How to do level match with headphone as load

[FINFET]

Previously I used to level match my audio electronics by using a multimeter directly on the other end of the audio cable. My multimeter is capable of measuring a 1000Hz signal, less expensive multimeters may only be capable of measuring up to 400Hz but that doesn' matter. I play a sine sound signal and match the levels at the end of the cable without connecting the cable to a transducer. However, some people may not consider this method rigorous enough as the levels may vary at different frequencies and with different amp damping factors and load resistence. In reality, level matching two audio electronics can be a challenging task, even if these factors are taken into consideration. Are there any better methods to level match audio electronics that you know of?

When it comes to matching levels for speakers, measuring SPL at a certain distance directly can be quite straightforward. However, level matching headphones with SPL is hard. Is there a tool available that can accurately measure voltage at the headphone side when the other end of the cables are connected to the headphone? (I think I can DIY a tool with some wires connecting to three points on that trs plug but I'd like to know if people are using better tools)

 

[HarmonicTHD]

Previously I used to level match my audio electronics by using a multimeter directly on the other end of the audio cable. My multimeter is capable of measuring a 1000Hz signal, less expensive multimeters may only be capable of measuring up to 400Hz but that doesn' matter. I play a sine sound signal and match the levels at the end of the cable without connecting the cable to a transducer. However, some people may not consider this method rigorous enough as the levels may vary at different frequencies and with different amp damping factors and load resistence. In reality, level matching two audio electronics can be a challenging task, even if these factors are taken into consideration. Are there any better methods to level match audio electronics that you know of?

When it comes to matching levels for speakers, measuring SPL at a certain distance directly can be quite straightforward. However, level matching headphones with SPL is hard. Is there a tool available that can accurately measure voltage at the headphone side when the other end of the cables are connected to the headphone? (I think I can DIY a tool with some wires connecting to three points on that trs plug but I'd like to know if people are using better tools)

Yeah. DIY. Split the cable. One strand to the HP and the other to the multimeter.

 

[maxxevv]

That's matching the input signal levels. Not the SPL which is Sound pressure levels.

A given signal level with a specific energy output will give different SPLs to different speakers and headphones as their sensitivity and resistances are not the same.

A microphone capable of measuring the output volume / SPL accurately should give a more qualitative as well as quantitative comparison IMO.

 

[HarmonicTHD]

Correct. Matching Signal Levels. I thought that is what the OP wanted as he talked about his multimeter. Maybe I misunderstood.

 

[FINFET]

Thanks for your replies but I think I am even confused by my own question, sorry that it's not clear enough. Level matching two headphones directly is quite impossible as we know they have differen FR so I think my questions are actually two:
1. to compare different audio electronics (dac/amp, cables) with the same headphone, I need the same voltage levels with this headphone as load.
2. to compare different headphones with the same audio electronics, but I'd like the volume to roughly match each other.

The first one seems simpler as I can do the DIY to try to connect a working headphone with my multimeter or buy some specially made split cable or something. The second one is not so easy in my opinion, I'm not sure if there's a common method or agreement to do headphone comparisons with their volume similar to human ear even with different FR. It looks like an integration math problem with the equal loudness contour or something when it comes to how we should set levels to roughly match two headphones.

 

[jae]

Use a calibrated microphone and measure it with REW? You can normalise measurements to 400hz, 500hz, 1000hz etc to compare them or just take a weighted SPL measurement directly in the software

 

[FINFET]

Use a calibrated microphone and measure it with REW? You can normalise measurements to 400hz, 500hz, 1000hz etc to compare them or just take a weighted SPL measurement directly in the software

I see you are right I think it might be the only way when we need to level match headphone volume. But that might need a stable dummy head to match different headphones with microphones and something like a Neumann ku100 or even much cheaper alternatives are certainly out of my budget reach. I may need to carefully measure the centimeters from the speaker to roughly the position of human ear and test a rough volume from it.

Regarding the "same headphone, different electronics" part, I may still have to use my multimeters on different frequencies. I'm trying to mod my headphone cables on the headphone side, so that I can get voltage when the cable is plugged into the headphone and driving the load. But I'm not good at this DIY stuff..

 

[jae]

I see you are right I think it might be the only way when we need to level match headphone volume. But that might need a stable dummy head to match different headphones with microphones and something like a Neumann ku100 or even much cheaper alternatives are certainly out of my budget reach. I may need to carefully measure the centimeters from the speaker to roughly the position of human ear and test a rough volume from it.

Regarding the "same headphone, different electronics" part, I may still have to use my multimeters on different frequencies. I'm trying to mod my headphone cables on the headphone side, so that I can get voltage when the cable is plugged into the headphone and driving the load. But I'm not good at this DIY stuff..

Yeah, I think for this purpose you don't really need to break the bank, really. There's https://www.minidsp.com/products/acoustic-measurement/ears-headphone-jig which costs $300 but probably overkill just for this... for iems you can get a clone iec711 coupler from china which is usually under $100. As for a calibrated microphone there's the $80 umik-1 and just use a ruler or caliper to make sure the microphone is a similar distance away from the headphone driver, measuring I suppose only a single channel (and now you still have a very useful umik-1 you can use for correcting loudspeakers or even just recording stuff). I think if your goal is level matching this is quite adequate.

 

[jae]

You could also do a very practical thing and wire up a good quality but cheap electret capsule mic such as one of these https://micbooster.com/22-primo-microphones and take a measurement at the opening of your canal with each headphone to be compared as I explained with REW, this is probably quite effective if it's just a matter of getting good numbers to match volumes with weighted or otherwise.