Speaker Break In and How to Do It Yourself

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bluesfendermanblues
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Re: Speaker Break In and How to Do It Yourself

Post by bluesfendermanblues »

In US you have 60Hz on the outlets.

In Europe we use 50Hz.


So maybe if you are in EU you should use a lower voltage, in order not to har the speaker. 50hz means larger cone/spider movement.

Should the voltage applied also be lowered by 20%?
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bluesfendermanblues
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Re: Speaker Break In and How to Do It Yourself

Post by bluesfendermanblues »

double
Last edited by bluesfendermanblues on Fri Feb 19, 2016 8:12 am, edited 1 time in total.
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Re: Speaker Break In and How to Do It Yourself

Post by bluesfendermanblues »

triple
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pdf64
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Re: Speaker Break In and How to Do It Yourself

Post by pdf64 »

bluesfendermanblues wrote:a real "8" ohm speaker usually has a lower ohm reading.

If you put 9 V ac into a Greenback (http://celestion.com/product/24/heritage_series_g12m/) clone which measures 6.57Ω across its poles
I think you may be getting ac impedance confused with dc resistance.
The impedance of any particular speaker type at any particular frequency will likely be different to other types, and, especially at the bass end, will also vary according to the cab and room it's in.

At bass frequencies (eg <150Hz), speaker impedance can be anywhere from slightly above its dc resistance to >10 times its nominal impedance.

Have a look at the charts issued for Eminence speakers to see for yourself, eg http://www.eminence.com/pdf/Governor.pdf

As Jim probably hasn't used a 50Hz signal to break in his speakers, he may not be able to answer your query, without undertaking further work, which may be rather onerous.

As you suggest, I agree that reducing the power levels a bit would have less potential to damage the speakers.
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Re: Speaker Break In and How to Do It Yourself

Post by bluesfendermanblues »

pdf64 wrote:
bluesfendermanblues wrote:a real "8" ohm speaker usually has a lower ohm reading.

If you put 9 V ac into a Greenback (http://celestion.com/product/24/heritage_series_g12m/) clone which measures 6.57&#8486; across its poles
I think you may be getting ac impedance confused with dc resistance.
The impedance of any particular speaker type at any particular frequency will likely be different to other types, and, especially at the bass end, will also vary according to the cab and room it's in.

At bass frequencies (eg <150Hz), speaker impedance can be anywhere from slightly above its dc resistance to >10 times its nominal impedance.
Hmmmm, no not really :-)

The impedance/frequency curve, of any dynamic speaker unit, relates to how the speaker coil (in a magnetic field) relates to different frequencies.Which mean

In this concrete case we are discussing sending a signal with a fixed frequency (60 or 50 HZ) to a speaker (coil) and how much a given voltage (@60Hz) translates to wattage wise.

However, looking at the impedance curve @60 hz the resistance is 15 ohm (and 10 ohm at 50hz)...

So
Your Eminence @60hz will only "See"
9 v = 15 x I
=> I = 0,6 =>
9v x 0.6A = 5.4 watt

Your Eminence @50hz will only "See"
9 v = 10 x I
=> I = 0,9 =>
9v x 0.9A = 8.1 watt

With a sensitivity of 103.2 db that is still very loud and will create a LOT of movement in that speaker ;-)

This makes even more sense to me
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Re: Speaker Break In and How to Do It Yourself

Post by pdf64 »

Yes, though note that the sensitivity is down to ~88dB at 50Hz.
And that is when mounted on a baffle (actually a wall of the test room!); without one, at low frequencies, there will be a significant degree of acoustic cancellation from the opposing polarity wave emanating from the rear of the cone.

For a different case, the impedance / power dissipation at 50 and 60Hz may be rather different, eg http://www.eminence.com/speakers/speake ... el=EPS_12C
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Re: Speaker Break In and How to Do It Yourself

Post by Scumback Speakers »

I tested the 50w Marshall clone with a 16 ohm setting, taking the voltage reading directly from the jack on the back panel of my 4x12 cab I used.

