Passive radiator, build your own - Page 2 - 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 11th November 2009, 03:21 AM   #11
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
NICE thats huge.!
  Reply With Quote
Old 11th November 2009, 03:40 AM   #12
diyAudio Member
 
pheonix358's Avatar
 
Join Date: Jul 2008
Location: Stockport South Australia
Quote:
Originally Posted by pheonix358 View Post
I always liked the idea of a large passive with a wirewound pot across it's terminals, the pot alows you to tune the passive.

Terry
I didn't explain that very well. You use another woofer, cheaper usualy, as the passive, wire a wirewound pot across the terminals. The resistance across the voicecoil acts as a brake giving you variable tuning. After the system has been run in and you are happy with the tuning you can replace the pot with a fixed resistor.

If you want to see the effect yourself, take any woofer, by hand check how easy it is to move the cone. Now short the terminals and check again, much harder to move.

Terry
__________________
What we don't understand is called magic.
  Reply With Quote
Old 11th November 2009, 05:42 AM   #13
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by gooki View Post

And since we're talking PRs, here's my baby:
Thats a big one
Please tell, what is it
And what monster do you use to push it

btw, I get virus/trojan warning every time I visit earthquakesound
  Reply With Quote
Old 11th November 2009, 06:41 AM   #14
gooki is offline gooki  New Zealand
diyAudio Member
 
Join Date: Dec 2008
The PR in the pic was created by a local company Arvus (The Arvus Group of New Zealand - Inspired Innovation Since 1983). Their Bladder Buster sub featured one 27 inch passive radiator (24 inch cone) and 6 x 12 inch subwoofers. I purchased just the PR to experiment with high output bandpass enclosures.

As for the Earthquake website, I get the same warning. You'd expect an established company like Earthquake to fix something like that ASAP, but it's been two weeks. My guess is their site is hosted on a shared webserver, that got infected (either that or it's a false warning). That, and their company seems fairly non active these days.

Here's the quoted text from the SLAPS page:
Quote:
SLAPS12 & SLAPS15
(Symmetrically Loaded Audio Passive System)

Click the image to open in full size.

* Super wide edge surround 1.75" in diameter.
* Flat diaphragm with a total diameter of 12" or 15" - including surround.
* Mounting depth 1.75".
* Required space clearance for forward and backward excursions 3.5" in each direction.

Earthquake's symmetrically loaded passive radiator - SLAPS is designed to produce maximum bass from a shallow space. As its name indicates, the SLAPS integrates identical components in its suspension. The structure itself is made of a custom designed aluminum ring. the ring carries, on each of its sides, a one-piece flat diaphragm with a super wide edge surround; the diaphragms on both sides are identical in structure, hence perfectly symmetrical resistance to inward and outward movement. The diaphragms are spaced 1" using a weighted solid ring for tuning purpose. The SLAPS-12 excursion exceeds 2.5" in each direction.

Earthquake's symmetrically loaded passive radiator allows the user to tune an enclosure - very low, without having to increase the enclosure volume. The SLAPS can be widely used in car as well as in home audio applications; wherever subwoofers are needed to be tuned at low frequency, without increasing the enclosure volume, and without the need to deal with the traditional shortcomings of port tuning such as: port noise, port length and availability.

Typical passive radiator designs greatly suffer from non-linear forward and backward excursions; its forward movement inhabits different resistance from its reverse movement due to spider limitation, thus making its response inaccurate. Further, a typical passive radiator is built using speaker basket that is 4" to 5" deep, making its application more cumbersome than practical.

Earthquake manufactures products for the car and home audio markets, most of which are geared toward high power applications and bass. In car audio competition circles, SPL is "the name of
the game". Bass freaks scramble to add a dB or two to their audio systems; using the SLAPS is a sure way to achieve the goal. In home audio applications, especially with the advances in Home Theater systems, low bass is a must to complete the circle. The SLAPS can be used to tune subwoofer enclosures to attain the desired results.

Copyright © Earthquake Sound, Corp. - All rights reserved.

