Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Measuring driver parameters vs the data sheet values
Measuring driver parameters vs the data sheet values
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th February 2019, 01:07 AM   #1
ggidzinski is offline ggidzinski  United States
diyAudio Member
 
ggidzinski's Avatar
 
Join Date: Nov 2016
Default Measuring driver parameters vs the data sheet values

I'm making the transition from building established designs to starting from scratch. I'm currently working on a low cost full range/neo tweeter design for a computer (learning at a low cost point) and I just measured the free air parameters of a Fountek FR88EX full range driver using DATS2. I calibrated the leads and the 1K ohm resistor measurement and was careful with the weighted VAS measurement. I am surprised at how different my measured numbers are vs. the data sheet. Is this typical or have I likely done something wrong?:

-------Meas----DS
Re----6.15----6.0
Fs-----133-----95
Qts---0.97---0.47
Qes---1.27---0.62
Qms--4.11---1.96
Vas---0.59----1.27


Thanks,

George
__________________
Musician since 1961, fell in love with audiophile equipment in 1969 when I first met the mesmerizing blue glow of a vintage McIntosh and JBL L300ís. DIY fever started in 1978 watching a pair of Klipsch hornís being built in a garage.

Last edited by ggidzinski; 8th February 2019 at 01:14 AM.
  Reply With Quote
Old 8th February 2019, 01:26 AM   #2
wintermute is offline wintermute  Australia
just another
diyAudio Moderator
 
wintermute's Avatar
 
Join Date: Aug 2003
Location: Sydney
Measuring driver parameters vs the data sheet values
Hi George, It is worth having a look on Fountek's site to see if they have any information on how they do their measurements. Not all manufacturers do it the same way. SB-Accoustics, and Seas both have information on their sites about their testing method. I found out recently that Seas uses 2V for their drive signal which is much higher than what something like DATS uses I believe.

break-in and even pre-measurement warm up procedures may affect the results.

Does the DAT's use MLS signals or swept sine for doing the measurement? I found that some (and only some) drivers give widely different results with mls compared to swept sine. Other drivers will give almost identical results with either.

Your fs above is the biggest discrepancy, break in may be affecting this, but fs was the thing that I found with some drivers was way off with MLS testing.

Tony.
__________________
Any intelligence I may appear to have is purely artificial!
Photography (another hobby)

Last edited by wintermute; 8th February 2019 at 01:27 AM. Reason: typo
  Reply With Quote
Old 8th February 2019, 02:21 AM   #3
hollowboy is offline hollowboy  Australia
diyAudio Member
 
Join Date: Jul 2007
Location: 'straya
Check both your drivers. It might be that you've been unlucky and have a faulty one.

I once got four "full range" drivers from P Audio, and found that 3 were nicely on spec, but one had a weak magnet.

Midrange (cone driver) horns; low relevance of magnet strength and Qts
__________________
This edit signature thingy is seriously hard to find
  Reply With Quote
Old 8th February 2019, 02:28 AM   #4
ggidzinski is offline ggidzinski  United States
diyAudio Member
 
ggidzinski's Avatar
 
Join Date: Nov 2016
I just checked the other driver and the numbers are similar. Fs is even off more at 144Hz.

George
__________________
Musician since 1961, fell in love with audiophile equipment in 1969 when I first met the mesmerizing blue glow of a vintage McIntosh and JBL L300ís. DIY fever started in 1978 watching a pair of Klipsch hornís being built in a garage.
  Reply With Quote
Old 9th February 2019, 03:04 AM   #5
wintermute is offline wintermute  Australia
just another
diyAudio Moderator
 
wintermute's Avatar
 
Join Date: Aug 2003
Location: Sydney
Measuring driver parameters vs the data sheet values
Try running them at the manufacturers stated fs at close to max excursion for 5 minutes before doing your T/S measurement and see whether you get any difference.

Tony.
__________________
Any intelligence I may appear to have is purely artificial!
Photography (another hobby)
  Reply With Quote
Old 9th February 2019, 03:40 AM   #6
ggidzinski is offline ggidzinski  United States
diyAudio Member
 
ggidzinski's Avatar
 
Join Date: Nov 2016
Is that a one time break in step or an every time warm up step? Just a sine wave at Fs?

Thanks,
George
__________________
Musician since 1961, fell in love with audiophile equipment in 1969 when I first met the mesmerizing blue glow of a vintage McIntosh and JBL L300ís. DIY fever started in 1978 watching a pair of Klipsch hornís being built in a garage.
  Reply With Quote
Old 9th February 2019, 05:06 AM   #7
wintermute is offline wintermute  Australia
just another
diyAudio Moderator
 
wintermute's Avatar
 
Join Date: Aug 2003
Location: Sydney
Measuring driver parameters vs the data sheet values
Hmm I was thinking that I picked that up from SB accoustics tech note http://www.sbacoustics.com/index.php...le/-/view/191/ and that it was to be done before each measurement.. however it seems maybe they are suggesting that it will actually break in the driver (I thought it would take longer than that).

They do state it should only make 10-15% differnce, which seems in your case to not be enough to account for the differences.

This is the link to Seas info on their T/S measurements DATASHEETS

As you can see Seas and SB are using different drive levels (which will definitely give different results). a woofer measured at 1V will almost certainly show different T/S params to one measured at 2V.

I guess the other thing I should ask is what your mounting method is for the driver?

Clamped securely (in some sort of frame) in free air away from any nearby objects is ideal. Don't sit the driver on it's magnet, especially if it has a vented pole piece.

Tony.
__________________
Any intelligence I may appear to have is purely artificial!
Photography (another hobby)
  Reply With Quote
Old 9th February 2019, 05:22 AM   #8
DRONE7 is offline DRONE7  New Zealand
diyAudio Member
 
Join Date: Aug 2008
Life is a lottery... Specs are Puffery.... Work with what you have..... measure over several days and variables=driven/ambient/up/down/flying around those magnificent men in... whoa...!!!
Then average and build... Don't let the math get in the way of the enjoyment...

Entropy rules... Devices 10 years on a shelf will not measure as manufacturers specs... work with it
YouTube

Last edited by DRONE7; 9th February 2019 at 05:31 AM.
  Reply With Quote
Old 9th February 2019, 05:47 AM   #9
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Measuring driver parameters vs the data sheet values
I hav eposted this before but can’t find where:

Quote:
T/S parameters, extremely useful though they are, are not perfect: they are a snapshot of a driver's behaviour under a given set of circumstances; it does not necessarily follow that these hold good under other conditions (they rarely do), so it is advisable to make allowances for these variations in the design stages.
Most people look at T/S and see a set of scalar numbers, but in reality they are a function of current (or voltage) -- they change with weather too. If one does not take care to account for these changes you end up with something that doesn't work all that well. For instance a typical tightly tuned bass reflex, with a driver with a non-flat T/S curve, will only be correctly tuned for one drive level. Not only does this mean that they will be in tune at only one volume level, given the dynamics in music, they will only be spot on at one level in the music and be progressively out of tune with changes in the dynamic levels.

You have no doubt noticed that Scott & my designs favour fairly high ratio vent aspect ratios (or volume fill damping). This adds an R to the vent and, analogous to a grid-stopper, and gives them a greater tolerance to non-flat T/S curves. Nothing models this, and requires an experienced eye to extropolate from what is modeled.

These are the numbers i measured:
Re: 6.17
Fs: 107.14
Qes: 0.90
Qms: 3.12
Qts: 0.70
Vas: 1.23
dB/2.83v: 85.1
Sd: 2762
BL: 3.00
Mms: 1.95
Cms: 1130

We used the factory numbers to design the Fountek Five and that worked out well.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 9th February 2019, 07:58 AM   #10
TBTL is offline TBTL  Germany
diyAudio Member
 
Join Date: Oct 2013
Qes, Qms, fs, Vas are related to the suspension stiffness which is not constant. Try comparing BL, Re, mms, sensitivity if you want to know if the values stated in the data sheet are fair.
  Reply With Quote

Reply


Measuring driver parameters vs the data sheet valuesHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Anyone have a data sheet for these ??? Dagwood Parts 3 3rd February 2013 10:07 AM
U3090MG (Display Driver Vishay-TFK) for FV112 Futuba Data Sheet wanted tiefbassuebertr Solid State 8 31st January 2012 09:21 AM
How Do I Measuring Driver 'Acoustic Data' Loren42 Multi-Way 23 16th March 2010 05:37 PM
op amp/dac data sheet help Smiffy Parts 11 13th December 2004 09:14 PM
data sheet KCC Parts 5 6th January 2004 10:03 PM


New To Site? Need Help?

All times are GMT. The time now is 04:04 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki