30 HZ from a 10 X 7 box - Page 4 - 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 8th July 2013, 01:03 AM   #31
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Yes-go from the red circle to one of the blue ones.

I admire a man who makes it easy to answer the question.


Qts is the total Q of the woofer you are starting with, free air. It is 0.43 instead of 0.45? So much the better.

Thiele-Small's original work call for a speaker with free air Qts of 0.38, (usually shortened to 0.4 in the real world, Qts is not that exacting). Put it in a box equal to the Vas, and it will be maximally flat down to the drivers free air resonance frequency, Fs.

So the ideal would be:

Qts = 0.38, (or 0.4)
Vb, (box volume, internal) = Vas
Fb, (frequency of box tuning) = F3
-3 dB down point = F3

That is the "classic bass reflex" Thiele-Small came up with-they came up with others too, but that is the first one. Your speaker and your projected box size is very very close to that.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 8th July 2013, 01:07 AM   #32
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Okay,gotta go for a half hour or so, but yes, alignment vs displacement.

Theoretically a driver with a free air Qts above 0.38 requires a box larger than Vas and a tuning frequency above Fs. However, your alignment is so close to the classic bass reflex, you are only off by a little, that you can fudge it with no problem. And your F3 and box size will be about what you were aiming for.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 8th July 2013, 02:47 AM   #33
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Quote:
Originally Posted by fwbutler View Post
I do not understand your comments about the Qts? the TB1138 has a Qts of 0.43. do you mean a desired Qtc?
Qts = Free air total Q of driver

Qtc = Total Q of driver in closed box.

We are doing bass reflex, also known as ported. We don't have to worry about Qtc.

To find the response curve of a ported box, we only deal with:

Qts
Fs, (free air resonance)
Vas, (definition is not important, just remember it is given in cubic measure)
Vb, (volume of air in the box)
Fb, (frequency box is tuned to via port)
F3, (-3 dB down point)


Just for the record, Qtc= [sq rt (Vas/Vb) + 1] times Qts

But like I said, that is stuff useful for closed box calculations.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 8th July 2013, 02:59 AM   #34
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Not to overload, but I checked out the frequency response of the TangBand 1138 at their website. Pretty smooth up to 1,000 Hz, but there's peak around 1,500 Hz.
http://www.tb-speaker.com/detail/1208_03/w5-1138sm.htm
Attached Images
File Type: jpg tang band 1138.jpg (55.1 KB, 112 views)
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 8th July 2013, 03:36 AM   #35
diyAudio Member
 
fwbutler's Avatar
 
Join Date: Sep 2012
Location: Hillsboro, Oregon
probably cone breakup above 1.5k on the W5-1138SM look at the W5-1138SMF a very different speaker. wonder what the F stands for?
Attached Images
File Type: jpg tb 1138SM F.jpg (66.8 KB, 111 views)
  Reply With Quote
Old 8th July 2013, 04:19 AM   #36
diyAudio Member
 
fwbutler's Avatar
 
Join Date: Sep 2012
Location: Hillsboro, Oregon
What the difference is I do not know. Different Vas and Qms
Attached Images
File Type: jpg TB 1138's.jpg (68.0 KB, 109 views)
  Reply With Quote
Old 8th July 2013, 06:29 AM   #37
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
LOL, the different listed parameters might just be the variation from speaker to speaker.

Bass wise, the two speakers seem to be within 1 dB of each other in the bottom half octave. That's really close.

The F speaker seems to have cone breakup between 1,000 Hz and 2,000 Hz as well, but nowhere near as radical especially if you want to crossover at 1,500 Hz.

If you tune either speaker to 45, you'll get a slight bump from 45-90 Hz, but it won't be large. Speaker excursion is smallest at the tuning point, (Fb), and for excursion reasons I really don't think these small speakers should be driven below 45 Hz or so. But it's up to you.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 8th July 2013, 06:32 AM   #38
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Just taking a guess, the SMF version of this speaker looks like it might be intended for someone who wants to cross over higher than in the SM version.

If I could hazard a guess, the F might stand for "full range". It isn't full range of course, but the response curve for the F looks like it is more useful for someone wanting to cross over higher.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 8th July 2013, 07:03 AM   #39
diyAudio Member
 
fwbutler's Avatar
 
Join Date: Sep 2012
Location: Hillsboro, Oregon
looking again at the speakers,The SM has a neo magnet and costs twice as much, the f has an iron, Ferrous magnet, maybe that is the difference.

The better one is cheaper??

Last edited by fwbutler; 8th July 2013 at 07:07 AM.
  Reply With Quote
Old 8th July 2013, 09:14 AM   #40
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
I am not a crossover expert, but it looks to me that the F one has a smoother response to work with. In fact, if you can eliminate that peak at 2,400 Hz, you have something approximating a natural 6dB/octave rolloff.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  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
Which woofer does 30-1000 Hz / JBL 2235A Equivalent audiothings Multi-Way 25 5th November 2010 02:38 PM
Sanity check request for 30 Hz Tapped Horn pk Subwoofers 17 13th April 2010 06:44 AM
10-25 hz, is it necessary for HT or Music? Daveis Subwoofers 236 26th October 2008 03:31 AM
Boosting 25-30 hz qguy Subwoofers 2 13th January 2007 03:10 AM


New To Site? Need Help?

All times are GMT. The time now is 11:52 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