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The Wandering Topic Audio/Video Discussion Thread


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#41 MKtheater

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Posted 12 April 2016 - 03:03 AM

if the static charts say 99 dB at 10 the max output comparison charts only read 96-97. It seems to match up for the other other drivers, just curious. I usually just scroll through the comparison burst and then it really close I look further, not that I am changing anything anytime soon.

#42 Ricci

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Posted 12 April 2016 - 03:44 PM

if the static charts say 99 dB at 10 the max output comparison charts only read 96-97. It seems to match up for the other other drivers, just curious. I usually just scroll through the comparison burst and then it really close I look further, not that I am changing anything anytime soon.

 

Do you mean the max level long term sweep measurement? Those are limited by the frequency range that has the highest excursion and also heat build up in the coil. That may not be 10Hz. In the case of the XXX's the excursion maximum was at more like 25-30Hz. This is pretty common in the test cab with drivers having a higher qtc in that cab. The burst comparison chart is distortion limited. The graphs under the static charts show the distortion limited burst data and the maximum displacement limited output with no regard for distortion (functional xmech). Each of the 3 charts show different information. If you are looking to see which drivers have higher maximum displacement before damage, that is shown on the static burst chart like I linked in the previous post. When we do the next site update we are talking about adding that to a comparative chart.



#43 Ricci

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Posted 14 April 2016 - 02:16 PM

Re: Xmax ratings...When these are based on distortion it is usually measured with the driver in free-air and the driving signal is at the driver resonance. Impedance is very high, efficiency is very high, current induced in the coil is low so BL distortion is kept in check. This is a best case scenario for the driver producing a lot of stroke with minimal distortion. Put the driver in a cab and use signals below the system resonance and distortion will increase dramatically.


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#44 lilmike

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Posted 14 April 2016 - 06:12 PM

@ Ricci: Aren't you kinda crossing the streams here a bit?

 

A distortion-based x-max number is a DRIVER spec, not a system spec. It should be measured in a manner that is repeatable on a per-driver basis, showing us what the driver can do, and helping us define what the driver's limits are.

 

As soon as that driver is in a cabinet, it is part of a SYSTEM, and the driver-specific measurements are no longer the only parts of the equation in play and are no longer valid on their own. The cabinet and the driver both have effects, which define the limits of the system as a whole. 

 

I completely get what you're saying though, a distortion-based "x-max" of a driver in a system should be vastly different than the same sort of measurement of the driver alone because of the remainder of the system that's in play. The nature of the difference is due to the nature of the cabinet used. The driver measurement should be the best-case scenario.


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#45 Ricci

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Posted 14 April 2016 - 08:13 PM

Yeah I am a little. I just wanted to point out that the xmax spec, even if it is based on distortion is usually a best case and only really applies in that case. Everything changes once loaded as part of a system and the signal changes. I've been looking at some type of IMD test again but that looks like it might be best done on the driver free-air and close mic'd. Still struggling with how to standardize it. Looks like using standard voltages would be least painful. How to easily generate the signals and capture is another.



#46 lilmike

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Posted 14 April 2016 - 09:13 PM

Do you use SoundEasy at all?

 

Bohdan just announced V21. I don't have it in hand yet, but should within a couple days. That said, don't expect me to rip out some measurements next week or anything, I am still at the point where I can BARELY use it, the learning curve's still very steep. Anyhow, reading the announcement this morning, I noticed this in the release notes:

 

"28. THD/IMD Analyser and Nonlinear Method 2 are now implemented as single dialogue boxes with multiple display areas.

29. Time-domain display in THD/IMD Analyser implements auto-scaling for frequencies below 100Hz.

30. Reduced screen flicker during frequency sweeps in THD/IMD screen.

31.

 Generator 3 in THD/IMD System can be frequency modulated by Generator 2. Together with standard frequency sweep, this creates special signal for subwoofer testing."

 

Needless to say, this is interesting, and may be applicable to this sort of testing. I do need to read the updated manual sections and learn more. 

 



#47 Ricci

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Posted 15 April 2016 - 11:40 AM

I am aware of SoundEasy but have never used it. That does appear to fit the bill.

#48 Funk Audio

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Posted 15 April 2016 - 03:49 PM

Yeah I am a little. I just wanted to point out that the xmax spec, even if it is based on distortion is usually a best case and only really applies in that case. Everything changes once loaded as part of a system and the signal changes. I've been looking at some type of IMD test again but that looks like it might be best done on the driver free-air and close mic'd. Still struggling with how to standardize it. Looks like using standard voltages would be least painful. How to easily generate the signals and capture is another.

What about having the low frequency tone played some percentage(tbd) of the CEA2010 burst output for that frequency.



#49 lilmike

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Posted 15 April 2016 - 05:20 PM

I am aware of SoundEasy but have never used it. That does appear to fit the bill.

 

I just received the update files, I'll let you know once I get things installed. Still have a few other things on my "to do" list...

 

So far, it hasn't been "easy", but it is some powerful software. I've barely scratched the surface of what can be done with it at this point. 



#50 lilmike

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Posted 09 April 2017 - 06:14 PM

Digging up and resurrecting this thread, cause I didn't think it was worth creating a new one...

 

Anyone else following this little project?

 

http://www.diyaudio....94a-ak4490.html

 

Looks like the dream box I have been waiting for to use with ARTA and SoundEasy.

 

Unfortunately, it's a little bit out of my price range (like an order of magnitude). Still, figured I'd pass it on in case any of you are interested.



#51 BeastAudio

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Posted 13 April 2017 - 07:29 PM

@Beast

 

Perfect avatar is perfect.

 

tumblr_msfp3yGUgJ1rp1z8qo1_500.gif

 

It comes with a sad heart to inform those that don't know, but the brilliant actor Charlie Murphy passed away yesterday. What a said day it is. 



#52 Ricci

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Posted 13 April 2017 - 07:51 PM

It comes with a sad heart to inform those that don't know, but the brilliant actor Charlie Murphy passed away yesterday. What a said day it is. 

 

Yeah that was one funny dude. R.I.P.

 

I just realized he's gone and so is Rick James AND Prince. Kind of a nutso coincidence really. Them true Hollywood stories were too funny to survive I guess.



#53 Infrasonic

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Posted 13 April 2017 - 10:05 PM

Yeah. Found out yesterday. Lost his battle with leukemia, so I hear. That's sad. :(

 

He was one cool cat.

 

He will be missed.






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