Coaxial drivers?

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bbaker6212 said:
"exotic" drivers - Fertins, Phy's, AERs, etc. It's hard to make an educated purchase since you can't find reviews, hear them first ... and day ain't cheap!

To spend this much money you have to hear them, preferrably with your own kit, OR be very well off...

You are only a 20 hr drive (+ 2 hr on the ferry) away. Why not come up? ChrisB & i could show you around...

or take a week & come up the coast...

dave
 
HPotter,

great driver, that Focal Audiom!
looks like a fine job you did 🙂
Let's see how much frequnecy compensation i will need for my 4 18" Beyma GT-200 (2 per channel) but i am positive they will need one. A baffle for 20Hz has about 4 meters width and i want 20 Hz flat!

Brad,
the PHY is well-suited for open baffle, extraordinarily well suited. Reto Luigi Andreoli uses it together with a iny tweeter in a baffle approx 1m x 1m. He charges about $7500 for it and gets it and people having heard it rave about it.
The acquaintant reporting that his 1.5 x 1.5 m baffle does rolls of at 100Hz (but he doesn't notice it subjectively) also uses a PHY. He is ultra happy with it. But he confesses the PHY doesn't have treble and that he does not like spekers having much treble so the speaker and he mate.

THe PHY needs a tweeter, no Q, any body having heard it seconds that. I cannot, i haven't heard it. And due to the colorations my buddy Hartmut reported from differnent speakers using the PHY i have no desire to try it out.

Why? because my Fertin has treble. Not spectacular trebles, but most plausible ones. Just right. I do ot even muse about an additional (super)tweeter.
And it has no coloration, atleast none i sense as non-transparent or find annoying. And it has a shout like any FR driver i heard so far, but it has the tiniest and nicest shout of all. And, it is almost infinitely transparent and has incredible µdynamix.
Then, the thingy to top an alnico magnet is a fieldcoil motor. The fertin has a field coil motor. I listened to several field coil drivers, both vintage and modern. They have a certain magic for sure. They sing like sirens.

No, the Fertin FLB20EX has no hole in its repsonse. If you cut two holes into your living rooms wall and mount two of them into the holes, you won't even need a subwoofer. AS Jean-Michel LeCleac'h reports, they run from 40Hz to 20kHz and sing.

Comparison to my Lowther PM6A, mounted in a backloaded horn: The Fertin has less stress, more transparency, more detail, more tone colours, more tone colour saturation. Before, there were a lot of noises in the music (mainly percussion 🙂 ), now these noises have become tones, having a pitch and a tone colour. For the record, my Lowther was an exceptionally musical sample, i did hear many Lowthers not singing that much. My impression: the frequency response is way smoother and more flat, not as up and down as the Lowther. But i have to measure this yet.
Comparison is a bit unfair as the Lowther did not run in an open baffle. but, no matter what others claim: the Lowther has not enough excursion for safe operation in an open baffle, it has +/- 0.5mm. I did not intend to risk it, i eventually wanted to sell it after test.
What i must report: concerning sonic entirety, smoothness, seductivity, the backloaded Lowther was outperformend by ANY paper cone driver in a preliminary-style open baffle. But the Fertin was far ahead, compared to other drivers in the open baffle. Second best (but too low efficient) was a noname paper cone, 3rd was a Focal 7N303 with tweeter.
wish it wasn't so difficult to find other people with experience with these "exotic" drivers - Fertins, Phy's, AERs, etc. It's hard to make an educated purchase since you can't find reviews, hear them first, and I assume there's no money back gurantee.
If you want to go with underground stuff, you cannot rely on other's reports because there are no others. You ar lucky if you fine one person knowing the name, even more luck to learn from his experiences. But you cannot rely on other person's reports anyway. You can rely on your own judgement. You can try out whether you are compatible with open baffle speakers in general (any paper cone driver and a piece of corrugated card board will do), you can narrow the choice by driver parameter and then you probably end up at one single driver. So did i. It was a thoroughly prepared chain of decisions and choosing the Fertin driver simply was the last decision in the chain. I doubt i will look back.

