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Author Topic: How to calculate an amplifier for a biamp speaker?  (Read 722 times)

Samo Serb

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Re: How to calculate an amplifier for a biamp speaker?
« Reply #10 on: October 03, 2018, 01:28:02 am »

With that amount of power, you probably can't set a low enough threshold to save the driver.
The amplifier is a fixed gain devise. You can't reduce its peak power potential. Turning down the dial on the front is nothing more than an attenuator and will only reduce the drive level that the power amp section sees. If you drive it hard enough you will still have the same wattage potential. Now, this can work provided you never drive the input of that amp till it produces X amount of power, but it is caveat emptor.

A fixed gain amp is pretty simple in nature. It takes X voltage in and converts it to X more voltage out. Some amps are 26db gain others 36db of gain, while others only require X number of volts of input to equal full output ( typically 1.4 volts ). No matter how you slice it, the amplifier will still produce its rated watts if you send it enough drive level to do so. Again the knob on the front is only an attenuator, so all it does is turn down the input drive level.

In short, you cannot take a 1000 watt amp and make it so that it will limit its output to only 180 watts. Now if you turn down the drive level enough and never exceed that drive level, the amp may only ever produce a fraction of its potential, but if you send enough drive signal, the amp will continue to provide power well beyond 200 watts.

Thanks Luke! I had a situation where I used this configuration... I understand that is not the best match, but people have brought me a rack with those amps and they asked for bi-amp:))
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Samo Serb

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Re: How to calculate an amplifier for a biamp speaker?
« Reply #11 on: October 03, 2018, 01:31:34 am »

I assume that you mean you want a maximum of 180w to the speaker under any upstream input condition.  Is that RMS or peak?

Ideally, you'd want to limit for both.  Is the 200w speaker rated cont, prog, or peak?

200w rms
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Tim Hite

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Re: How to calculate an amplifier for a biamp speaker?
« Reply #12 on: October 03, 2018, 05:29:35 pm »

The Lab Gruppen FP amps have input sensitivity adjustment DIP switches and Voltage Peak Limiter DIP switches in addition to the input pots. You can lock down quite a bit of their power to get them to where you need to be.

Setting up the VPL at 38V would give you around 180W per channel at 8Ω, 360W/ch @ 4Ω

So diode that would put you in the ballpark of being safe. . .

With that amount of power, you probably can't set a low enough threshold to save the driver.

The amplifier is a fixed gain devise. You can't reduce its peak power potential. Turning down the dial on the front is nothing more than an attenuator and will only reduce the drive level that the power amp section sees. If you drive it hard enough you will still have the same wattage potential. Now, this can work provided you never drive the input of that amp till it produces X amount of power, but it is caveat emptor.

A fixed gain amp is pretty simple in nature. It takes X voltage in and converts it to X more voltage out. Some amps are 26db gain others 36db of gain, while others only require X number of volts of input to equal full output ( typically 1.4 volts ). No matter how you slice it, the amplifier will still produce its rated watts if you send it enough drive level to do so. Again the knob on the front is only an attenuator, so all it does is turn down the input drive level.

In short, you cannot take a 1000 watt amp and make it so that it will limit its output to only 180 watts. Now if you turn down the drive level enough and never exceed that drive level, the amp may only ever produce a fraction of its potential, but if you send enough drive signal, the amp will continue to provide power well beyond 200 watts.
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Bad Quail
Sound + Light
Joshua Tree, California

Ken Webster

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Re: How to calculate an amplifier for a biamp speaker?
« Reply #13 on: October 10, 2018, 03:45:30 am »

I am just curious as to why nobody has suggested the old analogue solution using polyswitchs to protect drivers from over current?  Use ohms law to calculate the maximum current for the drivers load.  Then select the next polyswitch trip current below that value.  You still need to set both amps to the same gain for a balanced spectrum response but the polyswitch should prevent blowing out the drivers from over current as you can't limit the Amp's potential to a safe level.  I suppose there may be concerns about resistance noise, damping factor or some such but that is a way to achieve protection, that or a fuse but both solutions have historically been used for this purpose.

Ken
« Last Edit: October 12, 2018, 09:18:54 pm by Ken Webster »
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