2. amps-preamps
  3. 182257-2603

Bi-Amping: How can I determine relative output?

Long Story Short:  I have a 50w/channel pair of tube monos, and a 300w stereo solid state amp playing through a set of JBL 4367s. two way monitors.

The tubes are on the horn tweeter and the solid state is on the 15" woofer, crossover is apparently 700hz.

Doing absolutely nothing, some music sounds completely "normal" and some music sounds artificially bass heavy.

The solid state amp has gain adjustments for each channel.

I have a Fluke 115 multimeter, and access to plenty of test tones, but nothing to read SPL.

Is there a way to measure output at the speaker terminals such that I could dial the woofer amp down to "match" the tube amps?

If so, would this be more or less constant as the preamp driving the amps changes  volume, or would it only "match" (to the extent that it actually matches at all) at one volume level?

 

 

 

gthirteen
russ69's avatar
russ69
3,360 posts
 

One of the amps will need to have a gain adjustment. You'll need a sound level meter of some kind if you want an accurate adjustment. I tune my woofer towers by ear but YMMV. 

erik_squires
15,909 posts
 

Amplifiers are voltage amplifiers, and provide a fixed amount of gain (voltage out x voltage in).  There is a convention of 23 or 26 dB, but best to measure it. 

You can use an average multi-meter if you can find a 60 Hz test done.  At this frequency multimeters are spot-on. 

So, play a 60 Hz signal through both amps at the same time and set them so they output the same on the amps.

You don't have to go very loud.  A 5V signal is plenty to tell.

hiend2's avatar
hiend2
376 posts
 

Input sensitivities might be a little off so maybe as you turn up the volume one amp may give more power compared to the other

Buy a test tone CD and a sound level meter

Those old simpson sound level meters are good and cheap these days.

Good luck

 

holmz's avatar
holmz
2,328 posts
 

You might be better off just using the tube amp, or using 1 good amp.

carlsbad's avatar
carlsbad
1,551 posts
 

I like what Erik described above but in the end, you'll have to go with your ears.  My thought is that the songs that sound normal have room for more bass in them.  They might even sound better with the more bass to many or most people.  I would use a bass heavy song and turn it down until it sounds right.  Done.

More to discover