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Author Topic: d&b B22  (Read 21262 times)

Ivan Beaver

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Re: d&b B22
« Reply #30 on: November 15, 2016, 04:53:57 pm »



Though, I'd like to believe the more reputable manufactures wouldn't try to do such a thing. and stick within the intent of the distortion spec.


You might be surprised.

Some of the biggest and most respected "players" are the ones that "misuse" the specs the most.

But they get a "free pass" because of who they are and nobody would suspect them.

OF course, it all "comes to light" during a side by side listening.
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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!

radulescu_paul_mircea

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Re: d&b B22
« Reply #31 on: November 16, 2016, 12:29:54 am »

There are ways to measure output with distortions included.
CEA Max burst is a way.
It's a way of getting the max output at any frequency given, without passing a threshold.
Data-Bass.com is a page where one can find this sort of tests using 2 meters ground plane RMS SPL so one should add 9 dB for peak 1 m output.
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Ivan Beaver

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Re: d&b B22
« Reply #32 on: November 16, 2016, 06:10:49 am »

There are ways to measure output with distortions included.
CEA Max burst is a way.
It's a way of getting the max output at any frequency given, without passing a threshold.
Data-Bass.com is a page where one can find this sort of tests using 2 meters ground plane RMS SPL so one should add 9 dB for peak 1 m output.
I wonder where the "9dB" comes from.

If the signal has a 6dB crest factor, and the distance is 2M away (6dB from 1M), that would be 12dB, not 9.

With most speakers that are of a decent size measuring at 1 or 2M is simply not far enough away to get any sort of useful information regarding how loud that speaker will be at a distance.

With some cabinets, a 1 or 2M distance will give a higher number than you would experience if you were to use that number and figure out at a distance.

With other cabinets it will give a lower number than you would get at a distance.

To me-the whole purpose of the "1M" SPL has NOTHING to do with how loud it is is at 1M (nobody is actually that close), but rather is a number that is used in figuring out how far it would be at a distance.

That is why in many cases it is better to measure at 10M, so you "get rid" of any close measurement errors that would skew the whole purpose

If I am not mistaken, the CEA test is mainly for home theater purposes/users.  So the 2M distance would be better suited for that setup.

So it becomes important to use a proper test for the proper usages.

There are all sorts of "tests" that can be done, but if they don't provide useful information, or cannot be compared to devices measured others ways, they are not real useful.

At least that is my opinion
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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: d&b B22
« Reply #33 on: November 16, 2016, 08:30:38 am »

I wonder where the "9dB" comes from.

If the signal has a 6dB crest factor, and the distance is 2M away (6dB from 1M), that would be 12dB, not 9.



Hi Ivan, swept sine waves, so a 3db crest factor.
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Ivan Beaver

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Re: d&b B22
« Reply #34 on: November 16, 2016, 08:49:50 am »

Hi Ivan, swept sine waves, so a 3db crest factor.
But if you are adding 3dB because it is a sine wave-then you can also just add 3dB to other SPL specs as well.

I don't know of anybody (at least in legit speaker specs) who uses the "3dB crest factor of a sine wave" and adds that to SPL reading.

Sorry-but that makes no practical sense to me

If you wanted to start "playing that game", then we should just go ahead and rate all loudspeakers as twice their power capacity.

 It doesn't make them any louder, but gives a false sense of output and power capability based on a spec that is essentially "useless"-at least as far as I am concerned.

But that is just my opinion-----
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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: d&b B22
« Reply #35 on: November 16, 2016, 12:29:19 pm »

But if you are adding 3dB because it is a sine wave-then you can also just add 3dB to other SPL specs as well.

I don't know of anybody (at least in legit speaker specs) who uses the "3dB crest factor of a sine wave" and adds that to SPL reading.

Sorry-but that makes no practical sense to me

If you wanted to start "playing that game", then we should just go ahead and rate all loudspeakers as twice their power capacity.

 It doesn't make them any louder, but gives a false sense of output and power capability based on a spec that is essentially "useless"-at least as far as I am concerned.

But that is just my opinion-----

Ivan, I find great value in the data-bass specs.

I mean, take your specs which have much better disclosure than industry average. The TH-118 shows:  Max Output  137dBSPL/143DBSPL.
Are those max output specs measured, or just calculated from measured sensitivity and extrapolated off OEM driver power-handling?
If measured (hooray!)  Do you use 6dB crest pink? ... for the 6dB diff in specs?
Or do you use sine sweeps as in the sensitivity curves you show?
If using either sine sweeps for max output or simply not measured, what's the basis for the 6dB spread?
And will 137dB hold without compression? And at what distortion level?