As for the voltage amounts I posted, I tested it for what I felt was safe for long periods on the variac, at 60 cycles, because yes, I don't have a 50 cycle setup. So adjust accordingly.
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teemuk
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Re: Speaker Break In and How to Do It Yourself

Post by teemuk »

Yes, excursion is different with 50 Hz vs. 60 Hz.

But what I don't understand is how any of this has anything to do with speaker power ratings.

The point of the "burn in" rig is to flex and wear out speaker's suspension by introducing significant cone movement. Yes, you can hook it up to a rig that outputs sinusoidal waves at lowish cycle rate and as long as there isn't considerable over excursion or thermal issues the rig shoud work.

But acknowledge that speaker power is rating for -thermal power handling only-. It's a nominal value of output power average a speaker can sustain for certain time without damage by heat.

The rating ignores cone excursion effects.

And because lower frequencies require higher ecursions the speaker is easily damaged way below its "power" ratings when its asked to operate near its excursion limits. So your best bet is to ignore the power rating and simply listening whether the speaker motor still operates reliably or not.

Then again, most scientific research about speaker break in states you don't even really need such rigs. The burn in process can take hours in total, but within its very first seconds majority of burn in has already happened. Basically its enough to manually flex the cone/suspension to its limits few times. It's already enough mechanic stress to remove most of the "stock" rigidness of a completely new speaker. Push the cone of the new speaker up and down few times, whoah, you just about 90% burned in your speaker!

If it doesn't sound distinctly different by then it's because the burn in effects are not that astounding to begin with. Suspension loosens up a bit, resonant frequency shifts down maybe a hertz or two and the high frequency "nodes" change a bit of shape, which usually makes the speaker sound a bit "duller" than a new one. That's about it. It won't evolve into an entirely different speaker. Alternatively you can just crank your amp and play through the speaker a few seconds.

Basically, I wouldn't bother the trouble of building a dedicated rig for such a ludicrously simple procedure.
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Re: Speaker Break In and How to Do It Yourself

Post by Littlewyan »

I'll agree that speakers change a lot within the first few seconds. Although I will say my G12M Heritage Speakers actually changed a LOT over the course of a few minutes. I plugged my Express into them first and they sounded OK, moved over to the JTM50 and they sounded pretty good, moved back to the Express and they were awesome and keep getting better and better.

I think HiFi Speakers don't really break in much as I've read they use softer cones, whereas Guitar speakers use quite stiff cones. Not sure if thats true but that is what I've heard.

What we need is someone who can record a speaker when its new out of the box and then record it after 20 hours of playing time. It will take a lot of precision though. We'd need to have the speaker mounted in the same cab, cab in the same position, same room, same microphone placement, same sample played through the speaker (a guitar riff, not a song) and even the same room temperature if possible as I believe this can affect the tone.

https://www.youtube.com/watch?v=zlS_k4niVMs

This guy did it but I think some people questioned how precise he was about it.
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Re: Speaker Break In and How to Do It Yourself

Post by bluesfendermanblues »

@Teemuk and Littlewyan. IME Jim methods are tried and tested.

I have 45 years old Greenback speakers. And I never heard of any new speaker that can sound like my old speakers after a couple of minutes or ever from moving the cone and spider a couple of times. Really.

I usually apply 6.3 VAC from a Heater Voltage tap and give new speakers 5-8 hours. I never went higher voltage wise. This is why Jim's info is very exiting for me. I'll try a little higher voltage and longer duration of treatment, the next time I come around to breaking in new speakers.

In fact I have two Jensen p12Q's one in a 5e3 and one in a Gibson EH185 clone that Im working on. Both speaker were bought used. The first on only has a couple of hours playing time and still sounds quite stiff. The latter (in the Gibson cab) was bought locally from (another) Blues guitarist, who has played it on a lot of gigs, but eventually decided that he likes the bottom end in a Ceramic Weber instead. The p12q that I bought from him is buttery a sounds much better. (Same findings as in the youtube video above re a C12Q).

