Speakers distortion

[Krunok]

Sure, I'm also more interested in the loudspeaker.

Me too, but I simply cannot do it properly as furniture doesn't allow me to move speakers far awa from the walls.

But I was suggesting that what we "hear" may not be as simple as the (steady-state) distortion of the loudspeaker + room at the listening position, either.

Surely not, but that is what we can measure.

 

[sergeauckland]

Ok, fair point!

How do new numbers look to you?
They obvously aim to represent what distortion exists in the room, in a same manner frequency response measurement taken this way aims to represent response at LP.

I take it those numbers refer to distortion at 1kHz and an SPL of 70dB. If so, they look decent enough, although at 70dBSPL, I wonder how close to the noise floor the distortion products actually were. I hope that the 'LP' doesn't indicate that the tone came off an LP!

S.

 

[andreasmaaan]

This is what I got when measuring distortion the very same way I'm measuring frequency response:



There was 70-80 samples per each measurement and as you can see the numbers are much more consistent.

That certainly looks more consistent. I'd take it to be a more accurate measurement than the previous single-point measurements (but that would also be mostly hand-waving to some extent).

Surely not, but that is what we can measure.

Sure It's just a question of how to interpret the measurement.

 

[sergeauckland]

Maybe. But you'll still (more or less) perceive the direct sound as distinct from the sound field, at least in terms of spectral balance. I suspect you may perceive the direct sound quite distinctly from the sound field in terms of distortion, too.

Interesting this. Don't know if the perception of distortion can separate the direct sound with its intrinsic distortion from the delayed sound with its own room gain applied to the distortion. I haven't seen anything published about this.

S.

 

[Krunok]

Interesting this. Don't know if the perception of distortion can separate the direct sound with its intrinsic distortion from the delayed sound with its own room gain applied to the distortion. I haven't seen anything published about this.

S.

If I have to bet my money on it I would say we can't separate distortion, but it's hard to claim anything without detailed study.

 

[Krunok]

That certainly looks more consistent. I'd take it to be a more accurate measurement than the previous single-point measurements (but that would also be mostly hand-waving to some extent).

Sure It's just a question of how to interpret the measurement.

To me it looks quite obvious they would be converging to some value with a decent SDEV if I make 20 measurements.

So, is the mic in this scenario picking up the distortion I'm hearing when sitting at my LP?

 

[Krunok]

I take it those numbers refer to distortion at 1kHz and an SPL of 70dB. If so, they look decent enough, although at 70dBSPL, I wonder how close to the noise floor the distortion products actually were. I hope that the 'LP' doesn't indicate that the tone came off an LP!

S.

This is snapshot of the "silence" recorded with the same method:



LF noise is dominated by the cars passing nearby and 100 and 200Hz spikes are probably coming from the various machines working in the kitchen (owen fan, refrigerator, dish washer, heating system pump etc.)

 

[Krunok]

This is how it looks with louder tone in the RTA window with harmonics shown:



As I mentioned, when I listen music loud average SPL is at 75-80 dB but 1kHz tone at this SPL seems much louder and more irritating than music.

 

[Burning Sounds]

I prefer just to be happy that the distortion I measure is low enough not to be of concern even if I don't actually know what the number really is, just that it's not very high.

S.

Yes, this is my take on this, too. Just too many variables to make comparisons between speakers meaningful, I think.

Notwithstanding all the caveats mentioned in this thread here's a couple of measurements I exchanged with @RayDunzl in another thread earlier this year.

Even though the equipment and the room is the same the comparison between the speakers is not really that useful either given that the levels are different, but I'm quite happy with both.

Linkwitz LX521

Magneplanar 2.5r (30+ years old) with LX521 bass units

 

[Blumlein 88]

But in-room response affects distortion, correct? if you measure near field you will probably get a better picture of the distortion your speaker would have in anechoic environment but that is not really what you are listening when sitting in your chair at LP, right?

Yes the difference is you'll move your head around as you listen.

