Warming Voice Coils

[Mr.Si]

Hi all.

 

Ok, I've just been in a conversation with a fellow tech friend of mine and he was asking me if I'd ever warmed up the voice coils of my speakers before a gig, rather than just sending huge impulsive kick drums or whatever through them straight away?

 

The theory being that it helps keep the maintain the life of the speaker drivers.

 

Now I have to admit, I haven't ever intentionally done this or known it might be necessary until this conversation, but it's an interesting idea and we were wondering how many others might do this.

 

So...

1. do you do this?

2. do you think it is necessary?

 

Thanks,

 

Si

[Tarqs]

Not trying to be flippant but perhaps we all do it unintentionally by playing background music before the gig ?

 

Or being flippant – isn’t that what the support act is for ?

 

Interesting question though

[jayselway]

I think I do it without actually meaning to - as there is a nice tuner in the rack, which sends Radio 1 gently through the rig while I'm setting up.

 

Obviously not if it's one of those annoying jobs where they tell you to arrive while the guests are there!!

[bruce]

...a nice tuner in the rack, which sends Radio 1 gently through the rig while I'm setting up.

 

[cantankerous curmudgeon]

Ooohh no - not radio one!! It means when you eventually get round to starting the gig, you'll already be annoyed!

 

Or am I just showimg my age?

[/cantankerous curmudgeon]

[Simon Lewis]

I cannot think of any benefits from "warming up" the voice coils.... The HF driver VC has a low thermal mass anyway, and the LF driver won't warm up quickly with the impulse sound of a kick drum. This type of signal is likely to cause more problems to the mechanical components than the VC.

 

I do try pushing the system hard to check that my power supply is stiff enough, but not to put heat in the speakers - that will only lead to power compression!

 

Any music played beforehand is either at the client's request, or is my choice. "Practicing" band members get blasted with pink noise while I run Smaart ;-)

 

Now, where's my Val Doonican LP?

 

Simon

[Lamplighter]

Si

 

Back in the mists of time I remember " warming up" speakers that had not been used for a while. A low tone, say 10 Hz was used slowly increasing the level over several minutes. This had the effect of exercising the suspension and noticably increased the low frequency handling power of the speaker. Modern speakers don't seem to need this form of torture.

 

Brian

[SimonTheSoundMan]

There's also more than just the voice coil. The suspension needs to be worked to perform at its best. Also, the cone and the wood of the cabinet need to warm up to sound their best. It's a bit like warming a violin before an concert, the wood and the strings change their timbre.

 

The rest of the equipment needs to warm up also, both solid state and valves. Solid state takes around 30miins to an hour, valves usually take between 6 hours and 2 days.

 

Some say cable needs to be warmed up, but some claim it doesn't make a difference.

 

 

I have tested my hi-fi and a difference of 3dB to the frequency responce can be measured at some frequencies after running the hi-fi for a few hours. Now, that's low powered, just think of a room with arrays. The room can also change acoustics, try walking into a concert midway in the performace. It sounds eeire.

[paulears]

Hi Simon. Whilst agreeing totally with the comments on Valves, the differences in warm/cold performance on solid state equipment has always seemed to me to be quite small. The difference in cabinet temperature is not something I've ever seen data on. The physics of material properties changing with temperature is pretty solid stuff, but venue ambient temperature changes surely exceed those that arise as a result of frictional and pressure induced heating effects from the drivers?

 

Unless real evidence exists that has not been 'bent' by the hi-fi brigade, I can't really agree with this. The trouble with big systems, and I'm assuming that is what we are talking about, is that far more destructive artefacts creep in as soon as the audience arrive - I can't believe any of these temperature effects could be heard above the noise floor.

 

I'd like to see some data on the effects of a cabinets alteration of speaker performance as it heats.

[SimonTheSoundMan]

With cabinets, it's not temperature. "Warming up" is just a term that is used. Musicians have understood for years that playing an instrument will change the sound. I have tried it with two well used speakers, one which was running for a few hours, and one which was not. The bass was tighter, soundstage larger, trebles was calmer and warmer on the "warmed up" speaker.

