FR66s vs Ikeda IT-407 CR tonearms

Thanks, Ddrive. I guess there is a Krebs mod in my future; I own one "unit" of SP10 Mk3 that has been thoroughly updated and mounted in a massive slate and cherry wood plinth. I can hear a qualitative difference between it and my Kenwood L07D that may have to do with "fluidity", but I am still only thinking about the mod. R Krebs is a fine guy, however.

What headshell(s) do you and others use on your FR64S/FR66S??? The headshell is a major part of the equation, very major.

I have used a variety of headshells. I agree that these are important but need to be match with the cartridge. Unfortunately not enough is mentioned about headshells and leads IMHO. I like the Ikeda headshells for heavy carts and these have azimuth adjustment. The Yamamoto Ebony headshell is also good for medium/light carts but does not have azimuth adjustment. I like the Arche headshells the best though. Lots of flexibility in adjustments. For me, the headshell leads also play an important role. The Ortofon silver headshell leads is good. Which headshell and leads do you like?

Ddriveman,
Here is a photo of my Melbourne Dealer friend with Ikeda San a few years ago when he personally picked up his new Ikeda tonearm.
Even the personal thrill of accepting his arm from the great man himself did not cloud David's judgement...👀❗️
The FR-66s is easily the best tonearm he has ever heard.....😍👍

Yes...the performances of the FR-64s and FR-66s are very close to each other in tone, spatial abilities, cartridge matching etc....
Where the FR-66s differs is in a magical ability to sound relaxed and authoritative at the same time...👀🎶
No....it allows the CARTRIDGE to sound relaxed and authoritative...😃❗️
The major difference between the two arms IMHO...is that the FR-66s appears to disappear entirely from the audio chain, leaving a cartridge which is suddenly performing at levels beyond its design parameters...🎵🎼
And that I think, is the domain of very few arms on this planet...👀😎❓

Lets have a close look at the - still current design - Ikeda IT-345 and IT-407 tonearms.
These are 10" and 12"-tonearms which both do feature the classic detachable SME-bayonet headshell.
Their ancestors - the long out of production Fidelity Research FR-64s and FR-66s - do feature just the very same basic design ideas.
They too are 10" and 12" designs with the very same detachable headshell SME-bayonet.
Furthermore all 4 tonearms are dynamic balanced designs which allow the tracking force being applied by a special spring only.
But - the similarities stop here and there are fundamental differences between these two generations of tonearms from one designer - Isamu Ikeda.
The "modern" IT-345 and IT-407 tonearms are somewhat lighter in their effective mass AND - most important!! - are calculated with a different geometry compared to the earlier FR-tonearms !!
To put it in very simple words: you can NOT use the same adjustment jig on both - the IT- and the FR-tonearms.
The FR-tonearms can only be perfectly aligned with the Dennesen Soundtracktor.
Try with any other alignment tool of today - no matter if Bearwald or not....... no matter if IEC standard - and it will result in a misaligned cartridge and too little overhang thus in a pretty bad tangential curve with the zero-error points being too close together.
Do align them with a Denessen Soundtraktor and precise - absolute precise spindle center to bearing center of 231.5 mm for the FR-64s and 295 mm for the FR-66s and you will get sonic results which will open up your ears and minds.
Why??
These early FR-tonearms were designed in the late 1960ies and 1970ies.
Back then many of the records of the day and the past were cut pretty close to the label resulting in a fairly wide angle to track.
In the early 1980ies (remember....??) DMM-records hit the street and ever since then vinyl records grooves do stop at least an inch away from the label.
The consequence??
The geometry of the early FR-tonearms is different - it projects 2 zero-error points fairly wide separated and the 2nd fairly close to the label. Thus the curve is again very smooth resulting in VERY low maximum tangential error.
The later Ikeda designs do feature a different geometry with the 2 zero-error points MUCH closer together and the 2nd point at least 1.6 inch away from the label.
So - you cannot compare these 2 tonearm-generations if both are set up with the same alignment tool.
Or - you can only compare them if both are set up with the Denessen tool.
Yes, the IT-345 and IT-407 CAN be aligned with the Denessen - resulting in more effective length and a different overhang AND subsequently in a geometry with their 2 zero-error points wide separated and very similar to the FR-designs.
Then - and only then and under these conditions you can compare the two design generations.
But now you will run into the problem that you are still comparing apples with pears as the FR-tonearms do feature much higher moving mass and are optimized for VERY low compliance cartridges ONLY (SPU, FR-7 series - hardly any other....), while the IT-designs are lighter mass and will work well with todays 9-13 dyne x 10(-6) top moving coils. But...real life showed more than one time, a FR-64s handles any modern cartridge much better than any modern Arm (deeper Soundstage, superior detail and a much more real tone...simply much more close to the Real Thing than anything else. In a way...in a way, that circle is closed.