Warming Voice Coils

[phil dekked]

This particular forum seems to be occupied by an amazing bunch of people searching for the audio holy grail - as such, can't see much related to profesional audio?

 

Snake Oil by the drum full!

Much of what is on this site is truly amazing - worth the time looking around if you want to smile

 

Don`t quite understand what your saying..? :)

 

I only linked to that site as it`s some direct measurements of temp over a voice coil and the effect of a cooling device! The guy who runs it has fallen foul of PSW and the whole bass shootout thing ended in a slagging match between him and Tom Danley ( the designer of the Lab sub). I only found it thru PSW ...? Your right about the " snake -oil " bit...!

 

 

 

.p.

[paulears]

Sorry - what we have are pretty secure data on temperature rise. My only real problem with all this is that running tests that are designed to prove a fact, very often don't. The physics says that efficiency drops off as heat builds up. In a real situation, if you run power close to the drivers maximum handling, it starts to compress, and you increase power to get more and so on. In most cases real eared people out front hear this, and stop pushing it - surely the speed at which the temperature drops is more important? If the system isn't loud enough, then add more cabs and amps. I just can't see what the fuss is about. Adding extra cooling, to me, just shows that people haven't got a grip on reality. I went on one of the Soundcraft courses a few years ago, and big Mick Hughes was being questioned on this kind of thing. "what if you haven't got enough sub bass?" was the question - his answer "get more subs!" He didn't suggest esoteric cooling devices or fitting temp sensors on the drivers. COmmon sense rules! The way the golden eared people carry on, the next product will be voice coil remote temperature sensing - and I guess they probably even exist!

 

On some of these kind of forums, people spend inordinate time trying to squeeze the last drop of performance out of individual components, and seem kind of surprised they don't sound good when pushed - what does?

 

The original thrust of this post, after we kicked off was my thoughts on cabinet heating, not driver heating.

[phil dekked]

The way the golden eared people carry on, the next product will be voice coil remote temperature sensing - and I guess they probably even exist!

 

On some of these kind of forums, people spend inordinate time trying to squeeze the last drop of performance out of individual components, and seem kind of surprised they don't sound good when pushed - what does?

 

The original thrust of this post, after we kicked off was my thoughts on cabinet heating, not driver heating.

 

Yep! What you say is "right" but how will things move forwards if the answer is to just buy more boxes..? Surely the destructive experimenting will result in the long term with feedback to the driver manufacturers and then better products The original post was about cabinet heating and this is caused by the heating of the air around the driver. So the two are linked...?

And yes voice coil temp` sensing is here and if used with a built in dsp / amp unit in an active box can only result in a better more reliable product?

 

.p.

[Simon Lewis]

Phil,

 

The issue with the add on heat sink appears to be thermal hysteresis when the system is pushed hard. Manufacturers do pay careful attention to heat management - c.f. ferrofluids, vented gaps, aluminium VC formers or even the forced air cooling as used in some Community enclosures.

 

Many will build finite element analysis models to predict exactly how heat will dissipate and how they might improve matters. However, thermal limits are just part of a loudspeaker's failure modes, and the modern boxes that use motional and thermal feedback to extract maximum output without distressing the amplifier / drive unit combination do so with an exact knowledge of each component's operational characteristics.

 

The add on device shown in this web page achieves good cooling, but does not seem to give too much more usable audio!!

 

Simon

[jamesperrett]

This kind of debate can call on the support of equally qualified people for both views. It really depends on the design of the system in question. Some cone suspension materials seem to respond to running in while others don't.

 

I'll bet that there is also an element of psychology in some cases too. I often find that I get used to a sound and think that things sound better than they really do after a while. It is only when I switch back to listening on a better system that I realise that the sound was not really that good after all.

 

If we expand the topic to include amplifiers then I would say that only badly designed amps sound different when they warm up. Well designed amps take temperature differences into account and work equally well whatever the temperature.

 

Cheers

 

James.