[floobydust]

 Ed,

 All of my topics are worthwhile....

 Regards, KM

[Ed Schilling]

Kevin,
You are correct, sorry! My bad.

I will be interested to find out how they measure. When I saw your first post I did not realize "very sparse specifications" meant "none that are useful"! It's still kind of mind boggling that there are none or that they are so hard to find.

Ed

[floobydust]

 Come on Ed, there were several useful specifications... 16 ohms and 15W rated power... sensitivity of 95dB is nice to know and you can measure free air resonance yourself and calculate cone area easily but beyond this... very sparse to start with. I'll be interested to see what your measurements show. Time will tell with these.... we'll see.

 Regards, KM

[Ed Schilling]

Kevin,
You're a funny guy! If I actually had them I could do full measurements But that will be a while I'm sure.


I want MMs and QTS. The 16 Ohm makes the 95db  "not exactly the same as if it were 8 ohms".  I swear, from what I see, I can't for the life of me understand why this is supposed to be a "super driver". I've read (now) everything I can find on them and my "BS meter" has not dropped in level and has actually gone up a few notches.

You know, I still have everything needed to build ribbon tweeters up to 48 inches long. And I can run a full set of measurements on them.

If anyone is interested for only 5,000 bucks I'll build you a 30" ribbon super tweeter. A pair will set you back 7,5000. The first one is harder than the second.

I want in on this stupid expensive, can't possibly be worth it, but somebody will buy it (even without specs) market. And I am not joking about the ribbons. I really can produce them. Matter of fact I'll build a planar woofer to go with them for another 5K/pair. I am NOT joking this time. The prices are for the bare drivers only. And BTW....my ribbons are not shielded and will ruin a CRT from 3 feet away but TV is bad for you anyway. All it takes is money and apparently people have plenty. Doesn't a 30" hand built, matched pair of ribbons sound intriguing? Lead time after payment is about 2 months.

Ed

[DaveC113]

Ed,

The guy behind the Feastrex drivers is an older Japanese man, can't speak much english.... He was instructed on how to use a woofer tester at rmaf, and is going to publish measurements soon, from what I've been told.

BTW, I'd take a pair of 30 ft. ribbons... only $75k? 

Dave

[Ed Schilling]

Dave,
Yes, I know. Still mind boggling to me. Isn't there other software? I'm pretty sure "software" is not even needed. Drivers have been measured long before "woofer tester". I used to do it. How can you come up with a sensitivity figure and not  the other measurements?

And please do understand, I really liked what I read about him and his ideas. He even looks like a "nice guy"! I'm sure he is. But nonetheless, to be selling drivers without basic specs is baffling to me. How can they even be "matched pairs"? Didn't someone at some time during the design process measure them? If so, then why not "production pairs"?

Like I said, at this point I am interested and curious....they are the "right size" but still am very  skeptical. There are a LOT of drivers that sound spectacular (Bandor for instance) but that doesn't make them practical in my opinion.

Dave, the ribbons would be 30 INCHES (I fixed it, thanks!) for 7 1/2 thousand. Of course one could buy some BG for much less, but mine will be "hand made" and from what I can tell that should make them worth the cost. I'll use the highest quality,thinest available,  aluminum foil (I have plenty left) for the ribbon BTW. And silver wire to wire it up and your choice of fancy capacitor for the cross over.

I can build it as a true ribbon with xformer or a planar hybrid. I've done both. As a matter of fact if you can come by some of the big AMT diaphragms I can even build you the magnet structures for them. They will be expensive, but hey, again, they are hand made!

Ed

OH yea, I am a older American who doesn't speak much Japanese. Not so sure about the "gentleman" part though.

[floobydust]

 Ed,

 I agree... you would think they would have a more complete set of published specifications, especially in today's age of technology. Still, I look back at what meager specs we had for good drivers like the old KEF B139.... didn't really have much useful data beyond power handling, free air resonance and a recommended enclosure and crossover... and a frequency plot. Yet, the B139 was a huge success in it's day and more detailed specs followed later.

http://www.hifiloudspeakers.info/Anatomy/KEFDocuments/KEFDriversLeaflet/HiFiDriveUnitsp3.html (this is all we had in 1975).

 Anyway... back to the Feastrex. I guess there are many ways to match driver parameters... anything from sensitivity to free air resonance, voice-coil characteristics, response curves... pick some and match em up. One also needs to define what "matching" implies, such as a percentage range for specific parameters, whatever the decision is. Can't tell you how many "matched pairs" of tubes I received over the last few decades that were anything but. Using a tube-tester (even a mutual condunctance type doesn't cut it) and curve tracers are just not that common. I literally have to match a full set of tubes for the SET amps as there is no feedback and you really have to ensure that a stereo pair of ampifiers have the same gain, frequency response, output noise, distortion, sonic character, etc. It's a lot more difficult than most would think.

 I don't know what specifics they (Feastrex) use for matching but I was told that they are provided in matched pairs, call them production pairs if you like. I'm also fine with a 16 ohm impedance (less loss in a cable run)... sensitivity would still be measured with 1-watt at 1-meter... but instead of 2.83 VRMS, you just use 4.00 VRMS. For my 2-watt tube amps, I move a wire underneath to the 16-ohm lug. If you're using a solid-state direct-coupled amplifier, too bad... you lost half your power (and hopefully learned a valuable lesson, tubes are still better  ). But.... I still think these drivers are in a position to make a significant impact in our little audio circle of SD speakers. I think it's worth trying out several enclosure designs to hopefully bring out the best in them.

 Regards, KM


 

[floobydust]

 All, received this from Lotus Group USA (importer for Feastrex in the USA). Hate to cross post but manufacturer supplied specifications and some DIY enclosures for the D5nf driver are shown here.

http://puremusicgroup.com/yabb/YaBB.pl?num=1191708798

 Regards, KM

[Ed Schilling]

Kevin,
Can't argue with anything you said, 30 years ago it would be "situation normal".

I'd point out however that KEF didn't need to supply specs. They gave you the cabinet and crossover the speaker was designed for!  I figure when the Man. says "recommended enclosure" and "recommended crossover type and freq." they know what they are talking about. How could it be possible for anyone to better the factory's recommendation?

Just think how much better your TL would have been if you'd followed their instructions and not built one but a "reflex system" instead?

Kidding of course. And you are right. Whether or not the things really are the cat's meow won't depend on "specs", that's for sure.

Ed

[planet10]

They are not really an OEM company and their drivers are sold primarily for the DIY market.

Most of Fostex's business is selling studio gear to muscicians, diy speakers is just a small part of their market. Fostex is a small subsiduary of Foster which is if not, one of the largest OEMs in the world.

Most of the Fostex recommended enclosures are either bass reflex or TLs (masqerading as horns)

dave

[planet10]

Still, I look back at what meager specs we had for good drivers like the old KEF B139.... 

When i was selling KEF in 1976 i had published specs... fully as comprehensive as you get today, but in a different format. Here is a scan of those same published documents.

http://homepage.mac.com/planet10/TLS/drivers/images/B139small.GIF

dave