Tannoy MG15

[Hooch500]

I posted something a while ago about a midrange colouration with my 15's mounted in corner Yorks.
Out of idle curiosity I pulled the drivers out and found that the foam gaskets are pretty much at the same level as the frame. I had backed off the torque on the nuts to a bit more than finger tight but obviously this wouldn't matter once the foam had compressed. Im thinking this is a likely cause of my issue, the next question is are they available or is it something I can buy elsewhere and cut ?

 

[Hooch500]

Just as an added thought - the fact that the square section gasket sits in a captive channel makes me think that there are an awful lot of MGs with the frames touching the baffles ! Obviously this isn't possible with a normal flat gasket sitting on a flat frame surface.

 

[cooky1257]

Indeed, something I've raised in the past.

 

[Tony L]

If you leave the drivers out of the cabs for a day or two chances are the foam rubber will relax a bit. None of the three pairs I’ve owned seemed to have suffered.

The tightness is a fascinating thing and one I can’t easily assess as it is hard to see the sides of the drivers in the cab, but I’m pretty sure the alloy baskets in mine are touching the baffle, they are just not tightened much beyond that. My suspicion is you want that contact, but also the damping properties of the rubber, which would be negated by over-tightening. I arrived at the correct (subjective) tension for mine after much playing about, and I’d definitely advise doing the same. Basically if it sounds better it is better. Just be patient and don’t be afraid to try literally just finger-tight.

Also be aware things like how tightly the back door of the cab is screwed on makes a audible difference too, the very last thing you want to do is to build a giant conga drum, so as loose as you can get without rattles is likely right. A dull no-‘note’ thud is way better to my ears than anything approaching a hollow ring. The Tannoy driver dumps a heck of lot of energy onto that panel. Get into a BBC cabinet mindset here. I’m a total convert to screwed cabs!

 

[Hooch500]

Indeed, something I've raised in the past.

It's quite interesting that the original colouration I had was around female vocals, when I think of it since I slackened the bolts its gone further down. Effectively I suppose I've just tuned it to a different frequency !

 

[Hooch500]

If you leave the drivers out of the cabs for a day or two chances are the foam rubber will relax a bit. None of the three pairs I’ve owned seemed to have suffered.

The tightness is a fascinating thing and one I can’t easily assess as it is hard to see the sides of the drivers in the cab, but I’m pretty sure the alloy baskets in mine are touching the baffle, they are just not tightened much beyond that. My suspicion is you want that contact, but also the damping properties of the rubber, which would be negated by over-tightening. I arrived at the correct (subjective) tension for mine after much playing about, and I’d definitely advise doing the same. Basically if it sounds better it is better. Just be patient and don’t be afraid to try literally just finger-tight.

Also be aware things like how tightly the back door of the cab is screwed on makes a audible difference too, the very last thing you want to do is to build a giant conga drum, so as loose as you can get without rattles is likely right. A dull no-‘note’ thud is way better to my ears than anything approaching a hollow ring. The Tannoy driver dumps a heck of lot of energy onto that panel. Get into a BBC cabinet mindset here. I’m a total convert to screwed cabs!

Do you think the frame should touch at all ? I'm thinking a light contact might be worse than clamped. I'm thinking front mounting won't have this issue as the gasket would always be in contact ?

 

[Hooch500]

Do you think the frame should touch at all ? I'm thinking a light contact might be worse than clamped. I'm thinking front mounting won't have this issue as the gasket would always be in contact ?

I am clearly think too much !

 

[Tony L]

Do you think the frame should touch at all ? I'm thinking a light contact might be worse than clamped. I'm thinking front mounting won't have this issue as the gasket would always be in contact ?

Just play with it. Expect to take a good week or more fiddling and learning! I’m pretty sure mine are touching the baffle, but only finger-tight, i.e. literally just tightened until you hit a slight resistance as the basket touches the baffle, beyond that the rubber foam does its thing. I’m sure the ‘zone’ is to get it rigid and coupled but damped and non-resonant, and that is actually quite a small target to hit. With a driver of such size and mass along with so many bolts (I have the full eight) you really don’t need to go tight to stop it moving.

 

[Hooch500]

I packed behind the foam inserts to raise them slightly. Problem solved. Midrange resonance banished. Lockdown has its benefits, my business may be going tits up but finally got to the bottom of it ! Thanks again.