Passive Radiators for SPL?

Just curious if it has ever been attempted.

Passive radiator theory sez: Pretend the drone cone is a giant port. The port area is the Sd of the cone. The port volume is dictated by the amount of mass loaded on the drone cone (equivalent to air mass within the imaginary port). You can stuff a monster amount of port area into a small space by swapping air mass for cone mass.

So, has it been attempted? Was it successful?

I never would do it. But I have friends in sq that use them. They add some.

heck fish its only jan and u made 200000 boxes so far.. whats 1 more going to hurt....try it!

Lol. Yea ..I only try what I think will gain. And I think a port is more effective ..

People say that if you can manage the port area, a vented box is more efficient.

I'm imagining a SB1 system that has 2 active 10's... and 6 10" PR's (normal 2-3 cf rectangular box). For $60 on P-E you will have a port area of 3 * Sd ... 1800 sq in of port. That's a 25" diameter circular port from a tame looking 2-3 cf box.

Plus it would make me giggle to watch a box "explode" when you burp... like when Daffy Duck eats dynamite on the old cartoons.

Interesting link about head-to-head comparison. Apparently, when you tune them the same... PR and Ported have almost identical response. The only acoustic differences are from the physical differences between a port and a drone cone.

LINK to comparison

It may not revolutionize SPL... but then again, it may.

chrisbaldelli wrote:

Just curious if it has ever been attempted.

Passive radiator theory sez: Pretend the drone cone is a giant port. The port area is the Sd of the cone. The port volume is dictated by the amount of mass loaded on the drone cone (equivalent to air mass within the imaginary port). You can stuff a monster amount of port area into a small space by swapping air mass for cone mass.

So, has it been attempted? Was it successful?

Am I retarded? This makes absolutely no sense to me, way over my head.
Far as I know a passive radiator gives your subwoofer a little more freedom (like a port does) but doesn't let some of the crappy sounds out that ports can create. So IMO only useful in SQ setups.

We have seen increases back in the day with some Crossfire.
2 15's
and 4 15" radiators
gained about 3.2db

DJMDMA wrote:

We have seen increases back in the day with some Crossfire.
2 15's
and 4 15" radiators
gained about 3.2db

Gained 3.2 db from sealed to passive radiator or from ported to passive radiator or did you have a port and a passive radiator?

From port to sealed passive
Just the overall moving mass help alot from the radiators

I guess I can understand that. The radiators are actually acting like subs, so in a sense its like gaining cone area. Where you from in Iowa? Do we know each other?

I am on the Omaha NE border.
I am sure I met you before but man the past 10 years have been a blur

DJMDMA wrote:

We have seen increases back in the day with some Crossfire.
2 15's
and 4 15" radiators
gained about 3.2db

Was that in a Dodge Neon?

Thanks for posting DJMDMA! 3.2 dB is a pretty ridiculous gain.

I'm guessing the success is alot like why we fiberglass boxes and round corners... When pressures get high, small inefficiencies become large problems. With PR, you're reducing the peak pressures inside the box by converting the energy into a low pressure, high surface area vibration... very similar to why walls and Street A boxes work.

From what I understand, you need an SPL sub (one that has enough suspension to stay stable without air stiffness from a box). Most people recommend a 2:1 ratio of PR:cone area, and attempting to match the actively displaced air (Sd of woofers * Xmech of woofers = Sd of PRs * Xmech of PRs).


To clarify the theory, ported boxes use the air volume within the port to change the phase of the back wave (sound in the box) into something useful. It's tuned at a specific frequency, which is directly related to the perceived mass of air within the port volume. That's why tuning frequencies change with temperature and altitude.

PR's work very similarly but instead of an air mass, it's metal weights attached to a freely moving cone. The port area is analogous to the Sd of the cone. The port volume is analogous to the total weight of the PR (Mms+added weight). Ie, tuning is lowered with more weight.

I was starting to understand then you wanted to clarify and you lost me after that.

chrisbaldelli wrote:

People say that if you can manage the port area, a vented box is more efficient.

I'm imagining a SB1 system that has 2 active 10's... and 6 10" PR's (normal 2-3 cf rectangular box). For $60 on P-E you will have a port area of 3 * Sd ... 1800 sq in of port. That's a 25" diameter circular port from a tame looking 2-3 cf box.

Plus it would make me giggle to watch a box "explode" when you burp... like when Daffy Duck eats dynamite on the old cartoons.

You may want to get clarification on the rules before you try this. I would think the passive radiators would count towards your number of subs.

instead of more or less weight, would a stiffer PR lower tuning? maybe adjustable stiffness PRs (if thats possible, im sure its not impossible) would allow the tuning to be changed on the fly, (or electricly as freq changes. (that would be superfly) creating a big flat response. Watch ya think?

bojangles wrote:

chrisbaldelli wrote:

People say that if you can manage the port area, a vented box is more efficient.

I'm imagining a SB1 system that has 2 active 10's... and 6 10" PR's (normal 2-3 cf rectangular box). For $60 on P-E you will have a port area of 3 * Sd ... 1800 sq in of port. That's a 25" diameter circular port from a tame looking 2-3 cf box.

Plus it would make me giggle to watch a box "explode" when you burp... like when Daffy Duck eats dynamite on the old cartoons.

You may want to get clarification on the rules before you try this. I would think the passive radiators would count towards your number of subs.

yeah, i thought of that last year. imagine a huge rectangular passive radiator that covered the whole b pillar and had 2 foot of excursion. then stuff 20 woofers behind it and make it dance. probably would be like a 4th order w/ no port.

dbdaddy wrote:

instead of more or less weight, would a stiffer PR lower tuning? maybe adjustable stiffness PRs (if thats possible, im sure its not impossible) would allow the tuning to be changed on the fly, (or electricly as freq changes. (that would be superfly) creating a big flat response. Watch ya think?

I don't think a passive radiator is going to affect your tuning. Your still going to need a port for that. As far as it being legal, I'm sure it is, the only thing might be if it looks like a subwoofer you might have to show that it is actually a PR and has no wires hooked up to it.

Anybody heard of a veravent? Kinda like a passive, it used a breathable material instead a moving cone to manipulate the vol. in box.

I like the idea of using PR in a 4th order. HMMM. Thankfully Boston makes passives too.

I think for high power spl aplications a (PR)'s cone would just get pushed out when the active subs are used. One of the team members from Ace's audio told me that happened to him; on his 6 subs 1 was not connected and when tested the pressure pushed the cone out.