Sunday, 28 April 2013

My long and winding way with vintage Tannoy speakers

One day (around 1996) I got a phone call and the guy who bought my GRF Rectangulars was on the line. He still was very happy with the speakers, he told me that he had sprayed them with black paint like piano laquer. I thought "what a brilliant idea" and I did just fall into thoughts about other peoples very different ideas of taste, their education, social background and their general turns, when a word like a lightning called me back into the telephone call: Tannoy Monitor Red. He did ask me if I were still looking for a pair of Monitor Reds? He really said M o n i t o r  R e d ! He told me that he just had aquired several pairs of 12'' speakers from the austrian broadcast, but does not have an idea to use them. So he did remember, that I was looking for a pair, which he now offered to me.
Five days later I had a pair of the rare speakers in my hands. It took me a hour and they had been screwed into the Chatsworth cabinets, which were originally designed with a volume of 69 liters for the 12'' chassis. In one minute I had forgotten about the former 10'' Monitor Golds with their lack of low frequency volume. These never could make me forget that they originally are made for near field monitoring use. In this special set up they are good, but listening to them with more distance they show their limits. But now I liked immediatly the larger 16 Ohm version better than anything else I had owned from Tannoy till that time. The 12'' Monitor Reds have a extremely well balanced tonality with very good dynamics, due their lightweight paper cone and lighter voice coil. The crossover makes the lf-cone playing as fullrange speaker, which is very different from any later 12'' successor in the Tannoy line. The sensitivity is as well a bit higher, I would expect a minimum of 3 db and the dynamic abilities are very good for a twelve inch speaker. Due to a lighter voice coil and their impedance shift to 16 Ohms it makes a noticeable difference to the later types in dynamic disciplines. The 12'' Monitor Red has a better accentuated middle tonality and a improved high frequency dispersion of finest resolution. Some of this effects might be a result of the more simple crossover design with oil caps and better inductors than the later types. As a result the speaker seem to have less phase shifts within its tonal spectrum and a more liquid presentation.

Pair of Monitor Red 12'' 

In combination with my excellent power amplifiers, the legenday Leak TL12 point one and my Platine Verdier turntable fitted with SME 3012/II and SPU I had got a extremely musical, dynamic and warm playing set up. To me the 12'' Monitor Reds were the ultimate Tannoy speakers at that time. For me they  bettered the 15'' version with a improved tonality in the important middle frequencies, as well the elegant slim cabinets can be placed in the most rooms without problems (waf).

My Chatsworth cabinets had been all the time in quite rough condition, they were functional but not very nice to look at. So I decided to rebuild them with new made cabinets. I did use almost the same sizes but made them 5 cm deeper and 5 cm taller. I orientated my plans at the original Tannoy drawings from the seventies for their enclosures like the Arden, Berkley, Cheviot, Devon, etc.. My new cabinets were made from 21mm multiplex hardwood for the frame. The baffle construction was double layered to improve the rigidity were the speaker is mounted, so it added to 45mm plywood there. Heavy bracing with 5 cm solid wood rods supported the strength of the construction. When the cabinets had been finished I directly realized that they had almost the double weight of my former Chatsworths, … a good sign?!.
I lined the speakers like the original Tannoy enclosures from the 1960ties with heavy stuffed pillows at all framing sides in order the damp the inner reflections. I did use bed cloth heavily filled with rough nature lamb wool for that reason. I did screw the baffle and the back panel with 16 screws each to the inner frame, the speakers had been screwed through with nuts to the baffle.
Than the first listening test... It ended up completely disasterous. All the musical behavior, the middle tonal balance, the finesse of the high frequencies were shifted into a harsh, edgy and superficial presentation with a booming bass bump at the lowest end. I could not identify my former speaker in any detail. I was completely frustrated after all that work. I did try to do everything as best possible solution. Unfortunately this first experience happened at a late evening, so I did build the chassis back into the Chatsworth cabinets and had a chance to listen how good they are.

Baffle double strenght 45mm plywood and pillow damping with bitumen underneath after original drawing from 1970ties enclosures

On the next day I went to the wood dealer in order to cut two new baffles from 12mm lightweight plywood. This material was originally used by Tannoy for their older cabinets. Like all well known speaker manufacturers of the vintage era, Altec, JBL, Stephens, EV, etc., Tannoy used in the fifties thin plywood (12-16mm with only 5 layers) made from northen woods, like pine for their enclosure constructions. Tannoy changed that design not before the 1974ties enclosures encountered the market, all of them were reflex constructions made from MDF particle boards with heavy internal rugging boards, after the typical measuring tests for that decade.

I just did cut the wholes for the chassis with a jig saw into the material, nothing asthetically advanced – just functional. I mounted the speakers from the backwarded side with ordinary wood screws – not to tight – on to the baffles. I replaced as well the back panels with the 12mm plywood. From my former cabinets now only the heavy frame did exist anymore.
Now it sounded very good, all the substancial hardening of the most frequencies was gone, the tonal harmony was back and dominated the sound qualities of these enclosures. It sounded a bit different than the old cabinets, almost in every frequency but with a better tonal resolution. They had kept the important musical homogeneity and its important tonal balance of the Chatsworths.
This new enclosures were constructed like a guitar or other wooden musical instruments and used the resonant capacities of the body as support for the presentation, rather than beeing a dead piece of furniture. All books from the 1970ties into the eighties about speaker enclosures did pronounce the property of resonance freeness as the most basic lesson.
Now I did learn my first real lesson about cabinet making and tonal harmonies of wooden materials in combination with heavy low qt drivers, like the early Tannoys. For me this was a very important basic lesson on which I could build up in the coming future, when I planned to make cabinets for such speakers.

The slightly enlarged (89 l) cabinets on basis of the Chatsworths here shown in final stage with earlier 12'' Monitor Silver speaker.

To my taste the smallest possible cabinet with good results using Tannoy speakers.

Read on soon, Volker