Newbie here! - Need help with Tannoy bass driver

[jmoutinho]

Hi all!

Although I'm a long time lurker around the forum, I'm still a newbie and don't have the knowledge to actually provide helpful inputs to anyone...
Still the forum has already helped me find valuable information in various subjects.

This time I'm looking for advise with a problem I have with the bass driver of a Tannoy Mercury m2 speaker

What happens is that the driver stutters intermittently, as if the connection is interrupted.
I've already resoldered the wires that go to the terminals, to no avail...

Is there anything else I can check, or is the driver blown?

Thanks in advance for your help!

Cheers!

 

[johnnyx]

Check the tinsel wires between the speaker terminals on its frame, and the cone.
You will have to remove it from the box to do this.
You will need some way to measure continuity.

 

[jmoutinho]

I checked with a multimeter, and there is continuity. I removed the dust cap without major damage, but I'm not sure I will be able to do the same with the rest of the cone, to have access to the wires...

I've made a video of the problem to see if it can shed any light on possible causes...

Thanks again!

 

[Galu]

You don't have to perform surgery to check the tinsel wire connections. They are located at the rear of the cone as johnnyx describes.

 

[Galu]

Looking at the video, I wonder if the voice coil former has become detached from the loudspeaker cone?

The glue can become brittle with age or the speaker may have been overloaded.

 

[johnnyx]

Looking at the video, I wonder if the voice coil former has become detached from the loudspeaker cone?

Listening to it, I think this is more likely. There is no intermittent silence, just an intermittent lack of low frequencies.
Run a thin bead of glue between the cone and the coil former.
Perhaps someone could suggest the best glue to use.

 

[jmoutinho]

That's a good shout... I'll try and add a bit of glue around the coil former. Although moving the cone manually, it seems to move the coil pretty evenly, and I can't see any gaps. But it's certainly worth a try.

There is no intermittent silence, just an intermittent lack of low frequencies.

This is exactly what happens!

Here's a picture of the only spot I can see there is a bit less glue:

Thanks again, I'll keep posting updates!

 

[Galu]

Has the currugated rear suspension (the spider) become detached from the cone/voice coil assembly?

Perhaps more photos (and not taken so close up) would help.

 

[jmoutinho]

The spider seems well attached (both inside and outside).

Here are some photos.

 

[Galu]

Thanks, those photos are clearer and I can see the spider is attached.

I suppose there could be an intermittent connection where a tinsel wire is soldered to the voice coil wire on the voice coil former.

 

[jmoutinho]

Well if that's the case I don't think I will be able to resolder that connection without damaging the cone...
The joints are covered in some sort of blue paint...

Meanwhile I've applied a strand of glue around the coil former.

 

[jmoutinho]

One more piece of information during my last tests:

When I check for continuity with the multimeter, it shows continuity, but no resistance. I think it should show an Ohm reading similiar to the driver's impedance, right?

Also, if I move the cone manually while the multimeter's probes are on the terminals, for a few moments I get a resistance reading.

Is there anything to conclude from that?

 

[Galu]

Use your multimeter on the resistance setting - not the continuity setting - and check again.

The DC resistance of the voice coil will be a bit less than the nominal impedance of the driver, say 6 ohm for an 8 ohm driver.

 

[Logon]

Perhaps someone could suggest the best glue to use.

The following webpages seem informative enough 😉

https://prostech.vn/adhesive-voice-spider-assembly/

https://prostech.vn/adhesive-for-speaker-assembly-frame-basket-bonding/

P. S.: Out of curiosity, I would like to know if you've also checked the welds solidity/conductivity of the 2 faston connectors on the basket.

 

[raymondj]

A question regarding the video, is the rubber or foam cone surround creased in two places, or possibly it is a mark?

If it is creased maybe they have had an accident in a previous life, I am not sure how this would give you the sound issues you are experiencing ?