Frequency measurements without speakers?

[Boomzilla]

In the past, I've always measured speaker outputs as a means of determining frequency response. But Mr. KeithL recently pointed out that running the signal through the speaker(s) introduces several orders of magnitude of variation that isn't there in the source signal. This is due to the speaker's non-linearities, the amplifier's interaction with the speaker drivers impedance and their crossover impedances, and the room environment.

So I'd like to measure low level (preamplifier output) frequency response without the variations introduced by the downstream amplifier/speaker combo.

I could measure with an AC voltmeter at different frequencies, but instead would like to have a frequency response curve generated & recorded in a graphic format. Is there inexpensive software or hardware that will accomplish what I want? If so, what?

Thanks - Boomzilla

[MusicHead]

Not used it myself, but this might be what you are looking for?

audio.rightmark.org/products/rmaa.shtml

[millst]

I've done it with REW and a firewire-based audio device from MOTU. I only used it for microphone input at first. Then, it didn't get much use with the XMC-1, because of Dirac. However, I did feed the XMC-1 inputs directly into it a few times to verify that bass management was working properly (for a thread here).

[DYohn]

What is it you are trying to measure, raw FR of line-level signals? You'll need a function generator to create the signal and an oscilloscope at least to measure the output. Or an audio analyzer. And some training on how to use them.

[AudioHTIT]

I’ve used AudioTools RTA or FFT functions on iPadOS or iOS, but now that analog inputs are going away there’s an A2D process which can color the results.

[Boomzilla]

What I'm trying to do is:

Measure the actual effects of tone controls
Measure the actual frequencies of high & low pass filters
Measure the actual effects of balance controls
Measure the actual THD + noise

[AudioHTIT]

Aug 1, 2021 13:31:29 GMT -5 Boomzilla said:

What I'm trying to do is:

Measure the actual effects of tone controls
Measure the actual frequencies of high & low pass filters
Measure the actual effects of balance controls
Measure the actual THD + noise

With AudioTools I measured the effect of the G3P FM Loudness Contour at various levels (directly off its outputs), which would be similar to tone controls, but again it required an A2D conversion.

Edit: It seems any ‘software’ based solution would require an A2D conversion.

[monkumonku]

Aug 1, 2021 13:31:29 GMT -5 Boomzilla said:

What I'm trying to do is:

Measure the actual effects of tone controls
Measure the actual frequencies of high & low pass filters
Measure the actual effects of balance controls
Measure the actual THD + noise

But even if you measure the "actual" effects of these things at their point of output, they'll still be affected by the load they are driven into, i.e., speakers.

[Boomzilla]

Aug 1, 2021 15:28:35 GMT -5 monkumonku said:

But even if you measure the "actual" effects of these things at their point of output, they'll still be affected by the load they are driven into, i.e., speakers.

Absolutely true. But I'm not reviewing speakers - just electronics in this case.