Breaking in drivers

[KevinTams]

Just bought a pair of Max Pentivent 15" bass drivers. Qts 0,75, Fs 24Hz.
I will use these underneath my Goodmans 201's on an open "U" baffle.

What is the best way to break these in before mounting them? I've bolted them together facing each other on my bench and connected them to a 150W amp.. Do I drive them with white noise or a signal from my signal generator at Fs? I've read both opinions and I'm not clear. Also what volume should I use and for how long?

thanks
Kev

[Nuuk]

I can't answer your question Kevin but I shall be most interested in your opinion of the Pentivents. As you may now, they are my choice for dipole subs to go with my 201 open baffles eventually!

[KevinTams]

It was you put me on to Ian at Nightfire and he eventually persuaded me to give them a try? Nice bloke Ian and seems very knowledgable. He also sent me 2 pairs of tweeters on a sale or return basis but they're a bit pricey and if either don't really shine I'll probably go for the seas tweeter from Wilmslow audio.

I'll let you know in a week or 2.

Kev

[Nuuk]

Nice bloke Ian and seems very knowledgable.

Yes, that's what I thought! He seems to genuinely want to help rather than just sell something! Standing by.

[pikkujöpö]

I would also like to know the answer,received the Jordan jx92s drivers today and the enclosures are far from completion.

Is it a good idea to just lay them sideways to the floor(carpete) and run them with moderate sound level?

[keyser]

i don´t think breaking in is really needed, but i´m not sure. it is said some surrounds need to move before they completely settle and get a constant stiffness.
A good way to run them in would be to place one unit on its magnet, and putting the other woofer on top of it, membranes face-to-face. Then connect one unit out of phase, and you won´t hear much.

[Ron E]

If you are not measuring them to design a box for them, there is no need to break them in. Even if you wanted to measure them, there is little need to break them in for long periods.

Many experts say that a few seconds of exercise near xmax are all that is needed, DIYers will try to tell you that you need hours or days. Some claim to see large reductuions in Fs and increases in Vas, but I tend to question the measurement conditions. Fs and Vas can be very temperature dependant, and also signal level dependant.

Of the woofers I have measured, none have shown break in effects I would consider significant. One small 4" midwoofer pair I measured went from 85Hz to 77Hz Fs immediately after some exercise, then the next day the Fs was 85 again. My 12" woofers didn't change at all. Some measurement systems will spit out T/S parameters to 6 significant figures and make you think you are getting really accurate measurements. Well, I hate to say it, but T/S parameters are an approximation - frequently accurate to only ~5% or so.

[kimbo]

I wouldn't rest them on their magnets to run them in for two reasons.
1. You will do a really good job of picking up any tiny metal (iron or steel) particles that are in the carpet or on the floor, some of which will be almost microscopic dust. This is unlikely to do any harm but why risk the chance of getting crap into the gap?

2. If your magnets have a vent hole in the rear, you shouldn't block it up as by doing so you will force the speaker to vent via the dust cap and where ever else it can.

In fact, when I was running my Vifa 8" drivers in (bolted vertically to a temporary jig well off the floor) before testing, using a signal generator set just a bit above Fs, I noticed a strange faint sound when using large excursions. I found that this was the air 'breathing' in and out of the vent going thought the magnet. It was not that loud that it would be heard out of the box, but if you put your cheek close to it there was a suprising amount of air bouncing in and out.

I too was a little uncertain if break in was necessary, but it made sense and so I gave them a good workout perhaps 10 - 20 hrs each just to make sure, before making my measurements. The change of parameters was pretty slight however.

[xyrium]

Of course, depending on how much current they can handle, I wonder what the 50/60Hz signal from a wall socket would do?

[wintermute]

You wouldn;t want to plug it in direct!!!!! but I have heard that people use a transformer for this purpose.... not sure what voltage though...... 30V with 8 Ohms should be around 100W I think,