Before i forget it, you have to build a power supply for the field coils. And ... the Fertin's honour good tube gear. You probably will be condemned to tube amplifiers once you heard it with a good tube amp. 🙂
 
Re: Fertins

Dice, thanks allot for all your input.
I must admit, I like the way you can easily tweek the sound of the driver by varying the coil voltage. That's something you can't do with other standard drivers. I've heard that transmission lines behave very similar to open baffles expecially if you treat cabinet reflections well (ie deflex panels, etc.), but TL's have even better bass. I wonder what the Fertin's sound like in a good TL cab? I bet Planet10 could recommend a gone one - he seems to know allot about TL's.

Btw, which Fertin are you using - the 20EX?

It's hard to believe the PHY is lacking in the highs what with it's built-in Piezo tweeter. I guess they designed it to have low output and a generally mellow/laidback sound.
 
Dice,

The more I read about those Fertins of yours, the more I want them.😉 Just to have a proper perspective and sort of comparison, I'm using currently 2 Triangle 6" drivers (T160 448) in MTM configuration with Raven tweeter in an open baffle. If you familiar with Triangles, how would they compare to Fertins?
As to open baffle, you are right. After trying it once, I would never go back to a closed enclosure.🙂
 
HPotter,

5 years ago i heard the Triangle in a TQWT enclosure, together with a Forstex ring radiator horn tweeter.
Very musical indeed, i could have grown old with that speaker. But it beamed immensely (due to the horn tweeter but also to the wide paper cone). However, it needed a tweeter. The Fertin FLB20EX does not (yes, i had my ears checked lately, i still hear flat up to 17kHz).
Which also makes the XO simpler phase-wise.
From memory i would say the Lowther PM6A had better detail resolution but worse sonic entirety and was not as musical as the Triangle. In Germany, TMK the general distributor of Triangle is the guy who runs the Auditorium 23 in Frankfurt. To get one from him is like handed down from high, like a divine grace. Outlaws like me may not get one and so i had no Triangle driver pair for tryout. However, when i decided to go with open baffle, i always had the Triangle in mind as a backup solution and hoped to get access to them via French friends for the case i need them.
Having listend to the Fertins, there was no actual need.

The Fertin outperformed my Lowther PM6A, wrong, it boiled the Lowther in oil, detail-resolution-wise, as well as sonic-entirety-wise. Spooky.

Brad,

let me put it the other way around: which drivers not to choose. Avoid any driver endangered by bigger excursions. Lowther, REPS, AER for instance.
Because in fullrange open baffle mode, the diaphragm will work like the proverbial piston, it will make excursion, lots of it.
For that reason, i decided to use my Fertin in combination with an open baffle subwoofer and to free the fullrang driver form big excursion for the benefit of the range from 120 to 20000 Hz.

Best choice for open baffle is a driver having Qts of 0.4 or higher, 0.6 or 0.8 does ot hurt. But also drivers with a lower Qts have given good results. I tried out how an Altec 414-8C sounds fullrange. Very nice, listened about 4 weeks to it. Did not intend to let it be 4 weeks, intended were 2 hours. The Altec has Qts of 0.2 .

Of course, the driver will have the Qts shown in the data sheet. So if you are not happy with the LF roll-off a Qts of 0.2 generates, take another driver. But apart from that, Thiele-Small parameter do not have the same importance as for use in an enclosure.
As far as the low end is concerned, you most probably willl run the driver on its roll-off, too. You could call that roll-off acoustic short-circuit. This short-circuit comes in with a slope of 6dB/octave. So you will need an equalisation for that, a step response filter. Or you decide to miss it and live with a VERY slender low end.
Resonance frequency: you may have noticed that in their frequency response most drivers show a very tiny ripple (or no ripple at all) at their resonance frequency. IMO it is not necessary to pay attention to where the resonace frequency is located. For my subwoofer, i use Beyma 18" GT-200 resonating at 38Hz. But i intend to use them until 20 or 25 Hz . Room resonances will make suich a mess there that the tinytiny ripple of the driver resonance will drown in it.

