Nelson Pass: The Slot Loaded Open Baffle Project - Page 13 - 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 5th September 2011, 12:51 AM   #121
diyAudio Member
 
Join Date: Dec 2002
Location: Illinois, USA
To follow up my previous post (#119). The implication is that the driver diaphragm actually will move less for a particular SPL than the same driver in free space must move. I submit that this is the source of most of the disagreement on the subject.

Jeremy
  Reply With Quote
Old 5th September 2011, 01:15 AM   #122
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Article accessible from here

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 5th September 2011, 01:23 AM   #123
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Loving the thread, but mighty annoyed as I can't access Nelson's article: The Slot Loaded Open Baffle Project Article By Nelson Pass Is this a problem at my end or is the website down?

Perhaps it was taken down for violating the laws of physics.

  Reply With Quote
Old 5th September 2011, 01:24 AM   #124
diyAudio Member
 
vacuphile's Avatar
 
Join Date: Apr 2011
Location: Seaside
Quote:
Originally Posted by kropf View Post
To follow up my previous post (#119). The implication is that the driver diaphragm actually will move less for a particular SPL than the same driver in free space must move. I submit that this is the source of most of the disagreement on the subject.

Jeremy
No, it is slightly more complicated than this.

The driver diaphram will move less, because of increased acoustic loading. The intertwined result is a lowering of back EMF, causing the impedance of the driver to go down, and therefore I to go up. More energy enters the driver and gets transferred into acoustic energy, but with less cone excursion. Like with horns and correctly tuned BR's.

vac
  Reply With Quote
Old 5th September 2011, 01:26 AM   #125
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Quote:
Originally Posted by kropf View Post
To follow up my previous post (#119). The implication is that the driver diaphragm actually will move less for a particular SPL than the same driver in free space must move. I submit that this is the source of most of the disagreement on the subject.
Actually, my point is fundamentally that the response is asymmetric. I don't
actually care whether it is more efficient on the whole.

If you want to decide that the front loading is causing less excursion of the
diaphragm and thus less output on the rear, that would be OK with me.
  Reply With Quote
Old 5th September 2011, 01:31 AM   #126
Pano is online now Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Link works fine for me in the USA.
  Reply With Quote
Old 5th September 2011, 01:35 AM   #127
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Quote:
Originally Posted by bocama View Post
If the pressure and the volume displacement are bigger in the front (the potential and kinetic energy) as you seem to think it is.
I think the volume displacement is essentially the same, as stated previously.

  Reply With Quote
Old 5th September 2011, 01:40 AM   #128
CLS is offline CLS  Taiwan
diyAudio Member
 
Join Date: Jun 2005
Location: Taiwan
Let's come back to "DIY" portion of things.

This is what I've done during the weekend (when you guys were busy on debating...)

Click the image to open in full size.
They'd be lying on floor anyway, so i skipped one of the walls. The white stuff are foam strips for better sealing with floor. Simple, quick and dirty, my style



Click the image to open in full size.
The front(upper) baffle is not completed yet. That'll be provided by another section of the system. Despite short of baffle area, it's still workable.

The woofer is 18" (Sd=1140cm^2), the slot is 91cm wide by 5.5cm high (500cm^2), which is about 44% of Sd. With such aspect ratio, I guess the effect of 'compression' would be higher than the number suggests.

.....
  Reply With Quote
Old 5th September 2011, 01:48 AM   #129
diyAudio Member
 
Radugazon's Avatar
 
Join Date: Aug 2010
Location: Sulawesi
Have you measured the FS ?
  Reply With Quote
Old 5th September 2011, 01:48 AM   #130
diyAudio Member
 
Join Date: Apr 2005
Location: Sitting behind the 'puter screen, in Illinois, USA, planet earth
Hi

I believe you will find that if one made a simple sealed box using the same size baffle and same number of drivers, one with and one without slot loading, that they would measure identically at the low frequency end as the “velocity transformation” is accompanied by a corresponding reduction in the area. The result is "slot loading" has essentially no effect on the radiation efficiency at low frequencies.

As sreten suggests, it will alter the directivity up high and higher up (at frequencies where the woofer spacing would produce a narrower pattern) , the depth of the port will produce a cancellation notch at frequencies where path length from the driver radiation to the closed end is N quarter wavelengths (the reflection returns 180 degrees later).
Also, the mass of air at the exit and compliance of the air in the slot form a resonator which the drivers are couple to and this is like the low pass filter in a band pass system. This adds a small extra mass to the total moving mass too.
This can provide a gain at the higher end of the spectrum as well as an acoustic low pass filter. Now your entering horn territory.
Best,
Tom Danley
Danley Sound Labs
__________________
Bring back mst3k and futurama
  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
Need help for my first Open Baffle project anilva Multi-Way 8 22nd January 2010 12:00 AM
First open baffle project Moondog55 Multi-Way 18 10th August 2008 04:35 AM
open baffle project mastarecoil Full Range 25 29th November 2007 05:08 AM
another Open Baffle project Tomac Multi-Way 1 14th September 2006 09:11 AM
Which is the nicest open soucre power amp between 40 - 60 Watts from Nelson Pass? Onvinyl Pass Labs 5 21st July 2006 12:55 AM


New To Site? Need Help?

All times are GMT. The time now is 02:28 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