Lowering Fs. - 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 24th January 2013, 02:04 PM   #1
diyAudio Member
 
Join Date: Feb 2011
Location: Colorado, USA
Default Lowering Fs.

I have a pair of discontinued Dayton 15" PA woofers I would like to use in a pair of home subwoofers: Dayton Audio PF385-8 15" Cast Frame Driver 4" VC 295-080

38 Hz seems a little high for a subwoofer, and the sensitivity is high so I though adding mass to the woofers might be the way to go. I know some of the classic British manufacturers used to use something that looked like epoxy and sand to add mass to their woofers, and JBL adds lead mass rings to the top of the voice coil assembly.

Opinions, ideas, comments?
  Reply With Quote
Old 24th January 2013, 02:39 PM   #2
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

In theory you can add about 100g to the 100g cone to drop
Fs to 27Hz and bump up the Qts to 0.5. AS Vas remains
the same due to higher Qts the ideal box size increases.

How the suspension and surround would cope with
the extra mass I'm not sure, probably would be OK.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 24th January 2013, 02:57 PM   #3
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
Hi audiomagnate,

For home use you may want to look around for information on the RiPol (Ripole) by Axel Ridtahler. Here is one link: RiPol-Subwoofer .

Regards,
__________________
Oliver
  Reply With Quote
Old 24th January 2013, 03:17 PM   #4
diyAudio Member
 
Join Date: Feb 2011
Location: Colorado, USA
I already have a pair of very nice cabinets, 3^ft in size.
  Reply With Quote
Old 24th January 2013, 03:18 PM   #5
diyAudio Member
 
Join Date: Feb 2004
I would just put them in decent sized sealed boxes (Q=.707), eq/transform the heck out of them, and a 8th order butterworth high pass at about 25-30hz to keep from bottoming them out.
  Reply With Quote
Old 24th January 2013, 03:50 PM   #6
diyAudio Member
 
Join Date: Feb 2011
Location: Colorado, USA
BIG sealed boxes- around 7^ft!

Any input on the epoxy/sand mixture?
  Reply With Quote
Old 24th January 2013, 06:16 PM   #7
diyAudio Member
 
Join Date: Aug 2003
Location: Santa Cruz, California
What you want is a Linkwitz transform. Park the woofers in your boxes, figure out the system Q & F3, then LT to the desired cutoff.
  Reply With Quote
Old 24th January 2013, 07:47 PM   #8
diyAudio Member
 
Join Date: Sep 2008
I don't see any advantage in adding mass. Just use EQ like LT or PEQ.

The only help you could get by adding mass is if the suspension is very non linear and swamping the cone motion, and the added mass pushes the mass controlled region down enough to limit the distortion, assuming the electrical motor is linear enough. Although by that point it's better to get another driver. IMHO.

Fs is an outdated way to look at subwoofers from an age where passive crossover was the only option and EQ was unheard of. IMHO of course.

I would take advantage of the relatively low Qes and large box and go with it. Fair amount of stuffing too.
  Reply With Quote
Old 24th January 2013, 08:31 PM   #9
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
with 100gr added to 100gr cone, your 95db SPL will dump to 88db
but is it really only 100gr ?

had it been at around 20hz I would say fine, but considering its around 30hz, I would say its a bit on the low side
also consider the lowish Xmax is made to match the higher 38hz Fs

sounds like they could be very nice bass guitar woofers
  Reply With Quote
Old 25th January 2013, 01:57 PM   #10
diyAudio Member
 
Join Date: Feb 2011
Location: Colorado, USA
Quote:
Originally Posted by tinitus View Post
with 100gr added to 100gr cone, your 95db SPL will dump to 88db
but is it really only 100gr ?

had it been at around 20hz I would say fine, but considering its around 30hz, I would say its a bit on the low side
also consider the lowish Xmax is made to match the higher 38hz Fs

sounds like they could be very nice bass guitar woofers
Had what "been around 20hz?"

I really don't like the way it sounds now in the 3^ft cabinet, sealed or vented, boomy and thumpy, so I'm going to give it a shot. I can keep one cabinet stock and listen to the difference. They will be used in a multi sub (five) system for smoothing in a low sensitivity setup, so the sensitivity cut doesn't matter to me.

Last edited by audiomagnate; 25th January 2013 at 02:06 PM.
  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
Lowering B+ voltage blue lander Tubelab 41 31st May 2013 07:20 PM
Lowering B+ in PS h00hbt Tubes / Valves 39 14th February 2011 08:12 PM
lowering Qts MCPete Multi-Way 4 31st December 2008 11:09 PM
Lowering HT waner Tubes / Valves 7 29th May 2006 10:31 AM
lowering the voltage Lowjacker Power Supplies 7 11th March 2006 09:11 AM


New To Site? Need Help?

All times are GMT. The time now is 08:12 PM.


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