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Speaker Cone Warm Up

#23
KJung said:
I have not, but others swear they have.
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I've measured it, on many occasions. If I'm planning on a cab testing session, which I alway do outdoors, and the temperature the night before is going to fall below 60 degrees I keep the cab to be measured in my house that night rather than in my unheated shop. A driver that's at 50 degrees can have an f3 10 to 15 hz higher and broadband sensitivity 3 to 4dB lower than one at 75 degrees.
 
#24
koobie said:
Here's some questions for you speaker guys:
What about the effects of power compression? Isn't this where efficiency (and perceived amount of bass) goes down, rather than up?
How hot do voice coils typically get on a driver at or near it's rated wattage? How long does it take for woofer voice coils to get 'warmed up' on an average driver? I know of tweeters being cooled with ferrofluids, are many woofers treated in this way?
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Hopefull Bill F. or Greenboy or someone will pipe in here.

First, I think that would have the opposite impact on what the OP is hearing. Also, my understanding is that the power ratings of cabs are designed to reflect the power level that the drivers can handle without significant compression, even when pushed all night. I could be wrong.

IME, my Epifani's (neo's) and Berg's (ceramics) cruise along wonderfully from the first downbeat to the end of the gig, regardless of the volume I'm playing (of course, I never push the speakers beyone what they were designed to do as far as I can tell)... always clean, no distortion, and they seem to sound very much the same gig to gig and set to set.

I'm over my head here, so I'm in for the ride. I love this stuff!
 
#26
Great discussion guys...I don't think anyone is wrong. All of the explainations play a part in the sound of our cabs.

Temperature was offered up and I would suggest that temp combined with the gain or loss of humidity of a room also play a part in how the sound develops and travels through a room.

Over the years I have noticed that I can have a nice crisp sound going for the first set, only to go nuts when my low end got mushy playing to a full room the 2nd and 3rd sets. Then when the room starts clearing out, doors start opening, allowing temps and humidity changes, all the low end sometimes disappears.

Just another angle... :^)
 
#27
seamonkey said:
The speed of sound in air is different and different temps. Couldn't this have an effect on the box tuning?
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Not enough to be readily audible.
my understanding is that the power ratings of cabs are designed to reflet the power level that the drivers can handle without significant compression, even when pushed all night. I could be wrong.
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Wrong you are. :crying:
Power compression is caused by heat in the voice coil, and is unrelated to the driver thermal rating. Power compression is rare when drivers run at up to 200 or so watts, and almost unavoidable when drivers are run at over 400 watts. It's very rare that any driver fed more than 500 watts will actually be able to use that power for anything other than to create more heat, which lowers efficiency even more. It's even possible for a driver output to go down with additional power input. For this reason driver ratings higher than 500 watts are pretty meaningless in real world use.
 
#28
billfitzmaurice said:
Not enough to be readily audible.
Wrong you are. :crying:
Power compression is caused by heat in the voice coil, and is unrelated to the driver thermal rating. Power compression is rare when drivers run at up to 200 or so watts, and almost unavoidable when drivers are run at over 400 watts. It's very rare that any driver fed more than 500 watts will actually be able to use that power for anything other than to create more heat, which lowers efficiency even more. It's even possible for a driver output to go down with additional power input. For this reason driver ratings higher than 500 watts are pretty meaningless in real world use.
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Cool, thanks for that clarification. That being said, I again have never really experienced any of this stuff. My 500-1000 watt cabs with 500-750 watts pumping into them, running at volumes that don't cause distortion (at least that I can hear) sound even from one set to the next, and sound pretty much the same when the room feels a little cool versus a little warm:D

Per your explanation, I rarely apply more than 200 watts per driver, and mostly much less, which is maybe why I don't hear the impact of any of this stuff. Also, it's rare that a cab has an RMS rating that suggests much more than 200 watts per driver, so it does seem that there is a pretty good correlation between recommended wattage and power compression not being much of a problem, which was my earlier, if poorly stated, point.
 
