Do old drivers beak in - again?

[Pano]

What do you think? Do vintage drivers that have been sitting for years need to be broken in again? Do they get stiff sitting up?

The reason I ask is that I've had a number of vintage drivers thru here - 50s, 60s, 70s vintage. When first run, they almost all sound way too bright, too shouty. My reaction is usually "Yuck!, Who'd want to listen to that?" So they go on the shelf for another day.

But recently I put a pair of full range 8" Danish "Voice of Music" drivers on open baffle. (They are probably Philips) At first they were bright, bright, bright. Had to put a 1.7 mH coil in series to tame them.

After some days, or weeks playing, they got smoother and smoother - or duller and duller. Had to drop down to 1.5, then 1.0, now 0.7 mH. And it sounds like they now need no more than about 0.3 mH, maybe less.

Anyone else find this with vintage drivers?

[Graham Maynard]

Found it with modern drivers too.

The compliance re-'sets', hence the T-S characteristics too.

Cheers ........ Grahan.

[qwad]

no disrespect to graham and all the other more knowledgeable folk around here , [ call me a sceptic]; but l think the only thing getting burnt in are your ears gradually getting used to the sound, hence the perceived changes in sound quality of the speaker you are listening to . [without prejudice] l am yours sincerely, cheers T.C.

[Scottmoose]

Not entirely. It depends how you load them. Driver with very light diaphram, very powerful motor, very stiff suspension & loaded in a horn which controls excursion = takes a long time to fully come on song. Same driver in a box where excursion is less well controlled will come to optimum much sooner as it's suspension components etc will loosen up from factory fresh much quicker.

[Graham Maynard]

Hi qwad,

Scotmoose raises interesting points. Akin to designing a horn according to the driver as-is, not for measurements taken in an enclosure, but to design enclosures to the driver when run-in, or the enclosure response will drift away from optimum instead of work into it.

Thus OB LF drivers will hit optimum more quickly because they are completely unloaded. Makes me smile. Speakers as well as amplifiers genuinely needing to 'warm up'.

When a driver 'runs-in' its Fs becomes reduced and therefore its low and low/mid sensitivity falls as well; not much, but measurably, and not just due to hearing desensitisation. The change in reproduction quality is due to the change in the driver suspension stiffness, and more noticeable than the figures suggest due to the overall balance becoming relatively shifted.

With reduction in Fs, both Qms and Qes degrease as Cms and VAS increase, and LF excursion increases hence increasing possibility for increased distortion of mids/highs via a wider-range driver.

I have measured driver Fs after 'running-in', put it away, and then measured before re-using only to find that the Fs had returned to 'as new' specification. This is why manufacturers of Pro drivers quote T-S characteristics after;-
>> **T-S parameters are measured after an exercise period using a preconditioning power test.
The measurements are carried out with a velocity-current laser transducer and will reflect the long
term parameters (once the loudspeaker has been working for a short period of time). <<
as quoted by Beyma on their spec sheets PDFs.

Hi Michael,

It might be worth sig-gen measuring the Fs of the next oldie before you put it on a baffle, and then measuring it again after a week of running.

Cheers ......... Graham.

[Pano]

Originally posted by qwad
but l think the only thing getting burnt in are your ears gradually getting used to the sound

Oh, I know that's part of it. =) But I'm carefull not to let that influence me too much. I have reference drivers to check against.

Pity I did not measure T/S and FR first. I have seen them change on many a new driver, but never tested old.

[GM]

Originally posted by Graham Maynard

This is why manufacturers of Pro drivers quote T-S characteristics after.....

Greets!

As noted, during the so-called break-in period the T/S parameters shift in complementary ways, so the net effect on box design is nil if you measure say, a new driver before/after the break-in exercising or a physically cold or warm one due to where it's been stored.

Prosound manufacturers OTOH heat up the VC enough to raise Qes up to at least what it's likely to be on average in use (or at least they use to for their own designs), which of course is somewhat higher than a HIFI/HT is likely to be, so mostly moot if you design based on the advice to oversize the cab 10% to account for driver, etc. volume losses since only the smallest cabs would lose this much. If you tend to play it at ~live levels though, I've found raising Qes ~20% to design/tune the cab to be an acceptable trade-off between being slightly under-damped on average Vs audible transients induced thermal power compression.

WRT old and/or heavily starched/whatever drivers, what most audibly changes is the diaphram's material's compliance/breakup modes, so in the case of the latter, when someone posts it took 'X' hundred hours to break-in their big buck 'FR' driver, I interpret it as worn out and needs replacement for if the manufacturer wanted it this 'limp', they wouldn't have spent the time/$$ to alter it so much.

WRT ears 'burning in', I agree, your first impression is always the most accurate once the initial break-in is performed and what folks will hear when first exposed to your perceived (if done by ear) tonally balanced system, so factoring in our extreme hearing sensitivity centered around 2 kHz, adding a BBC 'dip' is a good idea if the driver doesn't already have one built in. At minimum it needs to be billiard table flat through the ~250-3000 Hz 'phone BW'. If horn users did this they probably wouldn't be damned so much.

As always though, YMMV.

GM

[Bob Brines]

I agree that

1. The T/S parameters will "reset" to a measurable degree, but as GM points out, this is probably not audible.

2. Depending on how long you have put the speakers away and how different the "new" speakers are, you will have to break-in your ears again.

YMMV, but I think it's real.

Bob

[adason]

I have observed similar break-in with vintage drivers as panomaniac describes. I was given set of eight fullrange drivers from church, old Soundoliere?...anyway, they were eight identical drivers, all the same age. I removed 70 volt trafos and put two of them in small closed boxes. They did not have much bass at first. Bright. After a while, few weeks of use in the basement, they sounded better. Nice rounded sound.
When I replaced another pair of the same drivers into the boxes, situation repeated. I can easily compare sitting-in and broken-in drivers. I can replace only one speaker and compare left-right. Break-in is real. It's a mechanical thing. The same with the car. Breaking-in my ears? I do not think so.

[AndrewT]

break in of ears seems perfectly possible.
Break in of new drivers, I have experienced.
Break in of old drivers? But the Fs does change with use. I did before and after tests and Fs also varies considerably with temperature.