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Author Topic: Labhorn CEA-2010 distortion  (Read 399 times)

Mark Wilkinson

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Labhorn CEA-2010 distortion
« on: May 10, 2018, 09:42:00 am »

I decided to try REW's CEA-2010 routine  on a Labhorn, having just just tested my DIY sub with it..

Results for both are below.
In fairness to the Labhorn, it's just a single box, and who knows how tired the drivers are....I made the Labhorns within the first year of the original plan being posted.

For those who aren't familiar with CEA-2010, my layman's take is that it is a harmonic distortion test more for home audio, particularity home theater, than for live sound. 
It uses 6.5 cycle sine bursts on 1/3 octave freq centers to measure harmonic distortion. 
The test is a pass/fail that allows decreasing amounts of harmonic distortion for higher harmonics, with the idea higher harmonics are less tolerated by the ear.
Josh Ricci's excellent data-bass site uses the test and has good info on how it works, ... I wish I could make measurements and present tables with his expertise...but I've reached my level of digging in ...



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Art Welter

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Re: Labhorn CEA-2010 distortion
« Reply #1 on: May 11, 2018, 02:28:31 pm »

Mark,

Did you record the peak voltage levels for the CEA-2010 tests?
If not, any rough estimates?

Art

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Mark Wilkinson

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Re: Labhorn CEA-2010 distortion
« Reply #2 on: May 11, 2018, 05:06:29 pm »

Mark,

Did you record the peak voltage levels for the CEA-2010 tests?
If not, any rough estimates?

Art

Hi Art, no..... hope that's next.

I simply ran a 200ft speaker cable out the front door, to subs out in the yard, and then listened to my house do the pulse-rattle boggie haha
Didn't want to lug the test racks out just for this....

But I do realize without taking voltages, it's more about curiosity than anything else....
I think with voltages and listening, the pulses could let setting HPF, and peak limiters, be really dialed in....in real-world-like fashion.

I kinda hate to even guess what peak voltages were, other than to say, they were about all a single channel of a PL380 had to give.
I'll find out next time, and will post...
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Ivan Beaver

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Re: Labhorn CEA-2010 distortion
« Reply #3 on: May 12, 2018, 07:28:27 am »

One thing to be careful of when doing the 2010 tests.

Look at the maximum SPL of your mic.

At those levels, a lot of mics (even expensive ones) will start to overload.

So even if the rest of your system is not clipping (you need to be sure to monitor that as well), the mic may be clipping.

It is a "good idea" to have a mic that will handle at least 6dB more than the highest levels you are expecting.  Obviously even more is better for a more accurate result.

Clipping anywhere in the chain is a real possibility when doing this test.

It is also real easy to "run out of amp" when doing this.

What is interesting is what happens to various designs when you run down below tuning.  Sometimes the distortion rises VERY quickly.

Not that this is suggested operation, but is fun to test.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Mark Wilkinson

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Re: Labhorn CEA-2010 distortion
« Reply #4 on: May 12, 2018, 10:11:15 am »

One thing to be careful of when doing the 2010 tests.

Look at the maximum SPL of your mic.

At those levels, a lot of mics (even expensive ones) will start to overload.

So even if the rest of your system is not clipping (you need to be sure to monitor that as well), the mic may be clipping.

It is a "good idea" to have a mic that will handle at least 6dB more than the highest levels you are expecting.  Obviously even more is better for a more accurate result.

Clipping anywhere in the chain is a real possibility when doing this test.

It is also real easy to "run out of amp" when doing this.

What is interesting is what happens to various designs when you run down below tuning.  Sometimes the distortion rises VERY quickly.

Not that this is suggested operation, but is fun to test.

Good points Ivan, thx.

On the measuring side, I use a isemcon EMX-7150 with REW set to clip at 145dB.
So 2m 'should be' ok at 140dB, but I know I need to back up to 4m and compare/verify.

On the signal side, yeah...next time out I plan to check levels all the way through the chain, and read final voltage at the sub.

Your comment about testing below tuning .....  I couldn't hit the kill button any faster when trying stepped sine down there...wow, can things go south quickly  ;D
The CEA bursts really feel safer there...I'm definitey going to try dialing in HPF with them..
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Ivan Beaver

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Re: Labhorn CEA-2010 distortion
« Reply #5 on: May 12, 2018, 11:29:36 am »

Good points Ivan, thx.

On the measuring side, I use a isemcon EMX-7150 with REW set to clip at 145dB.
So 2m 'should be' ok at 140dB, but I know I need to back up to 4m and compare/verify.

On the signal side, yeah...next time out I plan to check levels all the way through the chain, and read final voltage at the sub.

Your comment about testing below tuning .....  I couldn't hit the kill button any faster when trying stepped sine down there...wow, can things go south quickly  ;D
The CEA bursts really feel safer there...I'm definitey going to try dialing in HPF with them..
Just something else to "be careful" of.

Very often meters on gear can be "slow" in showing the levels.  With the pulses used in 2010, things could clip before the meters show it.

So it is a good idea to keep the levels below "the meters" if possible.

I have found that pretty often with even "moderately powerful" subs, you need to bridge amps in order to get enough voltage swing.

With these pulses, you can sometimes (depending on the amp) go below the rated bridged impedance, because the strain on the amp is not as much as with music.

What I do, is to start each band down low and bring it up while watching the display.  This keeps you from over driving a particular freq band.

You can get some weird things happening if you are not careful.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!
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