Speaker Ground Terminals??? WTH?

[watchnerd]

I just recently discovered that some speakers have ground terminals, something I've never seen before despite being in the hobby for decades.

It seems like it shows up on some Tannoys and a few other brands.

Apparently you're supposed to hook the ground wire back to your amp.

What's going on here?

What problem is this solving?

Is it specific to high efficiency speakers and/or tube amps?

 

[NTK]

Here is their explanation. I'll let you decide if it makes any sense.
https://kb.musictribe.com/musickb/v...TMINSTER-ROYAL-GR-How-do-I-ground-my-speakers

 

[restorer-john]

What problem is this solving?

Is it specific to high efficiency speakers and/or tube amps?

Maybe they are grounding the driver basket frames?

An excuse to sell special single core 'grounding cable' at the point of sale perhaps?

 

[watchnerd]

Here is their explanation. I'll let you decide if it makes any sense.
https://kb.musictribe.com/musickb/v...TMINSTER-ROYAL-GR-How-do-I-ground-my-speakers

I find in interesting....

It's not like it's a big profit item to add a 5th post and grounding wire is cheap.

They're not making magical claims.

But when would it ever be needed?

 

[watchnerd]

Maybe they are grounding the driver basket frames?

An excuse to sell special single core 'grounding cable' at the point of sale perhaps?

Are driver frames normally grounded at all?

Or in some other way?

 

[Julf]

Are driver frames normally grounded at all?

No.

 

[Cbdb2]

Very strange. Especially since most power amps negative speaker terminals are conected to the ground pin of the power plug, grounded.

 

[waltzingbear]

there are now more amps being made out there that are push pull. So, yes, it can be a bad idea to run the neg terminal to ground. Does it make a difference to the sound, when it is not ground but floating? I have no idea.

 

[Julf]

there are now more amps being made out there that are push pull. So, yes, it can be a bad idea to run the neg terminal to ground. Does it make a difference to the sound, when it is not ground but floating? I have no idea.

Sure, balanced and bridged amps don't connect the "negative" speaker terminal to ground. It doesn't matter. It is in any case irrelevant - the question here is if separately grounding the driver chassis makes any difference. At the power and impedance levels involved with speakers it clearly doesn't. When was the time you heard hum or buzz from a speaker when the speaker wasn't connected to an amp?

 

[Blumlein 88]

Yes, do they say what the green terminal connects to internally? If someone has one of these class D amps and thinks the black outputs are ground this might be very bad.

And even more so, this is a case where they need to provide measurements of ground vs no ground.

 

[Blumlein 88]

"The Prestige line employ a unique fifth speaker terminal in addition to a bi-wire pair...With the driver chassis grounded via the 5th terminal, and by using appropriate speaker cable, this proven technology ...electrically earths the driver chassis to dramatically reduce radio frequency interference circulating in the hi-fi system. Eliminating this RF ‘noise’ brings substantial improvements in mid-range clarity and further enhances the soundstage imaging."

So RF isn't mid-range. Hmmmmm. The same worry about RFI messing with digital or something or another?

RFI is a real issue with condenser microphones, but they have lots of active gain along the way, and higher impedances. I'm thinking it would take peculiar and unlikely conditions for this to matter with speaker voice coils.

 

[GrimSurfer]

This would have the same effect as wiring the cold connector of a male-to-male RCA plug to the shield on a 1-conductor RG59 coax cable. Only in this case, the speaker basket drains all the way to ground.

I can see some electrical hazard in this approach (fault in a double insulated piece of gear upstream, or a failure/removal of a ground pin in a piece of pro gear upstream). As for an audible difference, it might make one in a very high RF environment where anything hitting the basket or shield would drain back to ground. Especially an RF source operating at a frequency that excites the roughly parabolic basket.

But I can't really see how it would make a difference given that the basket is electrically isolated from the voice coil by the spider. This leaves EMI as the reason for such an arrangement because this could, in theory, affect the magnetic field of the driver motor. But a drain wire wouldn't do anything in such cases because magnetic flux doesn't behave like the flow of electrons between points of different potential. (Even though the two are related)

But JHC, you'd need to be operating an MRI machine next to a speaker to have such an effect on the voice coil via the basket. This is because the magnetic field of any decent driver at the voice coil would massively exceed an ever larger field several feet away.

