"Breaking in" speakers

Message

kesslari · #1 Post by **kesslari** » Fri Feb 29, 2008 1:15 pm

I read in another thread about "breaking in" drivers with a 30 hz tone for 20-30 hrs.
How necessary is this (vs. just playing at low volumes for the first 30 hrs or use or so)?
THanks...

Sydney · #2 Post by **Sydney** » Fri Feb 29, 2008 1:34 pm

How necessary is this (vs. just playing at low volumes for the first 30 hrs or use or so)?

I wouldn't say necessary, but from my experience feeding a signal at low frequency just speeds it up.
Any and all play time will loosen things up.
* As far as the necessity, break-in to me is a precaution, to:
A: Find a speaker problem BEFORE installation in a cab and...
B: I don't want to hear the break-in in a cab, where it is much louder and obnoxious, and not representative of the final sound.
* I guess it's sort of like trying a product before putting it to use ( and having to return it, if there is a problem )

wespaul · #3 Post by **wespaul** » Fri Feb 29, 2008 1:55 pm

So on a new build (T39 in my case), will I be disappointed with the sound until the new driver is broken in? How much does the sound change? Thanks.

kesslari · #4 Post by **kesslari** » Fri Feb 29, 2008 2:00 pm

So this is done before installation in the cab?

Can someone point me to a detailed step-wise description?
thanks...

Sydney · #5 Post by **Sydney** » Fri Feb 29, 2008 2:04 pm

will I be disappointed with the sound until the new driver is broken in? How much does the sound change?

I haven't heard a T39 with a fresh driver to know.
It's seem to me that I have read posts from some forum members who were initially disappointed, ONLY to be pleasantly surprised after some play time, and the driver settled to spec.
* for what it's worth I bought drivers from individuals who were disappointed with the sound after initial listening tests. These were Vifa woofers with rubber surrounds, I suspect that rubber surrounds might need some more break-in than other surrounds ( because they seem to take longer than their non rubber counterparts ). With time they sounded great

kesslari: I do it BEFORE installation - in free air.
Pretty simple and straight forward - Just hook up a signal source ( an amp connected to CD player, a signal generator or WTII ) and play for few hours.
Lately, with the aid of WTII, I can track the progress.

#6 Post by **Bill Fitzmaurice** » Fri Feb 29, 2008 2:16 pm

Sydney wrote: I suspect that rubber surrounds might need some more break-in than other surrounds. With time they sounded great

Most of the benefit of break-in comes from flexing the spider.

Sydney · #7 Post by **Sydney** » Fri Feb 29, 2008 2:47 pm

detailed step-wise description

This is from The Loudspeaker Design Cookbook:
"all cone speakers should be "broken-in". The suspension will undergo most of the loosening up ( the resonance frequency can decrease by as much as 15% ) after 5 to 10 hours of play. You can accomplish break-in with a signal generator set for a 25Hz sine wave feeding a power amplifier. Use just enough power to achieve moderate cone travel, and run this for at least an hour"
* I've watched the progress and a lot of change happens initially, approx 90+% after 24 hours, with subtle changes after that.

jbell · #8 Post by **jbell** » Sat Apr 05, 2008 9:53 am

I'm guessing my break-in technique lacks a little, as it seems like any tuba's I build get louder over the next few weeks of use, even with break-in.

I've been using a 12volt 4amp transformer, and just running 60hz. I take 2 drivers and place them face to face, and it moves both cones over 1/8th inch.

Coupling both drivers lowers the pitch, but by how much I'm not sure.

Is this really a true break-in cycle?

I'm assuming it's better than nothing.

Sydney · #9 Post by **Sydney** » Sat Apr 05, 2008 2:32 pm

In light of what was posted by Stan Graves in REVIEWS:
"my T39's were almost 3dB louder after 100 hours of use than they were built. "Break in" really does help."
Perhaps larger woofers or some models require longer time.
When you can measure impedance, you know quantitatively, observing the drop in Fs.

Sat Apr 05, 2008 3:20 pm

After some twelve years my old EVM 12L settled in at an Fs of 48 Hz. 90% of the driver break in can be accomplished in 24 hours, but the process goes on for all intents and purposes indefinitely.

SoundInMotionDJ · #11 Post by **SoundInMotionDJ** » Sat Apr 05, 2008 5:32 pm

Sydney wrote:In light of what was posted by Stan Graves in REVIEWS:
"my T39's were almost 3dB louder after 100 hours of use than they were built. "Break in" really does help."

To clarify...I measured the T39's at completion of the build using a 100Hz signal and 2.8v of input @ 4m. I re-measured using the same setup after about 100 hours of use. As build (with less than 2-3 hours of use): 83dB After 100 hrs: 86dB

That is 1-2dB less than the SPL charts will predict. Still, given the informal nature of the test...that was more than close enough for my taste...well, the after 100 hours numbers were anyway.

--Stan Graves

bgavin · #12 Post by **bgavin** » Sun Apr 06, 2008 10:56 am

I think there is a whole lot of validity to that measurement. The 4m distance certainly eliminates any possibilty of dB changes resulting from any slight changes in measuring distance.

I assume the measurement was taken at ground plane?

SoundInMotionDJ · Sun Apr 06, 2008 12:21 pm

bgavin wrote:I think there is a whole lot of validity to that measurement. The 4m distance certainly eliminates any possibilty of dB changes resulting from any slight changes in measuring distance.

I assume the measurement was taken at ground plane?

6" above ground plane...that's how tall my table top mic stand is...

Edit:

The speaker and mic were setup using the relief marks in a concrete sidewalk in front of my house. So the distance was "exactly" the same.

I did the measurement with the same T39 in both cases...#1. I numbered each sub to keep the parts straight as I was building - so I can tell them apart.

--Stan Graves

Pixelmaster · #14 Post by **Pixelmaster** » Mon May 19, 2008 5:57 pm

I just completed a build of two O15TBs but did not break the woofers in prior to final installation. At this point I really don't want to completely uninstall the drivers.

Question(s):
If I want to run a 30hz test tone for several hours (?) will it help any to minimize the "noise" this process will generate if I remove the back panels on the cabinets?

Also, how loud should the test tone be as it is running?

I've heard that if you are not careful you can burn out a voicecoil if this process runs too long with too much current.

Thanks

AntonZ · #15 Post by **AntonZ** » Mon May 19, 2008 6:16 pm

30hz at some 10V was recommended for the 8" in my T18/AT. Should probably do the trick for your 15" as well, but you may want to start way lower than that and gradually increase, since 10V can be pretty loud into a finished cab in the home. I'd try with the back off indeed. If 10V is not too loud in your place, leave it at that for 24 hours.

I could not hear a single unmounted 8" upstairs in my "shop", but it was a somewhat uncomfortable rumble in other parts of the house. So I did a few 6 hour break in periods during daytime over 4 or 5 days.