Measuring speaker output at multiple power levels

[CustomSpeakerPods]

Reduce the recording level.

Excellent advice!!! That appeared to help, though I'm using windows 11, and the adjustment interface only gives me a percentage (which I reduced to 50%). Measurements had repeatable results after making this adjustment!

How do you recommend I test? White/pink noise? What is the best way to record this information in REW (or do I need another software?) RTA? Measurement does not have the ability to test using noise.

 

[Sokel]

Excellent advice!!! That appeared to help, though I'm using windows 11, and the adjustment interface only gives me a percentage (which I reduced to 50%). Measurements had repeatable results after making this adjustment!

How do you recommend I test? White/pink noise? What is the best way to record this information in REW (or do I need another software?) RTA? Measurement does not have the ability to test using noise.

You also have to adjust those to your target:



You can also see distortion as you increase power like I did in this post:

"System" SINAD

Would the concept of "system" SINAD (from source to speakers) be useful in component selection for a good stereo system? Let's assume a listening SPL of 85dB @ 1m, and a room noise floor of around 40dB SPL. Assuming +20dB headroom for signal peaks, and another -20dB noise headroom. A system...

www.audiosciencereview.com

(about the percentage adjustement of your mic,just right click on the percentage and change it to db)

 

[CustomSpeakerPods]

You can also see distortion as you increase power like I did in this post:

Wow! I didn't even know what that button was for... Sorry, I'm a total newb with REW. Been using it for a while, but only for very basic stuff. What other information would be interesting to present/record?

 

[CustomSpeakerPods]

I have done some testing with the information gathered here (Thank you all).
Setup:
Speaker: Single Kicker ST7 4ohm
Source: Car stereo head unit (Kenwood DMX125B) connected to computer via bluetooth (I know, not the best, but it's what I have at the moment)
Amplifier: DS18 GFX-2.2k1
Measurement Microphone: Dayton Audio UMM-6
Software: REW
Microphone input setting (windows): 50%
Microphone position: 1 meter above center of speaker
Wattage measurement: Frankencobbled Arduino voltage and amperage sensor
Location: Desk, speaker on rubber mat, small amount of foam attached to wall to prevent echo.

Test:
Sweep from 200 - 10kHz
Level: 388mV
Protection: nah
256k Length (5.5 seconds)
Sample Rate: 48 kHz

Volume 10: 0.95 watts
Volume 20: 16.9 watts
Volume 30: 127 watts
Volume 32: 147 watts

 

[CustomSpeakerPods]

Explanation: (correct me if I am wrong)
It appears that this speaker, even with a non-linear response, can reproduce equally at levels from 1 watt up to 147 watts with little to no change in response. Testing up to the max RMS wattage is still to be done, but I'm scared.

 

[CustomSpeakerPods]

How would I explain the distortion values? or is there something else that would be more interesting for my purposes?

 

[Sokel]

You might try to see distortion %,just change the upper left drop menu from SLP to %.

 

[RayDunzl]

How would I explain the distortion values?

Top left - select dBr

Shows how loud the distortion product is relative to the fundamental level

 

[fpitas]

Yes and no. What do I test with? Sweep, white noise, pink noise?
Do I limit the frequency range as per your statement about the Xmax? (which in itself is an interesting mode of the test; how does the frequency range change with power?) I noticed during a quick bench test at higher wattage (125W) the sound starts to 'clip' (completely observational, just sounds static-y), is this due to reaching the mechanical limits at lower frequencies?

It does seem like you were starting to bash the coil against the pole piece. And in real life that may be the limitation for these drivers. I think I'd try 1/3 octave white noise. As to what center frequency? I'd look at a SIM in whatever box you think is appropriate to see the lowest frequency where the maximum power is allowed before reaching the Xmax limit.

 

[Deleted member 48726]

Explanation: (correct me if I am wrong)
It appears that this speaker, even with a non-linear response, can reproduce equally at levels from 1 watt up to 147 watts with little to no change in response. Testing up to the max RMS wattage is still to be done, but I'm scared.

