Passive radiator

[bigbud747 10+ year member]

I was looking around on Audiopulses website and came across what is called a passive radiator. I found out it is a replacement for a port, but I don't understand how it works. It just looks like a sub with no motor. Could somebody please explain how one works, and if anyone has used one before, it would be great to hear there experiences.

http://www.audiopulse.com/products/passive-radiators/vmp

Thanks.

Click to read more...

 

[bigbud747 10+ year member]

its a thing. it does stuff

Your a dumbass Go crawl in a hole and die. I actually need a real answer from somebody who knows what they're talking about.

 

[MikeyB 5,000+ posts]

bump cuz Im interested as well

 

[Millertime1028 10+ year member]

Basically used instead of a tuned port, used to extend the low frequency response. . The response is similar to a ported system, but the cut-off frequency tend to be slightly higher. Also the cutoff slope is steeper.

 

[dcole18 5,000+ posts]

Basically used instead of a tuned port, used to extend the low frequency response. . The response is similar to a ported system, but the cut-off frequency tend to be slightly higher. Also the cutoff slope is steeper.

kinda... i could hit ungodly lows with my Vmp/3hp combo (~19hz @ 135 dbs)

 

[dragnix 5,000+ posts]

it allows you to create a ported box out of a small sealed box...fucking A

 

[dcole18 5,000+ posts]

it allows you to create a ported box out of a small sealed box...fucking A

duh //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[kovemaster559 5,000+ posts]

it allows you to create a ported box out of a small sealed box...fucking A

x2

 

[newusername 10+ year member]

A passive radiator actually works very similar to a port in an enclosure. In what is commonly called a "ported" enclosure, you have a mass of air that resides in the port. When the driver oscillates (moves forward and backward), the air mass in the port is excited by the compression and rarefaction of the air molecules in the enclosure. The advantage, as we all know, is increased output and lower driver-induced distortion for a given output.

So how does a passive radiator (PR) work? Well, the port works the exact same: it is excited by the compression and rarefaction of the air molecules in the enclosure (this work is done by the driver). The PR moves in and out, in the same way that the air mass in the port moves in and out.

If they behave the same, why choose one over the other? The big advantage a PR holds is in achieving a low resonant frequency (often referred to as a "tuning" frequency) in a reasonable space. With a port, low resonant frequencies require longer port lengths for a given port surface area. And as the driver's output increases (read: moves more air), the surface area required for the port to keep turbulence down increases as well...and this turns into an even longer port. What you eventually find is that your port takes up a lot of space and becomes a pain to work with. In place of that, we can drop in a PR or two and keep all the space that would have been lost with the port. You also lose the port resonance and air turbulence you get with a port.

Why isn't everyone using PR's? Couple of problems...most obvious is the cost. A good, high displacement PR can cost over $100. High displacement PR's are often a necessity because an effective PR system generally has PR's that can displace 2x the Vd of the drivers used in the system (ie. 4x the Sd*Xmax) If you need to use a couple for your design, this adds a lot of cost to the build, whereas your standard port will only cost you wood (or if you're really smart, whatever your local PSP dealer charges you for a flared PVC port). Second, the selection is limited: one of the only sources that I know of right now for a good, high displacement PR is from Acoustic Elegance. The other downside is that PR's are more lossy than a port. Still, the advantages often outweigh the disadvantages.

Look for a few really cool PR's coming from Exodus Audio/DIYCable in the future.

 

[dcole18 5,000+ posts]

i thought about getting one of those pr's from AE... they look really nice

 

[Millertime1028 10+ year member]

Check out this crazy passive

 

[MikeyB 5,000+ posts]

I wonder if I could do something like this with my btl?

 

[dcole18 5,000+ posts]

I wonder if I could do something like this with my btl?

2 18" passives would do the trick

 

[Megalomaniac 5,000+ posts]

thing about a PR is it is not practical for use in the car IMO. Most people have space constraints to begin with, and to use a pr for lets say a 12" sub you need a 15" PR or roughly 2 12" PR for that single 12". and most people dont have the space to actually fit that even though the box size is still xx cubes it just throws your dimensions off. if that makes any sense..

In a house i could see it be done, but then again you are in a house, more than likely you have plenty of space where you dont need to worry about makin a normal size ported box.

PRs are pretty cool and amazing how it works, but in then end its just not practical....IMO

 

[rollerdj 10+ year member]

good read devildriver. i'm getting ready to do a PR for my HT build. how do i figure how much weight to add to the PR to get the right tuning though?