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How much power for a DE-250?
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citizensc View Drop Down
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    Posted: 26 September 2018 at 10:53pm
Hi Guys

How much power would YOU give a B&C DE-250 high passed at 3khz playing techno/house? 

Currently, I am giving mine 80 watts but I think that's a little shy. A constant theme on this forum is having amps with ~4x the power of the compression driver. Would you really give a DE-250 240 watts?? 

How much power compression do compression drivers experience, is it the same story as a normal driver with a paper cone?

Is the limit at 3k thermal or mechanical do you think? 

Thanks for your replies. 
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Just because you have an amp that produces 80w connected to the driver doesn't mean it is absorbing 80w all the time, it's probably only suffering fractions of that power most of the time and that is the point.. lots of headroom for dynamics.

Power compression is even worse in CDs because there is very little coil movement to force air over the windings and thermal failure is the primary danger.
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Originally posted by Conanski Conanski wrote:

Just because you have an amp that produces 80w connected to the driver doesn't mean it is absorbing 80w all the time, it's probably only suffering fractions of that power most of the time and that is the point.. lots of headroom for dynamics.

Power compression is even worse in CDs because there is very little coil movement to force air over the windings and thermal failure is the primary danger.

So you would set the limiter to give way more than 80 watts? Right now I'm using a QSC plx1602 to power them so I have about 300 watts I can give them. 

How far would you go? 120 watts? 180?? 240?? I'd like to keep it relatively safe but I don't want to lose a whole bunch of output doing so. 
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Watching this thread intently. I have a pair of Selenium D205i crossed at 1.2k from JBL M252s. Need to power these properly too.
Nothing is foolproof because fools are so ingenious
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DE250 is a 60W driver, 120W program. So 80W is about right. But the whole concept of asking how many watts to give etc. is just wrong.

You set your limiters so that 60W RMS will never be exceeded. If you got only RMS limiter, then though. If you got RMS and peak limiters, you can allow 2dB peaks above RMS threshold.

Amount of watts is irrelevant as such and depends heavily on each track played.
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Points: 2574 		Post Options Post Options   Thanks (0) Thanks(0)   Quote njw Quote  Post ReplyReply Direct Link To This Post Posted: 27 September 2018 at 6:48pm
With my comps I've always used an amp that gives around 4x the rms of the driver, set the level on the comps to give a nice balanced sound and then set the limiters to kick in at the same time as the limiters on the bass and mid. Far from an exact science I know but it's what I've always done and I've never lost a comp driver.
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You want plenty of headroom on compression drivers, personally I just use the same as whatever is on the mids (often mids channel A, highs channel B of the same amp).

The point is, if your system is so unbalanced that the power handling of the compression drivers is the limiting factor, there's something seriously wrong.  I always assume that I'll run out of headroom/power handling on the lower ranges first and stop turning it up, long before I hit any kind of limitation of the HF.
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Originally posted by citizensc citizensc wrote:

So you would set the limiter to give way more than 80 watts?


No. Are you hitting the limiters now? If you are is it just occasionally or is it all the time? If it is occasionally I'd open them up to program power but if you're already hitting them hard then leave it alone.
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Sorry to reopen this topic

Just wondering if a compression driver gives any warning signs when its close to the limit? 

Does it get physically warm to the touch? Or does the VC just burn up without heating the rest of the driver up? This is for Xtros specifically so I can literally just walk up and feel it. 
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Small format CD's usually just evaporate without warning. Sometimes on larger units the diaphragm can shatter before the coil burns, so you get quiet/distorted output. You may feel some warmth on the back cover if it has been running at near maximum power for quite some time, but that's not a good indication of the actual coil temperature, which will be much higher.

There are two thermal failure modes - instantaneous evaporation of a section of the coil wire due to a sudden massive transient, and glue failure causing the coil to loosen and fall off/bind in the gap, caused by long-term overpowering. 

At one club I worked at, some large format EV compression drivers had started to sound "odd" - when disassembled, the diaphragms showed signs of flexing (small discoloured circular marks were visible) - the metal was reaching its stress fracture point and the diaphragm had started to lose stiffness where the marks were. We replaced them. 
It's rare though, for anyone to be checking closely enough to catch things like that. The difference in sound was small but they would probably have failed entirely the following week.


Edited by studio45 - 16 October 2018 at 2:20pm
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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Conanski View Drop Down
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Originally posted by TMH Music TMH Music wrote:

I have a pair of Selenium D205i crossed at 1.2k from JBL M252s. Need to power these properly too.
You mean D405 I hope?
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Originally posted by Conanski Conanski wrote:

Originally posted by TMH Music TMH Music wrote:

I have a pair of Selenium D205i crossed at 1.2k from JBL M252s. Need to power these properly too.
You mean D405 I hope?

Er, nope!!! They are definitely D205ti.
Nothing is foolproof because fools are so ingenious
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