Voltage limits?

Is this amp OK?
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Contrasseur
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Joined: Thu Feb 20, 2014 6:06 pm

Voltage limits?

#1 Post by Contrasseur »

How are voltage limits determined? Why does the 2510 have a ~35v limit and the S2010 have a~28v limit when the xmax parameters are 4mm and 4.2mm respectively? On the other hand, the BP102 has a 6.2mm xmax and a ~35v limit. Why is that, and how could I calculate the voltage for drivers that aren't mentioned?

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DJPhatman
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Re: Voltage limits?

#2 Post by DJPhatman »

For non-subwoofers, it is the PE, or thermal limit, of the driver used. For subs, it is a delicate balancing act between the drivers T/S specs, like Vas, Qts and Xmax, versus the throat and rear chamber pressures. There are no hard and fast equations, unless you are skilled at using horn simulation software. Please also remember this is Bill's Intellectual Property, or IP for short. If you must know how the limits are arrived at, head off to your local university that offer degree programs in Audio Engineering. <tongue-in-cheek>
I know money often seals the deal, but seriously, quality is an investment, not an expense... Grant Bunter
Accept the fact that airtight and well-braced are more important than pretty on the inside. Bill Fitzmaurice

Grant Bunter
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Re: Voltage limits?

#3 Post by Grant Bunter »

+1 to DJP's post.
The short answer to using non recommended drivers and getting a voltage limit is: ask.

IME, a non recommended driver that had listed TS specs linked or posted, that turns out to be ok for a given cab, will have Bill running it through his sims to give you a limit when you ask nicely.

One of the variables not posted by DJP is impedance. Xmax and impedance are the 2 most critical factors IIRC. Followed by other significant factors.

And the classic example there is a Lab 12 vs a 3012lf in a T39.
When you see in the plans "output isn't about Watts, it's about driver displacement", you might think that a lab 12, with it's greater Vd, would have a higher displacement limit than the 3012lf, but it doesn't. Partly because of the lower impedance in the lab 12.

While we get a simple limit in volts in the plans, that voltage = displacement limiting...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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