Maybe I missed it, but are you testing the driver in free air?

 

[sam_adams]

How would I explain the distortion values? or is there something else that would be more interesting for my purposes?

It is generally recognized that distortion levels above 10% indicate that the driver is operating outside of its linear Xmax rating. In your graph, the levels of 11% and 14% indicate that the driver is operating close to or at its Xmech level and has no more travel available. Additionally, looking at the THD level alone will not tell you if the driver is harmonic distortion bound. You must look at all of the harmonic distortion levels to see where in the frequency spectrum the driver is actually exceeding the 10% distortion level.

One more thing, if you are intent at being taken seriously as a vendor or distributor, you need to acquire equipment that is better than the bottom rung of hobbyist devices. For measuring software, REW is absolutely unmatched in its capabilities, but a UMM-6 mic is a poor choice for a measuring device. Consider purchasing at the very least an Audix TM-1 or move up to something like an Earthworks M23/M23R, M30 or M50. You should also consider purchasing a high-quality audio interface device that will work with the mics previously mentioned.

 

[CustomSpeakerPods]

Maybe I missed it, but are you testing the driver in free air?

Yes, I am testing them in free air at the moment. Since I have so many speakers to test I figured this would be easiest for me.

 

[fpitas]

Yes, I am testing them in free air at the moment. Since I have so many speakers to test I figured this would be easiest for me.

A box restricts cooling air flow. Just something to think about. I recall a JBL test where aiming the port at the driver inside the box made a significant difference to cooling.

 

[CustomSpeakerPods]

One more thing, if you are intent at being taken seriously as a vendor or distributor, you need to acquire equipment that is better than the bottom rung of hobbyist devices.

Excellent advice. Other than the mics, do you have a recommendation for the audio interface device? Ideally it would be able to replace my head unit for output to interface directly with the low level RCA inputs of the amplifier (or have a strong enough amplifier... and won't break the bank), and have an input for the microphone. I don't know if anything like this exists as a single unit.

It does seem like you were starting to bash the coil against the pole piece.

Is there some good, semi-technical reading regarding distortion and how to analyze the data from REW (I would love the ability to determine this on my own)? I am beginning a journey to a place out of my own realm and would like some guidance.

 

[CustomSpeakerPods]

A box restricts cooling air flow.

Agreed. I am sitting the drivers on my desk at the moment. If I have a driver with a 'cooling' vent on the back of the motor I will raise it up to not restrict the airflow.

 

[CustomSpeakerPods]

For the amplifier output I recently received a Hantek 1008C USB scope. I understand that this is probably not the best device, but for the price I figured it would be a good starting point.

 

[fpitas]

Is there some good, semi-technical reading regarding distortion and how to analyze the data from REW (I would love the ability to determine this on my own)? I am beginning a journey to a place out of my own realm and would like some guidance.

I'm a guy that listens to twin 15 inch woofers at about 80dB so I'm not the guy to ask. But generally a SIM program will get you close if you have accurate T/S parameters. I use AJsealed or AJvented to see that stuff, but there are lots of them out there.

 

[CustomSpeakerPods]

I'm a guy that listens to twin 15 inch woofers at about 80dB so I'm not the guy to ask. But generally a SIM program will get you close if you have accurate T/S parameters. I use AJsealed or AJvented to see that stuff, but there are lots of them out there.

I'm more in the 140dB range at the moment.
I am interested in learning about THD and how to understand the data. This is what I was asking... sorry for the confusion.

 

[fpitas]

I'm more in the 140dB range at the moment.
I am interested in learning about THD and how to understand the data. This is what I was asking... sorry for the confusion.

Gotcha. I'm not a REW user, but lots of guys here are. But like was said above, once you hit 10% THD, things are going south fast.

 

[CustomSpeakerPods]

Gotcha. I'm not a REW user, but lots of guys here are. But like was said above, once you hit 10% THD, things are going south fast.

Do you mind giving me a quick analysis of this distortion data?