Setting HPF/LPF with DMM? Theory inside.

[ultimate157 5,000+ posts]

I was just thinking about how I set my filters. The analog knob on most amps are never really that well marked as to where the filter is set (Some only have the min/max values printed)

Electrically speaking, -3db is 1/2 the wattage.

So far my thinking is this: You set your gains correctly with ZERO filters enabled. Play a test tone equal to your desired crossover frequency and record the voltage; This should equal what you set your gains to. Turn on the filter (high or low pass) and adjust to your desired voltage.

Now, you've set your gains to a specific wattage, at a certain impedance, and you've measured the voltage.

Say you set your gains for 150w at 4 ohms. This would come out to 24.49v. If you halve the wattage to 75w at 4 ohms, then the voltage should be 17.32v at 80hz with the filter on and set.

Am I getting to something here ? Discussion?

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[ultimate157 5,000+ posts]

Anyone?

 

[helotaxi 5,000+ posts]

That's exactly how you do it to get a specific frequency.

 

[ultimate157 5,000+ posts]

That's exactly how you do it to get a specific frequency.

Good to hear I was thinking straight //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

 

[squeak9798 5,000+ posts]

As helotaxi said, that's correct for setting to a specific frequency.

My only caution would be that it is a little....pointless.....in most instances. Crossovers should be set according to their affect on the sound, not some generally arbitrary number that may or may not be the best setting. Using a DMM and formula to set the crossover to a specific frequency is generally not the way to go about adjusting the crossover for maximum performance.

 

[helotaxi 5,000+ posts]

^^^RTA/ear are the best way. You can use the DMM to get a baseline (for speaker protection for example) but the final settings should be done according to what sounds right, not some arbitrary predetermined value.