calculating power of each Driver.

[Aucosticraft]

Hello,

I was wondering how calculations are made for getting power rating of each driver used in multi-way system. Like let me say. I have 2 way system rating 10w with Fq response of 120Hz to 20 Khz . Well the design is completed to give a perfect flat response in the mentioned frequency range. To achieve the response I use crossovers , attenuator, Impedance equalizer, this all stuff absorb some energy. so what is the calculation for this. Also after using the above attenuator and crossovers the power rating of drivers required would not be same say 10w for each. I guess this depends on where the crossover point is set. so finally if I say my system can handle 10w continuous over the given range. then possibly the mid-woofer I would need to use would only be 7.5W where the tweeter can just be 3W. I mean that was just for example.

So is there any software available for the calculations, or can anybody actually help me with actual calculation method and equations.

[Aucosticraft]

Hey guys... Its two days now.. not a single word. no one here actually calculate ? I am sure we got many sharp brains here. Must be aware of calculations.

[John Sheerin]

In a typical situation, you would get a driver that's rated for continuous power handling that's greater than what you need. Then you would design your enclosure and crossover to make sure that with the max voltage you intend to apply to the speaker, the excursion will not exceed the limits of the driver. If you'd like to get more detailed than that, you'd calculate the voltage versus frequency at the driver for a given input voltage to the crossover network. Then since you'd know the impedance versus frequency of the driver, you could calculate the real part of the impedance and then calculate the power dissipated in the real impedance. Then you could calculate an RMS dissipated power by taking the square root of the quantity sum of the squared power divided by number of power data points. A pseudo excel formula would be RMS=sqrt(sumsq(P1:Px)/count(P1:Px))

But no, I don't imagine most people calculate things this way. If you use the simple method I outlined, you'd be fine in most cases.

[richie00boy]

It's complex due to the many filters and attenuators etc. Also, driver power handling is itself not a hard and fast rule and subject to range depending on the program material and crossover design.

So in short don't get too hung up on it.

[454Casull]

sound.westhost.com has a page about this somewhere.

[thosuk]

Why Do Tweeters Blow When Amplifiers Distort?

[Aucosticraft]

John, Richie, Casull & Thosuk,

Thanks for your reply,

I am went through the link that you provided. Also thinking deep on suggestion given by John.

I am thinking If its possible to Simulate this using Orcad- Pspice.

A detail of each component would have to be entered for more precise calculation. say, Exact equivalent circuit of speaker.Then the crossover network. That should include dc resistance of coil used.

cause i think there is no software readily available that can do the job for us. Although I am not getting stuck on the calculations. but its always good to know. how much power is wasted? And actual power that each driver needs to handle.

Can I get some help or direction in getting the simulation done on orcad - pspice.

[John Sheerin]

I'm not a big spice user so I can't help there, but I can tell you it isn't too tough to do in excel. Then there's no need for an equivalent circuit for the speaker - just import an impedance curve that you measured.

As far as the power dissipated by the crossover components, you mainly need to worry about the resistances of the components.

[speaker dave]

Originally Posted by Aucosticraft

Hello,

I was wondering how calculations are made for getting power rating of each driver used in multi-way system.

I think you are asking how to measure or calculate how much of the input gets to each driver in a system.

I've found the easiest way is to feed pink noise into the system input (even frequency shaped noise such as the EIA shape used for power testing) and then measure, with a true RMS meter, the voltage across each driver.

So 10VRMS input might give 8VRMS on the woofer and 3VRMS on the tweeter. V sqrd over R will give the approximate power. You can also use this method to see if your power resistors are good for some rated system input.

You can do the same thing with voltage curves across each unit, but you must consider not only the network drop but also the bandwidth across that unit.

David S.

[thosuk]

This might be helpful.
Bullock and White's Home Page
Go go bottom of page and download passfil.exe (Passive Crossover Component Stress Analyzer).
There's other Bullock and White stuff as well.