Mods on Tannoy DC drivers

[ginetto61]

Hi !

i have some pairs of cheap Tannoy DCs and i received the following advice about mods that could be carried out on them ...

Gino,
I personally wouldn't bother making the HF unit mounting lossy, Tannoy don't (and I would say they are slightly more clued up than 'we')..... looking at the pictures further, making the mount lossy could cause it to vibrate in Unknown ways, due to the HF unit suddenly gaining an active Center of Gravity.
And wandering C of G's (there are many C of G's in an aircraft btw(not factoring in Center of Pressure shifts)) in an aircraft leads to Many interesting things.
Though one could try making the hf mounting lossy AND 'encapsulate' it with a lossy material to hold it - still too much 'ache' for maybe no gain...

@Ginetto,
I have an 8 inch tannoy DC and had be toying before with the same idea of "decoupling" the tweeter assembly too. However note that the transition between mouth of waveguide and speaker cone is crucial ( see Tannoy III LZ, on another tannoy) and by intoducing an offset due to the thickness of damping might create more problems than it solves. Maybe try what tannoy do on some of their monitors, there is a brace right behind the DC and a blob of "putty" pressed in between the tweeter magnet and the brace...

Comments very welcome.
Regards, gino

 

[ginetto61]

Hi just to explain better this is the driver ...

and this is the frame sandwiched between the tweeter and the woofer magnet

An externally hosted image should be here but it was not working when we last tested it.

Normally the vibes generated by the woofer are transmitted to the tweeter because they are rigidly coupled.
So the idea would be to decouple the tweeter from the woofer with the interposition of some damping material (e.g. rubber gasket )
Easy to say difficult to do properly i understand
Thanks, gino

 

[sippy]

Originally Posted by C37 View Post
@Ginetto,
Maybe try what tannoy do on some of their monitors, there is a brace right behind the DC and a blob of "putty" pressed in between the tweeter magnet and the brace...

This bit of putty is between the hf magnet and the brace in the 609 - IF that bit of putty is 'valid' as damping, my names Isambard Kingdom Brunel.
One of my 609's has this putty / the other don't (I took it out) and shock horror I cant hear any difference.
I did have the thought - while in a HiFi shop!* - that one could make a fairly thin gasket by rolling Blu-tak with a rolling pin between 2 bits of grease proof baking paper, peel one paper off, apply Blu to magnet and cut the HR hole / screw holes out with a sharpish knife.
Maybe use some springs between washers to allow for some 'give'.

If / When I get then 'copycabs' built, I will be butting the brace to the / a magnet a-la Planet10 'Holy Brace' style.
I'll Will add damping to the basket - very dense closed cell PU foam 'core', PU glued to the metal and that mess 'faired' with plumbers caulk and wrapped in re-cycled denim felt.
I might even go mad and foam / caulk round the hf / mid-bass magnet - treat the 'parts as one' so to speak.

I did this on a pair of Eminence Beta12LTA's and it was a great success, the baskets do not 'ring on' if I tap either the magnet or a bare metal edge on a leg
A 'Tink' not a 'Tiiiiiiiiiinnnnnggggg'.

*Guy in the Hi-Fi shop** is very clued up diy'er AND an owner of Tannoys, after I told him I owned Chesters and 609's, HE said the only thing to do was get the drivers re-built IF they needed it and build better cabinets for them....... or the same cabinets but hewn from better materials.

**He's also going to let me poke about inside 'some' B&W Matrix cabinets with a rule and Verniers..... those measures will go in the other thread

 

[ginetto61]

Hi and thanks for the valuable advice
While i still think that coupling a tweeter rigidly with a powerful and vibrating woofer is not a "nice" thing i will leave the DC as it is.
Any mod is going to be tricky and i could very well damage the driver.
A telling test could be a IMD measurement, with a powerful signal on the woofer and another on the tweeter and see for distortion products.
Unfortunately i have not the needed set-up.
I will work on it.
Thanks again and regards, gino