Fertin Full Range Speaker

Ecess

Member
2006-05-21 10:14 pm
Hello, what about a new full range speaker ?

Anyone has heard about Fertin speakers ?
They are build by Atelier du Haut Parleur in southern France.

They have conventional magnet speakers and electrically excited speakers. I have tried their 21 cm with both engines and I am very fond of them.

This little wonder has a carbon spider and a resonance frequency of 27 Hz.
It produces a distinct 20 Hz at the same level than the mid frequencies, say 300 Hz where it exhibits a 96 db sensitivity.

For testing I had mounted the speaker in a B&W 802 at the place of the top woofer. The lower woofer was short circuited for the experience.
It was drived by an Audio Research D120 set in symetric, with a 47 ohm serir resistor an a correction network to flaten the response.

I have pictures and spl curves for the setup that I could send by mail if required.
 

Ecess

Member
2006-05-21 10:14 pm
Hi, felixx.

The response curve is already with correction network. It is difficult to listen to a magnitude rise of 15 db from lower mid to trebble without an efficient correction network.

For the bass, you are rigth, I have spoken of 20 Hz while it was 27 Hz, thanks for this remark.

Speaking of trebble, I have notice for a bit of time that there is above 7Khz less musique informations than rise time or small pulses or peaks. These pulses and peaks bring presence and life to the musik provided they are in phase with the musik.
The property of full range speakers is that they warrant the phase issue and in turn the phase issue warrants the life of the musik.

To crossover them with super tweeters is a mixed experience of good and bad and to my knowledge more bad than good. But it is worth trying for the sake of the experience.

For the listening I have a much better trebble perception with the Fertin 21S which cut at 15 Khz than with the B&W802 that goes up to 25Khz. Is'nt that strange ?

The real difference is in the trebble directivity of full range versus the directivity of small dome speaker.
But there is the trick. Very few instruments deliver omni directionnal trebble.

What should do the reproduction of recorded musik ?
 
Peter Daniel...on this forum has this carbon full range driver into "infinite" open baffle design.

For the listening I have a much better trebble perception with the Fertin 21S which cut at 15 Khz than with the B&W802 that goes up to 25Khz. Is'nt that strange ?

Maybe because of the high raising response into 9k area.
Anyway the magic of single driver remains.I have Supravox 215 bicone on OB but still need supertweeter on top-Fostex T925A.
 

Ecess

Member
2006-05-21 10:14 pm
True the 9Khz peak plays a role in that perception.

I have considered to implement a rejection filter as I did for a 3Khz peak. But a filter is also a phase rotation.

I understand that the Fertin speakers have been often set in infinite baffle.

A box that handles properly the back emission may improve the basses without deteriorating the mid and trebble.
The Qt of the 21S (0.435) is almost ideal for a Voigt Pipe.
 
correction network for fullrangers

i will order the Fertin 20ex soon and plan on installing it into small open baffles so achieve a natural rolloff around 150 or 200 hz and complement witha boxed bass system activly crossed over and amplified .

i am very interested in the topic of correction network for Fullrangers .

i am also still looking for a good bass crossover with phase alignment and also something to measure in room frequency response to determine how my driver rolls off and where to xover the bass .

another intersting topic would be impedance matching between amp and FR or what damping factor is best ?

what i read so far is that Set amps with lower damping factors ae better suited for FR .

malcolm
 

Ecess

Member
2006-05-21 10:14 pm
Hello Malcom.

From what I could read the Set Amp is a One watt amp with a 6.6 Ohm internal resistance.

1 - One Watt might be enough if no correction network were applied on the speaker. But the 20 EX Fertin needs correction. So one watt is too short.

2 - I understand from those who use the 20 EX that the internal amp resistance should preferably be higher, 15 or more ohms.

3 - Simple amps well adapted will probably be the F1 (80 ohms) or F2 (15 ohms) of Nelson Pass. Their power range (5 to 10 watts is more adapted than the Set Amp).

4 - A single End class A with 300B or 845, might be very good as well.

4 - An other choice might be the Amperotron of Jean Marc Plantefeve, see the net.

5 - You might as well try to use your F3 and play with the NFB of it in order to increase its internal resistance.
May be you should ask Nelson how far you may decrease the NFB of F3 without encountering problems.
 
felixx said:
Peter Daniel...on this forum has this carbon full range driver into "infinite" open baffle design.

[...]

Maybe because of the high raising response into 9k area.
Anyway the magic of single driver remains.I have Supravox 215 bicone on OB but still need supertweeter on top-Fostex T925A.


Such an IB setup in one wall with a dual cone off axis would be useless for most drivers. Blackforest Audio also use it off axis, probably due to the rise.
 

lrntglls

Member
2005-11-08 3:12 pm
It's important to see the driver and the amp as one unit. properly matching a low qts driver with a high internal imedance amp as its benefit in the bass output of the driver.


One interesting article on the subject at: http://www.paulspeltz.com

By D.J. Tomcik - Part 1- The amplifier damping gactor and its application to speaker performance.

The Fertin 20ex has a qts of 0.416 . A critically damped driver has a qts:0.5 It would still perform better with a high impedance amp. Jean-Marie Semblat is using the Fertin monoblocs with an internal impedance of 8 ohm with good bass in open-baffle. But the 20ex can be used with success with a variety of amps; rom the 1.5w trancendent OTL (here you can have 16 or 32ohm made to increase the power in OTl) to different set amp, chip amp and current amp. You can also adjust the voltage to gain some lf ; the 20ex being a field coil.

Whereas if you have a really low qts, like the emspeaker LB12 with a qts: 0.24 ; then it becomes very important to choose a higher impedance amp to raise its qts to an acceptable level. You get the benefit of the low qts+strong motor + a high acceleration factor which are characteristics that brings life to music. As the use of a super-tweeter with the 20ex, and I quote Peter Daniel: ''You wouldn't think those highs could be produced by a full range driver, they are so good''. When I ask peter Daniel why he chose an infinite baffle instead of a open-baffle: His answer was: to get more bass and a more precise soudsatge and he didn't mind being without the ambiance that the back wave provides.
 

Ecess

Member
2006-05-21 10:14 pm
Thank you, IrntQlls, for the article on critical damping. There we enter the deeps of the matter.

New Fertin full range speakers are coming. They have no rubber suspension any more but very light tiny carbon rods to replace it. They have also a brand new spider made of carbon and very stong motors.

They reach Qts of less than 0.1 with acceleration factor greater than 1300 ! Never seen before ! We all know that low Qts means good speaker. We have only to admit they need different amp to be driven by.
Their critical damping requests amps with high internal resistance that you can adjust to need.

To experiment with these units, I use high power voltage source amps and variable high power resistor in serie with the speaker.
In a given box, it is very easy to adjust the resistor to proper flat bass response.
 

lrntglls

Member
2005-11-08 3:12 pm
I've been hammering away this point for some time

Another interesting document on high efficient driver and the

internal impedance of the amp is:

se amplifier output impedance by Edwardo B.E.Lima part 1and2

It came from (Glass Audio 6/97).

Low qts means good speakers

Cherel could you explain more about this. I know that this

is a characteristic of the model 7. We have 0.2 for the 20ex mod 7

and 0.07 for the AP13ex mod.7.