Passive radiators.....

[audion3wb]

Passive radiators used in DIY subs?

I know of their existence and I understand the theory of how they work. Which leads me to ask why I havent seen people incorporating them into their DIY subs. Wouldn't passive radiators be a good way to decrease box size and attain lower tuning without using a port? Would you use a sub that lends itself to sealed or ported design when using radiators? They allow more movement of air than sealed of course but they don't allow it to escape like a port so that makes me think a radiator is kinda riding the fence between sealed and ported.

Thoughts, explanations, school me please

 

[Matt34]

I know of their existence and I understand the theory of how they work. Which leads me to ask why I havent seen people incorporating them into their DIY subs. Wouldn't passive radiators be a good way to decrease box size and attain lower tuning without using a port? Would you use a sub that lends itself to sealed or ported design when using radiators? They allow more movement of air than sealed of course but they don't allow it to escape like a port so that makes me think a radiator is kinda riding the fence between sealed and ported.

Thoughts, explanations, school me please

I know one reason is due to the extra price involved and the fine tuning with having to add mass to the radiators.

 

[TLS Guy]

I know of their existence and I understand the theory of how they work. Which leads me to ask why I havent seen people incorporating them into their DIY subs. Wouldn't passive radiators be a good way to decrease box size and attain lower tuning without using a port? Would you use a sub that lends itself to sealed or ported design when using radiators? They allow more movement of air than sealed of course but they don't allow it to escape like a port so that makes me think a radiator is kinda riding the fence between sealed and ported.

Thoughts, explanations, school me please

Passive radiators are very difficult for the home constructor. A manufacturer can produce a passive radiator with the exact with the specs he wants. In any event a passive radiator is no different to a port and does not per se change the box size. There are few passive radiators to choose from. Another issue is that for most sub drivers it would be impossible to build a passive radiator with the required T/S specs.

It is not a very fruitful line of endeavor the home constructor, unless you use a woofer and passive radiator designed for each other. Peerless have such a combination.

 

[audion3wb]

Gotcha, I had a feeling that tuning issues might be part of the reason people don't DIY them much. I'll stick to ported in that case!

 

[CSS/XBL]

We have just launched our patent-pending Adjustable Passive Radiators which allow users to easily experiment with adding weight without removing the APR once installed.

Bob

 

[WmAx]

I know of their existence and I understand the theory of how they work. Which leads me to ask why I havent seen people incorporating them into their DIY subs. Wouldn't passive radiators be a good way to decrease box size and attain lower tuning without using a port? Would you use a sub that lends itself to sealed or ported design when using radiators? They allow more movement of air than sealed of course but they don't allow it to escape like a port so that makes me think a radiator is kinda riding the fence between sealed and ported.

Thoughts, explanations, school me please

As already stated, the PR sub operates exactly on the same principle as a ported sub. It requires the same type of sub to work well in PR as it does in ported. When talking about high output subwoofers, it takes usually 2x the surface area in PRs plus very long stroke. In addition, mass is only one variable. The T/S parameters of the PR must match up with the subwoofer it's used with. You can't just use an PR with any sub and simply adjust the mass and have it work. A well designed slot vent sub has no compromise - and as far I'm concerned - PRs are not that desirable for subwoofer use except in special applications where space is at such a premium that you can't provide for added volume that a proper slot port occupies.

-Chris

 

[TLS Guy]

We have just launched our patent-pending Adjustable Passive Radiators which allow users to easily experiment with adding weight without removing the APR once installed.

Bob

I can't see how that product would have much utility.

 

[CSS/XBL]

Hi,

A number of PRs available do have the possibility of adding weight to a tube or bolt at the back but the unit would need to be removed to make that adjustment. This simplifies things and allows users to experiment with different tuning options fairly easily. Some of the competing products do not include the extra weights which we do. It certainly allows commercial designers to tweak a design which can then be ordered with a fixed amount of weight at a reduced cost.

One of our portable PA clients will experiment with different tuning depending on the venue hall and the type of gig happening.

Bob

 

[TLS Guy]

Hi,

A number of PRs available do have the possibility of adding weight to a tube or bolt at the back but the unit would need to be removed to make that adjustment. This simplifies things and allows users to experiment with different tuning options fairly easily. Some of the competing products do not include the extra weights which we do. It certainly allows commercial designers to tweak a design which can then be ordered with a fixed amount of weight at a reduced cost.

One of our portable PA clients will experiment with different tuning depending on the venue hall and the type of gig happening.

Bob

With respect, you do not understand the mathematics of passive radiator tuning. You can't just focus on mass.

 

[MJK]

With respect, you do not understand the mathematics of passive radiator tuning. You can't just focus on mass.

Could you provide a little more explanation for that statement? Maybe some of your mathematics would help me understand. Tuning a port's length is just adjusting the amount of air mass in the port that acts on the box spring stiffness. Granted, the passive radiator has some suspension stiffness associated with it so you need to factor that into the box sizing, then you can adjust the mass to tune the system. I noticed this product the other day and thought it was a great idea. Why so negative, what am I missing?

 

[DanWiggins]

With respect, you do not understand the mathematics of passive radiator tuning. You can't just focus on mass.

Hi,

Actually, for a given Sd you really only need mass to determine tuning. The suspension stiffness is a very weak 2nd order function, and unless you have an extremely low compliance suspension (such as 0.15mm/N or less), the effect of compliance on the actual system tuning is irrelevant. This is because the spring of the air inside the box is the dominant compliance of the PR, meaning that you simply need to adjust the Mms of the passive radiator to change the tuning.

 

[annunaki]

Dan,

Are you the Dan Wiggins from AdireAudio/AcousticVisions?

Welcome aboard in any case!

 

[DanWiggins]

The one and the same... Suffice to say, I've done a few speakers and PRs in my time.

 

[annunaki]

Dan,

I hope you are enjoying it here.

What went down with Adire Audio? I assume that DIYcable.com is something you may be involved with? No?

Many of the drivers use the same names as your products from Adire. You had some nice drivers. Nice ones for the DIY community here that is for sure.