Help, new to all this

[bennyblanco916]

Hey, so short background, I have been in car audio for about 20 years now but only on the spl side of things. Back then, I only cared about subs and amps nothing more..fast forward to today, I jumped over to the SQ side and find it very interesting how everyone in SQ is learning or knows how to measure speaker or amplifiers ... my question is, what is the process to measuring amplifiers? The only equipment I have at the moment is a laptop using REW, a small Oscilloscope, and a umik 1 mic... I see plenty of videos and post of people sharing the THD of certain equipment but never show the steps they used to get those measurements..... so, I basically need help with what equipment and steps I need to take car amplifier measurements...thank you

 

[staticV3]

I basically need help with what equipment and steps I need to take car amplifier measurements...thank you

To measure an Amp, you need:

• an ADC with low self noise and distortion (audio interface/Cosmos ADC/QA403)
• a load that reflects real world conditions (resistive or reactive dummy load, or just a speaker if you can handle the noise)
• in case of class d: a filter to prevent switching noise from messing up your measurements (e.g. AP AUX-0025. Can be DIYed)
• cables to connect it all

 

[DVDdoug]

very interesting how everyone in SQ is learning or knows how to measure speaker or amplifiers

The main thing that affects "sound quality" will be frequency response (from the speakers, in the room/car). That's assuming your not pushing your amplifier(s) into clipping or over-driving your speakers.

And of course, the quality of the music you're playing matters. And, it's mostly the recording/production, not the format. (You may want to avoid MP3 or other lossy compression, but good high-bitrate MP3 can sound awesome on an awesome system!)

I've never heard distortion from an amplifier unless it was broken or over-driven into clipping. Your oscilloscope can show clipping but I don't think you can see (or hear) 1% distortion so you may have to push the amp a little "harder" into clipping before you see it.

Most amplifiers also have very-flat frequency response.

If there's an audible defect or weakness from an amplifier (or other electronics) it's usually noise. Noise is tricky to measure because there's more than one way to measure it. You've probably heard hiss from those "high SPL" setups. And probably some other nasty noises from the car's electrical system!

Speakers tend to distort more than amplifiers (assuming no clipping) and REW should be able to help with measuring the overall distortion.

Since you're into SPL, I probably don't have to warn you about burning-out speakers with high wattage continuous test tones!

 

[LTig]

To measure an Amp, you need:

• an ADC with low self noise and distortion (audio interface/Cosmos ADC/QA403)
• a load that reflects real world conditions (resistive or reactive dummy load, or just a speaker if you can handle the noise)
• in case of class d: a filter to prevent switching noise from messing up your measurements (e.g. AP AUX-0025. Can be DIYed)
• cables to connect it all

• a voltage divider and a limiter to prevent the input ADC from being destroyed by too much voltage.

 

[AnalogSteph]

• a voltage divider and a limiter to prevent the input ADC from being destroyed by too much voltage.

One of them guys:

Measuring Speaker and Headphone Outputs With Focusrite Scarlet 2i2 v3

I would like to measure the output of some tube amps using my 2i2. I am considering getting an oscilloscope too (

www.audiosciencereview.com

Resistor values will vary depending on attenuation required. With some interfaces you may want to use their line inputs instead for lowest distortion (e.g. Scarlett 4i4 4th gen or Tascam UA-2x2HR come to mind).

Note that we are talking good amateur-level measurements with little if any automation and e.g. using REW. A few hundred bucks and a bit of elbow grease will get you pretty far though. Sure beats spending 50 grand on an AP system for most of us. (Well, even an RME ADI-2 Pro and the AP software would generally be a better deal...)