AFAIR, Siegfried Linkwitz (www.linkwitzlab.com) does not compensate his subwoofer resonance either (and he compensates anything else)

The Altec example shows that it is of eminent importance to choose a driver without any rudeness or wild resonances in its frequency and phase response. The driver simply has to be a very good driver with extraordinary detail resolution. High efficiency does not hurt, but is not necessary. I would prefer drivers with a supersmooth waterfall diagram.
In the Far East, the Altec 414 and 416 are chosen by 9 out of 10 ultra-Fi freaks in homebrewn 4-way horn systems, serving as bass speaker in vented Onken enclosures. They are used that way because they sound so §$%&in' good (and do so up to 3kHz for the 414 and 2 kHz for the 416).

The driver unravels 100% of its virtues when tried out in an open baffle. And if it has no virtues, it unravels that, too.
Let your ears be the judge. Oh, and before i forget it: Avoid round baffles, take square, better rectangular ones and mount the driver slightly out of center.

All for now.
 
dice45 said:
HPotter,

5 years ago i heard the Triangle in a TQWT enclosure, together with a Forstex ring radiator horn tweeter.
Very musical indeed, i could have grown old with that speaker.

You are right about that. Before I tried Triangles I've been changing speakers almost every year. Since I put them in my system in 1995 I still don't feel the urge to upgrade (unless somebody raves about Fortins😉 ).
And an open baffle is a way to go. I would say that the best bass is achieved that way.
 

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Dave---I always thought a phase-plug was the structure in a compression driver that equalizes the path lengths from the various parts of the diaphraghm to the throat so they arrive at the throat in phase, therefore no response cancellations. The structure is, literally, a plug, a device inserted into the throat. That thing on your link is a protrubence. Of course a protrubence CAN be used as a plug, know what I mean. 🙂
 
Tom Brennan said:
I always thought a phase-plug was the structure in a compression driver that equalizes the path lengths from the various parts of the diaphraghm to the throat so they arrive at the throat in phase

That is a phase plug too. The two are related to one another, the purpose of the protruberence [a very Zappa -ish kinda word as in large mammalian] in the case of a larger cone halves the distance across the cone and in directing HF energy.

The relation of the two is similar to baffle diffraction with edge reradiation slowly morphing into baffle step loss as the frequency goes down.

dave
 
Here's part of an email reply I got from Mr. Fertin (Michel Prin)himself... A man obviously proud of his product!

" Our driver works quite well on an open baffle as small as 80x130 cm but it will give more energy in a TQWT or any transmission line . Gap is 18mm deep and coil is 12mm this alloy +or- 3mm movement in full field . The basic difference with Lowther is much less coloration in mid range and much better reliability the Phy is not a full range it's magnet is too small for high frequency . The 20EX goes flat to 21K ."

If it's true, he has every reason to be proud 🙂
 
Brad,

AFAICT, he can be proud. 21kHz i cannot check with my ears anymore, but treble end is one of the most natural i ever heard. Should vinylsavor or hifidaddy join this thread, they probaly will second this driver needs no tweeter.

One thing, the Fertin show a considerable break-in phase, 100 hours are not enough for that. Mine still improve.
When they were new, they were fantastic already, but BRIGHT! . They have darkened and opened sonically since then.

You asked which model i have, i have the FLB20EX 8" fieldcoil driver. What hardly can be seen on the website's pixes:
The driver has a whizzer cone and a phase plug. (A phallus symbol but not as spectacular as Bert Doppenberg's dildos, oops, phase plugs, oops-oops, used in his Oris horns, does he buy them by the dozen in Erotic shops ? ROTFL 🙂 Dave, this is a better example 🙂 )

Volker Kühn who distributes Fertin in Germany said to me that his TL design using the 20EX is terrifc but if he compares it to the open baffle, the baffle wins.
My hint: Forget about much bass, strive to right bass. And for the rest of the spectrum, the open baffle wins anyway.

