Matching amps through measurements

[jbucla2005]

I'm using two different sets of amps to power Vandersteen speakers, and want to know how to measure the outputs of the amps with a multimeter to know how to match the levels. How do I do this?

 

[Sokel]

I'm using two different sets of amps to power Vandersteen speakers, and want to know how to measure the outputs of the amps with a multimeter to know how to match the levels. How do I do this?

???
Two different monos?

Or just passive biwiring?

 

[Sokel]

In any case,put your DMM in AC scale,play a 100Hz or so tone AT LOW level and just place the probes one on each binding post (+ and - )
Keep the duration short and DON'T SHORT THE PROBES!

Try a couple of different levels going to loud-ish (AGAIN,WITH CAUTION) and it should be ok.

 

[jbucla2005]

???
Two different monos?

Or just passive biwiring?

Two sets of mono amps.

1. two Kenwood L-05M amps driving the bass
2. two Fosi ZA3 amps driving the midrange / treble

I need to test the L-05M's to determine the output, then match the ZA3's to that level with the volume knobs (on the ZA3's). The L-05M's do not have a volume control.

Or if possible, I'll just measure the ZA3's if I can figure out how to get them to output 100watts instead of 120watts.

 

[Sokel]

Two sets of mono amps.

1. two Kenwood L-05M amps driving the bass
2. two Fosi ZA3 amps driving the midrange / treble

I need to test the L-05M's to determine the output, then match the ZA3's to that level with the volume knobs (on the ZA3's). The L-05M's do not have a volume control.

Whatever you do,keep it short (seconds) .
Find your test tones,prepare them,make sure the levels are low,hit play and measure.
Do it with the speakers connected,some amps don't like to work with open load.

 

[Elgrosso]

if you want to level match shouldn’t you use a mic? (even a simple app if not umik/rew)
Voltage needs might be very different per section.

 

[jbucla2005]

if you want to level match shouldn’t you use a mic? (even a simple app if not umik/rew)
Voltage needs might be very different per section.

How do I match the levels of the bass with the mid-range / treble? Just play a 1k Hz sine tone and match dB output? Isn't the bass supposed to be louder?

I'm using four mono amps to power a single set of speakers.

 

[Elgrosso]

I’m guessing you don’t have a mic and rew?

With an rta app on your smartphone you could measure each section playing pink noise. Phone at the same level, let’s say 1meter away. Then adjust the fosi to match or to your liking. You should see the effect of the crossover.
It’s not super accurate especially on both ends of the spectrum but better than nothing.
Even just an spl meter might work.

There’s probably better apps now, I used this years ago, maybe there’s some mini-reweq on there?

 

[antcollinet]

How do I match the levels of the bass with the mid-range / treble? Just play a 1k Hz sine tone and match dB output? Isn't the bass supposed to be louder?

I'm using four mono amps to power a single set of speakers.

No, you want to get a flat frequency repsonse into the speaker. In room this should result in a downward sloping FR

So All amps need to be the same gain - fix an input voltage, then adjust the volume control to get the same voltage on the output, as Sokel has described in the third post above.

If after that you want to further adapt the frequency response (for example to increase the bass) then this should be done with tone controls, or equalisation upstream of the amps.

 

[staticV3]

@jbucla2005 you can match both the bass amp and treble amp with a 100Hz test tone, as you can safely assume flat frequency response for the amps.

You don't want to use different test tone frequencies for both amps, as your multimeter likely rolls off above ~1kHz.

 

[jbucla2005]

I’m guessing you don’t have a mic and rew?

With an rta app on your smartphone you could measure each section playing pink noise. Phone at the same level, let’s say 1meter away. Then adjust the fosi to match or to your liking. You should see the effect of the crossover.
It’s not super accurate especially on both ends of the spectrum but better than nothing.
Even just an spl meter might work.

There’s probably better apps now, I used this years ago, maybe there’s some mini-reweq on there?

I don't have a mic and rew, but I do have an rta app. This is easy enough so I will try this before trying to measure the electrical outputs of the amps. (but good to know about that too.) Thanks.

 

[antcollinet]

I don't have a mic and rew, but I do have an rta app. This is easy enough so I will try this before trying to measure the electrical outputs of the amps. (but good to know about that too.) Thanks.

Don't try to use a mic or anything measuring actual sound - since that will be heavily influenced by your room response.

 

[jbucla2005]

Don't try to use a mic or anything measuring actual sound - since that will be influenced by your room response.

I think I just need to get an idea by looking at where the crossover happens, and adjust based on that.

 

[antcollinet]

I think I just need to get an idea by looking at where the crossover happens, and adjust based on that.

No, you need to get the output of the amps at the same level.

You cannot do this by measuring the ouput of the speakers.

 

[Blumlein 88]

I’m guessing you don’t have a mic and rew?

With an rta app on your smartphone you could measure each section playing pink noise. Phone at the same level, let’s say 1meter away. Then adjust the fosi to match or to your liking. You should see the effect of the crossover.
It’s not super accurate especially on both ends of the spectrum but better than nothing.
Even just an spl meter might work.

There’s probably better apps now, I used this years ago, maybe there’s some mini-reweq on there?

Not nearly as accurate or simple as using a voltmeter. Noise can interfere and positioning must be exact.

 

[Blumlein 88]

I think I just need to get an idea by looking at where the crossover happens, and adjust based on that.

You can level match both with 100 hz. Gain. Is not going to change between 100 hz and a few thousand hertz.