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PD.186 / 186.2

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ArthurG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ArthurG Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2014 at 5:32am
Originally posted by MarjanM MarjanM wrote:

The moment when you get exited about the fact you got a pair of sparkling new 12 inches you want to test for the first time. Priceless.
Then you measure them. One has a Fs of 77Hz the other one is 115Hz.
Ooops.
Originally posted by KidCreole KidCreole wrote:

I was at the factory in Thailand years ago talking to their tech guy. He admitted to me that he sometimes draws the graphs has he sees suited with a pencilShocked
ahah more P.Audio horror stories. Why I'm not surprised ? LOL Dead
I could also tell a lot about how rubbish P.Audio is but I have no time now. PM me if you want to be disgusted about this company...
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ArthurG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ArthurG Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2014 at 5:52am
Originally posted by fourway hornloaded fourway hornloaded wrote:

A speaker store in Praque measured the T/S:

good-old PD186: http://www.prodance.cz/files/dl/1/1979/TS_PD186.pdf
PD 186 MARK II: http://www.prodance.cz/files/dl/8/15605/PD186_2.pdf

Interesting site, they also have measurements of RCF LF18P400 and 'G400.

I'm not sure if I'm yet ready to accept that the reincarnation of what I thought to be the greatest mid-BL 18" driver available has a Qts between 0,52 (published) and 0,67 (measured).
hmm these measurements have some problems. I've looked at other files from the same website, well it seems that this guys lacks methodology and has no clue on what he does...
First, we don't know the pre-conditioning for these measurements,  ie are all drivers new, out of the box  or used ? Does he perform soft parts break-in (for example 30Hz free air for 2 hours at defined power) ? we don't know...
Second, why did he change the added mass for these 2 tests (100g for PD186 and 140g for v2). If you change measurements conditions, you can't get correct data and comparison between drivers of the same category can't be done...
Third, this added mass is way too low for a driver like PD186. Usually, it is recommended to use an added mass close to the driver mms. For an 18", I personally use 200g
Fourth, consequence of point 3, to find a mms of 124g on a driver with a beefy 25mm tall / 5" copper voice coil is impossible ! Voice coil alone is close to this mass...
I found other problems but they are minimal.

All in one, it's 200% sure that this measurement on PD186 v1 is completely wrong and very questionable on V2.

Sorry guys, but don't trust the files on this amateurish website...

--Arthur
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fourway hornloaded Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2014 at 11:31pm
Thanks Arthur!
I'm on the guesswork side and I do like an answer from someone with experience in measurement. I did see the different weights used for testing, but could not extract any info out of that. Of course I really really don't like to believe that the PD186.2 has a 0.67 Qts. Fact is, MK1 works like a dream, both low and quite puncy, up to 180 Hz in my bins. If it does so having a 0,5 Qts... fine, I'll just learn more about T/S. Regarding my PD186/Nd9300 problem from the other thread (the Nd9300 with 'useful' T/S bottoms out whereas the 'funny-T/S' PD186 does not) user Corel and I had an interesting discussion, which made me care more for suspension stiffnes. One thing that PD186 has, compared to other drivers, is a stiff suspension. A real double voice coil as well. So in the end, maybe we've just got to (I've just got to) get used to the fact that proper bass drivers can have a Qts over 0,39.
Robert.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fourway hornloaded Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2014 at 11:34pm
I meant double suspension where I wrote double voice coil. ...must have been the high Qts...
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ArthurG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ArthurG Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2014 at 1:58am
Robert,

so many times I said that T&S parameters only tell half story. So many times I had to argue that a high qts is not a problem, even when used in a scoop. I hope that this discussion will finally become pointless.

In the case of your PD186 vs ND9300 observation, I need to look at the drivers to give a definitive answer but suspension (surround + spider) geometry vs xmech (absolute maximum mechanical excursion) is a very important factor at high power behavior. Translating to our case, maybe (it's a guess so maybe is the important word), ND9300, due its deeper and larger spiders + triple roll surround, allows the voice coil former to hit more easily the back plate than PD186 and its much more limited excursion ability (M-roll surround and small spiders). Suspension mechanical limit makes far less noise than a former hitting the back plate...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fourway hornloaded Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2014 at 10:20pm
That's what I've been thinking too. From pushing the cones by hand, I think the Nd9300 has more excursion capability than the PD186, but it's too loose to protect itself.

It's obvious that suspension braking the cone's movement at high excursion is hardly noticable in a bass driver if you don't do a direct comparison to a more potent driver.

I compared two different top bins the other day by turning up the volume. From a certain point onwards, the cheaper one just would not go louder when turning up the volume. At lower volume, both had comparable sound quality, but when turning up, the better one would go louder and louder whereas the cheaper one would remain at medium volume and eventually start to distort. (that's where most pubs go wrong in having a cheap system 'because it we don't want it too loud')

Next thing on my list is a direct comparison between said bass drivers (and maybe some others) in identical stacks. I'll share my findings. In the meanwhile, I'll be studying how suspension stiffness influences all other T/S parameters.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aztor Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2014 at 5:31pm
The problem is when you sim with the old specs and you are expecting a certain result ( Ts-para of 186 ). But in reality you should have been simming them with 186.2 ts-para.And getting a different result. 

Its like buying an apple and getting a banana. You might like the banana and be happy, but it's not the fruit you expected. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2014 at 8:01pm
Originally posted by Aztor Aztor wrote:

Its like buying an apple and getting a banana. You might like the banana and be happy, but it's not the fruit you expected. 

+1 Clap


Fail to believe Large Audio firms accept drivers with wild tolerances, and excuses why they are so.

Maybe they get the quality drivers, and the private/small buyers get the ...



Edited by levyte357- - 09 May 2014 at 8:06pm
Global Depopulation - Alive and Killing.
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ArthurG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ArthurG Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2014 at 2:12am
Originally posted by levyte357- levyte357- wrote:

Maybe they get the quality drivers, and the private/small buyers get the ...

good Lev, you start to understand...

BTW retail is the end of the chain in pro audio drivers business. OEM is where volume and money are. And of course during R&D stage, its a talk between engineers with all proper equipment to test and approve a driver ; not the hobby folk that has no clue of what he's buying...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2014 at 9:52am
I knew this was inevitable at the moment Eminence got their hands on PD.
Too bad. Another legend goes to the history.
Marjan Milosevic
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https://www.facebook.com/pages/MM-Acoustics/608901282527713
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PauliePaul Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2014 at 6:05pm
Originally posted by MarjanM MarjanM wrote:

I knew this was inevitable at the moment Eminence got their hands on PD.
Too bad. Another legend goes to the history.


I despair, I really do.

Nice bull cartoon though…
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JR.junior Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2014 at 8:35pm
Originally posted by MarjanM MarjanM wrote:

I knew this was inevitable at the moment Eminence got their hands on PD.
Too bad. Another legend goes to the history.


Broken Heart
Support the scoop technology, larger mouth plays louder!
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