I asked this question now and then.but never really got a definite answer. So far it seems to me that passive radiators are effective at their resonance frequency. But outside it they still add a little low end blurry background..muddying the sound. Plus they are moving 180 degrees out of phase or produce sound with 360 degree delay. Would it be safe to say that passive radiators are another way to cheat bass out of smaller volume. Bass is less composed and accurate than from a sealed box
I see lots of discussions on the pros and cons of the passive radiator (PR).
PR enclosures seem to have a sound of their own, but I'll keep your thread rolling with this opinion:
"When PRs are done correctly they create bass that is as tight as a sealed box enclosure, but with extra low frequency output."
PR enclosures seem to have a sound of their own, but I'll keep your thread rolling with this opinion:
"When PRs are done correctly they create bass that is as tight as a sealed box enclosure, but with extra low frequency output."
Whose opinion is that, and what's an example of such a (commercial) speaker system?
Not a KEF, I hope.
Is a PR enclosure not like a reflex enclosure in that, above the cabinet resonance, the sound from the PR is partially in phase with the driver, and it is only below the cabinet resonance that it becomes out of phase?
EDIT: I've just seen rayma's post. I obtained the opinion here: https://audiokarma.org/forums/index.php?threads/passive-radiator-faq.179906/
Passive radiator somewhat similar to Vented.
Both have trade offs.
In nutshell they offer more bass response , but have a sharper cutoff response.
If they were always out of phase, it just wouldn't work at all.
fortunately they do work.
Just like a vented system which behaves different below tuning frequency.
You get similar results with passive. Sharper response cutoff.
Hence the descriptions of enclosure types related to the response of a filter.
Sealed has cutoff rate of 1st order filter
Vented and passive have 3rd or 4th order filter cutoff rate.
So your assumption is correct....but
the cancelation you expect only happens below tuning.
hence why ported and passive have sharper cutoff rate.
which is where the cancelation happens, below tuning not above.
Benefits are still similar as well, more bass response in the pass band
And just like vented systems, the measured response has more bass.
But since cone movement is restricted near and at tuning frequency.
overall accuracy and transients are restricted near tuning frequency
Both have trade offs.
In nutshell they offer more bass response , but have a sharper cutoff response.
If they were always out of phase, it just wouldn't work at all.
fortunately they do work.
Just like a vented system which behaves different below tuning frequency.
You get similar results with passive. Sharper response cutoff.
Hence the descriptions of enclosure types related to the response of a filter.
Sealed has cutoff rate of 1st order filter
Vented and passive have 3rd or 4th order filter cutoff rate.
So your assumption is correct....but
the cancelation you expect only happens below tuning.
hence why ported and passive have sharper cutoff rate.
which is where the cancelation happens, below tuning not above.
Benefits are still similar as well, more bass response in the pass band
And just like vented systems, the measured response has more bass.
But since cone movement is restricted near and at tuning frequency.
overall accuracy and transients are restricted near tuning frequency
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Commercial speakers that use passive radiators are becoming more common
https://buchardtaudio.com/collections/passive-speakers/products/s400-signature-edition-graphite-oak
https://www.focal.com/en/pro-audio/monitoring-speakers/shape/monitoring-speakers/shape-65
https://buchardtaudio.com/collections/passive-speakers/products/s400-signature-edition-graphite-oak
https://www.focal.com/en/pro-audio/monitoring-speakers/shape/monitoring-speakers/shape-65
For high-pass behavior......
Just a driver by itself has an approximate third-order roll-off. (Put that driver in a box and it's second-order, ultimately.....just at a lower frequency.)
A conventional driver in a dipole arrangement has an approximate third-order roll-off. Depending upon the dipole baffle scheme.
Dave.
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Think the AR-3a is a sealed box, since they invented it. Looks like -12dB/octave on the graph.
https://audio-database.com/AR/amp_speaker/ar-3a-e.html
https://audio-database.com/AR/amp_speaker/ar-3a-e.html
AR didn't invent sealed boxes. 🙂 Villchur pioneered the acoustic suspension scheme, but there were myriad sealed-box systems before that.
Anyways, getting off track from the OP's query. As mentioned, a passive-radiator system functions much like a typical vented box system. It just allows to achieve that result in a much smaller box where vent dimensions and other factors might be prohibitive.
Dave.
Anyways, getting off track from the OP's query. As mentioned, a passive-radiator system functions much like a typical vented box system. It just allows to achieve that result in a much smaller box where vent dimensions and other factors might be prohibitive.
Dave.
AR invented the air suspension woofer, not the "closed box" speaker.
Those early closed boxes were really infinite baffle systems, with a high resonant frequency.
Those early closed boxes were really infinite baffle systems, with a high resonant frequency.
this model using a spring is pretty accurate
passive radiators add out of phase bass. which may be ok and significant at resonance frequency. with 360 degree out of phase delay at resonance frequency. but then there is extra movement outside resonance frequency that blurs the sound. blurry low end background.
portsi think allow higher excursion of the drivers. so they dont really radiate sound. well except the port noise. ports allow drivers move at higher amplitudes.
which in theory is more distortion.
basically closed box seems like the best of 3 world for home use when you don't need concert level volumes
closed box only has standing waves
open baffle like magnepan speakers is the best in theory right?
passive radiators add out of phase bass. which may be ok and significant at resonance frequency. with 360 degree out of phase delay at resonance frequency. but then there is extra movement outside resonance frequency that blurs the sound. blurry low end background.
portsi think allow higher excursion of the drivers. so they dont really radiate sound. well except the port noise. ports allow drivers move at higher amplitudes.
which in theory is more distortion.
basically closed box seems like the best of 3 world for home use when you don't need concert level volumes
closed box only has standing waves
open baffle like magnepan speakers is the best in theory right?
ABR and bass-reflex speakers use exactly the same principles. The ABR has mass, the port in a bass-reflex speaker contains air which has mass. Each mass bounces on a compliance presented to the mass by the air in the speaker box - and in conjunction with the ABR suspension in the case of the ABR.
Is it only below or below and above and beyond resonant frequency.
Basically I am thinking that passive radiators produce most of the sound at resonant frequency with 360 or so degree delay. So for every 2 bass impacts there is one passive radiator impact with 360 degree delay from active driver
And outside resonant frequency lower sound levels but with 180 degree out of phase
Obviously I am talking within the passband where it´s supposed to work/help, not way off where it just becomes "a hole with some thingy floating in it"
By the same token, air in a vent also moves 180 degrees out of phase well below resonant frequency.
yes but vents don't produce sound. they act as an active driver suspension tuners. they allow drivers to move at its xmax. more air movement or bass from active driver.