Martin Logan ForceForward technology - does anyone understand what it is?

[paulspencer]

I stumbled across this on Martin Logan's website and it has got me curious as I don't understand exactly what they are doing on first reading. Perhaps someone can make better sense of it than I can. It appears as if they are claiming unipole bass (dipole with the rear pole removed). Could this be so?


Our engineering group pioneered a calibrated woofer system integrated with a tightly controlled network to dramatically reduce this problem by directing the low frequency energy only in the forward direction—ForceForward.



The diagram above shows the path length between the front and rear woofer and the resultant net room bass. By shifting the energy below 100 Hz in time (phase) we condition the distance relationship between the two drivers in such a way that the energy arrives at a sum in the front, yet results in a null in the back. This causes a near complete absence of energy between the rear wall and the speaker and a coherent wave front directed forward, resulting in easier room placement and more uniform bass throughout the room.

The best part is that you can place your MartinLogan's in a much wider range of configurations—closer to the front wall for instance—and still enjoy the same incomparable bass power, staging, and fidelity.

[paulspencer]

Here is the link to the original article on the ML website

[Chris8sirhC]

I'm pretty sure its just a dipole, do a search for dipole subs on this forum.

[Grahamt]

t appears as if they are claiming unipole bass (dipole with the rear pole removed).

That's what it seems like to me too, but you know more about this than I do.

[DSP_Geek]

It's a cardioid. Here's more data without the marketing speak:

http://www.meyersound.com/products/c...s/psw-6_ds.pdf

Meyer's been doing this for a while, and it was old when they started (not to take anything away from John Meyer, who's a major audio guru a la Burt Rutan for aeronautics).


Francois.

[paulspencer]

Thanks DSP, that makes sense to me now ...

The phase of the second rear facing woofer is shifted so that is cancels some of the output of the main woofer. This changes the polar response of the combined woofers so that the interaction with the rear wall is reduced. The cost of doing this is that you get less output with two woofers than you would have with one.

Probably not something that I'd want to try, but interesting.

[ScottG]

If its true to form (and I doubt it is as good as the marketing dept. says it is) its a 2nd order gradient (a super cardoid).

The only way I can see this being acomplished without a digital delay is by having the drivers magnets touching each other with front driver having a steep crossover (and increased delay) and the other having a shallow crossover (with almost no delay) Perhaps a low pass 24th LR on the front driver at around 100 Hz and a 1st order crossover for the rear driver (which is operating out of phase). Of course both drivers will have to be custom made to overcome output loss via higher "Q"s.

[Konrad]

Is it much different from what a rear mounted slave would bee?

[paulspencer]

Originally posted by Konrad
Is it much different from what a rear mounted slave would bee?

It's not a passive radiator if that's what you mean. Both drivers need to be active drivers as the rear driver needs to play a signal that is modified in some way for cancellation to occur.

[Konrad]

Well the passive radiator has some kind off passive bandpass assistance and canseling out of bandpass.
Assisting the rear radiator in a bandpass fasion it will also cancel below, add in bandpass, and for the hipass i can only guess....

Half the trick here as i see it is the behavior "riding the wave".