My new (vintage) Tannoy Cheviots!

[DSJR]

You need new pepperpots guv'nor I reckon. Apparently this was one reason why the treble went even more spiky in the mid 70's than it already was. It was also discovered in the 1980 era revamps that the gauze over the tweeter horn was un-necessary, but it's so fine I wonder if it was there to disguise the shabby pepperpot castings. Whatever, I'd check with Lockwoods at some point although you've probably re-assembled everything now..

By the way, a Lockwood refurb entails the whole moving part from surround to new aluminium voice coil, hence the cost. They claim the performance is far better than new.. I'm sure that if you've heard other drivers with the slight alteration you're making and they're good to you, then all should be fine. Crossovers next

[walpurgis]

No Dave, I'll sort it myself. It should clean up if done right and I'll give it a wipe of fine clear laquer. I doubt if there's any in front of the tweeter diaphragm or on the sides where the coil and former go over the horn/pole piece, I can't see any using a bright torch. The tweeters sounded very sweet when I demoed these, so I'm not expecting problems. The gauze will be left as is.

I'm aware of Lockwood's services. They're only up the road from me. They reconed my mate's Chevenings with LRM10 cone assemblies. It was a nice job actually.

Geoff.

[DSJR]

Sorry geoff, I meant the holes in the tweeter waveguide. PLEASE make sure the holes in the casting are even all the way round and properly profiled, as they look a bit rough from the angle of the shot you've provided.

I do envy those who take their own drive units to bits this way. Tannoys look to have been built with this in mind. My Spendor BC2 bass units apparently have an audible reflection between the larger diameter (compared to BC1) voice-coil centre dust covers and the pole piece and it's been suggested by a key chap at Spendor that I remove these dust-caps as done in the SP1 driver which was loosely based on the BC2/SA2/Prelude driver and fit a "phase plug" as Spendor now do I think. The doping on my bextrene cones is in pristine condition still and I'm absolutely terrified of tearing it in a botched attempt at removing the dust-caps..

[walpurgis]

The waveguide on Tannoys circa 1980 was not as well machined as earlier examples, but this does not seem to affect the sound.

Leave your Spendor cones well alone Dave! What happens to older Plasticote treated cones is that the slightest disturbance will cause the coating to lift and continue peeling. If you try to remove the dust caps you'll pull off the coating too.

The biggest problems the BC2 and BC1 had were the Bextrene cone 'squawk' (which KEF and B&W also had). On the Spendors it was not quite so evident though, its a colouration your ears adjust to anyway. And, there's a bit of port 'chuffing' at the bottom end at high volumes. I won't comment much on the awful Coles/STC/ITT super tweeter (it really is horrible sounding), other than to say, Rogers went to the wonderful Celestion HF2000 instead on their Export Monitor which was a closely similar design. Fortunately the super tweeter on the Spendors does not cover much of the audible spectrum.


Geoff.

[walpurgis]

This morning,

masked off the tweeter to prevent crap going in!



Slicing through adhesive and old surround under the rubber trim on the inner flange face.



One trim ring in perfect condition. It'll clean up well enough to re-use and now I've got to clean the speaker chassis inner flange face to accept the new surround.



I'm having a rethink on the surrounds. The mounting face on the speaker chassis is wider than anticipated and although the outer roll on the new fabric surround just clears, I don't want to risk the surround making contact during large extensions when driven. So, it looks like the poly/foam single roll surrounds may be used after all.

More later.

Geoff.

[walpurgis]

Latest.

One cone fitted with new surround. properly bonded under the bracing ribs which are now also re-bonded at their termination. No, the surround is not the wrong way round, its just the effect of the lighting.

The speaker chassis needs a bit more cleaning up, then the cone goes back in later today.



Dealing with the minor surface corrosion in the horn throat. Magnet gap masked and mouth of pepperpot wave guide covered with a dollop of bluetack.



The corrosion now gone. I rubbed it off with very fine emery paper and then wiped on acrylic laquer to seal the surface against recurrence. The corrosion left minor discolouration which is of no significance.





Note: never use wire wool, wire brushes or anything made of steel near speaker magnets. Any loose bits will contaminate the coil gap, etc.




More later.

[walpurgis]

Back on track at last.

After many weeks of delay and misfortune, two pairs of surrounds that didn't fit properly and waiting for suitable surrounds to come from Australia and then stripping off dodgy surrounds and starting to fit good ones, I'm back in action.

Below, new surround bonded to cone and cone spider centralised, blobs of blu-tak used to check that the cone will move freely and concentrically before glueing the outer edges of the surround into the speaker chassis, because once that's done there's no going back.



Next photo, the cone now fixed in place, with the circular edge trim fitted and the cone is moving nice and freely. With a bright torch I can see that the coil former is properly concentric to the horn/pole piece, no wedges were used. This driver is basically finished.



Now to start on the other one!

[walpurgis]

Refurbished driver now installed back into cabinet. I've tried it out and it sounds very good. I'll be able to comment in depth when both speakers are finished.



Grille in place after spending a couple of hours pushing 'pulls' back through the fabric with needle nosed tweezers, the previous owner must have had a cat. A few grubby marks were cleaned off the material with a damp cloth.

[realysm42]

Good work; how long has it taken in total?

[walpurgis]

Good work; how long has it taken in total?

You'll laugh Martin, I started in July, but had repeated problems with inadequate cone surrounds. Then I was on holiday for a while. When I got back I ordered good surrounds from Australia and they took nearly a month to get here. By this time I was getting a bit fed up and waited a few weeks to get cracking again, however all's going well now.

Another driver to overhaul and a bit of cabinet finishing to do. Once that's out of the way I may experiment with internal wiring and crossover components. Although to be honest when I bought these, I had a long demo (with knackered surrounds) and they sounded absolutely marvellous, so I don't think they are likely to need much enhancement and have to say the 3128 dual concentric drivers make these by far the best Cheviots I've heard, far smoother and cleaner than any HPD 315 I've owned and better even than my old 12" Monitor Gold Chatsworths.

Here's a shot of the unit I have to strip down tomorrow. It doesn't show you much, but the surround is truly stuffed!