NEW MRTW CIRCUIT FOR CALIPER, CALI-SIG, DUETTA (ALL), DIVA M

[Graz]

This came about from a sincere hatred for the Caliper (original) MRTW unit as it employs a finicky, difficult and variable MRTW ribbon return system that not only degrades over time, but is variable in humidity, and affects long term crossover response stability. I have been doing these Caliper ribbon units for nearly 12 years and have to say I really dislike the original design, as a quarter turn on a clamp screw can kill the actual ribbons mercilessly!!

I developed a new interface for these about 5 years ago to solve this problem in the Calipers, and it actually;-

1) brings their sound quality up to beyond a Caliper Signature

2) Allows for assisted shaping of their upper frequency

3) Allows a lesser priced (shorter) Caliper Signature actual ribbon unit to be used

4) makes their measured parameters accurate to <0.03 of an ohm typically

5) Increases their life and stability

6) Allows for easier future MRTW ribbon replacements, without the stress of the original circuit system -
VERY user friendly for subsequent replacements.

7) decreases electrical degradation, and seems humidity independent

8) Decreases the chance of ribbon fractures at the clamps

like all "magic bullets" it's not a cheap system. It uses the finest quality components to not only lift the original design but take it to previously inconceivable levels of quality, letting the KLM5 ribbon do it's work unhampered by multiple and variable pressure contacts.

Installers are aware of this modification for the Caliper, and a couple have probed over time to see if I would supply this kit in a form that would suit the Duetta's (all), Caliper Signature and Diva mid-range.
Well - to be honest I just never got around to doing it! So now I am going to fix that. Benefits 4-8 apply for the other speakers when fitted with their own adaptation of the return circuit.

Available to be fitted by myself or Installers this mod is now offered, using Audiophile very high grade wiring, and quality connections, the PARTS kits cost;-

Caliper (includes full interface) $350 - only suitable for the original Caliper

Caliper (all types) (no interface) $240
Duetta (all types) (no interface) $280
Diva MR (no interface) $300

All plus postage costs at cost.

Actual ribbon prices on top of the return kits of course - though the Caliper kit actually allows for the lesser priced Caliper Sig ribbon to be used.

Fitting the kits initially is a task for an Installer and best done as part of a full restoration. Once the kit is fitted - MRTW's become easier for user replacement for future replacements.

Retrofitting of speakers already restored by Installers is possible though better to do this when the MRTW is replaced for safety - contact your Installer-Agent for details!


Take care - Graz

[Vansloneker]

That's a very useful kit and if ever my times comes I'll probably want to include it.

[Zardoz]

Hey Graz,

Will this effect the Xover circuit for a Diva? I have rebuilt mine and no longer have the switches, so I was curious if it would mean that I might need to tweek the resistance a little, or something.

Thanks

[Graz]

All benefits, no drawbacks - completely compatible.

The main effect of this circuit design is to absolutely lock the circuit in at it's predicted best-case measurements. When the original ribbons were made there was often a large variation on the backed ribbons (0.4 - 0.5 ohms window). With my ribbons, and the return circuit the typical window decreases to better than 0.1 of an ohm from reference. The typical complete channel balance between the lowest reading (Caliper) of these ribbons is <0.02 of an ohm - using my ribbons of course! Considering the length of the circuits these are good readings imho.

Short answer = knowing what I know I would not restore a speaker without this modification, the benefits far outweigh several times the expenditure in any other area of a hi-fi system, including xover parts.


Take care - Graz

[WongKN]

Hi Graz,

With this 'new' ribbon, does that mean that both the MRT and bass ribbons are only available via installers from now on, i.e. the MRT ribbons which used to be owner installable will no longer be available for this purpose ?

Thanks and best regards,
Wong KN

[Graz]

This actually is not a new ribbon, but the circuit that connects to it. Think of it as an absolute rebuild, that can use the KLM2 or KLM5 ribbon unit. It can be fitted to an existing installation with extreme care BUT I would caution against it.

I continue to make all MRTW's available to home installers with the exception of the Grand MR and TW, and with extreme warnings against home installations being attempted on the FR, and almost as much reservation about home installations being done on Scintilla's MR & TW.

This mod is best fitted when everything is apart really for best results...


Take care - Graz

[EldRick]

When you reduce the resistance of the path to the ribbon, does this not raise the output level of the ribbon relative to the bass panel, and thus cause a shift of the tonal balance?

[Graz]

Hello Rick

Somehow I missed this! Well - to be honest what this does is absolutely standardize the readings for each pair of speakers. There was a large tolerance window on the original manufactured Duetta/Caliper MRTW, and most/all of the disparities were found in the return circuit contacts. What this mod addresses for Duettas (all) /Caliper Sig is the joints that are variable and subject to corrosion. Such standardization vs a "perfect" installation generally equates to about 0.1-0.15 ohms on the fist day of an installation, like for like if all goes tip-top well with the original foil returns. They can be variable, believe me. What doesn't happen with the new returns is the gradual degradation that does occur with the foil returns.

btw - now all new wired circuit returns 2013 onwards are upgraded to a gold plated interface, prices remain the same. I will continue to supply the upgraded foil returns for those who like the old fashioned way of doing things


Take care - Graz

[Shibui]

Greetings after my long absence ...

I included these returns in my DSig rebuild, and they have not disappointed at all. In fact, my DSigs are revelatory, and are stellar performers throughout their frequency range. They have punched above their pay grade ever since the rebuild, regardless of the power amps employed. Honest.

Graz, your ribbons, and ancillaries are exquisite. Once again, THANK YOU for keeping our Apogtees alive and singing!

The forum looks quieter than I recall, but just as welcoming and informative. Your company and advice has been missed, and I am glad to jump back in once again. Still have the Apogee bug as always ...

[EldRick]

I had these installed as part of a K5 ribbon replacement and crossover upgrade from Rich Murray at True Sound Works.
I can't say what part the wire returns play in this, but my Graz'ed Duetta Signatures have never sounded better, and now sound as good to me as any speaker I've ever heard. Not bad for 24-years old.