Supravox:
Paper performance is better, way less moving mass, enuff Xmax, stronger motor, gummed linen supsension.
Theoretically they ought to be better. The 215-2000 is avaiable with an alnico magnet as well as with a field coil. It uses no whizzer cone (which is considered to produce all sorts of amplitude and phase nastinesses theoretically.) I cannot crosscheck that from own experinece, i just learned from others experimenting with FR drivers that the Supravox seems to have not enough and not dynamic enough treble. Too soft there. And i learned from a guy who treated his Supravox with Ennemoser C37 and later wished he had not done so. Lost contact, no idea whether the C37 developped its sonic long-term-beautification it is reputed for. Interesting for me is that he wished to enhance his sonics and that he took irreversible action for that with a driver costing $1000 each, more than the Fertin 20EX.

I do not wish to do so with my Fertins, be assured. Either i am more sane than the other guy (which i doubt 🙂 ) or something was wrong with his drivers to his ears. Or the drivers simply are as they were.

But i skipped Supravox for another reason:
their quality control seems not to exist at all. Quality of the delivered drivers seemed to be arbitrary back then. Ranging from sensationally good to non-working. Of course, the Supravox staff is very compliant concerning warranty claims, but did i want to try this out 3+ times in a row? No. Not at all.
Jean-Michel LeCleac'h reported several occasions of non-working Supravoxes including HiFi-shows, including the magnet coming off due to lack of glue. If they do not even manage to show up at a HiFi show with a working speaker !!!, then this is a no-show to me.

PHY piezo: i was adressing the tweeter-less "FR" driver. This piezo has gotten a better rep than piezos usually do but it still is a piezo. (I have worked with piezos, was designing an anti-theft-siren for automotive use, and i have seen the FEM simulations, the things are resonant-prone like hell. And i have listened to quite some variations, they sound awful. Still the best was the cheap Motorola horn with 6 beads in the horn funnel and a center phallus).
Andreoli refuses to use this tweeter, he uses the tweeter-less driver and his own tweeter choice.

Guess i'm thru with overdue QQ 🙂
 
Brad,

I haven't heard too many wide or fullrange chassis.
I heard Lowthers for example. Then there was a speaker with
a chassis from a german manufacturer called Stamm. I think
the speakers were Loth-X.

I also heard some very old Siemens chassis for movie theaters
and a cheap paper cone similar to Lowthers, but I don't
remember the manufacturer.

Haven't heard the Fostex you mentioned.

Thomas
 
Any more discussion of large coaxial drivers? Preferably in enclosures, not baffles, so not too high Qts drivers.

Beyma has quite nice looking 12" coax. Beyma Coaxial Speakers - Beyma 12KX coaxial speakers - Beyma 12KX 600 watt 12" coaxial speakers for all 2-way applications. Beyma 12KX coxial speaker and other Beyma 12" coaxial speakers here.

Anybody done bass reflex/ closed box speaker of that or similiar driver.

I believe that kind of speaker would be quite ideal for metal / heavy music where sound of recordings are not very best in terms of "hifi".🙂 Maybe you can archive more "live sound" with big monitor than with small 2-way which may have flatter responce and cleaner treble, for example.

Have good are those in terms of sq?
 
Any more discussion of large coaxial drivers? Preferably in enclosures, not baffles, so not too high Qts drivers.

Yesterday, at the Burning Amp Festival in Sausalito, there was a pair of speakers playing outside that a member originally put together for the Playa at Burning Man. They sounded really good! I'm not sure, but they may have been Lowthers. Not only did they sound great, they were works of art as well! They were covered in copper that was tacked to the multifaceted enclosures. They were supported by surveyor's transit tripods placing them at the ideal height.

Check the BAF site. I'm sure someone will post some pics and specific info in the near future.
 
Any more discussion of large coaxial drivers?

Not large size but extremely interesting development of coaxial drivers in new Genelec 8260A monitor:

http://www.genelec.com/documents/other/Genelec 8260A Technical Paper.pdf

They apparently use a foam waveguide for the tweeter in front of a small (5") coaxial driver. The sound waves from the mid driver section go through the waveguide without causing it to vibrate so there are no inter-modulation or discontinuity problems normally associated with the coaxial drivers. Well, not clear to me if it vibrates or not, it may be that it vibrates after all, but it is elastic anyway and solves at least the discontinuity problems and improves suspension. Very hard to DIY I guess, maybe we have to try it anyway...
 
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