Help me, I feel dumb. - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 14th January 2002, 04:02 AM   #1
BAM is offline BAM
diyAudio Member
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
Default Help me, I feel dumb.

For those of you who are mathematically-inclined, I need help converting something. I was using Mr. Linkwitz's closed-box spreadsheet to determine how much EQ I would need to make an ELF sub sound OK.

The spreadsheet asks for mechanical resistance in Ns/m and the Peerless web site only delivers it in Kg/s. I'm not in Physics yet, and I don't have a clue what to make of this and I'm hoping that someone here may know how to convert:

1.87 Kg/s to Ns/m

If someone knows how to do this, please help me, or show me how to help myself. I will be very grateful.

  Reply With Quote
Old 14th January 2002, 04:43 AM   #2
subwo1 is offline subwo1  United States
diyAudio Member
subwo1's Avatar
Join Date: Jan 2002
Location: North American Continent
BAM, below is a link where to find out that a newton is a unit of force. I used Google to find the site. It says:
"force push, pull, or weight newton= kg m/s2"

"1.87 Kg/s to Ns/m" If you multiply both sides by m/s, you get

1.87 kg m/s^2,
the same units that it says above are newtons.
That means both of the expressions are of the same thing.
I am not too good with math either, but I think I figured it right. Give Physics your best shot, I made it through 2 years, maybe you can go all the way.
  Reply With Quote
Old 14th January 2002, 04:48 AM   #3
paulb is offline paulb  Canada
diyAudio Member
Join Date: Jun 2001
Location: Calgary
A Newton is a kilogram-meter per second squared = kg.m/(s^2). So,
N.s/m = (kg.m/s^2)(s/m) = (kg.m.s) / (s^2.m) = kg/s.
Voila! They are the same units.
  Reply With Quote
Old 14th January 2002, 07:15 PM   #4
diyAudio Member
Join Date: Jan 2002
Location: Bucks County, Pa
This is a great utility for those type of conversions:

  Reply With Quote
Old 15th January 2002, 02:58 AM   #5
BAM is offline BAM
diyAudio Member
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
Hey, thanks. I may feel even dumber, but at least I have my answer. Thanks for showing me what was what.

Best wishes,
  Reply With Quote
Old 16th January 2002, 12:07 AM   #6
BAM is offline BAM
diyAudio Member
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
Default Duh...

What is meant by Qb?

I've never seen this referred to anywhere, on any DIY sites or in my DIY book from RadioShack.
  Reply With Quote
Old 17th January 2002, 07:41 AM   #7
diyAudio Member
Cloth Ears's Avatar
Join Date: Dec 2001
Location: Melbourne, Australia
BAM, has most of these elements, but not Qb (yet).

It's the Q of the enclosure with the speaker attached, like Fb is the box resonance frequency and Vb is the box volume. I've only really seen it used for sealed enclosures. For them:

This is supposed to be the ideal. The Fb should be at the same frequency as the F3, the F3 should be the lowest possible for the particular driver and transients should be 'good'.

These alignments generally have better transient response than their higher Qb cousins, but have a higher F3 point (although the bass rolls off more slowly). You can strike problems with excursion at the bottom of the drivers' range, as you don't get much suspension from the air in the box behind the driver.

These alignments are affected by the space (or lack of it) behind the driver. An example is Bob Carver's little sub. The air acts like suspension, as the amount of air being moved by the driver has become a significant percentage of the box volume. For this reason, you get 'not so good' transients, the F3 is higher than most lower Qb alignments, and there starts to be a 'peak' in the response just above F3 (it's about +1dB for Qb=1.0, maybe +3dB for Qb=1.2). Generally these alignments need a bit more amplifier power to drive the speaker and need a bit of EQ somewhere to smooth out the peak.

We are getting into 'Infinite Baffle' territory here. Some of the larger sub-woofers run this sort of alignment - but I don't know much about it. Have a look for those sub-woofers that are set up in a basement and you'll be on that track (I've seen one called 'Dancing Shivas', which is definitely I/B.

But in the end, it's just a figure...
"It is impossible to build a fool proof system; because fools are so ingenious."
  Reply With Quote
Old 17th January 2002, 07:53 AM   #8
Warp Engineer
On Holiday
AudioFreak's Avatar
Join Date: Oct 2001
Location: Queensland, Australia
boy ... Qb sounds an awful lot like Qtc
  Reply With Quote


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
Feel Im getting ripped of Mountnsea Car Audio 3 4th December 2007 04:34 PM
ever feel like a ninja? theChris Everything Else 0 25th April 2003 05:33 AM

New To Site? Need Help?

All times are GMT. The time now is 03:47 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2