 

[Blumlein 88]

This is what I got when measuring distortion the very same way I'm measuring frequency response:



There was 70-80 samples per each measurement and as you can see the numbers are much more consistent.

I was moving mic in a pattern similar to Diac Live points, 50cm left and right from the center position, 15cm up and down and 25cm in front and backwards.

So is that 70 db spl? I get numbers like that or better at that reduced level. My previous numbers in this thread were around 90 db spl.

I'll be interested in what I can get outdoors when I get the chance.

 

[Blumlein 88]

Perhaps we need professional help.
@Floyd Toole can you give us good info on speaker distortion measures?

Probably don't need to read the whole thread. At issue is whether it's possible using REW or similar to get distortion numbers that are meaningful in your listening room? Or is the only way in anechoic or outdoor conditions?

 

[Krunok]

So is that 70 db spl? I get numbers like that or better at that reduced level. My previous numbers in this thread were around 90 db spl.

I'll be interested in what I can get outdoors when I get the chance.

But what kind of music has 1kHz signal at 90dB? In that case bass would be at 100-105dB and I don't really listen at those levels. On the rare occasions I do I certainly don't care about distortions..

Btw, it was early in the morning and my boys were still sleeping. My idea with this measurement was just to check if I can get consistent (repeatable) distortion figures. Maybe we can agree to measure at 80dB so we can compare the measures in a more meaningful way?

P.S. this thread is not who's got better speakers but to get a feeling about distortion figures with different speakers.

 

[Krunok]

Perhaps we need professional help.
@Floyd Toole can you give us good info on speaker distortion measures?

Probably don't need to read the whole thread. At issue is whether it's possible using REW or similar to get distortion numbers that are meaningful in your listening room? Or is the only way in anechoic or outdoor conditions?

Maybe @JohnPM can help as well?

 

[Krunok]

Yes the difference is you'll move your head around as you listen.

I don't get what you're trying to say, maybe if you rephrase it..?

 

[SIY]

So no-one is doing GedLee measurements? Hmmm, I may need to correct this. But not today, I'm chained to the kitchen preparing New Years' dinner.

 

[Blumlein 88]

I don't get what you're trying to say, maybe if you rephrase it..?

Even when you think you are holding your head still there are small movements. More so when listening casually without trying to hold your head still. These movements are used by your hearing to effect what you hear. JJ has mentioned this now and again.

So maybe something like the mmm method your brain is doing this statistical calculation all the the time. Which will alter the effect of standing waves on what you hear vs what you measure.

 

[Blumlein 88]

snip...

P.S. this thread is not who's got better speakers but to get a feeling about distortion figures with different speakers.

Oh I agree. I was using lsr 305s as they are handy for this. They'll be handy to take outdoors if it stops raining here.

 

[andreasmaaan]

So no-one is doing GedLee measurements? Hmmm, I may need to correct this. But not today, I'm chained to the kitchen preparing New years' dinner.

I do them! But with a matlab script, and in any case you still need to have correct baseline distortion measurements to calculate them, something I only feel satisfied I can do reasonably accurately with individual drivers at this point.

 

[DonH56]

It seems to me one (rough) solution would be to fix the mic position, do a sweep to capture the response, then use that to adjust relative levels in the distortion sweep. The in-room response should not be affected by volume (until you knock something around, or down) so check at low level then do the higher-power distortion measurements. This could be automated; for each frequency, check the levels of the fundamental and each harmonic using low-level test tones, then incorporate that into the distortion reading.

This would not correct problems in the recording (sensing) chain, however, be it mic overload, input buffer or ADC distortion, etc. And moving the mic or anything else that could change the response will of course impact the results.

In the distant past I used a Matlab program that sequentially generated and recorded the fundamental and ten harmonic tones (or to 20 kHz, highest I chose to test) of the desired test tone at 60 or 70 dB SPL'ish in short bursts, then did a burst power sweep at the fundamental. A simple loop would step through multiple test frequencies. That used GPIB control of a generator and spectrum analyzer; these days you would just use a sound card or something like REW.

Can someone provide a link to the GedLee measurements for the thread-weary?