I've heard those with a Planet10 phase plug & Enable treatment. - that's the way to go, IMO.

Cheers!

You mean keep the whizzer but add a phase plug? I like the forward sounding midrange of the Fostex, wouldn't Enabling it ruin that?

[Scottmoose]

EnABL doesn't do anything measureable to the basic FR, although it may increase the downward dynamic range.

[chrisb]

Originally posted by cotdt


You mean keep the whizzer but add a phase plug? I like the forward sounding midrange of the Fostex, wouldn't Enabling it ruin that?

I'm currently putting the finishing touches on 2 different cabinet designs of Dave for FE167En & phase plugs, which had originally been prototypes (Demitri and Fonken67). Both had been extensively auditioned before sale to customers who had no idea what the war paint was about.

After well over 1 1/2 yrs of personal experience with 6 models of Fostex drivers in a wide variety of enclosures, I think I can safely assert that the EnABL treatment does not ruin what they do well. If the concept or buzzword of "downward dynamic range" doesn't make sense, think of higher resolution (finer grain structure) of low level inner detail, instrumental textural and spatial clues, and quite simply more overall coherency.

Unless you're a micro-surgeon, circumcising the whizzer is non-reversible. From what I've heard, I'd definitely keep them on the 166/167, but on the 206/207 that's a good question. The ribbon's XO and power handling, as well as the Fostex main driver's dispersion pattern through that pass band should be involved in the calculus. Absent accurate information on the latter, it could be a bit of a gamble

Fostex's published specs are notoriously "imaginative"?, certainly anecdotally not reliable for enclosure and I'd imagine XO design. Has anyone taken measures of any of the larger Fostex drivers with the whizzers removed?

[InclinedPlane]

Chris if you have alot of experience comparing enabled drivers to stock versions I'd very much like to hear what your impressions were. What changes about the driver? What area of the FR is affected?

[OzMikeH]

I've been using FE207E for a while, the whizzer on one of mine had a bad accident.

Before the accident I had Dave's phase plugs (absolutely essential on these drivers)
and a thin strip of open cell light weight low density foam about 10mm square tucked in behind the whizzer I cut a long strip and poked it in behind, cutting the end off and putting the ends together.

I used them with FT17H horn tweeters with a few ohms of series resistance (adjust to taste) and 0.47uF capacitors. What ribbons are you using?

Now that my whizzers are cut off ( the damage made it useless) I'm looking at my options. At this stage I'm thinking enabl treatment and RAAL 140-15D ribbons.

DO NOT cut your whizzers off for an improvement. It means you'll need a ribbon that goes low enough and is efficient enough. That will be quite expensive.

I intend to borrow a SPL meter and signal generator from work soon to work out the approximate slope of the high frequencies of my newly whizzerless FE207E. I'll publish the results here.

[cotdt]

I'm thinking of crossing over at 3kHz with a tweeter. Not sure the Fostex will pair well with a ribbon, maybe a soft dome tweeter would be better. Usually I cross much lower but since this is a full range driver I want to get my entire midrange from it.

[Geek]

A Fostex really shines in the mids. I wouldn't cross below 8K (for my tastes anyway).

Have a listen before adding a tweet. You may not want to add one then.

Cheers!

[chrisb]

Originally posted by InclinedPlane
Chris if you have alot of experience comparing enabled drivers to stock versions I'd very much like to hear what your impressions were. What changes about the driver? What area of the FR is affected?

Since my input into the design process is mostly regarding fabrication and cosmetic details, I guess I'm fortunate in not needing to pay much attention to measured parameters, FR, etc., so my comments will be entirely on subjective. Nor will I be drawn into the technical / objective debate, which if it's still continuing, has been going on long enough that some good measurements may now exist that purport to show what is happening. I'd suspect it won't be revealed by simple FR measures, but I couldn't care less how wrong I am about that - I'll just trust my ears.

In my experience the basic EnABL treatment does relatively little to affect the overall shape of driver's FR, but by whatever mechanism it's working on, the best description I can give is that of improved coherency in terms of time / space.

For example, textures and details of inner voices, ( such as the harmonics of the sympathetic strings on Harry Manx's Mohan Vina, which I've heard live in concert in former church venue) are more distinct. On well recorded material, the spread of soundstage between and outside/behind the axis of the enclosures is more seamless.

Some of the smaller FE series, specifically the FE126 / 127 have some distinct upper midrange resonances (more so on the 126), and a treatment pattern was developed to mitigate this, well before our discovery of Bud's "voodoo mojo" . In the case of these two drivers, the combination is synergistic.

As for phase plugs, in the case of the smaller drivers (FE126/127) , we've found that aside from the great care that needs be taken due to the location of the voice coil wire (it's very close to the dust cap seam and can easily be cut), that more is lost in terms of sensitivity and reduced excursion limit than is gained. OTOH, the whizzer coned drivers are definitely improved with the addition of phase plugs, with or without the EnABL.