#29
Wow. Lots of responces in just a couple of hours. FWIW I am not running a huge setup. My two working rigs at the moment are:

LMII with two old SWR Workingman's cabs (110T and 210T stacked vertically) that I use for my club rig. The band is 4 pieces and the drummer hits pretty hard. I have also used the LMII with a Berg 310, and with a pair of 112 Bergs. Unbelievably, the cheapo SWR cabs sound as good or better than either of the Berg rigs for this gig - moderate volume rock and blues with a flatwound strung Stingray 5, PBass, and Rob Allen Mouse. With this group I practice with plugs in because the space is tight, but rarely gig with them.

LMII (#2) with a Berg EX112 that I use at church. That group rarely gets loud and the drums are using brushes 75% of the time.

I can buy the ear fatigue idea to some extent. Usually I am struggling to tame the high end and get my lows to come through at the beginning and everything settles right in to sounding great after a half dozen tunes. I realize that reduced highs can sound like a boost in low end. However, I still don't get why the lowest notes ring better after I have been playing a bit. Maybe technique...but I'm not convinced.

I am using solid state amps and I really don't know if there can be a huge difference in the sound of the electronics. Coming from a mechanical background, I am much more ready to believe that the material in the speaker cones loosens up (expands) with the friction/cycling to produce the sound.

One of the reasons I sold my Berg 310 is because it came around much slower than my old junker SWR's that are only rated at 200 watts (the other reason is that the SWR stack was taller and lighter).
 
#31
I would not use the Berg310 as a reference point for Berg cabs. That was a rather thin sounding box to my ear, and I believe Jim ended up making replacement speakers for that particular box, which from what I understand helped, but not much.

Not sure what input you want from Tom, but he's at NAMM at the moment.
 
#33
On the Berg 310, I guess I liked the idea of it better than the actual cab. I love the Berg 112's when used alone. That amp & cab combination for my church rig is the culmination of a long development process involving at least 20 different combinations. The pair of 112's sounded great sometimes and not so much others, but that is another discussion.

I'm not discounting your opinion Ken, but I would like to see what others are lurking out there. I would like to think I'm not nuts, but who knows?
 
#34
Is it possible for the conductors in the Amp->Speaker cab wires to experience a significant change from heating over the first 30 - 60 minutes of usage at high volume?
Especially if the wires are small (18 AWG or smaller)?
 
#36
Trying to get an estimate of cab warm-up effect, I looked up Kapton, the old standby for coil formers. It has a useable temperature limit of around 500 °F. At this temperature, the resistivity of copper has increased by about 30%. Putting this into a typical speaker model, it decreases sensitivity by about 1 dB.

As for a few tens of degrees, the effect should be negligible. I would expect a bigger effect from the stiffness of the suspension, but even there, the box itself may be resisting cone motion more than the suspension is.

I think the biggest effects are ear fatigue, changes in room acoustics / noise as the crowd shows up, and my fingers thawing.
 
#37
LP75 said:
Is it possible for the conductors in the Amp->Speaker cab wires to experience a significant change from heating over the first 30 - 60 minutes of usage at high volume?
Especially if the wires are small (18 AWG or smaller)?
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Not enough to make a difference. Drivers don't work as well when cold because the mechanical parts stiffen, it's not an electrical issue.
 
#39
Wow! I never saw this topic discussed before. However, I have long suspected that hot speaker coils reduce efficiency and alter the sound characteristics.

I have always wondered if those folks who swear that ultra-expensive monster cable actually makes a difference were, in fact, being fooled by this inefficient hot speaker phenomenon. By the time they switched the cables, the speaker had cooled down and, of course, it sounded different and more efficient when they started them back up with the monster cables.
 
#40
The Diaper Geni said:
I've never noticed it, either.

But, like the OP, I have noticed a difference in my tone in the first 20-30 minutes of a gig. I have always attributed it to my hands and fingers getting warmed up. And the guitar player getting "his tone", which usually involves turning up his amp! :rolleyes:
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Not taking anything away from what the other guys said.. our church gets pretty cold over Sat night, so all of our gear starts out at between 45 - 58 degrees faren when we first power up.. Of course everything that was 'in tune' at the end of Sat rehearsal is way sharp now. But concerning the speaker cones and associated components.. I personally don't detect any tonal change as the heaters and bodies warm up the ambient temperature..
 

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