following file describes how the Tannoy MG15
crossover can be up-graded to modern standard, in this
case even very high standard using silver/gold caps and
foil coils wound on waxed paper. More options are
available to suit any budget.
Should you be one of the many MG15 owners, thinking the MG15 is just "it" - the one and only speaker - the upgrade kit here may be an option to further enhance performance. The crossover shown below was made for a client and is close to the best money can buy. Foil coils wound on waxed paper and capacitors made from silver/gold metalized polypropylene with pure silver leads.
Option #3: Wax foil coil
for bass and Superior Z-cap for bass section and tweeter
notch filter. For the tweeter series capacitors and
tweeter roll-off function silver/gold caps are used. Not cheap, but if
it has to be the best available.
The tiny 1.2 mH trafo* used by Tannoy
for the 15" driver is hardly optimal and although
the present crossover features film caps throughout, we
can do better these days. The two coils in the tweeter
section are re-used as a replacement for the tweeter
attenuation coil cannot be found and there's hardly a
rationale for a new one being better.
The thin wires and rotary switches are likely to further degrade the sound of the compression driver and below you will find a hard-wired replacement that will - I admit - not offer the convenience of the rotary switches. If tweeter level and tweeter roll-off has to be adjusted regularly, I suggest making a switch-board on the rear of the speakers where you by jumpers can configure the crossover to your liking.
The client for this up-grade also wanted a plug'n play solution, so the original speaker plugs were cleaned at wired to the crossover. Maybe not 100% optimal, but I guess it would be very difficult to hear any difference between this solution and a hard-wired connection to the voice coils
With the availability of original Tannoy schematics, everything looked straight forward. The crossover module received had the label LSU/HF/15/8 and LSU/HF/12/8, meaning suitable for 8 ohms version of either 12 or 15 inch drivers. So far, so good.
Dealing with vintage
British gear, be prepared to surprises.
After finishing the crossover it was obviously
tested on dummy loads as had been done on the
The only thing left to do is starting measuring component values in the original crossover. Quite tedious as most components need un-soldering.
The long and the short of it is this: The series coil wasn't 1.2 mH, rather 3.2 mH! And this despite the original crossover carrying the label LSU/HF/15/8 and LSU/HF/12/8 for an 8 ohms driver.
Two things come to mind here: Does my client have a 16 ohm drivers? Or - and this is more tricky - have the Tannoy folks tried to solve a potential 2 kHz bump. The latter requires some explanation.
I had this comment from Edward/CA on the caps. Having measured all the electrolytic caps to be spot on with regard to capacity, the 16 uF turned out to be actually 30 uF! It's unlikely a 16 uF cap would achieve double value due to age and either the label is wrong or the cap manufacturer really had a bad day at the assembly line. As stated above, be prepared for surprises!
How the tweeter roll-off function works
DOWNLOAD KIT SALE PRESENTATIONS (pdf file)
All kit and component prices may be subject to change and are always to be confirmed by Jantzen Audio Denmark.
Contact Jantzen Audio
for full quotation incl shipping. Remember to include address.
All technical questions to me at firstname.lastname@example.org
The finished crossovers
Silver-Z caps have
been replaced by Alumen-z and Silver-Z for level 1, thus a single 1.5 uF
Silver-Z will replace the two Silver/Gold caps
|Monitor Gold measurements|