Speaker cone outside neutral position at (too) high volumes - reason to worry?

[TV31]

I would be happy with your advice/ideas.
I recently purchased a second hand set of Spendor S5e. They sound fabulous but I have some doubts about the bass driver. At very loud volume and playing bass-heavy music the cone comes forward a little bit (just a couple millimeters) and does not return to the original position. It does still seem to produce normal sound and seems the move unrestricted. I gently pushed the cone back and it is as nothing happened. Is this something to be worried about? I should probably not play the music as loud but I am a bit afraid that there could be a problem with the spider for instance.

 

[Mammy Nun]

Ffs.......Its a wonder you can even concentrate on the music with such a problem.

 

[TV31]

@Mammy Nun, help my out here, what do you mean?

 

[Mammy Nun]

@Mammy Nun, help my out here, what do you mean?

looks like a 4 toed Ninja has sneeked into yer room and is about to steal yer speakers....if yer lucky......!!!

 

[Diamond Joe]

Not an issue I've seen before, but I would have thought that the cone should move in an out without too much resistance, I'd certainly expect it to naturally return to its original position when everything's been turned off, it doesn't sound right to me.

If I were in your shoes I'd give Spendor a quick call about it - 01323 843 474 or email: info@spendoraudio.com - they should be happy to help. Good luck.

 

[insider9]

Great advice by Diamond Joe.

Please don't mind comments #2 and #4. Most people on here are extremely helpful and comments as above are not the norm and in fact rather rare.

 

[Al ears]

Great advice by Diamond Joe.

Please don't mind comments #2 and #4. Most people on here are extremely helpful and comments as above are not the norm and in fact rather rare.

As stated get in touch with manufacturers. That displacement could be down to amplifier clipping damage.

 

[davedotco]

There are two effects that can alter the position of the bass cone.

Firstly, there is the possibility of a DC voltage appearing on the amplifiers speaker terminals. I small DC 'offset' voltage will move the coil backwards or forwards by a few mm causing the cone to be displaced, forward, in this case. It should be expected that the offset increases with power (volume) but the cone would normally return to the normal position when the power is reduced or the amp powered down. If you can get your hands on a multi-meter, it would be worth checking to see if this is the case

Secondly, the coil may be pushed so far forward in the gap that some part of the coil assembly 'catches' on the pole piece or front plate of the magnet which stops it returning to its natural position. This is quite common on hi-fi speakers that have been overdriven.

What appears odd is that the cone can be pushed back into position without ill effects, perhaps you can describe more fully what happens at lower levels and as the amplifier is wound up, are there any odd sounds for instance? How does the cone assembly feel when you move it by hand?

 

[TrevC]

If the speaker cone remains like that with the amplifier off it must be sticking in some way, but if it sounds OK no problem, if it returns to normal with the amplifier off there may be excessive DC on the speaker outputs on the amplifier. The second scenario needs to be sorted before it causes speaker damage.

 

[TV31]

Thanks for all the helpful comments.
I just had time for a proper analysis.
Not playing music, I can move the cone around without any restrictions, the resistance feels the same left and right, no locking or crackling etc.
At low volume everything sounds perfectly normal, no difference between left and right
At high listening volume, around 0db, It sounds fine, but when I put my ear close the the cone I can hear some very subtle ratles not present in the other speaker.
Going up to +2, +3db and playing heavy bass the cone moves forward, but sounds the same and seems to have unrestricted excursions. No clear drop in volume, still the subtle rattles.
When I switch off the amp, or even disconnect the speakers, the cone stays in the forward position. I can still move it around by hand like I could in the neutral position, no locking or crackling. To move it back to neutral I have to push a little bit harder and when it slides back there is clear fine crackling.

I don't have a great feeling about this...

 

[nopiano]

It seems that the speaker has been overdriven at some point, but not so badly as to wreck it. My guess is the voice coil has distorted slightly. Many users might never realise.

However, like you I'd never be happy, so see if you can get a replacement driver, and ask the manufacturers if it needs to be soldered or are just push-on tags.

 

[TV31]

Mmm, shame.
Isn't it strange that only one base driver would be damaged by being overdriven, and not the tweeters as well? Or might this happen when people play loud and crazy deep music? Or connect line-in to Phono stage on amp, boosting the lower frequencies?
Does damage occur by overdriving for longer periods or might this happen within a couple of minutes?

 

[nopiano]

Mmm, shame. Isn't it strange that only one base driver would be damaged by being overdriven, and not the tweeters as well? Or might this happen when people play loud and crazy deep music? Or connect line-in to Phono stage on amp, boosting the lower frequencies? Does damage occur by overdriving for longer periods or might this happen within a couple of minutes?

Could be a loud party, or a moments carelessness plugging in a device with the volume up - and pop goes the speaker!

 

[davedotco]

Mmm, shame. Isn't it strange that only one base driver would be damaged by being overdriven, and not the tweeters as well? Or might this happen when people play loud and crazy deep music? Or connect line-in to Phono stage on amp, boosting the lower frequencies? Does damage occur by overdriving for longer periods or might this happen within a couple of minutes?

Could be a loud party, or a moments carelessness plugging in a device with the volume up - and pop goes the speaker!

The coil is slightly missaligned causing it to rub in the gap at high levels. It may be overdriven or a slight manufacturing defect. If the speakers were newish, I would return them under warrantee.

One thing to try is to play some bass notes at the minimul level that causes the rubbing noise. Press hard on the chassis of the speaker in, say, the 12 and 6 o'clock positions, then do the same in the 9 and 3 o'clock positions. See if this alters the amount of noise, if it does you might be able to cure the problem by adjusting the tightness of the speaker fixing bolts. Careful though, if they are fixed using wood screws this might not be possible.

In effect, you are very slightly distorting the chassis of the drive unit which will very slightly change the position of the coil in the magnetic gap, I have saved many a speaker with this trick.

Note. Old Spendors had pretty heavy cones which could sag under gravity causing the same sort of issue. It was routine to turn the speakers upside down (either the drive unit or the complete speaker) so that the cone sagged back into the 'correct' position.