how do manufacturers determine frequency response? - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 19th December 2001, 10:49 PM   #1
pkgum is offline pkgum  Australia
diyAudio Member
 
Join Date: Oct 2001
Location: sydney
Default how do manufacturers determine frequency response?

how do manufacturers determine frequency response?
  Reply With Quote
Old 19th December 2001, 11:55 PM   #2
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
of an individual driver or of a speaker?
  Reply With Quote
Old 20th December 2001, 01:09 AM   #3
pkgum is offline pkgum  Australia
diyAudio Member
 
Join Date: Oct 2001
Location: sydney
of a speaker (subwoofer)

Example...Say that Velodyne says that its top subwoofer has a frequency response of xxHz - xxxHz

How did they come up with xxHz -xxxHz?
  Reply With Quote
Old 20th December 2001, 04:28 AM   #4
diyAudio Member
 
Join Date: Oct 2001
Location: 5280'
Quote:
How did they come up with xxHz -xxxHz?
They measure it.
  Reply With Quote
Old 20th December 2001, 05:55 AM   #5
JoeBob is offline JoeBob  Canada
diyAudio Member
 
JoeBob's Avatar
 
Join Date: Nov 2001
Location: Montreal, Canada
I do believe he wants to know if they use the f3 values, or whatever. I unfortunately don't know the answer, just think you misunderstood his question. Although I am curious myself.
  Reply With Quote
Old 20th December 2001, 07:56 AM   #6
pkgum is offline pkgum  Australia
diyAudio Member
 
Join Date: Oct 2001
Location: sydney
joebob is right..I want to know how they DETERMINE the figures

plz don't post obvious or stupid answers
  Reply With Quote
Old 20th December 2001, 08:28 AM   #7
argo is offline argo  Estonia
diyAudio Member
 
Join Date: Feb 2001
Location: Estonia
Risking to post obvious or stupid answer

It differs from manufacturer to manufacturer. Some measure, some calculate. Some tell -3dB, another -6dB and more often -10dB bass cutoff point. Many of them are just plain lying.

Argo
  Reply With Quote
Old 20th December 2001, 12:39 PM   #8
diyAudio Member
 
Join Date: Dec 2001
Location: Milano, Italy
just decide if some of the following is stupid....

- They have BIG anechoic room and measure the output
- by simulating the curve via software or calculations
- measuring the sub in different rooms to provide a 'real' figure
- asking their marketing dept. about what to print
and many more

Seriously, you did not asked an easy question: I guess that an universally recognized standard for low freq measurements is not existing, and each manufacturer uses the method they believe is best (some really influenced by mkt considerations and some honestly believing their way is the right one)

bye
sandro
  Reply With Quote
Old 20th December 2001, 01:40 PM   #9
pkgum is offline pkgum  Australia
diyAudio Member
 
Join Date: Oct 2001
Location: sydney
Just be confident when posting the answers....


The "obvious and stupid" part was just referring to VERY obvious answers like Thomas W's answer, "they measure it'

Everybody knows that...DUH

It was a misunderstanding anyway
  Reply With Quote
Old 20th December 2001, 02:05 PM   #10
diyAudio Member
 
Join Date: Sep 2001
Location: Fairbanks, Alaska
Default How woofers response is measured

pkgum,

I would suspect that most manufactures measure the response of woofers or sub-woofers in a similar mannor that I do. This method has been described in quite a number of publications and can be quite accurate.

The method involves taking SPL measurements with a calibrated measurement microphone very close to the cone of the woofer. A distance of 1/4 inch away is good.

An automated frequency sweep is done over the frequency range of interest and the woofer is driven hard enough to provide a reasonable listening level. Care is taken not to drive the woofer hard enough to slam the cone into the microphone at the woofer or enclosure resonant frequencies. A automated level measurement is done as the frequency sweep is done and the results recorded by software.

The measured SPL level is then be adjusted mathematically to any desired distance from the woofer cone. This method avoids nearly all reflections that a room may produce and gives good reliable results.

Computer programs do all of this very nicely. I use LinearX LMS and its calibrated microphones for doing this.

http://www.linearx.com/products/anal...LMS/LMS_01.htm

When a woofer has a port the same measurement is also done from right in front of the port without making any system level changes. The output from the port is then added mathematically and to the primary woofer output to get the overall extended low frequency response plot. The ratio of the woofer cone area and the mouth area of the port are taken into consideration when the math is crunching the numbers to adjust the relative effective SPL levels between the two.

It is almost impossible to measure a woofers response in any other way in the average room and prehaps even a very large almost dead room. Thus a lot of money can be saved by using the close in measurement method. No special room is required.

Putting a woofer closer to a wall or corner will increase the lows substantially, as will placing a woofer in a vehicle. Thus a flat measured response may not give a flat response when a woofer is in actual use.

If you do not have a copy of the Loudspeaker Design Cookbook, by Vance Dickason I would suggest picking up the latest version. It explains a lot and is extremely useful for anyone doing speaker building or measurement work.

http://www.audioxpress.com/bksprods/books/bkaa60.htm

I Hope all this helps.


John Fassotte
Alaskan Audio
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Determine crossover frequency of existing XO focal7C Parts 1 26th May 2008 09:07 AM
How to determine crossover frequency? maurycy Multi-Way 2 7th January 2006 03:29 PM
Is there a formula to determine the frequency at which... 454Casull Multi-Way 3 12th September 2004 10:57 PM
Doubts on Phase Response and Frequency Response dumrum Multi-Way 11 5th April 2004 10:39 AM


New To Site? Need Help?

All times are GMT. The time now is 05:43 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2