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 speaker stuff starting with Thiele-Small parameters
Measuring speaker stuff starting with Thiele-Small parameters
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 22nd December 2018, 11:48 PM   #1
DualTriode is offline DualTriode  United States
diyAudio Member
 
Join Date: Aug 2009
Location: Nor Cal
Default Measuring speaker stuff starting with Thiele-Small parameters

Hello,

I am packing up and moving.

There are too many speakers, some all original, others recones with OEM parts and others are Frankenstein speakers made with voice coils from one model cones from another model voice coil and frames from another. I have one set of 15 inch Frankenstein JBLs that are near 2235s maybe.

What I want to do in this thread is measure speaker stuff starting with Thiele Small parameters of the 15 inch Frankenstein JBLs.

This is just for fun. I have the time and space plus new to me Audio Precision APx1701 speaker measuring tools.

I am going to start by attaching the Frankenstein drivers to a fiberglass ladder to measure the Thiele Small parameters. I am thinking of using the added weight method as opposed to the known volume box to do the measurements.

Anyone with thoughts to add?

Thanks DT
  Reply With Quote
Old 22nd December 2018, 11:51 PM   #2
chris661 is offline chris661  United Kingdom
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
I use AA batteries with a tiny bit of blue-tack for the added weight method. IIRC, single AAs are 25g, which is a useful unit of weight.

Chris
  Reply With Quote
Old 23rd December 2018, 01:23 AM   #3
DualTriode is offline DualTriode  United States
diyAudio Member
 
Join Date: Aug 2009
Location: Nor Cal
Hey Chris,

Double A batteries sound useful and handy. The instructions I am looking at say to use plasticine, you know that molding clay stuff. I am a bit concerned that the oil in the plasticine will stain a paper cone, I will stick some to a white paper plate as a test to see if it stains or not.

I have the impression that the added weight method could be more accurate than attempting to guess the volume of a box and a driver.

Thanks DT
  Reply With Quote
Old 23rd December 2018, 09:33 AM   #4
PeteMcK is offline PeteMcK
diyAudio Member
 
Join Date: Feb 2002
Location: Western Sydney
you can also use coins (again with a bit of blue tack) as accurate weights
__________________
Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
  Reply With Quote
Old 23rd December 2018, 09:43 AM   #5
danny_66 is offline danny_66  Belgium
diyAudio Member
 
danny_66's Avatar
 
Join Date: Jun 2005
Location: Lierde
The best I've found are little magnets(5-10grams) like those that you find in closet doors.
Put one on each side on the cone so they attract each other,
also put a little piece of thick paper or cloth between the magnets and the cone to prevent scratches.
For larger woofers I put a pair of magnets on each side.

Easy to install and to remove without damaging the cone.
__________________
My RefSpeaker

Last edited by danny_66; 23rd December 2018 at 09:58 AM.
  Reply With Quote
Old 24th December 2018, 09:33 AM   #6
chris661 is offline chris661  United Kingdom
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
I've tried this, and would only recommend using ferrite magnets. Neodymium ones are far too strong, and won't let go of each other without trying to deform the cone - I was worried about ripping the cone at one point.

Chris
  Reply With Quote
Old 24th December 2018, 12:03 PM   #7
rscamp is offline rscamp  Canada
diyAudio Member
 
Join Date: Jul 2018
Location: Ontario, Canada
I can see where the strength of neodymium magnets could be an issue. But I think this can be addressed with one or a combination of these approaches:
  1. Use a small magnet - 1/4" dia. or smaller
  2. Use a magnet holder - to increase the size/mass and make it easier to grasp the magnets for removal
  3. Use layers of tape or a self-adhesive plastic/rubber foot - to place over the magnet to protect the cone surface and increase separation to weaken the force
  Reply With Quote
Old 24th December 2018, 01:04 PM   #8
danny_66 is offline danny_66  Belgium
diyAudio Member
 
danny_66's Avatar
 
Join Date: Jun 2005
Location: Lierde
Quote:
Originally Posted by chris661 View Post
I've tried this, and would only recommend using ferrite magnets.
Chris
Yes, I used ferrite magnets and also a thick piece of cloth between the cone and the magnets, this also reduces magnets forces.
__________________
My RefSpeaker
  Reply With Quote
Old 9th January 2019, 07:44 AM   #9
DualTriode is offline DualTriode  United States
diyAudio Member
 
Join Date: Aug 2009
Location: Nor Cal
Hello,

I am connecting the test tech together and booting up the software.

This is T/S Small Signal Parameters. Is there an industry standard small signal input voltage?

I will start out small and work my way up out of the noise floor.

Thanks DT
  Reply With Quote
Old 9th January 2019, 10:27 AM   #10
JohnPM is offline JohnPM  United Kingdom
diyAudio Member
 
Join Date: Oct 2008
This post suggests 100 mV.
  Reply With Quote

Reply


Measuring speaker stuff starting with Thiele-Small parametersHide 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
Thiele and Small Parameters Daem Multi-Way 0 16th June 2013 05:40 PM
no thiele small parameters H Burch Multi-Way 14 16th September 2012 01:39 PM
Thiele small parameters for tweeter jericho_tm Multi-Way 3 7th February 2012 09:57 PM
Thiele - Small parameters tomtt Multi-Way 0 25th March 2009 03:48 AM
Thiele-Small parameters Hoffmeyer Multi-Way 6 15th March 2006 02:12 AM


New To Site? Need Help?

All times are GMT. The time now is 04:23 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki