Speakers distortion

[Krunok]

You get an average.

Remember, the average person has one ball and one tit.

Remember that you can average in more detail. You will still get an average of 22 years young girl, 42 year MILF and 72 year granny, but at least your average will have 2 tits and no balls!

 

[Krunok]

There's benefits to measuring in situ and outdoors. Being indoors isn't increasing distortion from the speaker. So if indoors distortion is higher it's a measurement artifact or error.

It is, but at least you're measuring what you're listening.

 

[Blumlein 88]

Remember that you can average in more detail. You will still get an average of 22 years young girl, 42 year MILF and 72 year granny, but at least your average will have 2 tits and no balls!

That's why you window your averages.

 

[RayDunzl]

Try to read that pdf I posted, it is all desribed there much better than I can do it here.

Post a link that works, I'll look.

 

[andreasmaaan]

I think we can tentatively conclude from @RayDunzl’s measurements that the MLs are lower distortion that the JBLs. But if someone posted a measurement in their room with their mic I wouldn’t dare to compare it to either of Ray’s. Even when I see distortion measuremts taken under very rigorous (but not anechoic) conditions, but not the same conditions as each other, I am very cautious about drawing any conclusions. It’s one of the most difficult aspects of a loudspeaker to accurately measure. That’s basically my 2c

 

[Blumlein 88]

Have you tried really long sweeps? That would help with the noise.

 

[Blumlein 88]

That might be a question for @JohnPM

View attachment 19643

Nope, I had to RTFM.

View attachment 19644

If you are using a recording interface you wouldn't need to use the acoustic reference. Won't work with a USB mic however.

 

[RayDunzl]

Have you tried really long sweeps? That would help with the noise.

Even if the noise is rather constant?

 

[Blumlein 88]

Even if the noise is rather constant?

Yes the manual says so. Will help more with variable noise of course. The manual says it will work better than averaging several sweeps.

 

[pkane]

I know you can open up multiple measures and add them in the window.

I thought time align and vector average was the way to do this?

• Time align, which brings all the currently selected measurements into time alignment. If the measurements have been made with a timing reference (a loopback connection or an acoustic timing reference) the impulse response is shifted according to the measurement delay value, taking into account any IR timing offsets which have been applied since the measurement delay was calculated. Measurements which have been made without a timing reference are shifted according to the estimated IR delay. Time alignment can only be applied to measurements that have an impulse response.
• Vector average, which averages the currently selected traces taking into account both magnitude and phase. It can only be applied to measurements that have an impulse response.

 

[Blumlein 88]

I thought time align and vector average was the way to do this?

Stupid question, where in REW are these?

 

[RayDunzl]

Stupid question, where in REW are these?

Maybe https://www.roomeqwizard.com/help/help_en-GB/html/graph_allspl.html

 

[Blumlein 88]

https://www.ohl.to/audio/downloads/MMM-moving-mic-measurement.pdf

Incidentally, I think this is the broken link on using moving microphone measurement.

So now we can see what Krunok is talking about on the moving mic deal.

 

[Blumlein 88]

Maybe https://www.roomeqwizard.com/help/help_en-GB/html/graph_allspl.html

Thanks Ray.

I was looking in terms of Distortion and missed it under All SPL.

 

[Blumlein 88]

Did a little experimenting with sweeps and RTA tones for distortion measurement. I'm not sure we can get there from here.

With both I found moving the Umik 1 even a few inches could alter the distortion significantly. Sometimes 20 db for RTA use. Just for instance using a 780 hz tone and RTA several feet from speakers, I could get .134 % 2nd and .454 3rd, move it six inches resulting in 2.55% 2nd and 6.34% 3rd. Going 6 inches further gave a result of .444% 2nd and .874% 3rd. Obviously at least two are wrong for what the speaker is doing and probably all of them. Peaks and dips for standing waves are a problem.

Similar problems though of smaller magnitude with sweep based distortion measures. And whether you get a lower resulting distortion with long, short or medium length sweeps depended upon where in the room you put the microphone. Getting close to the speaker also didn't seem to help.

Or am I doing this all wrong?

 

[Hactar]

Going three-way (or more) instead of two will drastically reduce various types of distortion (including Doppler).

DSP and active crossovers make such speakers practical and easy to create, therefore even if driver technology doesn't change, DSP reduces speaker distortion - indirectly.

Any thoughts on why the JBL M2 is only a 2-way? Would that design benefit from a 3rd driver? It already has the dsp.

 

[RayDunzl]

Or am I doing this all wrong?

In-room measurements have their quirks...

But the room won't add harmonics that aren't there in the speaker to begin with (ignoring noise sources).

So there's some value in it, at least to me.

 

[Blumlein 88]

In-room measurements have their quirks...

But the room won't add harmonics that aren't there in the speaker to begin with (ignoring noise sources).

So there's some value in it, at least to me.

Well one obvious one is us panel speaker guys have less splatter around the room because of the speaker being more directional.

 

[andreasmaaan]

Did a little experimenting with sweeps and RTA tones for distortion measurement. I'm not sure we can get there from here.

With both I found moving the Umik 1 even a few inches could alter the distortion significantly. Sometimes 20 db for RTA use. Just for instance using a 780 hz tone and RTA several feet from speakers, I could get .134 % 2nd and .454 3rd, move it six inches resulting in 2.55% 2nd and 6.34% 3rd. Going 6 inches further gave a result of .444% 2nd and .874% 3rd. Obviously at least two are wrong for what the speaker is doing and probably all of them. Peaks and dips for standing waves are a problem.

Similar problems though of smaller magnitude with sweep based distortion measures. And whether you get a lower resulting distortion with long, short or medium length sweeps depended upon where in the room you put the microphone. Getting close to the speaker also didn't seem to help.

Or am I doing this all wrong?

Getting close should give an improvement, but perhaps only significantly so if the speaker is far away from any reflective surfaces and the room is relatively dead. For example, if there’s a 1:2 ratio between the the path lengths of the direct sound to reflected sound, that’s just a 6dB difference, and that’s not even counting subsequent reflections, which will reduce the difference even further. You can imagine that if you hope to benefit from getting close, that ratio will need to be very very low, indeed well within the room’s critical distance at all frequencies of interest, if the measurement isn’t to be dominated by room effects. What makes this probably uniquely more difficult than in-room amplitude response measurement is the comb filter effect. If a harmonic falls on a “tooth” of the comb, it just won’t show up in the measurement, and smoothing can’t fix this. Averaging a number of measurements might help, but it will still very hard to know your measurements reflect reality.

If you can take the speaker outside or have a very large space inside somewhere and can then get the mic quite close there, you’ll get a more reliable result I reckon. Otherwise you’re really just stabbing in the dark IMHO.

 

[Krunok]

Post a link that works, I'll look.

Here it is..

http://www.ohl.to/audio/downloads/MMM-moving-mic-measurement.pdf