Mattias

We used a 10" driver, the same cone area in a stamped metal basket with a 2:1 area ratio. The cost of this later piece was only a fraction of the driver - why would it be more? The cost in a driver is in the motor structure, eliminate that and the cost should only be a fraction of the original speaker. Then we used two of these levers. Result; +6 dB more output at far less cost than two drivers with motors. A single lever would have reduced this cost further, but we liked the packaging options of two better.

I think that you calcs have some problems.

When I look at the image below from Speak, I see:
A speaker in a sealed box and a small passive radiator connected to a bigger passive radiator with a rod. Peerless has 10" and 12" passive radiators but there is no 8.5" (12"/(sqrt(2))=8.5") passive radiator availible from them so it's not possible to get a 2:1 area ratio. (that's why I said 3 passive radiators)

Some things are unclear for me:
1. Should the big passive radiator be of the same size as the speaker?
2. Did you build the passive radiators yourself?
3. How did you build the lever?
4. Which speakers/passive radiators/components did you use to build the subwoofer?

Thank you for taking the time to answer my questions. I hope somebody else also will benefit from reading this

• Front lever

>Some things are unclear for me:
>1. Should the big passive radiator be of the same size as the >speaker?

It should preferably be about 50% bigger.

>2. Did you build the passive radiators yourself?

I was with a big company and we had a suplier build them.

>3. How did you build the lever?

As below with a few mods - the spider did not have a hole in is as shown in the drawing. This gave a larger gluing surface. We sued a frame to hold the parts, although once mounted the frame beomes unimportant.

>4. Which speakers/passive radiators/components did you use to build >the subwoofer?

Again, I was with Ford and we had everything custom made. This project was published in SAE and can be obtained. It shows how the theory worked as expected, the +6 dB gains were achived and the lever with one driver outperformed two drivers in about the same enclosure volume, fewer drivers and watts required with the lever.

If only I could get some company to make the actual lever, I know that this would be a popular approach. Maybe someday I will pay for the tooling and do just that. But I have other interests right now.

If you, or anyone else, wants to have these levers made and sold, I would give you rights, they are patented, to do this since I own them for most configurations of advantage.

• Practical lever construction