So I'm inclined to look at this ground terminal as snake oil.

 

[Killingbeans]

"The Prestige line employ a unique fifth speaker terminal in addition to a bi-wire pair...With the driver chassis grounded via the 5th terminal, and by using appropriate speaker cable, this proven technology ...electrically earths the driver chassis to dramatically reduce radio frequency interference circulating in the hi-fi system. Eliminating this RF ‘noise’ brings substantial improvements in mid-range clarity and further enhances the soundstage imaging."

Sounds like something that sells itself on pure paranoia.

The voice coil is encaged in a permanent magnet. Besides, the impedance back through the amplifier teminals is miniscule. RFI have no way of sneaking back that way.

If this actually gave "substantial improvements", then it shouldn't be a problem to prove it with measurements.

 

[watchnerd]

"The Prestige line employ a unique fifth speaker terminal in addition to a bi-wire pair...With the driver chassis grounded via the 5th terminal, and by using appropriate speaker cable, this proven technology ...electrically earths the driver chassis to dramatically reduce radio frequency interference circulating in the hi-fi system. Eliminating this RF ‘noise’ brings substantial improvements in mid-range clarity and further enhances the soundstage imaging."

So RF isn't mid-range. Hmmmmm. The same worry about RFI messing with digital or something or another?

RFI is a real issue with condenser microphones, but they have lots of active gain along the way, and higher impedances. I'm thinking it would take peculiar and unlikely conditions for this to matter with speaker voice coils.

This would have the same effect as wiring the cold connector of a male-to-male RCA plug to the shield on a 1-conductor RG59 coax cable. Only in this case, the speaker basket drains all the way to ground.

I can see some electrical hazard in this approach (fault in a double insulated piece of gear upstream, or a failure/removal of a ground pin in a piece of pro gear upstream). As for an audible difference, it might make one in a very high RF environment where anything hitting the basket or shield would drain back to ground. Especially an RF source operating at a frequency that excites the roughly parabolic basket.

But I can't really see how it would make a difference given that the basket is electrically isolated from the voice coil by the spider. This leaves EMI as the reason for such an arrangement because this could, in theory, affect the magnetic field of the driver motor. But a drain wire wouldn't do anything in such cases because magnetic flux doesn't behave like the flow of electrons between points of different potential. (Even though the two are related)

But JHC, you'd need to be operating an MRI machine next to a speaker to have such an effect on the voice coil via the basket. This is because the magnetic field of any decent driver at the voice coil would massively exceed an ever larger field several feet away.

So I'm inclined to look at this ground terminal as snake oil.

Is there something different / special about UK AC plugs that would make this more sane?

 

[GrimSurfer]

Is there something different / special about UK AC plugs that would make this more sane?

Not that I'm aware of. The plug pins appear different but function more or less function in the same manner (hot, neutral, ground), depending on whether the gear is double insulated or grounded. I'm not familiar with how homes in the U.K. are grounded/bonded but can't see how that would make a difference.

The voltages and AC cycles aren't significantly different (100, 110, 115, 120, 230, 240 is all classed as low voltage in electrical terms; 50 or 60 cycles presents no unique challenges).

 

[watchnerd]

A little more info here:

https://www.diyaudio.com/forums/multi-way/126888-grounding-loudspeaker-circuits.html

"Today, while reading J.A.’s review in Stereophile of the Esoteric MG20 Loudspeaker, I notice that the design employs 5 binding posts. According to the reviewer: “…one pair each for the tweeter and the woofers, and a fifth that grounds the amplifier’s output to the drive-unit chassis"

So, yes, apparently it connects inside to the drive chassis.

One comment alludes that Linn may do it, too, on some speakers.

 

[GrimSurfer]

A little more info here:

https://www.diyaudio.com/forums/multi-way/126888-grounding-loudspeaker-circuits.html

"Today, while reading J.A.’s review in Stereophile of the Esoteric MG20 Loudspeaker, I notice that the design employs 5 binding posts. According to the reviewer: “…one pair each for the tweeter and the woofers, and a fifth that grounds the amplifier’s output to the drive-unit chassis"

So, yes, apparently it connects inside to the drive chassis.

One comment alludes that Linn may do it, too, on some speakers.

Based on the writings in that forum, I'm more inclined than ever to view this as snake oil.