Last edited by gooki; 11th November 2009 at 06:53 AM.
  Reply With Quote
Old 11th November 2009, 10:54 AM   #15
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
The middle example in Fig1 is the SLAPPS principle. It should work very well, and replacement surrounds are available at a reasonable price. I suggest the PR should have up to 3x the Vd of the main driver, so use a bigger PR than your driven woofer. The Cerwin Vega double roll 'M' type are only a bit more than the common types, and they can move further.

Another thing you can do is nestle a smaller surround inside of a larger one. Philips has a patent on this idea, they have a narrow ring between the two surrounds.

Passive speaker - Google Patent Search

See fig7:

Passive radiator having mass elements - Google Patent Search
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 11th November 2009, 08:08 PM   #16
diyAudio Member
 
Join Date: Jun 2005
Location: Singapore
Quote:
Originally Posted by pheonix358 View Post
I didn't explain that very well. You use another woofer, cheaper usualy, as the passive, wire a wirewound pot across the terminals. The resistance across the voicecoil acts as a brake giving you variable tuning. After the system has been run in and you are happy with the tuning you can replace the pot with a fixed resistor.

If you want to see the effect yourself, take any woofer, by hand check how easy it is to move the cone. Now short the terminals and check again, much harder to move.

Terry
Wouldnt' that be different from a passive mass loaded PR? I mean, the passive coil would be damping or resisting the movement of the PR and dissipating some power across the resistor. The amount of damping and dissipation would be proportional to the velocity of the PR.

Not saying it wouldn't work, but how does that affect the tuning and behaviour of the sub? I guess it may actually result in a better 'damped' PR than the regular mass-spring PRs? Seems like you had good results with your application. How does it sound?
  Reply With Quote
Old 12th November 2009, 02:47 AM   #17
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
I dont know, but very often a low tuned BR design ends with either very impractical port length, or a too small port diameter

Is this where a PR could have huge advantage
  Reply With Quote
Old 12th November 2009, 03:45 AM   #18
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
"I didn't explain that very well. You use another woofer, cheaper usualy, as the passive, wire a wirewound pot across the terminals."

Ah, the old 'not quite passive radiator'.

Very lossy. More like the flow restrictor vents.
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 12th November 2009, 07:32 AM   #19
diyAudio Member
 
pheonix358's Avatar
 
Join Date: Jul 2008
Location: Stockport South Australia
"Not saying it wouldn't work, but how does that affect the tuning and behaviour of the sub? I guess it may actually result in a better 'damped' PR than the regular mass-spring PRs? Seems like you had good results with your application. How does it sound?"

In practice it is very similar to adding mass, ie, you can slow down the cone's movements. The good part is the effect is variable.

"I dont know, but very often a low tuned BR design ends with either very impractical port length, or a too small port diameter"

Yes, this si often a problem, consider though, the port does not have to be 'in' the enclosure. If you are going to put the speaker on a stand, you can use the port as the stand. Go silly with over large port dimentions and you start getting into TL territory. Still, something to think about.

" Very lossy. More like the flow restrictor vents."

Not in my experience, in fact it can be quite the opposite. You can acieve a very stiff PR if you choose to. The good thing is it makes for an easier build. You can be 'near to perfect' in your design and then by carefull measurement and turning a knob, get to exactly where you wanted to get. A PR is only a speaker without the back end. Just leave the back end in place and use it to your advantage. It is usually cheaper than a PR.

Terry
__________________
What we don't understand is called magic.
  Reply With Quote
Old 12th November 2009, 03:00 PM   #20
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
You can decrease the mechanical suspension by cutting out strips or 'pie pieces' from the spider.

And yes pjanda1, a drone without a rear suspension is what I call a flapper plate.
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  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
Passive radiator Chris8sirhC Subwoofers 4 5th August 2008 05:49 PM
Passive radiator jamikl Subwoofers 1 3rd June 2006 09:23 AM
passive radiator ??? Ahmad_tbp Multi-Way 20 29th March 2005 07:44 AM
Passive Radiator For ESS qdoc Multi-Way 0 8th July 2004 05:06 AM


New To Site? Need Help?

All times are GMT. The time now is 01:23 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