IME there's not much theory to this. It's just plain and simple fact that a well played-in speaker sounds much better.
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Littlewyan
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Re: Speaker Break In and How to Do It Yourself

Post by Littlewyan »

Oh I wasn't saying Jim's methods were wrong, I was agreeing with him. I simply stated that my speakers did change a lot in the first few minutes and keep gradually changing more over time. They are still quite stiff don't get me wrong, but I know they will loosen up over time. However as I'm not using his break in procedure (as I don't have anywhere I can carry it out) I'm just going to have to wait a LONG time (Celestion Speakers take roughly 200 hours of playing time to break in).

I mentioned recording a new speaker and the same speaker after 20 hours of playing as I think it'll be very interesting to hear the difference. You could hear the difference in the video that guy made, but when using distortion he was playing with a tone that no one would ever use (lets be honest), so it was a bit harder for me to hear the difference.
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Re: Speaker Break In and How to Do It Yourself

Post by Scumback Speakers »

teemuk, with all due respect, if you really think (or someone told you) that after you push down on a speaker cone a few times that it's 90% broken in, you must be using speakers with the softest/loosest spiders/suspension and cone parts on the planet. I've never had a new speaker do that, Celestion, Jensen, Eminence, etc. That thought sounds a lot like what Celestion posts on their site, which is just not true. Those speakers take a lot longer to break in than a few minutes or movements of the cone. Typically I find new Celestions take around 60-80 hours on the variac, or using a loud stereo for 10 hours per day for a week.

And the reason the voltage vs power handling of the voice coil is important is not just the heat imparted by the voltage to the coil, it's the amount of power sent so you don't burn up a plain paper voice coil like the KRAFT paper coils versus the usual nomex high temperature coils most popular in speakers these days.

That's why you want to keep the voltage sent to the speaker to around 25-35% (roughly) of the speaker's voice coil rating so you don't overheat it while it's being sent a steady signal.

If you were playing your guitar through it to break it in, there wouldn't be a constant signal since there are breaks in chords, solos, songs, etc. With the variac it's always sending a signal to the speaker, so you can't run it more than 33-35% without the risk of frying the voice coil.

I hope that explains it better for you.
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Re: Speaker Break In and How to Do It Yourself

Post by Jered »

If the voice coil is getting hot enough that you have to let it cool down, are you not doing damage?
teemuk
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Re: Speaker Break In and How to Do It Yourself

Post by teemuk »

Jered wrote:If the voice coil is getting hot enough that you have to let it cool down, are you not doing damage?
If it's too hot you're at least very near of introducing serious damage.

One thing to note is that heating the voice coil causes very similar effects as "break in" by mechanic wear. And in about similar magnitude. Difference is that after the voice coil has cooled down the shifted parameters again return back to initial conditions. e.g. If Fs shifted from 55 Hz to 50 Hz it will again shift back to 55 Hz when the coil has cooled.

The effect of break in is that similar changes are permanent.

So after breaking in a speaker for continuous periods you really need to cool it down to find out what permant effects the break in actually had. The initial effects may only be due to heat.

If you were playing your guitar through it to break it in, there wouldn't be a constant signal since there are breaks in chords, solos, songs, etc. With the variac it's always sending a signal to the speaker, so you can't run it more than 33-35% without the risk of frying the voice coil.
Exactly. The speaker power rating test setups are set up to emulate signals with certain crest factors. Basically the speaker is driven with clipped pink noise signal for a certain period of time, and the point where it fails due to thermal effects is the rated output power.

Not exactly a very precice rating method.

For example, the power rating derived this way is not analogous to average power of a sinusoidal wave driving the speaker, in fact it's valid for only certain conditions that are hardly ever met in practical, real life applications. (for example, the signal must have same crest factor as the signal used in test setup).

...And then we need to remember that the rating still ignores excursion effects and already because of that the real "safe" power rating will vary significantly throughout the effective bandwidth of the speaker.
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Re: Speaker Break In and How to Do It Yourself

Post by Jered »

OK thanks. I will take your word for it, you all know far more than i will ever know. What are your thoughts on this?

http://earcandycabs.com/product/speaker-break-in-cd/
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