Not sure how many watts you need but the Eastern Electric MiniMax amp has 4,8, and 16 ohm taps, The M20 integrated amp also has 8 & 16 ohm taps.
Check out the new Bottlehead Paramount kits (4/8/16 ohm taps) available in both 2A3/300B format.
Less expensive would be the Paramour (2A3) kits with the "iron upgrade". The upgrade iron may be be available (again) in a month, or two.
Imagine many manufacturers/models offer 8-16 ohm versatility.
As far as running 16 ohm drivers off 8 ohm taps I've found the sound to be cleaner (lighter/tighter LF's which highlight the HF's) when compared to the 16 ohm taps on one of my tube amps.
Can't say either way is right as my choice depends upon the specific driver/cabinet being used.
I've gone through more than a dozen different vintage single and coaxial drivers in the past three years.
Cabinet/baffle material & construction will probably alter the sound @ least as much as impedance matching (between 8 & 16 ohms).
Want fuller/looser bass then use less rigid baffle material (just an example).
Fertin specs the EX20 as an 8 ohm driver, so I assume yours are of special order/production.
Not familiar with field coil drivers, so don't know if you measure the static impedance in the same manner as that of later magnet design cone drivers.
I start by measuring drivers (with a multi-meter) to gauge what I'm starting with.
I've owned 16 ohm "marked" Tru-sonic 80FR's, which measured in the 3-13 ohm range.
Only a few pairs of the vintage drivers I've tried measured within 20% of spec.
My current matched pair of 80FR's come in @ just above 7 ohms and the previous pair @ approx. 13 ohms.
I checked the specs and they are 8 ohms. I was reading Dr Gizmo review of the PHY-30 and thought that the Fertin were the same. What can I say... I guess this really solve my problem. Now, those who have Fertin 20ex, what amp are you using and do you need a sub with these. Be kind, I'm just starting in this world of hi-fi and this isn' just a plug and play thing. Thanks.
Try searching Fertin @ audioasylum.com as there are a couple of owners/previous owners mentioned.
You may be able to contact them through the Email system.
If you have a scroll and/or keyhole saw and a drill (to cut the holes) you could first experiment with DIY plywood open baffles.
If you have more sophisticated tools, and know how to use them, then all the better.
It's important to use flat wood and to systematically tighten the drivers to the baffles (like an auto's oil pan/valve cover) as to not bend the driver frames, but other than this it's fairly simple.
I've made experimental OB's from scrap ply, a drill/scroll saw and a wood rasp (to bevel the edges of the holes) and I'm officially lame.
Inexpensive DIY OB's approx. 3' x 4' (and larger if possible) will allow you to judge whether added woofers/subs/HF drivers will be needed.
Securely coupling the drivers to a stiff/thick baffle generally offers a cleaner sound/more pronounced HF's.
The distance from the floor to the driver will also affect the bass/mid-bass.
I have not heard much of a difference between centering/offsetting the drivers, but placing them off center seems to be the preferred method of many.
The above variables are why I suggest cheap/DIY in the beginning.
I second dekay's advice for a good, inexpensive, diy amp. Don;t fret too much over the impedance, tubes have high output impedance (hence the output trannies) and love high impedance loads. Also remember, if you're measuring the Fertins with a conventional multimetre, what you get is the resistance rating Re (dc) -- not impedance Z(ac).
Again, as dk suggests, the baffle will be an important contribution to the sound. Why don't you try out PHY's "panneau plan" -- or Supravox's. They work very well.
As I mentioned in an earlier post, the field coil allows you to play with the drivers' characteristics to suit your tastes. More than most of us with fixed magnets can do!
I think that I'll go for the Phy-hp type of baffle at first, since they are easier to build. Later, I'll try to find a better design. As for the amp, I'm not the upgrade type so I need an amp that I'll keep for the next 10years. I wonder how these amps(Bottlehead) would compare to other amps, like Cary.I would spend more than 2500 since I've spent close to 2600 for the Fertin. But I think that I would rather spend more now and keep the amp for a long time. My drivers are leaving France today so I'll probably get them by Monday. I still have a lot of work to do. Thanks for your advices. If you have any other ideas as for my choice of amps, keep them coming.
Laurent: 2600 euro for the Fertins???? And I thought Supravox fields were expensive!
Why are you insisting in a branded amp (Cary, etc)? A competently made diy (or a local hobbyist's product) will easily serve your purpose and for many years to come!
Amps using 300b, 2a3, 6c series, 845 tubes should do fine. These are outrageously expesnive to buy branded!
Suggest experimenting with the drivers and various OB/cabinet configurations (with amplification available) before investing in a "long term" amplifier.
May be that you prefer something different than the Fertin's.
I've used gobs of SS & tube amps with many single driver speakers and the amplification choice, though important, is not of a first order priority.
If you like the sound of the speakers, then go from there.
Well, diyhifisupply.com has a few kits. Hagerman in the US has others. Look at JPO's site, you'll find many refs.
But again, I cannot agree more with d-k: attack the spkrs for now, the amp can come later. Enjoy!
I have to give my thumbs up for the Eastern Electric Minimax power amp. I've got one in my system* driving my newly acquired Avanti IIIs from the 4 ohm outputs. For an 8 watt amp, it really has a surprising control of the big Audiophysics - everything I could really want for reasonable in-room listening volumes. A bit of an audiophile bargain. And I'm not a dealer or distributor, just a (very) happy customer from Scotland.
* System: NA Spacedeck HD/Lyra Helikon/Dyna P75/RA Opus 21 cd/Minimax pre-power (with NOS tubes)/Audiophysic Avanti III
Laurentgilles, you will do well with any tube amp that has an 8 ohm tap and maybe a little better if it has 16 ohms.
When you drive a 16 ohm load using the 8 ohm tap, what happens is that the load impedance that the tube(s) see(s) is also increased. The output section will then make less power, but the distortion that the power tube or tubes make will be reduced! However, the transformer will make increased distortion due to some ringing, which will be minor.
Of course, a low-power OTL will drive a Fertin effortlessly, and with greater transparency than you will be able to get out of a transformer-coupled amp driving 16 ohms. So instead of limited choices, your speaker actually gives you a wider range of choice than many speakers do. Everything I have heard about Fertins suggests that they are *awesome*... Have fun!!