Just an idea I thought I would share with you
Commercial passive radiators does actually cost quite a lot
Chassis could be simple plywood
Or if proven to work, constructed directly into the sub
Surround should be available as repair component
The passive cone itself could be anything you can imagine
From the most simple to advanced laminated materials
The third one is a crazy idea from another thread
Surround is a bicycle tube
Airpressure should keep it in place
Thats the cheapes one
But may take some experimenting
But thats the fun part, right
Have fun
Commercial passive radiators does actually cost quite a lot
Chassis could be simple plywood
Or if proven to work, constructed directly into the sub
Surround should be available as repair component
The passive cone itself could be anything you can imagine
From the most simple to advanced laminated materials
The third one is a crazy idea from another thread
Surround is a bicycle tube
Airpressure should keep it in place
Thats the cheapes one
But may take some experimenting
But thats the fun part, right
Have fun
Attachments
Funny, i was just thinking of the same exact thing the other day. Two sets of surround with some offset between them should keep the 'cone' moving in one axis?
The bicycle tube idea looks real neat, but would be hilarious, as well as embarresing, if the sub literally blew up (both PRs cones bust out) during a loud explosion while watching a movie.
The bicycle tube idea looks real neat, but would be hilarious, as well as embarresing, if the sub literally blew up (both PRs cones bust out) during a loud explosion while watching a movie.
Tinitus, I made something like #1 many moons ago. Found it to be too much work when what Collo suggests is a good starting point. A plywood "basket", a piece of wood paneling, the sidewall of a small bicycle innertube, rubber cement and a whole lot of staples. Thanks for the memories.
Probably a good idea but some manufacturers do make the "flapper plates"
You can also add weight by filling the dust cap from the rear and painting the cone with multiple layers of PVA glue. To get really funky, you paint small coins onto the cone with it.
Good to see these suggestions coming out again. Just the sort of thing that piqued my interest when I was but a wee tyke.
All those years ago...
I did this when I was ~17 years old. I had a 12" Radio Shack woofer in a very big box and built in a passive radiator in it. I started with a big hole in the box (around 20") added a flat ring of rubber (truck inner tube) about 3" wide to this. The diaphragm was cardboard, 2 pieces with the rubber sandwiched between. The outer edge of the rubber surround was held in place by a plywood ring screwed through it to the box. On first play, it was a bit sloppy so I added a thick rubber band from the centre of the diaphragm to the rear of the box (makeshift spider).
In the end, it didn't sound bad - way more bass than the 12 could do alone but lacking any of the knowledge I have todayspin I could probably do better.
Looked excessively cool though.
In the end, it didn't sound bad - way more bass than the 12 could do alone but lacking any of the knowledge I have today
spin I could probably do better. Looked excessively cool though.
I once used a passive radiator from CSS that didn't have a rear suspension of any sort, just a big, fairly stiff surround (what I assume Cal meant by "flapper plate", it was made in Germany, I can't remember the brand). The diaphragm was mdf (ish), and had a bolt to which one could attach washers as mass. I used it in a small, low tuned sub with the MCM 55-2421, and it sounded good! (I gave it to a friend). I don't know that it is super linear, nor how long it will last, but it was fun and price was right. I actually choose that design because most of the inexpensive PR's (at the time at least) didn't have nearly enough excursion and mass to work in the box. It sure beat trying to tune that little box to 30hz with a bunch of PVC elbows!
I think you can do as well. The biggest problem (I think) would be getting a suspension that will allow enough excursion, but is also reasonably linear in the range you will use it. Even that little 8" sub could really get the 10" plate flappin'. I honestly really like the inner tube idea. You might need to play with the gap a bit. Glue would allow it to be pretty wide.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
I think you can do as well. The biggest problem (I think) would be getting a suspension that will allow enough excursion, but is also reasonably linear in the range you will use it. Even that little 8" sub could really get the 10" plate flappin'. I honestly really like the inner tube idea. You might need to play with the gap a bit. Glue would allow it to be pretty wide.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
To be honest, I wouldnt expect it to be optimal at loud SPL
On the other hand, I wouldnt expect ANY design with passive radiator to be optimal at loud SPL, but what do I know about it, not much really
I heard the first good one just recently, which got me interested
When others asked about modifying a cheap broken woofer into a passive radiator, I thought why the hazzle
It may never be any good
But Im a bit late it seems, when MJL did it the age of 12
But he may be disappointed if he think he can do better today(grin, lost the smiley)
I dont think that the spider and ordinary basket does any good in linearity
Its only needed fore a conventional design
And the ordinary design with a standard cone mounted with additional weight at the voice coil, I really dont think thats very good at all
Seems to me like it would be much better to have the weight spread over the entire cone
And I expect it to be more linear when in no need fore a spider
Another thing, I suppose we have much better tools today, calculating the design
The one I heard at båndseis place was just a rather cheap dayton, but careully adjusted with weight
How is this ScSp 10" fore a passive radiator, at 150EUR
And maybe you need two of them, pr sub
Thats a lot of money
On the other hand, I wouldnt expect ANY design with passive radiator to be optimal at loud SPL, but what do I know about it, not much really
I heard the first good one just recently, which got me interested
When others asked about modifying a cheap broken woofer into a passive radiator, I thought why the hazzle
It may never be any good
But Im a bit late it seems, when MJL did it the age of 12
But he may be disappointed if he think he can do better today(grin, lost the smiley)
I dont think that the spider and ordinary basket does any good in linearity
Its only needed fore a conventional design
And the ordinary design with a standard cone mounted with additional weight at the voice coil, I really dont think thats very good at all
Seems to me like it would be much better to have the weight spread over the entire cone
And I expect it to be more linear when in no need fore a spider
Another thing, I suppose we have much better tools today, calculating the design
The one I heard at båndseis place was just a rather cheap dayton, but careully adjusted with weight
How is this ScSp 10" fore a passive radiator, at 150EUR
And maybe you need two of them, pr sub
Thats a lot of money
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That's essentially what the Earthquake SLAPS passive radiators are.
And since we're talking PRs, here's my baby:
An externally hosted image should be here but it was not working when we last tested it.
Banned
Joined 2002
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
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
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:
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:
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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
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
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?
"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
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
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