Warming my vintage voice coils?

[robertbartsch]

I beleive in the mid 1960s and early 1970s most of the sound reproduction equipment was Altec and Crown. Anyway, before a concert and during the time people were entering the venue, the sound system was played at moderately low levels, typically for 1/2 hour or more with recorded music.

I was always told this was done to warm up the Altecs which, apparently back then, were not designed to handle large amounts of power.

Anyway, I have an old pair of 4312s in the basement that are driven by a 200WPC power amp and I often crank these to very high SPLs.

Question: Is it safer to warm these drivers for a while before I crank them or is this just wishful thinking? I assume the more modern drivers that can take some big power do not need to be babied before the big crank.

[JBL Dog]

I beleive in the mid 1960s and early 1970s most of the sound reproduction equipment was Altec and Crown. Anyway, before a concert and during the time people were entering the venue, the sound system was played at moderately low levels, typically for 1/2 hour or more with recorded music.

I was always told this was done to warm up the Altecs which, apparently back then, were not designed to handle large amounts of power.

Anyway, I have an old pair of 4312s in the basement that are driven by a 200WPC power amp and I often crank these to very high SPLs.

Question: Is it safer to warm these drivers for a while before I crank them or is this just wishful thinking? I assume the more modern drivers that can take some big power do not need to be babied before the big crank.

I know tube amps need to be warmed up to obtain optimum performance. Didn't The Grateful Dead use a bunch of Mac tubes amps for their "Wall of Sound"??

I've never heard of speakers needing to be warmed up.

[Tom Brennan]

My speakers have a remote starter so they're already nice and warm when I use them.

[robertbartsch]

Dog:
....Well that is interesting about warming the Mac tube amps for the Jerry Garcia guys. I've seen them live several times in the 1970s.

My recollection about the early days was that the reproduction amps were nearly always Crown DC300s, however, and these were solid state units that put out 150W per side; right?

[boputnam]

Didn't The Grateful Dead use a bunch of Mac tubes amps for their "Wall of Sound"??

I'm not sure about the PA, but Jerry always had a "rack" of them driving his "Truckers" cabinet stuffed with JBL's. Sometimes, their lights would go out, and Steve Parish would repatch, and off we'd all go again...

My speakers have a remote starter so they're already nice and warm when I use them.

Now that, is funny.

I've seen them live several times in the 1970s.

My first was Rochester, 1972. It became rather habit forming...

[JBL Dog]

Dog:
....Well that is interesting about warming the Mac tube amps for the Jerry Garcia guys. I've seen them live several times in the 1970s.

My recollection about the early days was that the reproduction amps were nearly always Crown DC300s, however, and these were solid state units that put out 150W per side; right?

Okay, had to look it up. They used eighty-nine (89) solid state MC2300 amps and three (3) MC3500 tube amps to power the "Wall of Sound".

http://en.wikipedia.org/wiki/Wall_of...(Grateful_Dead)

[grumpy]

Anyway, before a concert and during the time people were entering the venue, the sound system was played at moderately low levels, typically for 1/2 hour or more with recorded music.

I was always told this was done to warm up the Altecs which, apparently back then, were not designed to handle large amounts of power.

Pre-concert music?
This is often still done (the music part). Checks the sound... gets folks 'in the mood'...

Unless Altec had a materials-science problem with their adhesives,
this has the smell of an "old-wives tale." Leftover tradition from tube
warm-up days? ...possibly, but tubes warm up w/o signal.

[4313B]

The name of the game is to NOT have warm voice coils.

I personally hate the sound of power compression.

[edgewound]

Every physical thing is affected by thermal cycling....even voice coils. The time it takes to heat and cool a component will have an effect on it's life cycle.

When a voice coil is warmed before it's cranked to max power...short of clipping, of course...it will have less heat expansion related stress applied to the materials. Conversley, when the voice coil is turned down to a lower volume, it's allowed to cool a bit before being shut down, resulting in less of a cooling contraction shock.

Kind of like warming up and cooling down your age racked body before and after excercise....chances of injury are decreased substantially.

[grumpy]

Send the question in to "Mythbusters"

I'd be mildly interested in seeing a paper on the the results, including destructive testing
(in field or lab), that led the development of modern voice coil adhesives... whether
or not they were specifically developed for loudspeaker use.

This actually isn't too bad, info-wise:

http://en.wikipedia.org/wiki/Voice_coil

Generic loudspeaker adhesive example (variety required for different applications,
even within the same assembly):

http://www.hernon.com/speakerass.htm

[4313B]

Send the question in to "Mythbusters"

Absolutely!

[subwoof]

Well hauling a PA out of the band truck ( 15 below ) into a room full of happy hour drunks ( 75 above ) and expecting to plug and play in 30 min means SOMETHING ain't gonna be warm...yet...

Heating alnico magnets is fine for guitar amps ( they are *producers* ) for that "marshall sound" but slamming SR spiders to the max with old crowns that are just dripping with condensation is truly driving without brakes...

I fixed a pair of mac 2300's for a local dead-clone band in the early 90's

Each channel ran a quad K120 column and when he hit those PIERCING notes, ears bled all the way to the bathroom. With door closed. With NO PA help.

ring, ring

[JBL Dog]

Well hauling a PA out of the band truck ( 15 below ) into a room full of happy hour drunks ( 75 above ) and expecting to plug and play in 30 min means SOMETHING ain't gonna be warm...yet...

Heating alnico magnets is fine for guitar amps ( they are *producers* ) for that "marshall sound" but slamming SR spiders to the max with old crowns that are just dripping with condensation is truly driving without brakes...

I fixed a pair of mac 2300's for a local dead-clone band in the early 90's

Each channel ran a quad K120 column and when he hit those PIERCING notes, ears bled all the way to the bathroom. With door closed. With NO PA help.

ring, ring

Ironically, I was just loading the van for tonights shows. It's about 18 degrees here today. I have a roadie that will run around and set up the rigs. There's usually enough time for the gear to get to room temperture before the show starts. The fans in the computers will make a little noise when they're cold.

[jbl_man_uk]

I think speaker "pre-warming" is still done to this day in larger systems,freind has a 30kw turbosound system,he runs it at low power for an hour or so,just to drive off any moisture or dampness that the cones/coils may have picked up during storage,(as rigs of this size invariably are stored in large cold wharehouses,not nice warm houses!) ,before driving them hard,which seems to make sense.

[robertbartsch]

J-Man:
Interesting; this makes sense I suppose.

I've noticed that some of the latest JBL designs have cooling fins on the frames so I can assume from this that thermal issues are important considerations - at least for high powered drivers.

The warm up and cool down procedure sounds (no pun) good to me..... Hey, it can't hurt so why not practice this for pre-crank sessions where the equipment will be driven hard?