Linkwitz eq circuit - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

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 1st November 2004, 09:24 PM   #1
diyAudio Member
 
Join Date: Mar 2004
Location: Norway
Default Linkwitz eq circuit

Hello all.

I am in the process of building a set of Linkwitz's Phoenix speakers. I just need some dosh so that I can buy the Seas 8" Excel drivers and I'll be on a roll. All ICE powered, 500ASP's.
My problem is with the Thor sub. I have four 12XLS woofers for the dipole woofer, but I also have 8(!) Seas L21RNX/P woofers laying around from another project. I was thinking of putting 4 of these babies in each sub, sort of a Thor clone. The problem comes when I need to calculate the box size. I guess the Q should be 0,7. Is that all I have to do? Dimension the box for four drivers with a Q of 0,7. Then I calculate the Linkwitz EQ based on the f0 of the drivers in the box and the Q of 0,7? I think I can go all the way down to 20Hz or so, since 4 x 8" woofers have almost the same cone area as a 15" woofer. They are also long stroke, with a P-P of 14mm.

Hope anybody can shed some ligth on this.
  Reply With Quote
Old 1st November 2004, 11:24 PM   #2
diyAudio Member
 
cocolino's Avatar
 
Join Date: May 2002
Location: Bavaria (south of veal sausage equator)
Quote:
The problem comes when I need to calculate the box size. I guess the Q should be 0,7.
Q doesn`t necessarily need to be 0,7. Within restrictions (check the math of the formulars) Q can be almost anything.

That`s the beauty of the Linkwitz EQ - You can put a driver in a small enclosure (high-Q, high-fc) and with the LR-EQ You can make a low-Q/ low- fc driver out of it (of course within the mechanical and electrical restrictions of the driver).


Quote:
Is that all I have to do? Dimension the box for four drivers with a Q of 0,7. Then I calculate the Linkwitz EQ based on the f0 of the drivers in the box and the Q of 0,7? I think I can go all the way down to 20Hz or so, since 4 x 8" woofers have almost the same cone area as a 15" woofer. They are also long stroke, with a P-P of 14mm.
Also the target Q doesn`t need to be 0,7.
Actually I found that a lower Q than 0,7 is almost always better sounding (depends of the room and target fc). Don`t forget that at very low frequencies there is room gain. A box with linear free field response down to very low frequencies (as with Q= 0,7) would yield to amplification of those frequencies in a listening room due to room gain.
Besides more linear in-room response and better pulse response, lowering the Q below 0,7 has also another nice side effect - power capability increases and excursion is lower .
__________________
Christoph
STEAL the BEST - INVENT the REST
  Reply With Quote
Old 2nd November 2004, 09:41 PM   #3
diyAudio Member
 
Join Date: Mar 2004
Location: Norway
Hohum, I guess I am up for some trial and error then.
Thanks for the pointers.
  Reply With Quote
Old 2nd November 2004, 10:36 PM   #4
Ron E is offline Ron E  United States
diyAudio Member
 
Ron E's Avatar
 
Join Date: Jun 2002
Location: USA, MN
Quote:
Originally posted by cocolino
That`s the beauty of the Linkwitz EQ - You can put a driver in a small enclosure (high-Q, high-fc) and with the LR-EQ You can make a low-Q/ low- fc driver out of it (of course within the mechanical and electrical restrictions of the driver).

Besides more linear in-room response and better pulse response, lowering the Q below 0,7 has also another nice side effect - power capability increases and excursion is lower .
The pulse response advantage of <0.7 Qtc systems is overstated.
Power handling decreases with low Q systems because the compliance is higher in the compiance controlled region below resonance - so teh driver moves more with the same input.

Quote:
Originally posted by The Dudster
Hohum, I guess I am up for some trial and error then.
Thanks for the pointers.
Without knowing the driver parameters and your goals for the system, you aren't going to get much help. How much power do you have? How big a box can you stand? If it were me, for starters I would make a box for them that had a Q of 1 or so and then tune the LT to the approximate lowest modal frequency of the room and shoot for a Qtc of 0.7 or so. You can experiment from there.
__________________
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan
Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. Aldous Huxley
  Reply With Quote
Old 3rd November 2004, 07:20 AM   #5
Pan is offline Pan  Sweden
diyAudio Member
 
Join Date: Sep 2002
Dudster,

For sale: Seas Excel W22

Check out if interested.

/Peter
  Reply With Quote
Old 3rd November 2004, 05:29 PM   #6
diyAudio Member
 
Join Date: Mar 2004
Location: Norway
Quote:
Originally posted by cocolino
Ok, so I guess Q=0.7 is ok then?

The speaker paramaters are these:

Fs = 23Hz
VAS = 58 litres
QMS = 3,98
QES = 0,33
QTS = 0,30

If I input these values into LSPCAD Lite and optimize the closed box for Q=0,7 I end up with a box of 18,6 litres. Since I have four units that should be 74,4 litres. I will build two cabinets since I have 8 woofers, four in each. If I also increase the size of the cabinet sligthly to compensate for the volume displaced by the speaker units, it should be around 80 litres. That will be approx 43x43x43cm internal size. I know cubes are bad, but the 1/4 wavelength of the frequencies 50-20Hz are so long, 10-17 metres, that it shouldn't be a problem. Or am I wrong? Each sub will be powered by it's own 250W/8ohm ICE power amp. The same applies for the dual XLS phoenix woofers that I am building as part of my Linkwitz Phoenix system. I live in a apartment, so I can't imagine a need for more power than this.

Any comments about the stuff above?
  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
Few questions about Linkwitz' mic amp circuit 454Casull Analog Line Level 60 1st November 2012 02:50 PM
Linkwitz Transform Circuit skogs Subwoofers 1 26th October 2006 11:03 PM
Linkwitz transform circuit? Dxvideo Subwoofers 5 30th August 2005 02:20 PM
Linkwitz lm3886 circuit srfranci Chip Amps 1 30th October 2004 11:28 AM
linkwitz transform circuit pkgum Multi-Way 8 14th December 2001 12:08 PM


New To Site? Need Help?

All times are GMT. The time now is 11:19 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