Tannoy Monitor Gold crossovers

[Wakefield Turntables]

fooking hell Joe you were correct about them looking like monoblocks. Well done incidently, I'll keep you updated with my secret project

[The Black Adder]

Many thanks chaps... Just the finishing off to do now!

[Reffc]

Excellent work Joe and I look forward to the final outcome

If that big Russian military cap starts ticking or smoking...back steadily away to a distance or about a mile

[The Black Adder]

Excellent work Joe and I look forward to the final outcome

If that big Russian military cap starts ticking or smoking...back steadily away to a distance or about a mile

lol... that thing is inside the case... It dose look ominously nuclear to be honest. It has a lovely sound, totally suits the Monitor Golds.

[Ammonite Audio]

Hi Joe

Are you still using the little 4-pin Tannoy plugs, or hardwiring the crossovers directky to the LF and HF coil terminals? Also, did you settle on any particular autoformer tap for best HF balance?

I'm pretty much decided that I'm going to restore my Lancasters and will probably get Nick to do the crossovers, since he has my Sowter autoformers and you have been a good guinea pig!

[The Black Adder]

Hi Joe

Are you still using the little 4-pin Tannoy plugs, or hardwiring the crossovers directky to the LF and HF coil terminals? Also, did you settle on any particular autoformer tap for best HF balance?

I'm pretty much decided that I'm going to restore my Lancasters and will probably get Nick to do the crossovers, since he has my Sowter autoformers and you have been a good guinea pig!

Hi Hugo.

I'm am hardwiring to the drivers. The plugs are fine but can become crusty over time apparently.

I settled on yellow tap of which also jumps to the 50R resistor.

Any questions, just ask.. or PM.

Cheers

[sey]

Nice job, Joe!

[Wakefield Turntables]

Any idea on how we can get pics of joes reworked cross overs, now im in the market for some making I'd like to see what he's used.

[Reffc]

Hi Hugo.

I'm am hardwiring to the drivers. The plugs are fine but can become crusty over time apparently.

I settled on yellow tap of which also jumps to the 50R resistor.

Any questions, just ask.. or PM.

Cheers

Those wanting to have a go at DIY versions minus the crossovers need to be careful here! I guess you've used the autoformers Joe, so no circuit changes are needed.

If not using the autoformer and using a fixed value inductor, you will not have the correct values if you use the yellow tapping values. Yellow tap may be what Tannoy show in the crossovers as flat, but it is not the electrically flat tapping. That is the Green tap not the yellow.

Bear in mind when you choose an inductor value if it is a fixed inductor value, it should have the same inductance as the green tap which is about 2.9mH and not the 4mH of the Yellow tap.

Furthermore, the green is connected back to the orange tap which makes the reflected impedance ratio 2.0, so for a fixed inductor value, the correct value for the shunt resistor is not 50 Ohms, its 25 Ohms. 50 ohms at this point will put too much energy into the HF circuit at the expense of bass. Any less than 25 Ohms and you will stress your amp but not change bass/improve response.

With the autoformer in circuit you do not have to worry about these things but many DIY/Forum diagrams I've seen for DIY fixed value crossovers have been wrong because of these points. I'm happy to confirm and supply the correct values if anyone else is having a go at DIY fixed value crossovers minus the autoformers (don't forget that these act as step-up/down transformers as well as a variable inductor).

[Ammonite Audio]

Joe is using the new Tannoy MG autoformer very successfully 'reverse engineered' and supplied by Sowter, so your comments apply in principle, if not quite in detail.

Those wanting to have a go at DIY versions minus the crossovers need to be careful here! I guess you've used the autoformers Joe, so no circuit changes are needed.

If not using the autoformer and using a fixed value inductor, you will not have the correct values if you use the yellow tapping values. Yellow tap may be what Tannoy show in the crossovers as flat, but it is not the electrically flat tapping. That is the Green tap not the yellow.

Bear in mind when you choose an inductor value if it is a fixed inductor value, it should have the same inductance as the green tap which is about 2.9mH and not the 4mH of the Yellow tap.

Furthermore, the green is connected back to the orange tap which makes the reflected impedance ratio 2.0, so for a fixed inductor value, the correct value for the shunt resistor is not 50 Ohms, its 25 Ohms. 50 ohms at this point will put too much energy into the HF circuit at the expense of bass. Any less than 25 Ohms and you will stress your amp but not change bass/improve response.

With the autoformer in circuit you do not have to worry about these things but many DIY/Forum diagrams I've seen for DIY fixed value crossovers have been wrong because of these points. I'm happy to confirm and supply the correct values if anyone else is having a go at DIY fixed value crossovers minus the autoformers (don't forget that these act as step-up/down transformers as well as a variable inductor).