 

 

Solid state is not as dramatic as valves, I agree there. Capacitors can change their values when being used for a period of time, and also heat does have an effect. An electrical engineer would be able to tell you all about this.

[paulears]

Also, the cone and the wood of the cabinet need to warm up to sound their best.

 

The rest of the equipment needs to warm up also, both solid state and valves. Solid state takes around 30miins to an hour......

 

Come on Simon - you said the wood had to warm up. I'm happy that the properties of a driver can change when it's had a bit of a thrash, but the cabinet?

 

3dB difference? I'd get a new hi-fi - that's a massive drift, certainly more than the + or - on even a cheap spec - you should take it back and demand a refund!

 

You seem to have got a bit confused here - playing a decent instrument does bring about subtle tonal changes, but this is more prominent on woodwind and brass where both moisture and temperature differences occur when played. String instruments normally just need bringing to the ambient temperature of the venue - strings are also hygroscopic if they are not a man made product - so gut strings may well sound different as temperatures change, or more commonly when humidity changes.

 

6 days for a valve to stabilise - this is rather extreme.

 

Are you sure you are not a hi-fi audiophile who spends a fortune on daft things like speaker cable with arrows and low skin effect?

[SimonTheSoundMan]

I have worked in hi-fi for 3 years, however I did know the truth (we do not let the customers know the truth though. shhhh).

 

 

yeah your right, 3db is a lot. Haha. Dunno why that came into my head, my fingrs worked faster than my head. Sorry for quoting something I couldn't remember fully. :)

 

 

I like my braided CAT6 cable on my speakers, so strike me off that list. :)

[phil dekked]

Also, the cone and the wood of the cabinet need to warm up to sound their best.

 

Come on Simon - you said the wood had to warm up. I'm happy that the properties of a driver can change when it's had a bit of a thrash, but the cabinet?

 

 

 

Looking at the measurements that this guy did on the effects of pumping a lot of power into a hornloaded sub I wouldn`t count out the effect of heat in the cabinet itself.

 

Pi loudspeakers page

 

Measurement page

 

I`ve always been worried at the offset effect that heat puts into drivers with a small rear volume ( the air expands in the sealed chamber with heat , so pushing the cone forwards ( offset) and thus closer to xmax..?). So with that amount of heat pumping into drivers I`m sure cabinets must have some temp` change? I`ve personally felt the access covers on a set of Lab subs half-way thru an all-night stint and they were V.V HOT!

The advent of lighter , higher powered amps means that we`re putting a lot more power into the very in-efficient devices called loudspeaker drivers , and most of the in-efficiency is lost in.................heat!

 

.p.

[jpitkin]

The bass was tighter, soundstage larger, trebles was calmer and warmer on the "warmed up" speaker.

 

Are these not the things that pretty much all Hifi geeks say about anything that has been done to "improve" the sound of their hifi's?

 

Only change I've seen in drivers is when they've got a bit too warm, then they do start to sound different, maybe quite a bit quieter.

[Simon Lewis]

Only change I've seen in drivers is when they've got a bit too warm, then they do start to sound different, maybe quite a bit quieter.

 

Which brings us nicely back to power compression!

 

I didn't say that there were no differences when a loudspeaker was "warmed up", but that I couldn't see any benefits...

 

A high power bass driver usually has a temperature limit for the VC to former / cone joint of around 230 degrees centigrade. Poor designs will lose up to 6dB through the increase in voice coil dc resistance. That's a negative effect, and one that most manufacturers try to minimise through correct thermal management techniques.

 

I'm sure that some of the mellowing proclaimed by Simon with his HiFi background might be attributed to this mechanism.

 

Some research has been undertaken on the use of activated charcoal or similar adsorbants in loudspeaker enclosures to change the effective volume when the air pressure changes. This woudl have a temperature component associated with it, so the enclosure temp may play a part, but it's not easily reproducable, and might be swamped by the change in humidity and temperature when the audience some into the venue.

 

 

Simon

[paulears]

Pi loudspeakers page

 

Measurement page

 

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