So for me, data-bass (and also Production Partner), provide VERY useful info that goes way beyond anything else I can find.....as both offer distortion and compression data.
Without this data, max output specs are basically hokey IMHO..especially "peak" marketing speak.

Distortion tests of course require sine waves with their inherent 3dB crest.
I can easily see Jeff wanting to equalize a data-bass CEA "peak" vs the usual +6dB add on that's just on top of others' most likely simply calculated max output. Especially since data-bass is showing actual measured peaks at given distortion levels....

Both data-bass and Production Partner also provide very good detail into actual testing methodology..best data for the informed purchaser I know of...

Do folks know other good sites that provide distortion and compression tests?




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radulescu_paul_mircea

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Re: d&b B22
« Reply #36 on: November 16, 2016, 01:28:21 pm »

From real measurements made in free space with sine waves and also EIAJ and CEA burst signals and also full spectrum pink noise I can tell you for sure that the output DSL specifies in the Direct program on Continuous and Program settings correlates very well with the measurements. So one can get about 134 dB RMS sine at 55 hz and the power compression is around 2,5-3 dB and with CEA Bursts and pink noise I can get 137 dB . The Lcpeak measurement gave me 142 dB and never more from single even trying with a LabGruppen FP14000 bridged  so 14000 Kw peaks. I have used a high pass filter at 125 hz so no sounds over the could get the results higher.
At around 3800 watts applied for 2-3 seconds at a time to obtain the RMS value, i can tell you it is 134  dB  continuous output, but not for long :) anyway, the 18SW115 driver can thermally take about 950 Wh to get to a raise of +40 from 25 to 65 and then stabilize (in this enclosure where in the pass band you have an AVERAGE of about 15% efficiency) . More than that and you can destroy it. But that means one can use a signal with around 6-8 dB crest factor and be safe and also have usable 137 dB peaks.

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radulescu_paul_mircea

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Re: d&b B22
« Reply #37 on: November 16, 2016, 01:35:29 pm »

I don't think it matters if the standard is for cinema, outside, inside etc as long as it provides a useful and real insight of the performance of a given system. 2 m is a good distance for these kind of measurements and he made tests regarding this procedure. The measurements made at 2 and further than 2 meters were practically identical. ( but not theoretically, but the differences were smaller than temperature and humidity differences so no need to overkill. Also he obtained a better  signal to noise ratio when closer)
His methods are extremely useful, found to the absolute limits and also saying where they are better to be used.
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radulescu_paul_mircea

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Re: d&b B22
« Reply #38 on: November 16, 2016, 01:58:13 pm »

I fail to see how this is classified as INFRA.
Probably because most of the people have never really heard bass under 38 hz (comparatively with the rest of the spectrum) at full power and when they use a stack of 12 subs with that response curve (look at that response curve!!) that would probably generate over 132 dB at 30 hz at 10 meters, they will all concur it is a infra sub. Because of the rest of the response will be lower than under 40 hz, they will perceive them as being deeper in response.
Once one will let them to go flat up to 80 hz then all the infra sensation will disappear. Put any sub even with 6 dB more and an f3 of 23 hz but equalized to be flat to 80 hz and most people will say the D&B goes deeper .
There are many designs that will go lower and with more output under 30 hz than this sub but most of the designers are using them on more than one octave so these will be the Infra's .
I wonder how well they integrate them with their tops. I heard some complete systems here in Romania on several occasions and I always liked them. But I only tested and measured the JSub and JInfra without tops.
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Marjan Milosevic

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Re: d&b B22
« Reply #39 on: November 16, 2016, 04:22:13 pm »

I was with the crew doing a Prodigy concert this summer.
Main rig was EAW Anya 16 per side and 24 Otto subs.
Prodigy tours with their own set of 8 D&B J infras that was added to the system and used on an aux as a complimentary infra effect in some of the songs.
I was watching the laptop that was monitoring the system response live using Smaart.
I was very curious to see what the added 8 J inras will look and how low they will go during those short times they were used.
I got really surprised when i saw that J-infra added a lot of 38Hz content in a very narrow peak.
Nothing really infra there. it only boosted the low end for like 4-5db for a very short periods and that was it.
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