• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Thoughts on Passive bass Radiators

if a port and PR had the same cross sectional area, the mass would be the same. Since that would typically require gigantic port lengths, they end up being significantly larger (rule of thumb is to have PRs capable of displacing 2x as much air as the woofer) so either you use a single large PR with massive excursion or multiple smaller PRs.

Here are a couple of simulations of the woofer excursion between equally tuned PR and ported systems.

Depending on the PRs construction, the low freq behavior of the PR will change. In this case, it was a highly compliant PR with low Fs. Vintage PRs very well may look different.

PRExcursionShiva-X.gif


VBExcursionShiva-X.gif
 
Last edited:
then I'm stumped (thnx for the graphs) : then plz help explain what I've witnessed (many times) : is a woofer for a PR system typically lower in compliance? is it q?

Just found this : http://www.danmarx.org/audioinnovation/theories.html

"Pipe resonances and port standing waves are non-existent because there are no ports or vents in this system. Better driver stability below fB due to increased damping on the driver below fB. This is because of specific compliance characteristics of the PR which help to keep the driver under better control at subsonic frequencies."

is it that there is a difference between response of a signal input and damping? .... is what I have experienced a subsonic resonance (it sure has the look of a standing wave )
 
Last edited:
You can see the tradeoff in Dave's graphs: the port unloads at a higher frequency, but the passive parameters chosen are exceeding Xmax higher up, at 20 Hz. If that's an issue, the parameters need tweaking.... :yes:
 
barkerd said:
then I'm stumped (thnx for the graphs) : then plz help explain what I've witnessed (many times) : is a woofer for a PR system typically lower in compliance? is it q?

Just found this : http://www.danmarx.org/audioinnovation/theories.html

"Pipe resonances and port standing waves are non-existent because there are no ports or vents in this system. Better driver stability below fB due to increased damping on the driver below fB. This is because of specific compliance characteristics of the PR which help to keep the driver under better control at subsonic frequencies."

is it that there is a difference between response of a signal input and damping? .... is what I have experienced a subsonic resonance (it sure has the look of a standing wave )
Click to expand...

In your quote above is the answer, that is, when the frequency goes below the "tuning" of the enclosure (fb) at a high enough level, the damping of the enclosure unloads and allows the woofer to commit suicide.

This is why, as we venture through the mists of time to an earlier world, that fabled epoch when Vinyl ruled the Earth, people in that remote era used what was quaintly termed a "rumble filter." Archeologists assure us that these were widely used by the superstitious multitudes to ward off destruction of their woofers. Warps and wows were the bane of these primitive people, who it seems, occasionally also dropped the tonearm onto the record.

The use of these devices continued right up until the modern era, so strong was the belief that these "rumble filters" could save them.

This concludes today's lecture on Ancient History.

Best Regards,
TerryO
 
Here there are my speakers, that I bought about 10 years ago.They have been made more than 20 years ago by a local designer who is still active: they have a passive woofer, a 12 inches woofer, a Yamaha beryllium dome (from the NS-1000) and Seas Danish-made (Dynaco) tweeter. The crossover is also of very high quality. They sound excellent to me, better than several new speakers of highly praised brands that I've tested. Above all, they sound very natural and with great imaging. Bass is very tight and clean, without noticeable distortion or reverberance.

 
Last edited:
Let me take this a little further (and please tell me if I'm full of it). If one were to design a 2-way speaker you'd necessarily have to find a LF driver that can reach pretty far into the upper midrange. If box size isn't a big deal and you want it to supply deep bass as well, wouldn't it make more sense to use a 6" or 8" mid-bass driver with a 10" or 12" passive radiator than to try and find a ported woofer that can do mids without distortion, or can the port take care of the deep bass with a mid-woofer?
 
Ports and PRs = same thing

The same 6-8" driver would act almost identically. You just get a choice of using a passive radiator or a port to serve the same function.
 
My VMPS speakers (in my pic) have 10in passive thatis tuned with by putting putty on its center and it works well, I like a full range speaker and these dig down deep......I am -10db @16hz and flat at 24 .
 
All the Passive radiators designs I have tried sounded deep but slow! Never heard one that works. I see PS as a quick way to color the sound with lots of deep poor defined deep bass.
 
100% honest opinion, from owning them. They are not only ill sounding, they are more $, and take more room. Passive radiators are not the same of a tuned port, the port does not have a heavy ringing mass. It is like making a speaker with a coloration generator "build in", to make everything "bassy". Actually, the same effect can be done with a subharmonic generator. A device that adds deep base to the sound.
 
You must log in or register to reply here.

Similar threads

Wigwam Jones
Passive Radiators - What Happened?
Replies
16
Views
3K
Boto
Boto
S
Odd passive radiators
Replies
3
Views
934
Shel-e-bean
S
savv
Passive Radiators for ESS Tempest LX-5?
Replies
5
Views
2K
MarkAnderson
M
Theophilus Punoval
Passive Radiators
2 3
Replies
56
Views
8K
GordonW
GordonW
richd860
Passive radiators
Replies
4
Views
958
similost
similost
Back
Top Bottom