High Frequency Drive Unit Fixings

[ZeroPlex]

Hi,

I was reading through the manual of my speakers and it says to occasionally check the bass driver fixings for tightness, which is understandable, but it says DO NOT touch the High Frequency (tweeter) fixings.

I really cannot see what harm it would do to check that the tweeter fixings are secure?

Does the manual state this just incase you over-tighten the somewhat small (plastic) fixture, hence cracking/damaging it?

If you ever had to replace the tweeter, you'd obviously have to remove the fixings, fixture, and re-fit, so the above is the only reason I can arrive at.

The fixings on my speakers are hex head woodscrews.

Before I read the manual, I did check all the drive units for tightness, so reading about not to touch the tweeter fixings has left me somewhat paranoid.

Hopefully someone can ease my paranoia with a reason why they state this, or confirm that I am correct with the reason I arrived at.


Thanks.

 

[blueone]

What brand and model of speakers are these?

 

[Swerd]

I wouldn't worry much over it.

1. Rule #1 for fixing things: If it ain't broke, don't fix it!
   
   
2. If the tweeter face plate is plastic or fiberglass, and not aluminum, over tightening the mounting screws could easily crack the face plate. That is the most likely reason.
   
   
3. Woofers do vibrate a lot more than tweeters. It may be that the woofers vibrate strongly enough to loosen the screws over time, but the tweeters do not. It is good that your mounting screws have a hex head and not a Phillips head. It's too easy to slip with a Phillips screwdriver while tightening screws, and poke it through the speaker cone or dome. Which takes us back to rule #1.

 

[ZeroPlex]

Hi guys, thanks for the responses.

The speakers are Mission 775e's.

I've contacted a few people about this issue with one person saying that the 77 series Missions have spring loaded tweeters which have a specific torque setting for the fixings.

So as you tighten, it puts tension on the spring, whicn in-turn can apparantly affect the audio output.

I've had the tweeter fixture out of it's cabinet socket and there is nothing at all behind it, it's just connected by the 2 wires.

The fixing holes on the fixture are even counter-sunk, which would almost eliminate the chance of any warping, so I really cannot see how tightening the screws can have an affect on any spring inside the tweeter fixture itself?

This does make sense to any of you guys, or am I being wound up

 

[ZeroPlex]

Well, I think I have resolution on this issue.

The Mission 77 series tweeters are leaf-sprung, but it's just the 2 screws that secure the tweeter at the back of the black housing that have a specific torque setting.

I've been told, and this may be useful to others who may need to replace an indentical tweeter on this series of speaker, that the best way to describe the tightness of the screws is hand tight, plus a further 1/4 turn. This should get it to the correct torque, or very close.

I honestly couldn't see all along how the 4 cabinet woodscrews that secure the fixture from the front could have any effect on a spring loading in the tweeter housing itself. It just wasn't logical.

The reason they state to NOT touch the 4 cabinet woodscrew fixings in the manual is because they'll never need tightening due to low vibration from the tweeter, over-tightening the screws could stress the fixture too much causing damage, and given that the screws are so close to the delicate tweeter itself, you could easily slip with the tool and land on the tweeter.

If they didn't feel the bass drivers ever need to be checked for tightening, they'd say to NOT touch these aswell, but there is less chance of accident occuring with these larger/stronger fixtures, but there is still no need to drive them home tight. Just make sure they are secure every now and again.

I've included a pic below of the tweeter, in place, with the four fixings screws.

 

[j_garcia]

Actually, I think they might not want you to strip the CABINET if there are no inserts in the cabinet (bare wood), as much as or more than damaging the tweeters themselves. You can't just change the orientation of those tweeters and remount them since they only fit in one of two orientations due to the cuts.

 

[ZeroPlex]

Actually, I think they might not want you to strip the CABINET if there are no inserts in the cabinet (bare wood), as much as or more than damaging the tweeters themselves. You can't just change the orientation of those tweeters and remount them since they only fit in one of two orientations due to the cuts.

I'm not sure if I understand you correctly, but do you mean they don't want you to strip the pre-drilled screw inserts, which if you did and you made a new hole left or right of the existing, it would make the fixture impossible to fit?

Or perhaps cause damage to wooden cabinet itself behind the tweeter by over-tightening, hence possibly leaving you with no backing at all to mount the fixture?

 

[j_garcia]

Yes, if you strip out the cabinet, then there would basically be no way to mount this guy anymore since you cannot simply reorient the driver like you would be able to do with a tweeter that did not have reliefs for the midrange drivers. That is assuming there are no inserts in the cabinet.

My MTM speakers are similar to this but the tweeter is flushed below the midrange drivers so even if you stripped the cabinet, you could simply clock it a few degrees and screw it back in.

 

[ZeroPlex]

When the tweeter is unscrewed from the cabinet, there is a cut hole behind it to allow the tweeter housing that is screwed to black fixture to pass through.

You then have your four drilled holes for the 4 woodscrews when the fixture is in place.

From memory, the cabinet thickness of the hole was about an inch I think so would be pretty hard to break.

That said, when you are messing about with the screws alot, it does shave the holes slightly, and I have played about with them quite a bit, but always had plenty of grip regardless to hold the tweeter fixture in place.

If you ever stripped them so much that the screws wouldn't secure the fixture properly, you could always widen the plastic holes and use a larger screw. It wouldn't be very pretty though if the head wouldn't fit in the counter-sunk holes of the fixture though, although that wouldn't be an issue if you intended to use the protective grilles.

 

[tonedeaf]

I wouldn't worry much over it.

1. Rule #1 for fixing things: If it ain't broke, don't fix it!
   
   
2. If the tweeter face plate is plastic or fiberglass, and not aluminum, over tightening the mounting screws could easily crack the face plate. That is the most likely reason.
   
   
3. Woofers do vibrate a lot more than tweeters. It may be that the woofers vibrate strongly enough to loosen the screws over time, but the tweeters do not. It is good that your mounting screws have a hex head and not a Phillips head. It's too easy to slip with a Phillips screwdriver while tightening screws, and poke it through the speaker cone or dome. Which takes us back to rule #1.

I can't believe you mentioned poking a hole in the speaker dome.I just did that with a phillips screwdriver while modifying some older speakers.