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In the Forum: Audio Discussions
In the Thread: Constructing LF modules to the limits
Post Subject: Excursion distribution and tone below 20HzPosted by haralanov on: 9/25/2011
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 Romy the Cat wrote:
With use of multiple divers we accomplish exactly that - we spread the excursion of one large woofer to the let say 4 mini excursions of small woofers, minimizing the total participation of suspension in the entire ceremony. We spread not only excursion but also flux modulations, thermal compression of VC and many other factors that are much less at low excursion of the small drivers.

Yes, I agree with that. Actually I’m doing the same – to spread the excursion of one large woofer to multiple large woofers. This also lowers the flux modulations, thermal compression and distortion (just like with using multiple small woofers) but with the added benefit of huge sensitivity at lower frequencies, because for a given current flowing in the VC, the bigger driver has several dB more output, better acoustic control at Fs and better tone too. Controlling the cone movements at Fs with just efficient air loading of the cone, allows me to use softer suspension, which has very linear behavior at low to moderate excursions, so the drivers will actually operate in ultra-linear mode when used at just 4-5mm of total excursion. And because of the high sensitivity, every one of them will eat no more than 2-3 Watts to produce very high SPL at LF.
 
 Romy the Cat wrote:
Now about the tone. Petar, you use 60Hz first order and of cause the tonal concepts are important to you. In your estimation would you feel the same if you use 20Hz and 4th order? I did listen my ULF sections without the rest of Macondo, trying to get a sense if "tone" is something the I was able to hear in there. I did not recognize that there was anything in there that might have a tone. I did heard the dynamic compression but not tone per say. Can you put 20Hz and 4th order on your driver and share what you hear?

I plan to use my future woofer towers to 40-42Hz (first order), so I very much care of the tone at these frequencies, but in your case, using them below 20Hz with such a steep low pass filter, it is completely different situation and I think it doesn’t matter what kind of drivers produce that subsonic pressure. Nobody hears any tone below 20Hz, so practically it should be of no consideration. Of course I may be wrong about that – I don’t know, because I have never tried to use infra bass channels. Maybe the only requirement for the driver is to have very low Fs in order to prevent excessively eating of power in order to move/push the cone below its Fs…
 
Best regards,
Petar

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