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Precision Devices T/S specs unreliable?

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rubjel View Drop Down
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    Posted: 01 March 2018 at 5:36pm
Hi, I am in the process of designing a midbass horn using Hornresp.
I have done simulations with alot of drivers from different manufacturers, but every time I try to put in T/S parameters for a PD driver there's trouble. The cross-calculation of parameters in Hornresp disagrees with all 4 PD driver specs I have put in so far, and the errors seem to be quite substantial. This is very frustrating, so I sent an email to PD asking about this. They never responded.

Has anyone measured the T/S specs of their PD drivers and compared with the published specs?

Best Regards
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bass*en*mass View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 01 March 2018 at 5:43pm
only got measured t/s of a "well preconditioned/run in" pd154 here:

fs 38, bl 24, mms 135, vas 131, qm 5, qt/e 0.23/.24



Edited by bass*en*mass - 01 March 2018 at 5:57pm
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rubjel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rubjel Quote  Post ReplyReply Direct Link To This Post Posted: 01 March 2018 at 5:52pm
Thanks! Most of those measured specs are quite different from the published specs. Qms is way off, the published spec for qms is 20,44 and yours is 5! Most of the others seem to be around 20% difference..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RoadRunnersDust Quote  Post ReplyReply Direct Link To This Post Posted: 01 March 2018 at 8:58pm
given the production tolerance on speakers and the fact that they are only relevant to a small signal through the driver thats not too surprising

Gives something of an insight into the advantage that the commercial companies have when designing speakers when they can pay for tighter tolerances, etc. etc.
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rubjel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rubjel Quote  Post ReplyReply Direct Link To This Post Posted: 02 March 2018 at 4:51pm
I think it is surprising that the PD drivers are the only ones I cannot use to make simulations in Hornresp.
This is not an issue with any other driver manufacturer that I have come across so far. 
I am aware that there will be tolerances on these parameters, I read somewhere that 5-10% is normal.
Most of the measured specs for the PD154 are far from those numbers.
The most surprising thing for me is that they are not able to produce specs that correlate correctly with each other. Try to enter the specs of a PD driver in Hornresp and I can guarantee frustration.
Luckily there are many good alternatives to PD.

Best Regards

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Post Options Post Options   Thanks (0) Thanks(0)   Quote RoadRunnersDust Quote  Post ReplyReply Direct Link To This Post Posted: 02 March 2018 at 4:59pm
I've never seen any 3rd party T/S readings taken for PD drivers from reputable sources, across a spread of drivers, using new drivers (or uniformly run in drivers)... so 🤷🏻‍♂️
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 02 March 2018 at 5:00pm
Install WinISD, and fire up T/S param database editor.

Follow the help Info, about entering parameters in right order.

IIRC, you enter about 4x, and it will calc the rest.

Using this method, and testing the drivers in cabs, have proven/disproven the supplied T/S for many different drivers.

One driver I bought, the advertised BL was >30, actual was approx 25, which made huge difference in sound and Freq response.

Sold that driver, and bought cheaper driver in the range, with Superior BL, difference and increase in low end extension was immediately noticeable!!

WinISD is worthy!!!
Global Depopulation - Alive and Killing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 02 March 2018 at 10:13pm
You're never going to know the variation per manufacturer unless you can afford a shipping container from each, or are a manufacturer that has a QC process to reject out of spec delivered units. Just the statistical facts of life. And you have to sample constantly, because batch to batch production variation must also be considered. In an ideal world the factory would be doing all of this - and perhaps they do. But if they are sorting drivers by QC distribution before shipping I give you one guess what clients the best are going to, and the trade routes that the acceptable outliers are heading towards!

All we can say as small scale end users, is that we would expect a more expensive driver to have a tighter distribution about its published specs. And that's about it unless you fancy testing at least 20 off the shelf from different production batches.
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